Application Requirements for Smart High-Side Switches

Smart High­Side Switches
Application Note
What the designer should know
Short introduction to PROFET™ + 12V
By Stephane Fraissé
Application Note
Rev 1.0, 2010-12-15
Automotive Power
App. Note
1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
2.1
2.2
2.3
2.4
Introduction. Why High Side Switches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Short Circuit Hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
System Cost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Galvanic Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Other Switching Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3
3.1
3.2
3.3
3.4
3.5
Type of supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Module un-powered during stand-by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Module supplied during stand by . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Left/Right Front/Rear separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Secondary Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
11
11
11
12
13
4
4.1
4.1.1
4.1.2
4.1.3
4.1.4
4.1.4.1
4.1.4.2
4.1.5
4.1.5.1
4.1.5.2
4.1.6
4.1.7
4.1.8
4.2
4.2.1
4.2.2
4.3
4.4
4.4.1
4.4.2
4.4.3
Automotive Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Battery Voltage Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alternator Regulation Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alternator Ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Start-Stop Application. Regenerative Braking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Battery Voltage Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Discharged Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Battery Voltage Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jump Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Load Dump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reverse Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss of Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Umbrella Specification for Battery Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ambient Module Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Module Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Running Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stand-by Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Number of Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
15
15
16
16
17
17
17
18
18
18
19
19
19
19
19
20
20
21
21
21
21
5
5.1
5.1.1
5.1.2
5.1.3
5.1.4
5.1.5
5.2
5.2.1
5.2.2
5.2.3
5.3
5.3.1
5.3.2
5.3.3
5.4
Load and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamps / Capacitive and Resistive Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamps Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lamp Wattage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cold Lamp / Inrush Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Life Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Light intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Light Emitting Diode (LED) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard LED Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Advanced LED Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LED Cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inductive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Demagnetization Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Freewheeling Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Number of Activations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
22
23
23
23
24
24
25
25
26
26
27
27
28
28
28
Application Note
Smart High­Side Switches
2
Rev 1.0, 2010-12-15
App. Note
5.5
5.5.1
5.5.2
5.6
Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wire as a Parasitic Electrical load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Current in a Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Platform and Vehicle Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
29
29
30
6
6.1
6.2
6.3
6.4
Failures in the Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit Between Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
32
32
32
33
33
7
7.1
7.2
7.3
7.4
7.5
7.6
7.6.1
7.6.2
7.7
7.7.1
7.7.2
7.7.3
7.8
7.8.1
7.8.2
7.8.3
7.8.4
7.8.5
Power Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Charge Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Slope Control Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Losses Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switch Behavior with PWM Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROFET™ + PWM Limitations due to Power Losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROFET™ + PWM Limitations Due to Switching Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Case Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Power in PROFET™ + . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inverse Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Capacitive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output wired to Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inductive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Alternator Ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Consequences for PROFET™ + . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
34
35
36
36
37
38
38
40
41
41
41
41
42
42
42
42
42
43
8
8.1
8.2
8.2.1
8.2.2
8.2.3
8.2.4
8.2.5
8.2.6
8.2.7
8.3
8.4
8.5
8.6
8.7
8.7.1
8.7.2
8.7.3
8.7.4
8.8
8.8.1
8.8.2
Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Band gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROFET™ + Current Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROFET™ + Current Limitation Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Swing Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Temperature Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Restart Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PROFET™ + Life Time Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Activation Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss of battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit Between Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Undervoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switching Capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Battery Voltage Phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jump Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Load Dump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
44
44
44
45
46
46
46
47
47
50
50
50
51
52
52
52
53
53
54
54
55
Application Note
Smart High-Side Switches
3
Rev 1.0, 2010-12-15
App. Note
8.9
8.9.1
8.9.2
Reverse Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Loads with Symmetrical Polarity Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Reverse Polarity Protection for the Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
9
9.1
9.2
9.2.1
9.2.2
9.2.3
9.3
9.3.1
9.3.2
9.3.3
9.3.3.1
9.3.3.2
9.4
9.4.1
9.4.2
9.5
9.6
9.6.1
9.6.2
9.6.3
9.7
9.7.1
9.7.2
9.7.3
9.8
Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gate Back Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Influence on the Power Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sense Accuracy Improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sense Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Ground in OFF State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Ground in ON State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Observable Parasitic Effect of the Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Very high Ambient Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High Load Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short Circuit to Battery in OFF State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Short circuit to Battery in ON State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inverse Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load in OFF State with Bulb and Inductive Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load in OFF State with LED Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Load in ON state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partial Loss of Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partial Loss of Load during OFF state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Partial Loss of Load during ON state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current Sense Accuracy Improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current Sense and PWM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
57
58
58
58
59
59
59
59
60
60
61
61
61
62
62
62
62
63
63
64
64
64
65
66
10
10.1
10.1.1
10.1.2
10.1.3
10.1.4
10.2
10.2.1
10.2.2
10.2.3
10.2.4
10.3
10.3.1
10.3.2
10.3.3
The Micro Controller Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GND Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GND Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GND Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Different Ground for One System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss of Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Digital Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Absolute Maximum Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High level input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Undefined region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low level input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sense Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Load Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Minimum Load Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sense Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68
68
68
68
69
69
69
70
71
72
72
73
73
75
75
Application Note
Smart High­Side Switches
4
Rev 1.0, 2010-12-15
App. Note
11
11.1
12
12.1
12.2
PROFET™ + Scalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
High Ohmic Family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
PWM Power Losses Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Open Load Resistor Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Application Note
Smart High-Side Switches
5
Rev 1.0, 2010-12-15
App. Note
Abstract
1
Abstract
Note: The following information is given as a hint for the implementation of the device only and shall not be
regarded as a description or warranty of a certain functionality, condition or quality of the device.
This Application Note is intended to provide useful information to designers using PROFET™ + high side power
switch in the automotive environment as well as industrial. Starting from a design perspective, the Application Note
describes the application requirements and conclude at device level.
Table 1
Terms in use
Abbreviation
Meaning
A/D
Analog to Digital converter
AWG
American Wire Gauge
BCM
Body Control Module
CP
Charge Pump
CL15
So called for battery voltage turned OFF during park time of the vehicle
CL30
So called for battery voltage always present
CL58
So called for the battery voltage to the instrument cluster
CHMSL
Central High Mounted Stop Light
DMOS
Double diffused MOS
DRL or DTRL
Day Time Running Light
ESD
Electro Static Discharge
EMC
Electro Magnetic Compatibility
EME
Electro Magnetic Emission
EMI
Electro Magnetic Immunity
ECU
Electronic Control Unit
E²Prom
Electrically Erasable Programable Read Only Memory.
GND
Ground
GBR
Gate Back Regulation
GPIO
General Purpose Input Output
HSS
High Side Switch
I/O
Input Output (of a digital circuit)
IN
Input
ISC
IL(NOM)
kilis
Short circuit current
LED
Light Emitting Diode
LSS
Low Side Switch
mission profile
Represents the life cycle of the car, in terms of time, temperature, supply and hazard.
MOSFET
Metal Oxide Silicon Field Effect Transistor
OL
Open Load
[email protected]
Open Load in OFF state
[email protected]
Open Load in ON state
OEM
Original Equipment Manufacturer. In this document, car maker
Nominal current
Load current mirror factor
Application Note
Smart High-Side Switches
6
Rev 1.0, 2010-12-15
App. Note
Abstract
Table 1
Terms in use
Abbreviation
Meaning
OC
Over current
OT
Over temperature
OTS
Over temperature swing
OL
Open load
PROFET
Protected FET
PWM
Pulse Width Modulation
PLAMP
Lamp power, expressed in Watts.
PCB
Printed Circuit Board
RDS(ON)
Resistance of the channel during ON state
RPM
Revolution Per Minutes
SC
Short Circuit
Tier1
Supplier of the ECU to the OEM:
TA
TC
TJ
Ambient temperature
USM
Under hood Switching Module
VDD
VBAT
VS
ZSC
Micro controller supply voltage
Case temperature, or temperature of the solder
Junction temperature
Battery voltage, measured at the battery terminal
Supply voltage of the device, usually battery voltage
Short circuit impedance
Application Note
Smart High-Side Switches
7
Rev 1.0, 2010-12-15
App. Note
Abstract
ECU 1
Electronic Control Unit
LED
Lamp
Internal Device Signal
Generic Load,
component C, L and
R not 0
Internal Device GND
CHASSIS POTENTIAL
ECU Connector
FUSE
Current source
SWITCH
VBAT
CABLE
Battery
Alternator
Lead Battery
VBAT
Alternator with 3
phases winding
OUT
GND
Represents the physical
point of entrance in
device or ECU
drawing and meaning.svg
Figure 1
Drawing and Convention
Application Note
Smart High-Side Switches
8
Rev 1.0, 2010­12­15
App. Note
Introduction. Why High Side Switches.
2
Introduction. Why High Side Switches.
In the automotive system, a single electrical supply VBAT potential is available. Five possible solutions exist (refer
to Figure 2) to switch electrical loads ON and OFF. The automotive engineering community defines High Side
Switches as a switch commuting the battery voltage.
VBAT
VBAT
VBAT
VBAT
LOW SIDE
HIGH SIDE
VBAT
VBAT
H BRIDGE
PUSH PULL
HALF BRIDGE
SERIAL
commutation possibility of a load .vsd
Figure 2
Commutation Possibility of a Load
High Side Switches are used worldwide in automotive applications. Two reasons justify this choice, Short Circuit
hazards and System Cost.
2.1
Short Circuit Hazard
A Short Circuit (SC) hazard is more likely to occur to GND than to the battery voltage VBAT, thus switching from
the high side is considered safer than switching from the low side. Figure 3 represents all possible short circuits
in an automotive electrical system. The SC in green will result in the load being permanently ON load. The SC in
orange will result in stress to the switch. The SC in red will place stress on the complete vehicle electrical system
VBAT
Battery
SHORT CIRCUIT
TO BATTERY
SHORT CIRCUIT
GND
ECU
HSS
OUT
SHORT CIRCUIT
TO GND
VBAT
SHORT CIRCUIT
TO GND
Battery
SHORT CIRCUIT
TO GND
ECU
LSS
SHORT CIRCUIT
TO BATTERY
OUT
SHORT CIRCUIT
TO GND
Short circuit .vsd
Figure 3
Short Circuit Possibility
Application Note
Smart High-Side Switches
9
Rev 1.0, 2010­12­15
App. Note
Introduction. Why High Side Switches.
2.2
System Cost
A Low Side Switch, compared with an equivalent (same package and RDS(ON) class) High Side Switch is cheaper.
Nevertheless, at system level, using High Side Switches architecture is more cost effective. Figure 4 shows a
comparison between the 2 architectures. A LSS architecture will usually require an additional wire and fuse for
protection.
Fuse box
VBAT
GND
ECU
Battery
µC and
LOGIC
HSS
Fuse box
VBAT
GND
ECU
Battery
µC and
LOGIC
LSS
System cost comparison .vsd
Figure 4
System cost comparison
2.3
Galvanic Corrosion
High Side is often preferred to low side switch while in OFF state there is battery voltage present at the load. With
voltage present at the load along with humidity and time a bi-metal galvanic corrosion can occur at the connector
for the load. Since High Side does not have voltage present at the during OFF state the amount of corrosion is
much less.
2.4
Other Switching Solutions
Low side switches are mainly used in applications where one main switch protects several loads switched using
the low side.
Push-Pull switches are used in applications which require only one way of current and a very quick deactivation.
This architecture includes one HSS. Typical loads include the windshield wipers.
An H-Bridge is the most common method to drive bi-directional motors. Two HSS are used in this architecture.
Serial switching is used where a single failure (such as a short circuit to GND) would cause a critical safety problem
e.g. turn the load ON when not acceptable. Typical applications include the Airbag squibs and critical valves. One
HSS is used in this architecture.
Application Note
Smart High-Side Switches
10
Rev 1.0, 2010­12­15
App. Note
Type of supply
3
Type of supply
3.1
Module un-powered during stand-by
Figure 5 shows a typical application where the ECUs are de-powered when the vehicle is parked with the engine
off. This type of battery supply is commonly called KL15 (eg in Germany).
KL15
relay
Relay driver
KL15
ECU1
KL15
ECU2
KL15
ECU n
KL15
Battery
Energy Distribution
ECU m
KL15 topology.vsd
Figure 5
Clamp 15 application
3.2
Module supplied during stand by
Figure 6 shows a typical application where the ECUs remain powered when the vehicle is parked with the engine
off. This type of battery supply is commonly called KL30 (eg in Germany).
Energy Distribution
KL30
ECU1
KL30
ECU2
KL30
ECU n
KL30
Battery
ECU m
KL30 topology.vsd
Figure 6
Clamp 30 application
3.3
Left/Right Front/Rear separation
For safety reasons, supply redundancy is often necessary. Redundancy of the supply is often based on the
separation of the left and right side of the vehicle. This is where one battery line supplies all loads on the left side
of the vehicle and another line supplies all loads on the right side. The same redundancy can be found with front
and rear separation. Adding to this the KL15 and KL30 concepts, a complex ECU can be supplied by up to 8
different supply lines. Figure 7 shows such a supply architecture.
Application Note
Smart High-Side Switches
11
Rev 1.0, 2010­12­15
App. Note
Type of supply
3.4
Secondary Supply
Some modules also provide a secondary supply to sub-systems. This architecture is common in door modules
and climate systems which can be supplied by a dedicated battery feed switched from the master door or climate
ECU. Typical example is the KL58 supply line used to supply the dashboard.
ECU
Supply with all
battery feed
ECU
Supply with
Front battery
feed
ENERGY DISTRIBUTION BOX
CL 15L_F
CL 15R_F
CL 30L_F
CL 30R_F
CL 30L_R
CL 30R_R
CL 15L_R
CL 15R_R
Battery
ECU with
single battery
feed.
OFF in park
mode
ECU with
dual battery
feed.
ECU with all
battery feed,
unsupplied in
Park
Left Right Front Rear.svg
Figure 7
Complex and Mixed of supply line architecture
Application Note
Smart High-Side Switches
12
Rev 1.0, 2010­12­15
App. Note
Type of supply
3.5
Ground line
The ground (GND), in a car is the chassis. Therefore, GND is present everywhere and access to GND is always
available. In most cases, there is at least one GND pin per module connector. This GND pin is connected via a
wire to the chassis. Figure 8 shows different ways to realize a GND connection. On the left hand side is the
cheapest method. The most expensive but safest and recommended method is shown on the right and side.
Figure 9 show a picture of a GND connection realized on vehicle.
ECU
ECU
ECU
ECU
Ground line .vsd
Figure 8
Ground Line Concept
Figure 9
Ground Line Example
One consequence of this architecture can be that some modules don't have the same 0V (GND) reference. For
example (refer to Figure 10) a high current application such as power steering, starter motor or alternator doesn't
have the same 0V reference as the rest of the vehicle. This can also be the case for applications where the
connecting cable to GND is long or thin, causing a noticeable impedance. This ground shift voltage can be either
positive or negative. Infineon recommends ISO11898-3 (Low Speed CAN network ISO norm) as an umbrella
specification. This standard specifies a ±1.5V between ECU GND and chassis GND.
Application Note
Smart High-Side Switches
13
Rev 1.0, 2010­12­15
App. Note
Type of supply
Phase 1
µC
VBAT
Phase 1
LDO
e.g
Phase 2
XC2200
Phase 3
3
phases
Motor
Three phase
motor driver
Phase 2
e.g
TLE7185 E
IPB80N04S3-02
Phase 3
PCB traces
impedance
E.g 80A
GND
+
VSHIFT
-
E.g 80A
Ground shift high power .vsd
Figure 10
Typical high current application
To simplify this application note, vehicle GND and ECU GND will be considered the same, except where explicitly
mentioned. The appropriate terminology is ground shift voltage however this is commonly referred to as simply
ground shift. Ground shift represents the difference, VSHIFT between the 0V reference of the ECU and the real 0V
of the load. Refer to Figure 11.
VBAT
OUT
GND
+
VSHIFT
Ground shift .vsd
Figure 11
Ground shift description
Application Note
Smart High-Side Switches
14
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
4
Automotive Environment
4.1
Battery Voltage Supply
Only one supply potential, VBAT is available in the vehicle. This supply comes from the battery when the engine is
off and from the alternator when the engine is running. Figure 12 shows the typical supply topology. The battery
voltage is typically 12.6V (engine off) and 14.55V when the engine is running although this figure is different for
different OEMs. These values can vary in different phases of the mission profile. For simplicity, VBAT will be used
for both the real battery voltage and VALT, the alternator voltage (engine running).
ECU
Relay and
Fuse box
VBAT
V S30L
CL30 Left
V S30R
V S15L
CL30 Right
CL15 Left
CL15 Right
Battery
V S15R
V S58d
CL58
Alternator
GND
GND
Supply chain .vsd
Figure 12
Typical Supply Chain in a Vehicle
4.1.1
Alternator Regulation Loop
The alternator provides current as soon as the engine reaches idle (typically 800RPM). If there is no diode or
battery to limit the voltage, an alternator can provide a voltage of greater than 100V. The current the alternator can
provide is between 55A and 200A. This value is mainly dependant on the engine RPM and engine cooling. The
alternator current rating is defined by the total vehicle load. The regulation voltage is specified as a function of the
alternator temperature (TALT). The voltage usually decreases with temperature such that the maximum battery
voltage is reached when TALT is -40°C. Refer to Figure 13.
16,5
Regulation Voltage (V)
(V)
16
15,5
15
14,5
14
13,5
13
-40
-10
20
50
80
Alternator temperature (°C)
Figure 13
110
140
alternator regulation loop .vsd
Alternator Regulation Voltage Function of Temperature
Application Note
Smart High-Side Switches
15
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
4.1.2
Alternator Ripple
When the alternator is heavily loaded and providing its maximum possible current, the ripple on the supply line
cannot be neglected. VBAT looks similar to Figure 14. The frequency fAR and the voltage swing depends on the
OEM. As an umbrella specification, the following figures may be used: VAR = 3V peak to peak, fAR = [1kHz; 20kHz].
17,0
f AR
16,5
16,0
Alternator Voltage (V)
15,5
15,0
VAR
14,5
14,0
13,5
13,0
12,5
12,0
0
250
500
750
1000
Time (µs)
1250
Figure 14
Typical Alternator Ripple Voltage as a Function of Time
4.1.3
Start-Stop Application. Regenerative Braking
1500
1750
alternator ripple .vsd
The alternator can be a starter-alternator and it can also be used to realize regenerative braking. Each time the
car is stationary, the engine is stopped. Engine restart strategies vary between OEMs however the most common
method is when the driver releases the brake pedal. This restart will be called in the document “hot ignition”, in
contrario to “cold ignition” when the car driver turn the ignition key.
A significant increase in "hot ignition" starts needs to be considered. A typical figure is 30 "hot ignition" starts per
"cold ignition" start. Since the ignition phase is a severe power consumer (200A for hot ignition, 1000A for cold
ignition), it is necessary to recharge the battery quickly. This can be achieved by increasing VBAT artificiality.
Typically to 18V. An increase in VBAT results in an increase in electrical power. This increases the engine resistive
torque and hence engine gas consumption also increases. This is not acceptable except during braking when
kinetic energy is converted into electrical energy.
During acceleration, the resistive alternator torque can be too high and the alternator can be turned OFF during
severe acceleration. Figure 15 shows the shape of the battery supply voltage, assuming a starter-alternator with
regenerative braking.
As an example, a 14.5V regulated alternator providing 70A DC current corresponds to 1kW electrical power.
Assuming 30% efficiency, the mechanical energy required to provide this 1kW of electrical power is 3.2kW or 4
horse power (PS). Taking a standard 100PS engine, the driven alternator can offer up to 5% power increase.
Application Note
Smart High-Side Switches
16
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
Car speed
t
VBAT
18V
14.5V
12V
t
driven alternator .vsd
Figure 15
Battery Voltage as a Function of Car Speed.
4.1.4
Low Battery Voltage Supply
Low voltage supply phases can be either due to a weak battery (discharged) or during engine cranking. The weak
battery is a permanent state (from a semiconductor perspective) while cranking is a transient phenomenon.
4.1.4.1
Discharged Battery
A discharged battery is usually due to parasitic leakage current in the vehicle when it has been parked for too long.
The minimum battery voltage at which the car can still start is OEM dependant. This voltage is considered as the
minimum nominal voltage. Typically 8V.
4.1.4.2
Engine Ignition
The voltage during the ignition phase is complex to describe and the values are very dependant on the vehicle
OEM as well as the type of engine. All OEMs specify different ignition voltage pulses VCRK_MIN from 3 to 5.5V (refer
to Figure 16). VCRK_OSC is usually 7V and oscillations range from a couple of Hertz to 800Hz (800RPM). VBAT_STD
is the battery voltage during the engine stand-by phase and is usually 12.6V. VBAT_RUN is the battery voltage when
the engine is running and is usually 14.5V. For simplicity the red curve is used with VCRK_MIN = 3 to 5.5V, typically
4.5V. tCRK = 65ms, tLAUNCH = 10s and VCRK_LAUNCH = 5.5 to 8V.
VBAT
VBAT_RUN
VBAT_STD
VCRK_OSC
VCRK_LAUNCH
VCRK_MIN
t CRK
t LAUNCH
t
Cranking pulse .vsd
Figure 16
Ignition pulse
Application Note
Smart High-Side Switches
17
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
4.1.5
High Battery Voltage Supply
The reasons behind a high battery voltage are more numerous than a low battery voltage and include jump start,
load dump, faulty alternator regulation and high alternator ripple.
4.1.5.1
Jump Start
The jump start for a car (12V) is a situation where a truck battery (24V) is bypassing the battery to start the engine.
The voltage and the time of the jump start is OEM dependant. A worst case is 28V for 2minutes. For Truck, Jump
Start is defined when a special electrical equipement connected to power outlet supply for some minutes to 48V
the truck battery.
4.1.5.2
Load Dump
Load dump occurs when the battery terminal is suddenly disconnected while the alternator is providing current.
The battery is essentially a capacitor and hence stabilizes the system. Load dump can also occur during the
switching of high current inductive loads. Refer to Figure 17. When the battery is disconnected, the system
becomes unstable and the voltage rises until the alternator low side diodes reach avalanche, limiting the voltage
to Vloaddump. Some OEMs replace the diodes with Zener diodes. The advantage Zener diodes provide is to reduce
the load dump (avalanche) voltage to the Zener voltage. Vloaddump and tloaddump are specified by the OEM. After a
delay, (tloaddump) the alternator begins to regulate again and the voltage decreases. As an umbrella specification,
Infineon consider Vloaddump = 40V for tloaddump = 400ms. After the load dump event, a high ripple voltage is observed
on the battery line while the battery remains disconnected. As an umbrella specification, Infineon consider
VALT_MAX = 18V and VALT_MIN = 12V. The oscillation frequency is considered to be between 1kHz and 20kHz and
can be up to 10 hours long. Refer to Figure 18.
VBAT
ECU
Vd
Battery
Vloaddump
Id
Alternator
GND
VAZ(DIODE )
Load dump
configuration . vsd
Figure 17
Load Dump Configuration
VBAT
Vloaddump
VALT_MAX
VBAT_RUN
VALT_MIN
Figure 18
tloaddump
Load dump pulse .vsd
Load Dump Pulse
Application Note
Smart High-Side Switches
18
t
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
4.1.6
Reverse Polarity
A Reverse polarity condition exists when the battery supply line VBAT is connected to ground and the ground line
GND to the battery supply. Reverse polarity mainly occurs for two reasons. During the module handling and
installation, where some awkward movements can be assumed, or when the vehicle has a low battery and the
driver connects jumper cables incorrectly from an external battery (Start help), reverse polarity can result. The
voltage and time for which the vehicle can withstand this reverse polarity is defined by the OEM. As an umbrella
specification, Infineon considers -16V for 2mn at ambient temperature +25°C. Some loads such as a lamp or
resistor can tolerate current flowing in the reverse direction whilst others cannot such as motors, polarized
capacitors, etc...
4.1.7
Loss of Battery
In an architecture such as CL15, loss of battery is a normal case. In an architecture with shared fuse, when the
fuse blows due to a short circuit somewhere else, the loss of the supply line should not result in a module failure.
4.1.8
Umbrella Specification for Battery Voltage
To sum up the above discussion, refer to Figure 19.
Reverse
battery
Cranking
OFF
-16V
0V
2mn
120khours
25°C [-40°C;150°C]
3... 5.5V
65ms
-40°C
Nominal battery voltage
8V
10k hours
[-40°C;150°C]
Jump start
18V
10khours
[-40°C;150°C]
Load dump
28V
2mn
25°C
40V
400ms
25°C
Battery voltage range . vsd
Figure 19
Infineon Umbrella Specification for Battery Voltage
4.2
Temperature
The ambient temperature TA range in an automotive application is one of the harshest found in electronics. Only
space and aeronautical activities can be more challenging. If the minimum temperature is universally agreed to be
-40°C, the maximum temperature varies with applications, OEM, tier1, module housing, etc.. As an umbrella
specification, Infineon considers TA_MAX = +85°C for cockpit application, TA_MAX = +105°C for under hood
application.
4.2.1
Ambient Module Temperature
Ambient module temperature follows the seasons as shown in Figure 20. Ambient module temperatures are cold
in winter, hot in summer. While -40°C is considered to be the minimum temperature to start the car in winter, it is
not valid for every engine start in winter as the system heats up during driving. The same logic can be applied to
the hot season. It is possible to assume +85°C or +105°C for example, as the maximum ambient temperature (car
parked in summer) at start up, but it is incorrect to assume that TA_MAX = +85°C is a permanent condition during
summer. In other words, -40°C and +85°C are considered as starting points, but not as permanent conditions. As
an umbrella specification, Infineon considers an ambient temperature profile shown in Figure 21.
Application Note
Smart High-Side Switches
19
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
TA
TA_ MAX
TA_typical
TA_MIN
January
March
June
September
December
time
temperature over one year .vsd
Figure 20
Suggested Ambient Module Temperature, over one Year
Temperature
repartition
-40°C
TA typical
TA MAX
TA
temperature repartition .vsd
Figure 21
Suggested Temperature Distribution over Car Life Time
4.2.2
Internal Module Temperature
The devices, soldered on the PCB, are subject to the heat radiated by neighboring devices. Each module design
is different, hence the heat generated is dependent on the design of the module. As an umbrella specification,
Infineon considers a self heating of the module of +15°C in operation mode.
4.3
Ground
As described in Chapter 3.5, a ground shift VSHIFT can exist between the module ground and device ground.
Loss of ground should also be a consideration in module design. There are two possible failures which can cause
loss of ground, loss of device ground and loss of module ground. Refer to Figure 22. As a device supplier, Infineon
assumes any loss of ground to be loss of device ground unless explicitly indicated.
Application Note
Smart High-Side Switches
20
Rev 1.0, 2010­12­15
App. Note
Automotive Environment
VBAT
ECU
VS
Micro
controller
Voltage
regulator
GND
HSS
LOSS OF DEVICE
GROUND
LOSS OF MODULE
GROUND
Loss of ground .vsd
Figure 22
Loss of Module or Device Ground
4.4
Lifetime
The life time of one car / module / device is assumed to be 15 years or 131400 hours.
4.4.1
Running Time
Running time is an accumulation of time over which the module is in operation (micro controller active, load
activated or ready to be activated) is assumed to be 10 000hours. (~2hours per day for 15 years)
4.4.2
Stand-by Time
Stand-by time corresponds to the remaining time over 15 years where the module is not in operation. With the
above assumptions, this is 121400hours.
4.4.3
Number of Ignition
The number of ignitions cycles is determined by the strategy of the car OEM. As an umbrella specification, Infineon
consider 100 000 cold ignitions over the car life time. This leads to almost ~20 (18.6) ignitions per day. This number
doesn't include the additional start and stop cycles due to the future introduction of starter-alternators. 30 hot
ignitions are considered per cold ignition.
Application Note
Smart High-Side Switches
21
Rev 1.0, 2010­12­15
App. Note
Load and Application
5
Load and Application
The diversity of loads driven by high side switches is enormous. To cluster these loads is always challenging.
Nevertheless, three different categories can be outlined. Lamps or capacitive loads, Motors or inductive loads, and
LED or resistive loads.
5.1
Lamps / Capacitive and Resistive Loads
Switching lamps for exterior lighting always been the major application of HSS. By law, in every country, 20 lamps
covering 8 different functions must be implemented in a vehicle. Table 2 lists the required lighting including the
minimum wattage.
Table 2
N°
1)
Lamps Required by Law
Function
Abbreviation
Number of Load
Position
Minimum wattage
1
Brake light
STOP
3
Rear
3x21W2)
2
Park light
PL
4
2 Front, 2 rear
4x5W3)
3
Licence plate
LIC
1
Rear
1x5W3)
4
Fog
FOGR
1
Rear
1x21W4)
5
Reverse light
REV
1
Rear
1x21W2)
6a
Side indicators left
SI
3
1 Front, 1 center, 1 rear 2x21W2) + 1x 5W3)
6b
Side indicators right
SI
3
1 Front, 1 center, 1 rear 2x21W2) + 1x 5W3)
7
Low beam
LB
2
Front
2x55W5)
8
High beam
HB
2
Front
2x55W / 65W
1)
2)
3)
4)
5)
The number is arbitrary
27W in the NAFTA
7W in the NAFTA
Not required in the NAFTA
65W in the NAFTA
Additional lamps are often present. Table 3 provides a list of the more common optional lamps. On modern
vehicles there are typically up to 40 lamps covering more than 14 functions.
Table 3
N°
1)
Optional Lamps
Function
Abbreviation
Number of Load
Position
Wattage
2
Park light
PL
4
2 Front, 2 rear
4x5W2)
3
Licence plate
PP
1
Rear
1x5W2)
10
Side marker
SM
2
Center
2x5W2)
4
Fog
FOGR
1
Rear
1x21W3)
5
Reverse light
REV
1
Rear
1x21W3)
11
Fog
FOGF
2
Front
2x55W
12
Interiors
INT
From 1 to 10
Interior
From 1x5W2) to 100W
13
Cornering lamp
CL
2
Front
2x55W
14
Daytime Running
Light4)
DRL
2
Front
2x35W
1)
2)
3)
4)
The number is arbitrary
7W in NAFTA
27W in NAFTA
Required by law in some countries, can be realized with Low Beam
Application Note
Smart High-Side Switches
22
Rev 1.0, 2010­12­15
App. Note
Load and Application
5.1.1
Lamps Regulation
The United Nation Organization (UNO) has regulated automotive lamps in terms of mechanical structure, light
emission power and electrical power. These regulations can be found at UNO under the title "Agreement
concerning the adoption of uniform technical prescription for Wheeled vehicles, equipment and parts which can
be fitted and/or used on wheeled vehicles and the conditions for reciprocal recognition of approvals granted on
the basis of these prescriptions". The reference numbers are E/ECE/324 and E/ECE/TRANS/505, dated October
19, 2001. This document is considered the umbrella specification of Infineon in terms of lamp wattage.
5.1.2
Lamp Wattage
The lamp wattage is defined at a specific voltage with a percentage tolerance. Table 4 shows the most commonly
used lamps in terms of electrical wattage, tolerance and voltage.
The lamp current is dependent on the supply voltage VLAMP. Equation (1) gives the current, function of VLAMP,
supply voltage of the lamp. VREF is the voltage where the power of the lamp is defined.
I LAMP =
5.1.3
V LAMP P LAMPREF
----------------- × ------------------------V REF
V REF
(1)
Cold Lamp / Inrush Current
Before switch ON, the lamp is cold. To produce light, it is necessary for the lamp filament to reach a very high
temperature (above 1000°C). At switch ON, a significantly higher current is flowing in the filament. This current is
called inrush current IINRUSH. Depending on the OEM or tier1 manufacturer, a certain ratio is applied which relates
the nominal current of the lamp to the inrush current. As an umbrella specification, Infineon considers an inrush
factor of 10x. Figure 23 shows an ideal 27W bulb inrush current without any system limitation. Inrush current
increase while temperature decreases.
There is an inherent time required to turn the lamp ON which is defined as tLAMP_ON. Due to the inrush current, the
lamp turn ON time, tLAMP_ON cannot be defined unambiguously. As an umbrella specification, Infineon considers
the lamp is ON when the load current reaches 50% of the IINRUSH, the last retry in case of retry. Infineon considers
suitable a switch which allows a tLAMP_ON < 30ms.
Table 4
Electrical Wattage Lamp
Lamp
W
Accuracy
%
VREF
5
10
7
V
Max DC current
in A1)
Max Inrush Max PWM current
in A
A2)
Maximum current
A3)
13.5
0.5
5
0.7
0.9
10
12.8
0.7
7
1
1.3
10
10
13.5
1
9
1.3
1.8
15
10
13.5
1.4
14
2
2.7
21
6
12
2.3
22
3.1
4.3
27
6
12.8
2.7
26
3.7
5.0
55
6
13.2
5.2
50
7.1
9.7
65
6
13.2
6.1
60
8.4
11.5
1) At 18V
2) At 18V with light emission regulation (with duty cycle calculated in Chapter 5.1.4)
3) At 18V with 2% PWM
Application Note
Smart High-Side Switches
23
Rev 1.0, 2010­12­15
App. Note
Load and Application
70
IDS (A)
Vbulb (V)
60
I INRUSH
IL (A) and VL [V]
50
50% IINRUSH
40
30
20
t LAMP_ON
t LAMP_ON
10
0
0
0,005
0,01
Time [s]
Figure 23
Ideal Inrush of a Lamp
5.1.4
Life Time
0,015
0,02
Bulb inrush .vsd
The life time of a lamp is dependent on several parameters with one of the most critical being the supply voltage.
As a rule of thumb there is a life time reduction of 50% per volt increase for supply voltages above 13V. Ideally, a
constant supply voltage should be provided to the lamp. The cost of such a solution is prohibitive, in practice this
strategy is never implemented.
Another approach is to use Pulse Width Modulation to drive the lamp. The basic idea of PWM is to maintain
constant power in the lamp. The trick is to use the filament thermal inertia to absorb the PWM waveform, making
it invisible to the naked eye. The larger the wattage, the bigger the thermal inertia so the PWM waveform can be
lower in frequency. The PWM duty cycle is calculated using Equation (2), VPWM is the optimum lamp voltage.
2
V PWM
d = ------------------2
V LAMP
(2)
Typically values are VPWM = 13.2V in Europe and VPWM = 12.8V in North America.
5.1.5
Light intensity
The intensity of the light is linked to the lamp supply voltage. The aim is to minimize the light intensity fluctuation,
which is a function of the battery voltage. The PWM duty cycle, derived from the battery voltage measurement has
to be refreshed fast enough to eliminate light fluctuation. However a simple modification of the duty cycle
corresponding to a spike in battery voltage is not acceptable. A software strategy should be implemented to
leverage the battery voltage as for example Equation (3).
(VBAT(t) corresponding to the measured VBAT at the given quantum t)
V BAT ( t – 2 ) + V BAT ( t – 1 ) + V BAT ( t )
V BAT ( t ) = -------------------------------------------------------------------------------------------3
(3)
With this strategy, the system is able to react in a maximum of tMAX which is equal to three time t sample µC, the micro
controller sample period. tMAX is given by the OEM. As umbrella specification, Infineon consider tMAX = 30 ms.
Figure 24, is an example of PWM voltage regulation to 13V. These graphs show the worst case scenario when
fluctuations in the battery voltage occur just after a battery measurement.
VBAT is the real supply voltage of the system;
Application Note
Smart High-Side Switches
24
Rev 1.0, 2010­12­15
App. Note
Load and Application
d is the PWM duty cycle;
<VLAMP> matches the equivalent lamp voltage.
VBAT
t sample µC
16V
t MAX
14V
t
Duty cycle
tMAX
0.88
0.81
0.74
0.68
t
<VLAMP>
15V
13V
11V
t
PWM.vsd
Figure 24
Reaction Time and Strategy for PWM
5.2
Light Emitting Diode (LED)
LEDs are increasingly being used to replacing standard lamp bulbs. They offer a longer lifetime as well as lower
current consumption for an equivalent light intensity output. Two kinds of LED modules are often used, standard
and advanced. For the HSS designer, the difference between these 2 types of modules is negligible and they can
both be modeled as a resistive load. An advantage of a LED is that it starts to emit light, far much quicker than a
lamp, as soon as a voltage large enough to overcome the forward bias of the device is applied. This voltage
depends mainly on the LED color. A very small current (as an umbrella specification, Infineon considers 10µA) is
enough to cause a LED to glow. This justifies the usage of the ROL_LED in case open load diagnosis is required.
5.2.1
Standard LED Module
In a standard LED module, when one LED is an open circuit, the other LEDs are not affected. This behavior is
particularly desirable for rear lighting. The standard LED module, shown in Figure 25 consists of a series resistor
RLED to limit the current and a cluster of LEDs in parallel and serial. The advantage of this circuit is the simplicity.
The drawback is the continuous power loss in the resistor (at least 500mW) and the susceptibility to transient over
voltages and currents. This kind of LED modules are often found for rear light system. As an umbrella specification,
Infineon considers R LED = 50Ω, ROL_LED = 680Ω.
Application Note
Smart High-Side Switches
25
Rev 1.0, 2010­12­15
App. Note
Load and Application
IN
RLED
ROL_LED
OUT
Standard LED module.svg
Figure 25
Standard LED Module
5.2.2
Advanced LED Module
In an advanced LED module, when one LED is an open circuit, the entire module is OFF. This behavior is
particularly hazardous for headlights. The advanced LED module, shown in Figure 26 consists of a DC/DC
converter driving LEDs in serial. The advantage of this architecture is robustness and immunity to voltage
transients. The disadvantage is the relative electronic complexity of the DC/DC converter. As an umbrella
specification, Infineon considers the module OFF if VIN - VOUT < 7V. When the LED is broken, the module doesn't
consume more than 30mA max, typically 15mA (current needed by the DC/DC supply itself).
IN
DC/DC e.g
TLD5095
ROL_LED
OUT
Advanced LED module.svg
Figure 26
Advanced LED Module
5.2.3
LED Cluster
The number of LED per string, and the number of string are application and OEM dependant. Nevertheless, a
rough estimation can be realized in Table 5
Table 5
LED cluster
Function
Number of string
Number of LED per string
Standard / Advanced
Brake light
7 to 10
1 to 3
Standard
Park light
2 to 5
1 to 3
Standard
Side indicators left
1 or 2
7 to 10
Advanced
Side indicators right
1 or 2
7 to 10
Advanced
Low beam
1 or 2
9 to 12
Advanced
High beam
1 or 2
9 to 12
Advanced
Side marker
2 to 5
1 to 3
Standard
Application Note
Smart High-Side Switches
26
Rev 1.0, 2010­12­15
App. Note
Load and Application
Table 5
LED cluster
Function
Number of string
Number of LED per string
Standard / Advanced
Front Fog
1 or 2
9 to 12
Advanced
Daytime Running Light
1 or 2
7 to 10
Advanced
5.3
Motors
There is often a requirement to drive a motor in both directions. The driver architecture must then be an H-bridge
where two HSS are used. Some motors always run in the same direction, such as wipers, water pump, etc hence
only a single HSS is required.
5.3.1
Inductive Load
Inductive loads are described by inductance L and resistance R. At switch ON, the inductive load causes a slow
current ramp up, based on the time constant τ = L/R. At switch OFF due to the inductance, the current attempts
to continue to flow in the same direction which causes the load voltage to invert. Refer to Figure 27, which
demonstrates the general voltage and current characteristics of an inductive load at switch ON and OFF. Voltage
in blue, current in red, power in green.
IL
VBAT
R
7
6
5
4
VBAT
3
2
1
0
0,00
500,00
0A line
1000,00
1500,00
2000,00
2500,00
-1
VOUT
VBAT
20
10
IL
+
0V line
0
- 10
L, R
VOUT
- 20
- 30
- 40
PLOSS
-
250
200
150
100
50
0W line
0
-50
Inductive load .vsd
Figure 27
Inductive Load Switch ON / OFF
Application Note
Smart High-Side Switches
27
Rev 1.0, 2010­12­15
App. Note
Load and Application
5.3.2
Demagnetization Energy
As stated previously, each time an inductive load is switched OFF, a demagnetization energy has to be
considered. If the over voltage protection limit is known, this demagnetization energy can be calculated according
to Equation (4)
V S – V DS ( AZ )
L
R×I
E = V DS ( AZ ) × ---- × --------------------------------- × ln  1 – --------------------------------- + I

R
R
V S – V DS ( AZ )
5.3.3
(4)
Freewheeling Diode
To keep the current running, and to get advantage of the stored energy in the coil, a freewheeling diode can be
used. In such a case, current and voltage in the switch appears as shown in Figure 28 describing a load of 195mH
and 3.5Ω. The PROFET™ + in use is the BTS5090-2EKA. The battery voltage VBAT is set to 15V. PWM is set to
400Hz. From this example, it is observable that the power in the diode cannot be neglected.
3
Load current
2,5
Load Current (A)
VBAT
Load current without PWM
2
1,5
1
0,5
0
0
10
20
30
40
50
30
40
50
Time (ms)
VOUT
-
L, R
Power (W)
IL
+
0,9
0,8Power losses in the diode
0,7Power losses in the switch
0,6
0,5
0,4
0,3
0,2
0,1
0
0
10
20
Time (ms)
Freewheeling .vsd
Figure 28
Voltage and Current Profile with Freewheeling Diode in PWM starting phase
5.4
Number of Activations
The total number of activations (brake pedal depressed, low beam activation, compressor activation, etc..)
depends largely on the habits of the vehicle driver. This does not including extra switching done by the ECU e.g.
PWM, software retry strategies etc... The exact mission profile is usually given by the OEM, but nevertheless loads
can generally be placed in one of five categories as defined in Table 6.
Application Note
Smart High-Side Switches
28
Rev 1.0, 2010­12­15
App. Note
Load and Application
Table 6
Load activations per engine ignition
N° of activation N° of activation Type of load example
per ignition
Average
activation time
N° of activation
per year
High
30
Brake light, Side Indicators
< 1mn
220 000
High
30
Low beam with automatic activation > 1mn
220 000
Mid
1 or 2
Reverse, Interiors lamp
> 1mn
15 000
Mid
1 or 2
Low beam with manual activation
> 1mn
15 000
Low
1/3
High beam, Fog lamps
> 1mn
2500
5.5
Wiring
To completely define a wire, three parameters are necessary, the diameter, the length and the insulator materials.
The diameter and length give the electrical characteristics (Ω / km and Lcable / km). The insulator and the
environment gives the maximum current.
5.5.1
Wire as a Parasitic Electrical load
Although the wire is not a load, it has to be considered in automotive applications during the design phase. Wires
offer a benefit to the system by limiting surge currents such as bulb lamp inrush current thanks to parasitic
inductance (Lcable), as well as resistive (RCABLE). The wire will limit the current. On the other hand, the inductive
energy stored in the cable is sometimes not neglectable, especially for long wire harness found in truck or trailer
application.
5.5.2
Maximum Current in a Wire
Wires require protection from excessive current. The maximum current which can flow in the wire is time
dependent and defined by a square law function I²t = constant. The maximum current the wire can handle is limited
by the insulation material. The OEM defines the wires to be used in a vehicle and this information is usually kept
confidential. Figure 29 shows an example of the current time coupling limitation of a cable as a function of the
time.
The maximum current in the wire is a thermal law. This constant depends, as previously stated on the insulation
material and also neighboring cables. For example, a wire within a group of 20 wires in a wire harness will have a
lower maximum current rating than the same wire when it is not in a group. As an umbrella specification, Infineon
considers a reduction of 40% of the nominal current.
Table 7 sums up the types of wire often use in an automotive environment. Note that these values are indicative
and must be crossed-checked with the application and the OEM.
Table 7
Wire Characteristics as a function of Diameter
Cross section
(mm²)
Gauge
(AWG)1)
Impedance
(Ω/km)
Inductance
(mH/km)
Max DC current
(A)2)
50
0
0.4
1.1
228
25
3
0.8
1.16
150
10
7
1.9
1.20
85
6.0
9
3.1
1.25
60
4.0
11
5
1.30
45
2.5
13
7.6
1.36
34
1.5
15
12.7
1.4
24
Application Note
Smart High-Side Switches
29
Rev 1.0, 2010­12­15 App. Note
Load and Application
Table 7
Wire Characteristics as a function of Diameter
Cross section
(mm²)
Gauge
(AWG)1)
Impedance
(Ω/km)
Inductance
(mH/km)
Max DC current
(A)2)
1.0
17
18.5
1.45
19
0.75
19
24.7
1.49
16
0.50
20
37
1.55
12
0.30
21
56
1.65
9
1) Approximation only
2) Assuming Tambient = 85°C and wire alone in free air. Approximation only
Time to destruction (s)
1000
EXAMPLE
ONLY
100
10
1
0
20
40
60
80
Load current (A)
Figure 29
Example of Current Limitation of Wire Harness
5.6
Platform and Vehicle Diversity
100
120
140
wiring.vsd
With the aim of developing better and cheaper new vehicles faster, OEMs have for some years adopted a platform
strategy. This strategy offers the possibility of developing a generic module to address different vehicle platforms,
or different configurations within the same vehicle platform. A vehicle today is offered with 3 or 5 doors in sedan,
coupé, convertible, commercial or with towing capability. The diversity of models is huge. A platform approach
offers a great benefit to the OEM. At a module level, the challenge is in the flexibility which can be offered.
Figure 30 shows different HSS configurations to meet the needs of basic legal requirements, up to the high end
solutions required by some OEMs. The example given is of a reverse light and a fog light, with or without trailer
and with or without battery feed split. The example is not exhaustive!
Application Note
Smart High-Side Switches
30
Rev 1.0, 2010­12­15
App. Note
Load and Application
VBAT
Fog
The Law requirement
OUT1
HSS
HSS
OUT2
Reverse
OUT2
Reverse
ECU
VBAT_L VBAT_R
Fog
Splited battery
For safety
OUT1
H
HSS
HSS
S
ECU
VBAT_L VBAT_R
Fog
Same but
assuming trailer
At lamp
connector
OUT1
Reverse
VBAT_L VBAT_R
Trailer
OUT1
OUT2
HSS
Reverse
HSS
Left
OUT1b
OUT2b
ECU
Right
VBAT_L VBAT_R
Fog
Trailer
Reverse
O
OUT1
HS
HSS
HS
SS
S
S
HSS
H
S
HSS
SS
OUT3
OUT2
OUT4
Reverse
Fog
Trailer
ECU
Assuming
equipment on
each side both
lamps and trailers
VBAT_L VBAT_R
Fog
Trailer
OUT2
HS
SS
S
S
ECU
Trailer
Fog
Assuming
equipment on
each side both
lamps
HS
HSS
Trailer
Reverse
O
OUT3
HS
HSS
HSS
SS
HSS
H
S
HSS
SS
OUT4
OUT1
OUT2
Reverse
Fog
Trailer
Trailer
ECU
Platform approach.svg
Figure 30
Example of Different Vehicle with One Platform Approach for Same Function
Application Note
Smart High-Side Switches
31
Rev 1.0, 2010­12­15
App. Note
Failures in the Field
6
Failures in the Field
Possible failures in the field are usually linked to inter-connection (e.g., short circuit or open circuit load).
6.1
Short Circuit to Ground
The short circuit to GND is extensively described in the AEC Q100-012 documentation. This is considered as an
umbrella specification by Infineon. Figure 31 shows the hardware configuration of the AEC-Q100-012. The
chassis of the vehicle is the GND. The probability of a short circuit to GND is significant, compared with all other
possible short circuit events. This is a challenging aspect of designing with High Side Switches and will be
described later in Chapter 8, which is dedicated to protection. Without any kind of protection measures, the current
will be limited only by the wiring and thus will reach 14V / 30mΩ = 450A. This test is obviously destructive.
AEC short circuit hardware set up .vsd
Figure 31
AEC-Q100-012 Hardware Set-up for Short Circuit Test
The exact short circuit impedance is described in the AEC-Q100-012 document also, an extract of which is shown
in Figure 32.
AEC short circuit impedance .vsd
Figure 32
AEC-Q100-012 Short Circuit Impedance
6.2
Short Circuit to Battery
There is generally a low probability of a short circuit to the battery, nevertheless it is possible to reach a critical
situation with such a failure. Figure 33 shows a typical case where a short circuit is applied to one of the five
outputs of a given ECU module. When this switch allows the current to flow (in this case, in an inverse mode), the
Application Note
Smart High-Side Switches
32
Rev 1.0, 2010­12­15
App. Note
Failures in the Field
four other outputs and the module are all supplied by the switch. If the fuse or the relay connection to the supply
battery feed is broken, the complete module supply current will then flow from the output shorted to the battery.
SHORT CIRCUI T
TO BATTERY
VBAT
ECU
Fuse and relay
box
CL15 fuse CL15 switch
GND
GND
Short circuit to battery .vsd
Figure 33
Example of Stressful Short Circuit to Battery Case
6.3
Open Load
Open load can be caused by two phenomena, a broken wire or a broken load. Although this is not a critical
scenario, the application usually requires diagnostic information to be sent to the driver. Note that the definition of
an open load is usually OEM dependant. As an umbrella specification, Infineon considers RDIRT = 4.7kΩ resistor
to GND. By law, side indicators have to be reported missing by doubling the flashing frequency. All other open
load diagnosis are OEM requirements only.
6.4
Short Circuit Between Load
A short circuit between loads can occurs anywhere in the wiring path. Consequences can range from a complete
overload, similar to short circuit or a simple additional current with no adverse behavior, except for the unexpected
parasitic switch ON of another load. In Figure 34, the OUT2 switch will be overloaded by the higher load, while
OUT1 will virtually neglect the failure. In generally an OEM will request that this type of failure is diagnosed. Note
that the wiring can also be stressed by such a short circuit event.
ECU
VBAT
OUT1
SHORT CIRCUIT
BETWEEN LOADS
SHORT CIRCUIT
BETWEEN LOADS
OUT2
GND
500mA load
10A load
Short circuit between load .vsd
Figure 34
Short Circuit Between Load
Application Note
Smart High-Side Switches
33
Rev 1.0, 2010­12­15
App. Note
Power Stage
7
Power Stage
The power stage of PROFET™ + is a high side switch consisting of a vertical N channel power MOSFET. The
power MOSFET technology is called DMOS. The capability of this power element to pass current can be
expressed in terms of its RDS(ON). The smaller the RDS(ON), the higher the current capability.
7.1
Power Element
The power element for switches is a N channel power MOSFET (DMOS) in the majority of cases. PROFET™ +
also use an N channel power DMOS MOSFET as power element. Table 8 summarizes the advantages and
disadvantages of DMOS versus bipolar power structures, assuming the same specifications can be realized with
either technology. It is shown that DMOS offers better performance in short circuit robustness, high voltage
capability and chip size.
Table 8
Comparison between Bipolar and DMOS
Topic
Bipolar
DMOS
+
-
-
+
Accuracy
Offset
Process deviation
Chip area
Voltage capability
High current robustness
Current consumption
Input current
Figure 35 shows the differences between planar and trench (vertical) DMOS technologies. With identical RDS(ON),
it can be seen that the trench DMOS device is smaller. This also results in a smaller gate charge QG for the trench
DMOS device. Since the planar DMOS device is larger, less cooling is required and the EAS is better than the
trench DMOS device. In PROFET™ +, the supply is the drain which means that the supply is at the bottom of the
chip.
trench vs planar .vsd
Figure 35
Planar (Left) versus Trench (Right)
Application Note
Smart High-Side Switches
34
Rev 1.0, 2010­12­15
App. Note
Power Stage
The RDS(ON) of PROFET™ + can be described as a function of temperature (expressed in °C) See Equation (6).
Figure 36 provides the derating of RDS(ON), assuming 100% at maximum junction temperature.
R DS ( ON ) = R DS ( ON )
–3
150C
(5)
× ( 1 + ( T J – 150 ) × 3, 584 × 10 )
100
%
80
Relative RDS(ON)
90
70
60
50
40
30
20
10
-40
-10
20
50
80
Junction Temperature (Tj)
110
140
RDSON.vsd
Figure 36
Relative RDS(ON), Function of Junction Temperature TJ, base 100 at 150°C
7.2
Voltage Limitation
VS(AZ)
As with every device based on a given semi-conductor technology, PROFET™ + devices has a maximum voltage.
If this voltage is exceeded, the DMOS power stage and/or the logic will avalanche and the device will quickly be
destroyed. Figure 37 shows the influence of temperature on the zenering voltage.
55
53
51
49
47
45
43
41
39
37
35
-40
Figure 37
-10
20
50
80
Junction Temperature (Tj)
110
140
VSAZ .vsd
Min Typical and Maximum Avalanche Voltage, Function of the Temperature TJ
Application Note
Smart High-Side Switches
35
Rev 1.0, 2010­12­15
App. Note
Power Stage
7.3
Charge Pump
When the DMOS is ON, the output voltage is very close to the supply voltage VS. As the power stage is an N
channel power DMOS, the device requires a charge pump to provide a VGS ~ 7V. The concept of a charge pump
is described in Figure 38. In the first phase, the CLOAD capacitor is charged up to the VS voltage. In phase two, the
CLOAD is discharged through a diode into CCP, the charge pump capacitor. The charge pump runs at a frequency
of 2.5MHz. The voltage rises in steps of CLOAD / CCP, to theoretically twice the battery voltage. In practice, this
voltage is limited to 10V above VS. The ratio is CCP = CLOAD.
VS
VS
S1
VS
S1
S3
S3
- VS +
- VS +
TO GATE DRIVER
CLOAD
CLOAD
CLOAD
+
S2
CCP
+
CCP
VCP
-
S2
VCP = VS
+
CCP
VCP = VS (1+ CLOAD/CCP)
-
-
GND
PHASE 1
PHASE 2
Charge pump principle.svg
Figure 38
Charge Pump Block Diagram
7.4
Slope Control Mechanism
For EMC reasons (refer to Chapter 14), PROFET™ + devices have embedded slope control for both switch ON
and switch OFF. The actual switching event is divided into three stages. Refer to Figure 39. First, the gate of
MOSFET is connected to VS via current generator. tON_delay is linked to the necessary time for the gate to reach
~2V. Then the MOSFET switches ON quickly. A fast switch ON time is required to minimize switching power losses
(refer to Chapter 7.5). As soon as VOUT reaches ~70% of the supply voltage VS, the charge pump starts to drive
the gate to obtain the minimum RDS(ON) of the device. The slope is reduced due to the necessary time to completely
load the gate capacitance.
IN
t
VOUT
90% VS
70% VS
30% VS
tON
t OFF_delay
dV/dt
ON
dV/dt
tON_delay
OFF
tOFF
10% VS
t
Switching times .vsd
Figure 39
Switch ON and Switch OFF timing
Application Note
Smart High-Side Switches
36
Rev 1.0, 2010­12­15
App. Note
Power Stage
At switch OFF, a similar behavior is observed. First, the charge pump is disconnected and a strong current
generator IFASTGATEUNLOAD quickly discharges the gate charged of electrons until VOUT reaches ~70%. Then the
gate is discharged with a constant current IGATEUNLOAD until the gate voltage is zero. Figure 40 shows the block
diagram of the gate driver.
VS
VCP
I GATELOAD
To gate
of the power
MOSFET
IFASTGATEUNLOAD
IGATEUNLOAD
OUT
Gate driver .vsd
Figure 40
Gate Driver Schematic
The EMC performance when driving the HSS with a PWM waveform has been improved thanks to the addition of
current matching measures. PROFET™ + offers matching of the loaded current IGATELOAD and the unloaded
current IGATEUNLOAD. This matching can be found in all PROFET™ + datasheets under the Slew rate matching
parameter ∆dV/dt.
7.5
Power Losses Calculation
The power losses P in the device, assuming a resistive load RL, can be calculated as follow. (Refer to Figure 41).
The instantaneous power in the switch is the result of the load current IL multiplied by the drain to source voltage
VDS = VS - VOUT. The resulting curve is shown in Figure 41. A good approximation is realized by the orange
isosceles triangles and the rectangle.
The triangle has as vertex at PMATCH which is the physical point where the switch resistance corresponds to the
exact load resistance i.e. RDS(ON) = RL. Equation (6) gives the relationship between PMATCH and RL.
P MATCH
2
VS IL
VS
= ------- × ---- = ---------------2
2
4 × RL
(6)
As the drivers are very symmetrical, it is assumed switching ON tSON and switching OFF tSOFF times are identical
i.e. tSON = tSOFF. The area of the triangle represents the switching energy and is defined by Equation (7).
1
E SON = E SOFF = --- × P MATCH × ( t ON – t ONdelay )
2
(7)
The orange rectangle represents the energy ER(ON) lost during the ON state of the DMOS power element and is
easily calculated by Equation (8).
E RON = R DSON × I
2
L
× t RON
(8)
In conclusion, the power losses in the DMOS power element calculated by using Equation (9).
( 2 × E SON + E RON )
P = ----------------------------------------------t CYCLE
Application Note
Smart High-Side Switches
(9)
37
Rev 1.0, 2010­12­15
App. Note
Power Stage
t cycle
IN
VOUT
90% VS
tON
tOFF_delay
70% VS
dV/dt ON
dV/dt OFF
50% VS
30% VS
tON_delay
tOFF
10% VS
t
IOUT
90% IL
70% IL
50% IL
30% IL
10% IL
t
PLOSS
P MATCH
RDS(ON)* IL
t
tON
tSON
tSOFF
Switching Losses.svg
Figure 41
Power Losses Calculation
7.6
Switch Behavior with PWM Input
Pulsed Width Modulation is a special case where the cycle time, tCYCLE is the inverse of the PWM frequency fPWM.
There are four limitations of PROFET™ + which need to be considered when using a PWM waveform. These are
power loss, EMC emissions, switching time and diagnostic limitations. Power loss and switching time issues will
be described below. The EMC and diagnostic limitations will be described in dedicated chapters (Chapter 9.8 and
Chapter 14).
7.6.1
PROFET™ + PWM Limitations due to Power Losses
The feasibility of driving a load with a PWM waveform is often limited by the maximum power loss allowable in an
application. This is critical when the fPWM frequency is high or when the load has a relatively low resistance. (Refer
to Chapter 7.5 for details how to calculate the power losses). To calculate the maximum power losses an
application can support, refer to Chapter 7.7. Where the power losses are unacceptable for the device, the easiest
solution is to either reduce fPWM, or to use a device with lower RDS(ON).
Figure 42 shows the power loss in a BTS5045-2EKA when driving a 27W bulb. The PWM regulation voltage of
13V with PWM frequencies of zero, 100Hz and 200Hz is shown. The switching time is assumed to be tSON = tSOFF
= 120µs. Figure 43 shows the power losses in a BTS5045-2EKA when driving a 27W bulb, with a PWM regulation
Application Note
Smart High-Side Switches
38
Rev 1.0, 2010­12­15
App. Note
Power Stage
voltage of 13V and PWM frequencies up to 1kHz. From these graphs, it is clear that the BTS5045-2EKA has higher
power losses at higher PWM frequencies. Refer to Chapter 13.1 for detailled calcuation.
0,75
power losses with 200 Hz PWM
0,7
power losses with 100 Hz PWM
power losses with no PWM (W)
Power Losses (W)
0,65
0,6
0,55
0,5
0,45
0,4
0,35
8
9
10
11
12
13
14
15
Supply Voltage (V) V S
Figure 42
16
17
18
Power losses in PWM .vsd
BTS5045-2EKA Power Losses in PWM with a 27W Bulb Load. VPWM = 13V
4,0
power losses with 1kHz PWM
power losses with 400 Hz PWM
3,5
power losses with 200 Hz PWM
power losses with 100 Hz PWM
power losses with no PWM (W)
Power Losses (W)
3,0
2,5
2,0
1,5
1,0
0,5
0,0
8
9
10
11
12
13
14
Supply Voltage (V) V S
Figure 43
15
16
17
18
Power losses in PWM high frequency .vsd
BTS5045-2EKA Power Losses in high PWM frequency with a 27W Bulb Load. VPWM = 13V
Application Note
Smart High-Side Switches
39
Rev 1.0, 2010­12­15
App. Note
Power Stage
7.6.2
PROFET™ + PWM Limitations Due to Switching Time
To determine the minimum turn ON time, it is necessary to define when the DMOS power switch is actually ON.
This is assumed to be when the output reaches a minimum of 90% of VS. As described in Chapter 7.4, PROFET™
+s have a defined switching sequence. The minimum turn on time, tRON represents the minimum time the switch
ON. Refer to Figure 44. The specified turn ON time to 90% of VS, tON defines the fastest input pulse which will turn
the switch ON. With an input pulse of this length, tRON is smaller than the turn off delay, tOFF_delay which is the
smallest ON time a PROFET™ + reaches. A similar example can be used to show the minimum OFF time possible
which is limited by tON_delay assuming the switch is OFF if the output voltage is below 10% of VS.
tRON
TPWM
IN
VOUT
tOFF _delay
90% VS
70% VS
50% VS
30% VS
tON _delay
10% VS
t
t OFF
tON
minimum tON.vsd
Figure 44
Minimum tRON
tOFF_delay * fPWM is the smallest duty cycle, dMIN the device can handle. At this point, it is useful to compare
the PWM input parameters with the corresponding PWM output parameters. To perform this
comparison the accuracy, minimum and maximum duty cycle and maximum fPWM of the PROFET™ +
must be known. An example of this comparison is shown in Table 9. Improved accuracy and resolution
has been realized with better device symmetry (see Chapter 7.4). This can be measured by the
introduction of ∆tSW , the turn-ON/OFF matching parameter.
Table 9
PROFET™ + PWM Timing Limitation
Parameter
Period
min duty cycle at the output
min duty cycle at the input
max duty cycle at the output
max duty cycle at the input
Accuracy
fPWM =
fPWM =
fPWM =
fPWM =
100Hz
200Hz
400Hz
1kHz
1/fPWM
10
5
2.5
1
ms
tOFF_delay/TPWM
tON/TPWM
tON_delay/TPWM
tOFF/TPWM
∆ tSW / 2TPWM
0.8
1.6
3.2
8
%
2.5
5
10
25
%
99.2
98.2
96.8
92
%
97.5
95
90
75
%
0.5
1
2
5
%
Symbol Formula
TPWM
dOUT_MIN
dIN_MIN
dOUT_MAX
dIN_MAX
aPWM
Unit
It is important to note that the resolution is mainly determined by the software and the microcontroller. PROFET™
+ will have an influence on the accuracy of the resolution only.
Application Note
Smart High-Side Switches
40
Rev 1.0, 2010­12­15
App. Note
Power Stage
7.7
Thermal Considerations
PROFET™ + devices are embedded in exposed pad packages. Exposed pad packages offer excellent thermal
resistance (ZTH(JA) characteristics) between the junction and the case compared with non-exposed pad packages.
PROFET™ + devices in exposed pad packages also have better immunity to variations in the power supply and
power surges. Limitations to the system are based on two different thermal aspects:
7.7.1
Maximum Junction Temperature
PROFET™ + should be kept below TJ(SC) = 150°C. Equation (10) expresses this constraint mathematically.
T J ( SC ) – T MODULE
P MAXTJ = -------------------------------------------R THJA
(10)
A minimum of 1W (high ambiente temperature and/or bad cooling) and a maximum 2W are seen. Typically a
maximum of 1.4W gives good results.
7.7.2
Maximum Case Temperature
PROFET™ + case temperature should be kept below the destruction temperature of the PCB. This is application
dependent. As an umbrella specification, Infineon uses max TC = 130°C for standard FR4. Equation (11)
expresses this constraint mathematically.
T CMAX – T MODULE
P MAXTC = ----------------------------------------------R THJA – R THJC
7.7.3
(11)
Maximum Power in PROFET™ +
The maximum power a PROFET™ + can handle in an application is limited by the lesser of these two quantities,
PMAXTJ and PMAXTC. Table 10 provides some examples of how PMAXTJ or PMAXTC limit the maximum power of the
device for different values of ambient temperature and different thermal resistances. A maximum PCB
temperature of 130°C is assumed.
Table 10
Comparison between Exposed and Non Exposed Package with PCB Limitation = 130°C
Ambient Temp
Package
RTHJC RTHJA Max power due to Maximum power due to Maximum power
PCB temperature1) junction temperature2)
85
105
1)
2)
Exposed
1
30
1.6
2.2
1.6
Exposed
1
40
1.2
1.6
1.2
Exposed
1
50
0.9
1.3
0.9
Standard
15
50
1.3
1.3
1.3
Standard
15
60
1.0
1.1
1.0
Standard
15
70
0.8
0.9
0.8
Exposed
1
30
0.9
1.5
0.9
Exposed
1
40
0.6
1.1
0.6
Exposed
1
50
0.5
0.9
0.5
Standard
15
50
0.7
0.9
0.7
Standard
15
60
0.6
0.8
0.6
Standard
15
70
0.5
0.6
0.5
TC <130°C
TJ < 150°C
Application Note
Smart High-Side Switches
41
Rev 1.0, 2010­12­15 App. Note
Power Stage
7.8
Inverse Current
There are four main reasons for inverse currents in an application. The reasons are: driving of a capacitive load;
output wired to the battery (on purpose or by accident), driving an inductive load, and severe alternator ripple.
7.8.1
Capacitive Load
Figure 45 shows a typical case where inverse current can be observed.
+ VBAT_DROP -
ECU
- VDIODE +
I BAT
+
VBAT
+
+
VS
VOUT
IBAT _ECU
-
-
IINV
CL
-
capacitive load illustration .vsd
Figure 45
Capacitve Load and Inverse Current Illustration
CL is charged up to voltage VOUT. An inrush current IBAT_ECU applied inside the module induces a voltage
drop VBAT_DROP in the module's supply wiring. The consequence of this is that VS, the voltage supply of
the module can drop below VOUT. During a severe IBAT_ECU inrush event, the difference between VOUT
and VS can be sufficient to activate the internal parasitic diode (VBAT_DROP > Vdiode e.g. 300mV) or use
the RDS(ON) of the power DMOS to cause IINV current to flow.
7.8.2
Output wired to Battery
A short circuit to battery is very similar to the capacitive load except that a permanent inverse current can be
assumed. With a short circuit to the battery, VOUT is VBAT. VBAT_DROP can be more than 300mV permanently which
can create extra stress on the switch. Refer to Chapter 6.2.
7.8.3
Inductive Load
With an inductive load, such as an H bridge motor, the current can freewheel in either the low side or the high side
of the bridge again causing and inverse current to flow in the switch.
7.8.4
Alternator Ripple
Ripple caused by the alternator is common and is most noticeable when the alternator has a large load current.
As an umbrella specification, Infineon uses a ripple of 3V peak to peak at the module supply VS, with a frequency
of minimum 1kHz, maximum 20kHz. During the negative slope of the ripple, the capacitor, CL can be sufficient to
provide current to the load. In this situation, the switch is ON and the current is slowly decreasing until crossing 0
and continuing in a negative direction, limited by the RDS(ON) or the body diode of the switch. Figure 46 shows this
Application Note
Smart High-Side Switches
42
Rev 1.0, 2010­12­15
App. Note
Power Stage
situation, assuming a 3A resistive load decoupled with a 50µF capacitor and a ripple frequency of 1kHz ripple. This
example is based on the BTS5045-2EKA.
V B AT
I LOAD
17,0
3,5
16,5
2,5
16,0
Voltage (V)
15,0
0,5
14,5
-0,5
14,0
Current (A)
1,5
15,5
Alternator ripple
13,5
-1,5
Output voltage
13,0
Output current
-2,5
12,5
12,0
-3,5
0
250
500
750
1000
1250
1500
1750
Tim e (µs)
alternator ripple .vsd
Figure 46
Alternator Ripple. Voltage and Current of PROFET™ + with Capacitor as Load
7.8.5
Consequences for PROFET™ +
During inverse current, due to internal parasitic behavior, two kinds of phenomenon can be observed. With a large
inverse current IINV, well above the nominal current of the device, IL(NOM), a parasitic switch ON or OFF of a
neighboring channel can be seen (in devices with two or more channels of course). The second effect, described
in Figure 47 is where the DMOS power switch will not turn ON if the input on the IN pin is changed to high while
the inverse current is flowing (see case 3). In all other cases, the MOSFET switches according to the IN pin logic
level. The inverse current also impacts the diagnosis behavior. Refer to Chapter 9. The parameter IL(INV) in
datasheet represents the current below which no parasitic behavior of a neighboring channel or parasitic diagnosis
is observed.
IN
IN
CASE 1 : Switch is ON
CASE 2 : Switch is OFF
OFF
ON
t
IL
NORMAL
NORMAL
NORMAL
t
IL
t
INVERSE
NORMAL
DMOS state
DMOS state
OFF
ON
t
t
CASE 3 : Switch ON into inverse
CASE 4 : Switch OFF into inverse
IN
IN
OFF
t
NORMAL
NORMAL
INVERSE
t
IL
NORMAL
t
NORMAL
DMOS state
ON
ON
OFF
t
t
Behavior of PROFET™ + in Inverse Current
Application Note
Smart High-Side Switches
t
INVERSE
DMOS state
OFF
OFF
ON
ON
IL
Figure 47
t
INVERSE
43
Power stage Inverse conditions .vsd
Rev 1.0, 2010­12­15
App. Note
Protection
8
Protection
A comprehensive set of protection functions are one of the most important features offered by PROFET™ +
switches.
8.1
Band gap
PROFET™ + have an embedded band gap reference. Although the band gap reference is not a protection circuit
in itself, most of the protection circuits rely on this reference voltage. The band gap voltage is VBG = 1.25V. The
accuracy is 4% over temperature and supply voltage.
8.2
Short Circuit to Ground
As mentioned previously (refer to Chapter 6.1), a short circuit to GND is the most likely short circuit event in a
vehicle. As a result, PROFET™ + devices embed several mechanisms to protect against short circuits to ground.
8.2.1
PROFET™ + Current Limitation
As with all types of power MOSFET technology, the DMOS switch in PROFET™ + should not exceed a certain
power or current density. The power density reflects the power in the DMOS switch per unit of surface area. Since
the power PMOS = VDS * IMOS, and PMOS is limited to a constant, the IMOSMAX the DMOS can handle is then given
by Equation (12).
P MOS Cons tan te
I MOSMAX = ------------- = ------------------------V DS
V DS
(12)
Interestingly, with such an equation, a 0V drop voltage will lead to an infinite current. Obviously, this is theoretical
only, and the real current limitation, for low voltage drop, is related to wire bonding. The bonding cannot support
more current than a certain fixed value. The constraints, linked to the technology looks as the given curve
Figure 48. The blue curve matches the MOSFET power density only. The red curve sketches the overall device
limit. The protection concept should guarantee to limit the current below the device system limitation.
140
120
Destructive current (%)
100
80
60
40
20
0
0
2
4
6
8
10
12
14
16
18
20
Drain source Voltage V DS (V)
Figure 48
Power DMOS and Package SOA
Application Note
Smart High-Side Switches
44
Rev 1.0, 2010­12­15
App. Note
Protection
8.2.2
PROFET™ + Current Limitation Concept
PROFET™ + devices limit the current flowing through the DMOS switch. The reason for limiting instead of tripping,
is due to the fact that PROFET™ + devices are designed to drive lamps. As described in Chapter 5.1.3, lamps
have a significant inrush current at turn ON. To ensure a lamp is turned ON in the worst case scenario, it is
necessary to allow this inrush current to flow for a short period of time. The current limitation looks as described
on Figure 49, the blue colors reflecting the tolerance.
120
100
Destructive current (%)
80
60
40
20
0
0
2
4
6
8
10
12
14
16
Drain source Voltage VDS (V)
Figure 49
18
20
Device Current limit. vsd
Current Limitation
As described in Table 4, each lamp has an inrush. Figure 50 shows the consequence for the PROFET™ + when
turning on a lamp. The orange line represents the inrush current of the bulb. The device will be considered suitable
for a lamp when the IINRUSH will not touch the low current limitation (risk of accelerated aging) hence it may touch
the high limit one when VDS is smaller 3V. In that case, a restart due to an over temperature swing can be
observed.
60
InrushCurrent / Current limit (A)
50
40
30
20
10
0
0
2
4
6
8
10
12
Drain source Voltage VDS (V)
Figure 50
14
16
18
20
lamp Current limit. vsd
Turning ON 2*27W+5W with BTS5020-2EKA. Inrush versus Current Limitation
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
Protection
8.2.3
Temperature Swing Limitation
Severe temperature gradients on chip cause significant thermo mechanical stress and aging of the device to the
point of destruction. The smaller the temperature gradient, the higher the number of cycles the PROFET™ + can
withstand. A temperature swing of 60Kelvin minimum is a good compromise value to use for lamp turn ON and to
protect against severe short circuits. Figure 51 shows the hardware realization of the 2 x 20 mΩ BTS5020-2EKA.
Two temperature sensors, one measuring the DMOS, one measuring the chip temperature are compared. The
channel turns OFF when a too high temperature gradient is reached. To guarantee the functionality accuratly,
variation due to temperature and production spread is greatly reduced thanks to the use of the internal band gap
reference.
DMOS
Channel 0
DMOS
Channel 1
TEMPERATURE
DIFFERENCE
Logic of the Channels
temperature swing concept .vsd
Figure 51
Temperature Swing Limitation Concept
8.2.4
Maximum Temperature Limitation
The device (chip + package) is qualified for junction temperature up to TJ = 150°C continuous. Above, the over
temperature sensor of the chip is met. This sensor is typically activated at a temperature of TJ = 175°C. The
hardware designer should guarantee with its thermal design the device to operate below TJ = 150°C by verifying
Equation (10).
8.2.5
Restart Strategy
During the switch ON phase of a cold lamp, with a high battery voltage, the temperature rise in the device can be
higher than 60K. To ensure that the lamp is turned ON in less than 30ms (refer to Chapter 5.1.3), even under
these conditions, a restart strategy is implemented. When the temperature swing reaches TSWING = 60K min, the
device switches OFF for protection. When the temperature has decreased to TSWING_HYS 75% of TSWING, the device
restarts. 75% has been tested and confirmed as the best value to improve short circuit robustness, as well as the
most efficient to switch ON the load. Figure 52 shows a typical restart phase.
Application Note
Smart High-Side Switches
46
Rev 1.0, 2010­12­15
App. Note
Protection
T DMOS
T J( SC)
DMOS temperature
T SWING
T SWING HYS
se
ur e increa
temperat
Chip logic
t
HEATING
t
t
COOLING
temperature swing timing . vsd
Figure 52
DMOS Temperature Behavior during Restart Phase
8.2.6
PROFET™ + Life Time Limitation
Although significant design effort has been put into protecting against a short circuit to GND, PROFET™ + devices
are not indestructible. To protect the device, it is necessary to limit the number of restarts to a minimum. Refer to
Figure 53. The measured acceptable number of thermal event restart is in range of 5 to 20 maximum restart. The
application software should monitor the diagnostic line of the PROFET™ + shortly after switch ON and limit the
restart time (tRESTART) if necessary. The recommended value is tRESTART = 100ms mini, 300ms maxi, which results
in a range of N = 10 to 20, depending on the PROFET™ + cooling. If this type of strategy is not implemented, the
number of short circuit events that a PROFET™ + can handle will be limited.
Driver
command
t
IN
t RESTART
t
IL
I L(SC))
1
2
N-1
N
t
restart event limitation .vsd
Figure 53
Number of Restart Limitation
Thanks to this strategy, the definition of short circuit is as follows: If after tRESTART or N restarts, the device is still
reporting a short circuit, a short circuit condition exists.
8.2.7
Activation Limitation
Figure 54 provides a picture of a BTS5241L which has been exposed to repetitive short circuit stress. The channel
on the right hand side has not experienced any events while the other channel has experienced thousands of
repetitions. This provides a visual confirmation of the aging effect due to repetitive short circuit events.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15 App. Note
Protection
Figure 54
Device Exposed to Short Circuit Stress
As soon as a short circuit is detected, a plausibility check should be performed. This is achieved by changing the
IN pin status from LOW to HIGH again to ensure the diagnosis is correct. If a certain number of short circuit events
are detected, the system should then inhibit the function controlled by the switch until the next ignition cycle of the
vehicle starts.
To implement this strategy, a counter CDRIVE has to be created. CDRIVE is used to count the number of short circuit
events each PROFET™ + output has encountered in an ignition cycle (a short circuit cycle corresponds to an
event where after TRESTART, the device is still in short circuit). When CDRIVE reaches a predefined value, the load is
inhibited (i.e. no further activation).
Another counter, CLIFE is then incremented. CLIFE should be stored in a non volatile memory such as Flash or
E²Prom. Infineon provides the quantity CDRIVE * CLIFE in datasheet based on the short circuit robustness test. In
Chapter 5.4 a rough clustering of loads or load families based on the number of activations per ignition cycle was
given. Although the final decision always rests with the OEM, Table 11 provides suggested values for CDRIVE for
a given load family.
Table 11
N° of driver
activation
Load Family, Function of Engine Ignition
Load example
Average activation Plausibility check
time
realized by
Inhibition after
CDRIVE
High
Brake light
< 1mn
Car driver
3 to 5
High
Low beam
> 1mn
Car driver
3 to 5
Mid
Interiors
> 1mn
Application
5
Mid
Low beam
> 1mn
Application
5 to 10
Low
High beam
> 1mn
Application
5 to 10
Using Table 11, a software strategy can be implemented based on the number of activations per ignition cycle,
the average driver usage as well as the length of time of activation. A load which is known to be used often will
not need an automated retry. A load which is activated once in a while but for long periods of time will need an
automated retry. Figure 55 shows these two possibilities. TWAIT is usually selected by the OEM. (in the range of
1s to 2mn). Figure 56 shows a suggested software flow chart.
Application Note
Smart High-Side Switches
48
Rev 1.0, 2010­12­15
App. Note
Protection
Driver request
t
IGNITION CYCLE
IN
IGNITION
CYCLE
TRESTART
t
CDRIVE = 1
CDRIVE = 2
C DRIVE = 0
CDRIVE = 3
CLIFE = CLIFE +1
Driver request
t
IGNITION CYCLE
IN
CDRIVE = 1
t
TWAIT
TWAIT
Figure 55
IGNITION
CYCLE
TRESTART
CDRIVE = 2
C DRIVE = 0
CDRIVE = 3
CLIFE = C LIFE +1
software timing strategy .vsd
Software Strategy
New vehicle
CLIFE = 0
System OFF
Ignition ON
System ON
CDRIVE=0
Device OFF
Activation = driver wish
Device ON
Ignition ON
Diagnostic read out
SC ?
No
IGNITION
CYCLE
System OFF
Yes
Definitive device
inhibition
No
Yes
CLIFE > CLIFE max
Activation =
Driver wish
or
Retry strategy
Device OFF
CDRIVE=CDRIVE+1
CDRIVE > CDRIVE max
Yes
No
Device OFF
Device inhibition
CLIFE=CLIFE+1
System OFF
Ignition OFF
Figure 56
Software strategy.svg
Short Circuit Software Strategy
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
Protection
8.3
Short Circuit to Battery
A short circuit to the battery can be a very stressful event for a PROFET™ + device. Refer to Chapter 6.2 and
Chapter 7.8. Several workarounds can be implemented with the best solution being to place a diode in series with
the output. While this solution is good in theory, the cost is often prohibitive. An alternative strategy is to guarantee
that no excessive current will flow in the device. To implement this, the system must perform a short circuit to
battery test. If a short circuit to the battery is indicated, the battery supply line of the PROFET™ + must not be
switched OFF. If the battery's supply line is not available (for example due to a blown fuse), the alternative is to
use a semiconductor which will perform intelligent restart. At last, turn-OFF every device connected to the
faulty supply line in order to reduce the inverse current in the body diode. The three solutions are summarized in
Figure 57.
SHORT CIRCUIT
TO BATTERY
ECU
VBAT
Diode
solution
Fuse and relay
box
CL15 fuse CL15 switch
Switch kept ON
GND
Inhibition
of the
loads
GND
Short circuit to battery.svg
Figure 57
Short Circuit to Battery Protection Possibilities
8.4
Open Load
Open Load is not considered has a destructive case for the device.
8.5
Loss of battery
The loss of the battery while the switch is ON has no influence on device’s robustness when load and wire harness
are purely resistive. In the case of inductivity, the energy stored in the inductance brings additional issues which
should be handled with care. Figure 58 shows the system set up in that case.
Application Note
Smart High-Side Switches
50
Rev 1.0, 2010­12­15
App. Note
Protection
-
VRI +
R1/L1
-xV
+
VIS(AZ)
-
VS
-xV-0.7V
IS
IBAT
ZIS(AZ)
+
RIS
VIS
+
IN
VZ(AZ)
-
ZD(AZ)
+
VBAT
-
+
IL
ZDESD
VIN
-xV+6V
-
VDS(AZ)
ZDS(AZ)
OUT
-xV - 0.7V - 45V
RIN
-
+
GND
-xV
VLOAD
R2/L2
VGND
+
ZGND
+
0V
Figure 58
Loss of battery protection.svg
Loss of inductive load
Due to the inductivity, the current searches the easiest (lowest ohmic) path to flow. This path consists in the
freewheeling of the GND circuitry and of the over voltage ZD(AZ) diode. For that reason, it is necessary to let the
current flow in the opposite direction in the GND circuitry, otherwise thousands of Volt will be seen at the pins. The
power DMOS is big enough to handle the energy, the ZD(AZ) diode is less robust. An equivalent robustness would
mean a GND DMOS as big as the power DMOS which is financially not sustainable. PROFET™ + devices handles
inductivity of the wire harness, up to 10µH with the nominal current of the given device. In the case of applications
where currents and / or the inductivity should be exceeded, an external freewheeling diode, in parallel to the device
or in parallel to the load is necessary to handle the energy.
8.6
Short Circuit Between Loads
Short circuit between loads is usually detrimental to the application affecting PCB traces, connectors and wiring.
For PROFET™ +, the consequences depend mainly on which additional load is added by the short circuit.
As extreme example, a 55W lamp which is short circuited to a 5W lamp will bring no difference to the 55W
PROFET™ BTS6143D driver while the 5W PROFET™ + BTS5180-2EKA driver will effectively be short
circuited to ground.
Thanks to the embedded temperature swing limiter and restart strategy, the PROFET™ + will be able to turn the
over-load inrush ON. If the ambient temperature is below the maximum ambient temperature the system is
designed for, the PROFET™ + will either go into thermal shutdown very late or not at all. Nevertheless, it's life
expectancy will be reduced by the over current events.
To define the maximum current acceptable for a device the ZTH(JA) information must be known. Any current which
is applied for a period of time and leads to a temperature swing of more than 60K is considered to be outside the
nominal range. This current will accelerate the ageing of the PROFET™ +. As an example, Figure 59 shows the
maximum current that can be handled by each PROFET™ +.
Application Note
Smart High-Side Switches
51
Rev 1.0, 2010­12­15 App. Note
Protection
100
Max Current (A)
BTS5020
BTS5030
BTS5045
BTS5090
BTS5120
BTS5180
10
1
0,1
1
10
Time (s)
Figure 59
Typical Couple Current / Time to 60K Temperature Swing
8.7
Undervoltage
100
1000
temperarture swing current .vsd
A low supply voltage condition brings two challenges which must be addressed, protection and switching
capability. Refer to Figure 60.
8.7.1
Protection
Thanks to the internal band gap (BG) reference, PROFET™ + devices are protected in under-voltage conditions.
A valid band gap allows the device to turn ON. In this case, all protection mechanisms are functional. An invalid
band gap, due to insufficient supply voltage causes the PROFET™ + to turn OFF. When the BG is valid, the
charge pump (CP) voltage is not necessarily valid, however, the charge pump is monitored and BG will prevent
switch from turning ON when the CP voltage is invalid.
8.7.2
Switching Capability
The capability of a PROFET™ + to turn ON and to reach the correct RDS(ON) area is based on the charge pump's
capability to drive the gate of the power DMOS transistor (refer to Chapter 7.3). This is defined in the data sheet
by the supply voltage VS being the range VNOM. When the supply voltage VS is below this range, the situation prior
to reaching the under-voltage zone is of primary importance. If Vs is decreasing, the device is kept ON down to a
threshold in the range of VS(UV). This is assuming the IN pin is kept to a HIGH level. If Vs is increasing, the device
will switch ON when VS reaches the threshold VSOP(min). Figure 60 shows the behavior in the three areas of supply
voltage with respect to time.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
Protection
IN
VS / VOUT
R D S(ON ) *IL
V S(OP) min = 8V
VS(OP) ext = 4.5V
VS(U V) min = 2V
Turn ON delay
1.5V max
t
undervoltage behavior .vsd
Figure 60
Behavior during Undervoltage Reset and Ramp up test
8.7.3
Ignition
During ignition, and depending on the OEM minimum voltage VCRK_MIN, a switch which was previously ON can turn
OFF. Refer to Figure 61. When the VS voltage rises again, the switch will automatically restart and turn ON if the
IN pin is kept in the high state. During tLAUNCH, VS can be below VS(OP)min. As a consequence, the RDS(ON) can be
higher than specified. To avoid an intermediate state, every PROFET™ + is tested to provide a voltage drop of
less than 1.5V.
IN
t
V
VBAT_R UN
VBAT _STD
VCRK_OSC
VCRK_LAU NCH
VCRK_MIN
t
CRK
t
LAUNCH
t
Cranking pulse .vsd
Figure 61
Ignition Pulse and PROFET™ + Behavior
8.7.4
Low Battery Voltage Phase
During a low battery condition, a parasitic under-voltage turn OFF could occur, especially if a capacitive load with
IINRUSH peak current has to turn ON or if there is a short circuit to GND. Since the wiring is inductive, IINRUSH will
produce a VDROP voltage. Refer to Figure 62. VDROP can be estimated by Equation (13).
Application Note
Smart High-Side Switches
53
Rev 1.0, 2010­12­15 App. Note
Protection
R and L are the respective resistance and inductance of the supply line. ∆t corresponds to the PROFET™ +
switching time. IINRUSH is the worst case peak current of the short circuit current or current limitation. As umbrella
specification, Infineon consider L = 10µH, R = 20mΩ. Refer to Table 12 for expectable voltage drop during IINRUSH.
I INRUSH
V DROP = L × ------------------- + R × I INRUSH
∆t
(13)
Relay and
Fuse box
+
+
Vdrop
-
GND
ECU
I INRUSH
CLx
VSx
+
VS
Battery V
BAT
-
GND
undervoltage hardware set up .vsd
Figure 62
Low Battery Voltage Condition. Inrush and Inductive Wiring Influence
Table 12
Load and Maximum Instantaneous Expectable Voltage Drop
Load (W)
Inrush (A)
Maximum Voltage Drop (V)
5
5
0.35
7
7
0.5
10
9
0.65
15
14
1
21
22
1.5
27
26
1.9
2*27+5
57
4
3*27+5
85
6
55
50
3.5
65
60
4.2
8.8
Overvoltage
Overvoltage is considered to be everything above VBAT(SC). As described in Chapter 4.1.5, the main causes of over
voltage are external jump start and load dump. ISO pulses are described separately in Chapter 14.1.
8.8.1
Jump Start
Jump start is usually not a stressful situation. The only situation in which PROFET™ + devices cannot cope during
a jump start is during a simultaneous short circuit to GND at the output. This is considered a double fault, and it is
not usually required to survive such a coincidence. In this case, the device will survive a single short circuit event.
Turning OFF the load is recommended when the voltage increases above VBAT(SC). If the load is a lamp, this
procedure is even recommended to maintain the life time of the bulb.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
Protection
8.8.2
Load Dump
Load dump is an extreme application scenario for a PROFET™ + and can be destructive test due to thermal overstress. Refer to Figure 63. As soon as the VS potential is higher than VS(AZ), VIS(AZ) or VDS(AZ), the respective Zener
diode conducts. The temperature and current coefficients are positive which means that all the Zener diodes are
conducting almost at the same time. The load dump is specified with RI (internal load dump generator resistor)
which will limit the current. Note that this resistor is OEM dependant. The ISOV current flows via the sense
protection Zener ZIS(AZ), the logic protection Zener ZD(AZ), and the power stage Zener ZDS(AZ).
To define the robustness of the system against load dump, the currents and voltages of Figure 63 must be solved
(Millman theorem helps). When this is complete, a power calculation can be done to determine if the system is
capable of handling the total energy. Resistors RIS, RIN and RGND are used to limit the current (ISOV_SENSE, IDESD,
ISOVLOGIC respectively). It is important to note that in a load dump situation, the load is activated and some current
ISOV_LOAD flows. The choice of RGND is explained in Chapter 10.1.
~58V
-
VRI +
Ri
~11V
- VIS(AZ) +
IS
ZIS(AZ)
ISOV_SENSE
+
+
~10V
+
VIS
ID_ESD
VZ(AZ)
IN
-
+
VIN
VESD
RIN
ZDS(AZ)
60V
VDS(AZ)
+
-
VLD
ZD(AZ)
ISOV_LOAD
-
RIS
ISOV
VS
ZDESD
ISOV_LOGIC
OUT
-
~11V
+
-
GND
~11V
+
IGND
VLOAD
+
VGND
R;L;C
RGND
Overvoltage protection.svg
Figure 63
Over Voltage Protection. Example with 60V
8.9
Reverse Polarity
In reverse polarity situations where loads have symmetrical characteristics, such as lamps or resistors, the current
is allowed to flow through the load and the DMOS body diode. For loads such as inductive loads (motors, relays,
etc..) special care must be taken to ensure safe operation.
8.9.1
Loads with Symmetrical Polarity Characteristics
Refer to Figure 64. The following currents must be considered and limited with resistors :
Application Note
Smart High-Side Switches
55
Rev 1.0, 2010­12­15 App. Note
Protection
•
IDS(REV) :The parasitic body diode of the power DMOS is conducting. This means that current will flow in the
•
•
ISREV_LOGIC : This current will flow in Zener ZD(AZ), which acts as a diode.
ID_ESD : Since the pin GND is at a diode voltage (ZD(AZ)) above GND and the IN pin is more or less at battery
potential, the ZDESD diode should be protected with a resistor RIN. (this is valid for all the logic pins).
IIS(REV) : Via the sense resistor, the current will flow in the ZIS(AZ) Zener which will act as a diode.
load. The load will actually limit the current in the body diode power DMOS.
•
16V
16V
16V
+
VIN
VGND
15.3V
+
-
RIN
-
+
VIS
ZDESD
RIS
OUT
VESD(AZ)
+
0.7V
-VS(REV)
IDS(REV)
0.7V
-
ID_ESD
ISREV_LOGIC
IIS(REV)
VLOAD R;L;C
+
-
0.7V
+
IREV_GND
GND
7V
IN
RGND
ZD(AZ)
+
VZ(AZ)_D
VDS(REV)
-
-
-
+
ZIS(AZ)
IS
+
VIS(AZ)_D -
VS
0V
reverse polarity protection.svg
Figure 64
Reverse Polarity Protection with Symetrical Polarity Load. Example with 16V
8.9.2
Reverse Polarity Protection for the Load
There are many applications where the methods of protection against applied reverse polarity described above
cannot be used. Some examples are: the load is in a DMOS bridge; the load has an integrated freewheeling diode;
the load itself must be protected from wrong polarity as electrochemical capacitors; the load consists of an
inductance with PWM regulated current or the load has a small resistive component. In all of these cases, it is
necessary to block the current.
Application Note
Smart High-Side Switches
56
Rev 1.0, 2010­12­15
App. Note
Diagnostics
9
Diagnostics
The diagnostic functions embedded in the PROFET™ + is a function getting increasing importance driven by LED
and short circuit to GND requirements. PROFET™ + devices use a current sense method to offer complete
diagnostic coverage over the output current range. Diagnostics are synchronized with the input, meaning the
PROFET™ + always provides the status of the present state of the power DMOS and the logical signal IN i.e. there
is no memory effect.
9.1
Current Sense
Current sense is implemented using a current generator which provides a current proportional to the load current
IL. The ratio between IIS and IL is called kILIS. When a failure occurs the current generator is set to IIS(FAULT), the
maximum sense current the current generator can provide.
Refer to Figure 66. The current sense generator is based on the P channel MOSFET T4. The gate of T4 is driven
by op-amp OPA which set the voltage at T4 gate equal to the output voltage. The sense feed consists of the DMOS
transistor T2, which is not connected to the output, but supplies T4 only. As with all current generators, the current
sense is connected to a voltage supply, here VS. This means that the voltage at the IS pin, VIS should always be
smaller than VIS(RANGE) min, otherwise the current generator cannot provide the required current.
The maximum current supplied by the current generator is given by the parameter IIS(FAULT). The size of T4
determines the value of IIS(FAULT). There is no current limit mechanism or thermal sensor for T4 hence the system
designer should ensure that T4 is adequate protected. T1 provides protection against over voltage and ESD by
acting as a Zener diode. One limitation of T1 is that two PROFET™ + with different battery feeds can not share a
common sense line. This could result in one of the PROFET™ + supplying the other one through transistor T1.
VS
T3
T2
T1
Gate
driver
OUT
FAULT
DEN
OPA
T4
IS
sense for the baleze single.svg
Figure 66
Current Sense Generator
Application Note
Smart High-Side Switches
57
Rev 1.0, 2010­12­15
App. Note
Diagnostics
9.2
Gate Back Regulation
PROFET™ +s use gate back regulation (GBR). The aim of GBR is to improve the current sense accuracy at low
load current.
9.2.1
Influence on the Power Stage
The GBR monitors the drain source voltage VDS. As VDS is gets low, the gate driver partially reduce the gate
voltage to increase the channel resistance. VDS is limited to VDS(NL). Figure 67 graphs the VDS voltage on the left
hand side with and without GBR as a function of the load current. On the right hand side is a graph of the artificial
RDS(ON) for low load currents. These graphs are based on the BTS5020-2EKA.
1000
RDSON max
RDSON typ
100
40
RDSON (Ω)
Voltage Drop V DS (mV)
60
20
RDSON min
10
1
0,1
0
0
500
1000
1500
2000
0,01
0
Load Current (mA)
Figure 67
Gate Back Regulation Influence on Voltage Drop.1)
9.2.2
Sense Accuracy Improvement
20
40
60
80
100
Load Current (mA)
120
140
Voltage limitation .vsd
The main purpose of GBR is to improve the kILIS accuracy at low load current. Equation (15) is used to calculate
the current sense ratio kILIS where:
VOFFSET is the parasitic offset voltage of the op-amp. (it can be negative or positive)
VDS is the voltage drop in the power MOSFET which is RDS(ON) * IL.
kILIS0 is the target central value.
1
k ILIS = k iILIS0 × ------------------------------V OFFSET
1 + ---------------------V DS
(14)
From this equation, when the load current IL is going to 0, the klILIS spread is increased to infinite because VDS =
0V. GBR compensates for this behavior by limiting VDS to VDS(NL). Figure 68 provides the famous kILIS trumpet,
with and without gate back regulation.
1) Typical RDS(ON), worst case GBR
Application Note
Smart High-Side Switches
58
Rev 1.0, 2010­12­15
App. Note
Kilis ratio in %
Diagnostics
200
kilis w/o GBR
180
kilis with GBR
160
typical
140
120
100
80
60
40
20
0
10
500
1000
Load Current (mA) IL
1500
Figure 68
Gate Back Regulation Influence on kILIS accuracy, in %
9.2.3
Sense Resistor
2000
Gate back regulation .vsd
Refer to Chapter 10.3.
9.3
Short Circuit to Ground
9.3.1
Short Circuit to Ground in OFF State
Note that short circuit to GND in OFF state cannot be detected. When this failure occurs, the PROFET™ + does
not report a fault condition.
9.3.2
Short Circuit to Ground in ON State
A short circuit to ground in the ON state is detected by the logic as one of the three logic signals, "over current
OC", which comes from current limitation circuitry, "over temperature OT" which comes from the temperature
sensor and "over temperature swing OTS" which comes from the temperature swing sensor. As soon as one of
these three logic signals is high, the PROFET™ + is considered to be in a stressful situation which will result in an
activation of the sense signal IIS(FAULT).
Figure 70 describes the different signals involved on a large time scale, from the power DMOS transistor TMOSFET
temperature and IL load current to the logic signals shows for different failures.
It is interesting to zoom in on the point where the device restarts. At this point, the power DMOS transistor
switching ON and the load current has not yet reached the IL(SC) current limitation. In this situation, the OC signal
is not set to 1 and the OT or OTS are at 0. Without filtering, this would lead to a glitch in the output from HIGH to
LOW to HIGH. To avoid this, a small delay is embedded into the PROFET™ +. This delay is defined by the
parameter tsIS(OT_blank). Refer to Figure 69.
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Diagnostics
OT
t sIS(OT_blank)
OTS
Short circuit
OC
Short Circuit to GND Logic .vsd
Figure 69
Short Circuit to GND Logic
IL
I L(SC)
t
T MOSFET
TJ(SC)
t
OC
t
OT
t
OTS
t sIS(OT_blank)
t
tsIS(OT_blank)
Short circuit
t
Short circuit to GND . vsd
Figure 70
Hard Start Timing
9.3.3
Observable Parasitic Effect of the Strategy
This concept can exhibit parasitic diagnostics due to extreme temperature or load current conditions.
9.3.3.1
Very high Ambient Temperature
If the ambient temperature reaches a very high level and the switch is ON, a nominal current can be sufficient to
activate the maximum over temperature sensor. In this case, the current sense will oscillate between nominal and
IIS(FAULT). Refer to Figure 71.
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Diagnostics
T MOSFET
TJ(SC)
t
IL
IL(NOM)
t
OT
t
IIS
IIS(FAULT)
IIS(NOM )
t
High temp .vsd
Figure 71
Very High Ambient Temperature Diagnostic Parasitic Effect
9.3.3.2
High Load Current
If the load current is significantly high (Refer to Figure 59) in a cold temperature environment, this can be enough
to activate the OTS sensor. This will result in the same behavior as for the previous case i.e. the IIS pin can toggle.
9.4
Short Circuit to Battery
9.4.1
Short Circuit to Battery in OFF State
During a short circuit to the battery in OFF state, the output voltage of the PROFET™ + rises up to VBAT.
PROFET™ + have an embedded comparator to monitor the output voltage. If this voltage rises above VOL(OFF),
the device considers this as a fault condition and sets the sense signal accordingly. To prevent parasitic short
circuit to battery diagnostic when the ouput is floating (open load), an external pull down resistor RSC_VS = 47kΩ is
recommended. Refer to Figure 72.
Vbat
VS
IIS(FAULT)
SHORT CIRCUIT
TO BATTERY
OL
comp.
IS
OUT
+
GND
VOL(OFF)
RIS
RGND
RSC_VS
Short circuit to Vs.svg
Figure 72
Short Circuit to Battery Detection Hardware Set up
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9.4.2
Short circuit to Battery in ON State
A short circuit to battery in the ON state is more difficult to diagnose. Fortunately, the consequence of such an
event is simply that the sense current IIS is lower than expected. Depending on the short circuit impedance, it will
be diagnosed as open load in ON or under-load. A discriminating diagnosis should then be performed in the OFF
state.
9.5
Inverse Current
Inverse current is similar to short circuit to battery. Nevertheless, parasitic inverse current can bring additional
challenges to be overcome. Refer to Figure 73. If the inverse current is too high, a parasitic current IIS_INV will flow
at the sense pin IS.
IN
IN
CASE 1 : Switch is ON
CASE 2 : Switch is OFF
OFF
ON
t
NORMAL
NORMAL
NORMAL
t
IL
IL
NORMAL
t
t
INVERSE
INVERSE
DMOS state
DMOS state
OFF
ON
t
t
IS
IS
[email protected] ~ 0
IL / kilis
IL / kilis
Z
SC VBAT
Z
t
t
IN
IN
CASE 3 : Switch ON into inverse
OFF
OFF
ON
ON
t
t
IL
IL
NORMAL
NORMAL
NORMAL
CASE 4 : Switch OFF into inverse
NORMAL
t
t
INVERSE
INVERSE
DMOS state
DMOS state
OFF
ON
ON
OFF
t
t
IS
IS
Z
[email protected]
[email protected]
~0
IL / kilis
IL / kilis
t
[email protected]
~0
SC VBAT
Z
t
Inverse conditions.svg
Figure 73
Inverse Current Diagnostic
9.6
Open Load
9.6.1
Open Load in OFF State with Bulb and Inductive Load
During the OFF state, open load can be diagnosed using an external pull up resistor ROL. Open load in OFF is
detected using a comparator to check the output voltage. In normal operation, the load acts as a strong pull down.
When the load connection is lost or the load blown, the output voltage is pulled up to the battery voltage through
ROL. An additional switch is usually necessary to reduce the stand by power consumption of the module during
parking to prevent a permanent leakage current VBAT / ROL from flowing in the load. A PNP transistor, T1 such as
a BC807 will fit this requirement. This transistor can be shared by other devices which share the same battery
feed. The value of ROL depends on the OEM specified minimum parasitic impedance RDIRT. As an umbrella
specification, Infineon considers RDIRT as open load impedance 4.7kΩ as a minimum value.
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Knowing RDIRT, ROL can be obtained by the following Equation (15) where VBATMIN is the minimum battery voltage
during which the open load in ON diagnostic is performed. Refer to Chapter 13.2 for detailed calculation.
1
R OL < R DIRT × -------------------------------------V BATMIN 
 --------------------- 3V - – 1
(15)
ROL should be large enough to ensure that the power loss in this resistor can be neglected. Assuming a maximum
PRMAX of 250mW (pulsed during the open load diagnosis) ROL is defined by Equation (16).
2
2
V BAT
V BAT
R OL > ----------------- = --------------P RMAX
0, 25
(16)
ROL = 1.5kΩ is recommended value.
Vbat
T1
VS
IIS(FAULT)
ROL
OL
comp.
OUT
IS
+
ILOFF
GND
RIS
VOL(OFF)
RGND
RDIRT
Open Load in OFF.svg
Figure 74
Open Load in OFF Hardware
9.6.2
Open Load in OFF State with LED Module
LED modules are quite challenging to diagnose in OFF state. On one hand, the leakage current of the dirt
resistance is in the mA range. On the other hand, 10µA is sufficient to illuminate an LED. The only way to diagnose
either a standard or advanced LED module is to guarantee the voltage VOUT is below the illumination level. To
achieve this, the LED module must have a resistor ROL_LED at the input. Refer to Figure 25 and Figure 26. This
resistor is polarized by the ROL. In case of open load, the ROL will pull up the voltage as in the case of bulb. In
normal conditions, the ROL_LED will sink the current and limit the output voltage below the LED illumination
threshold.
9.6.3
Open Load in ON state
To determine if a PROFET™ + can diagnose an open load in the ON state, it is necessary to precisely define the
characteristics of this condition. As described earlier, an open load in an automotive environment is the resistance
ROL as a minimum. In the case of an LED module powered from a DC/DC converter, if one LED is blown, the
DC/DC converter will still consume some current. This current is defined by the OEM. As an umbrella specification,
Infineon considers an open load to be a current in between of 5 to 30mA. When the open load current range has
been defined, it is easy to determine the minimum sense current considered to be an open load, using the current
sense specification. Figure 75 and Table 13 shows an give open load currents considered.
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.
I IS
IIS(OL)
IL
IL(OL)
Sense for OL .vsd
Figure 75
Current Sense Accuracy at Small Load
Table 13
PROFET™ +s Open Load Definition
kILIS ratio typical IIS(OL) (µA) IL(OL) min (mA) IL(OL) max (mA)
9.7
20mΩ
30mΩ
45mΩ
90mΩ
120mΩ 180mΩ
3000
2150
1500
1500
550
550
4
5.6
8
8
21
21
5
5
5
5
5
5
30
30
30
30
30
30
Partial Loss of Load
Some applications use loads in parallel which can lead to partial loss of load. Refer to Figure 30.
9.7.1
Partial Loss of Load during OFF state
During the OFF state, a partial loss of load caused by losing one out of X loads cannot be detected.
9.7.2
Partial Loss of Load during ON state
During the ON state, diagnosis of the loss of one out of X loads can be realized using the current sense function.
Accuracy of the PROFET™ +, as well as the complete system accuracy can challenge the diagnosis. To answer
the question "can you diagnose the loss of xW, out of yW", it is necessary to determine the following as described
in Figure 76. Red color indicates min typical and max with one load loss, Green color indicates min typical and
max with nominal load.
Step 1, Which lamps are used? Different lamps have different accuracies. Refer to Chapter 5.1.
Step 2, Supply voltage range. Lamp current changes with supply voltage. Refer to Chapter 5.1
Step 3, Ground shift range. Refer to Chapter 3.5
Step 4, If PWM used and the PWM accuracy. Refer to Chapter 7.6
Step 5, Current sense conversion, kILIS accuracy?
Step 6, Eventual additional leakage current on the sense line?
Step 7, Sense resistor accuracy?
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Step 8, A/D converter accuracy ? A/D converter reference voltage, A/D resolution and LSB error?
ILL
IL2) Load current dependency to supply voltage
∆V
1) Unaccuracy of the load
∆
P
IL
3) Load current dependency to GND shift
2
1
∆GND
Vbat
Vbat
5) Current Sense Error
IL
IL
Vbat
4) Load current dependency to PWM
missmatch
3
4
∆kILIS
∆PWM
5
Vbat
IL
Vbat
VSENSE 7) Current Sense Resistor error
6) Current Sense Line offset
bits
6
8) A/D error
7
∆lk
∆ A/D
∆R
Vbat
Vbat
Vbat
longstoryshort .vsd
Figure 76
Diagnostic of Partial Load Loss
When all of this information is known, it is possible to determine if the PROFET™ + can diagnose a partial loss of
load. Table 14 gives the required PROFET™ + kILIS accuracy to detect the loss of specific partial loads.
Table 14
PROFET™ + Planned Load and Diagnosis
20mΩ
30mΩ
45mΩ
90mΩ
120mΩ
180mΩ
Load 2x27W+ 2x21W 27W+5 2x10W 2x5W 1x5W
5
Target 1x27W 1x21W 27W 10W 1x5W OL
diagnostic
Accuracy 10% 10% 20% 10% 10% 70%
@ 2A @ 2A @ 1A @500mA @250mA @20mA 9.7.3
Current Sense Accuracy Improvement
Sometimes, the current sense accuracy is not good enough to diagnose a required loss of load. In this case,
PROFET™ + devices offer a calibration strategy. In details, it means the application should “learn” the real kILIS
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ratio of the given device soldered on the PCB. This value should be stored in a non volatile memory. Figure 77
describes in details the reasons for unaccuracy and compensation effects.
IS
1/ Everything ideal
2/ Missmatch in the cells
IS
1
3/ Offset influence
IS
2
IL
IL
IL
3
IS
6a/ One point calibration
5/ Real GBR compensation
IS
5a
4/ Ideal GBR compensation
4
IL
IL
IL
IS
IS
6b/ Two points calibration
5b
IL
Figure 77
longstoryshort _empirestricksback .vsd
Calibration Strategy to Improve Current Sense Accuracy
Drawing 1 describes the ideal behavior expected. The load current is recopied with a certain reduction factor kILIS.
Drawing 2 provides the missmatch in the number cells. Going back to Figure 66, the ratio between the number of
cells of T1 and T2 give the kILIS factor. A missmatch in the cells of T1 and / or T2 causes the kILIS factor to be
different to the expected theoretical value. Drawing 3 describes the influence of the non perfect offset of the opamp.
Drawing 4 shows the offset compensation via G.B.R. Drawing 5 exhibits the kILIS accuracy the device can provide
over temperature, production spread, supply voltage etc...
Drawing 5a demonstrates the benefit of one point calibration. During testing of the module, the micro controller
learns the real sense current IIS_REAL, at a known IL_ CAL load current for calibration. The current sense is then
guaranteed to be in a conic stripe. The calibration in this case is compensating the offset of the op-amp.
Drawing 5b demonstrates the benefit of a two points calibration. Knowing IIS_REAL1 and IIS_REAL2, giving resp. IL_CAL1
and IL_CAL2, the current sense is then guaranteed to be in stripe. On top of the offset compensation, the calibration
procedure has compensated the missmatch in the kILIS factor.
9.8
Current Sense and PWM
(Refer to Chapter 7.6 for details). During PWM, the application still requires diagnosis. Of primary importance is
short circuit to GND information which is used to limit the number of short circuit events. (Refer to Chapter 8.2.7).
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PWM usage with current sense diagnosis can be limited by the inherent timing limitations of PROFET™ +. The
aim is to give valid current sense information as fast as possible.
tsIS(ON), the time required for the IN pin to transition from LOW to HIGH limits the minimum ON time necessary to
get valid sense information. tsIS(FAULT) also limits the minimum ON time to get valid short circuit information.
Table 15 sums up the minimum PWM duty cycle which can be used with a PROFET™ +.
Table 15
PROFET™ + PWM Timing Limitation
Parameter
Period
min duty cycle at the output
min duty cycle at the output for
diagnostic
Symbol Formula
fPWM =
fPWM =
fPWM =
fPWM =
100Hz
200Hz
400Hz
1kHz
5
2.5
1
ms
1.6
3.2
8
%
5
10
25
%
TPWM
1/fPWM
10
dOUT_MIN tOFF_delay/TPWM 0.8
dMIN
tsIS(FAULT) /T
2.5
Unit
When the current is established in the Power DMOS, the sense signal IIS takes far much lower time to establish.
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10
The Micro Controller Interface
10.1
GND Pin
Although the GND pin is not directly interfaced to the micro controller, GND is of primary importance in controlling
a PROFET™ +. Figure 78 shows the ideal GND protection circuitry. What ever the GND circuit chosen in the
application, this circuit can be shared with other devices having the same battery feed and only with these ones.
•
•
•
Region 1. For current in the magnitude of operating current (10mA or below), the voltage drop should be kept
to a minimum as a shift in the PROFET™ + GND potential leads to a shift in the input threshold.
Regions 2. To provide overvoltage protection for voltages above the breakdown voltage, the current through
the Zener diode ZD(AZ) must be limited to a few tens of milliamps. This limit does not apply for ESD protection.
Region 3. This ensures the necessary current limitation when reverse polarity is applied. The current in this
mode should be as low as possible (below IGND) to reduce the loss generated in the diode ZD(AZ).
IGND
2
10mA mini
GND
IGND
1
+
VGND
-
As small as possible
3
VGND
As small as possible
At worst 1.2V
GND ideal circuitry. vsd
Figure 78
Ideal GND Circuitry
10.1.1
GND Resistor
A compromise must be found in the GND resistor value which approximates the different regions of the above
characteristic. For over voltage (refer to Chapter 8.8) and reverse polarity (refer to Chapter 8.9) protection, the
value of the GND resistor should be as high as possible. The upper value is restricted by the ground shift potential
(VGND = RGND x IGND) caused by the operating current flowing via the GND pin. In practice, a value of 150Ω per
chip protected has proven satisfactory.
The main disadvantage of the GND resistor is high power dissipation in the event of an applied reverse polarity
(VS(REV)² / RGND). This leads to a relatively large resistor on the PCB. With 16V, 1.7W. 1206 package is necessary.
A capacitor can be used in parallel with the resistor which to limit the influence of IGND variation during switching
of the channel. A capacitor placed between VS pin and GND will filter the charge pump perturbations.
10.1.2
GND Diode
To protect against reverse polarity events, a diode can be used. The reverse voltage is limited by the reverse
breakdown voltage of the diode or the losses in the PROFET™ + generated by the load current. A suggested diode
is the BAS52-02V. The diode approximates only regions 1 and 3 of Figure 78 and does not protect against over
voltage or loss of battery. Refer to Chapter 8.5. In this particular case, a 1kΩ resistor can be used in parallel with
the diode. PROFET™ + are then limited in case of over voltage.
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10.1.3
Different Ground for One System
At least two different Grounds are defined at a system level and usually three are necessary for optimum design.
The chassis GND is the system 0V reference. The module GND is the 0V module reference. The module GND is
sometimes split into digital GND (reference voltage for the digital sections such as the voltage regulator, micro
controller, A/D converter, CAN transceivers etc.) and power GND (reference voltage for the power elements such
as LSS, HSS, H bridges etc.). A fourth GND can also be defined which corresponds to the device GND. These
different GNDs are shown in Figure 79. For simplification it doesn't describe the redundancy of GND wiring
connection as shown in Figure 8. In a real system, the GND schematic can be even more complicated!
VBAT
VBAT
OUT
OUT
Vcc
µC
GND
I/O
I/O
Vcc
IN
I/O
DEN
I/O
A/D
IS
µC
DEVICE
GND
GND
I/O
I/O
IN
DEN
DEVICE
GND
I/O
A/D
IS
GND
circuit
GND
circuit
DIGITAL
GND
ANALOG
GND
COMMON
MODULE GND
GND SEPARATED
ANALOG GND
DIGITAL GND
MODULE GND
CHASSIS
CHASSIS
Figure 79
GND Definition
10.1.4
Loss of Ground
GND concept.svg
According to Figure 79, up to four GND can be lost. In case of module GND loss, the PROFET™ + automatically
turns OFF or remains OFF. In case of analog or device loss of GND, the micro controller can play the role of a
parasitic GND via the logic inputs. To avoid this, a serial resistor (e.g 4.7kΩ) should be placed in between each
micro controller and PROFET™ + interfaces.
10.2
Digital Pins
All the digital pins of PROFET™ + are identical. The digital pins are voltage driven. An internal current source is
used to default the digital pins to logic level 0. Where a pin is not required, it is recommended to leave it open. If
this is not done, the ESD diode can be destroyed.
In binary digital circuits, there are two distinct voltage levels which represent the two binary states. In order to allow
for the inevitable components tolerances, two voltage ranges are usually defined to represent these states. As
shown in Figure 80, if the signal voltage lies in the range VIN(AMR)min to VIN(L), it is interpreted (by the power device)
as a logic 0. If the signal voltage falls in the range of VIN(H) to VIN(AMR)max, it is interpreted as a logic 1. The two
voltage bands are separated by a region in which the logic state is undefined. Voltages in this undefined region
should be avoided.
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DESTRUCTION
VIN(AMRmax)
VIN(H)
LOGIC 1 = ACTIVATION
VIN(L) UNDEFINED
LOGIC 0 = INHIBITION
VIN(AMRmin)
DESTRUCTION
input voltage.vsd
Figure 80
Two Distinct Voltage Ranges used to Represent two Values of Binary Variables
10.2.1
Absolute Maximum Rating
During two normal conditions, absolute maximum rating on input pins can be met.
Figure 81 describes the reason for the 6V absolute maximum rating. During the OFF state of the module, where,
the voltage regulator is OFF, a wake event is generated either by the communication (eg CAN, LIN, etc...), or by
a digital input. In such a case, the voltage at the I/O of the micro controller is limited by the Zener diode at the VDD
line and the ESD structure internally the micro controller. The current is limited by the serial resistor.
.
LDO is OFF (module in sleep mode )
LDO
VBAT
PROFET TM+
Suppressing diode
min 5.5 max 6V
VDD
+
VDD
Digital contact
Eg : door open
VDD
VBAT
-
CTC
~100µA
28...100k
+
+
68k
VBAT
1k
(wetting current)
-
6.5V
Micro controller
6V for I_0 pins.svg
Figure 81
Normal Application Condition to reach Absolute Maximum Rating
As shown in Figure 82, in order to activate the channel, it is necessary to pull the input pin up to VBAT, as it cannot
be assumed that the voltage regulator is operating. Nevertheless, the voltage at the input should not exceed 6V
permanently. To bypass the microcontroller, the easiest way is to use two diodes, such BAV 70S, in an OR
combination. The battery voltage is divided by resistor RLH1 and RLH2. A ratio of 1/3 will guarantee that even with
18V battery voltage, the input pin will not see more than 6V while a low battery voltage case such as 8V will provide
sufficient voltage at the input to guarantee the switching ON.
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VBAT
RLH1
Limp home logic
RLH2
VDD
PROFETTM +
RI/O
GPIO
+
IIN
IN
+ Vdrop +
LOGIC
IIN(H)
VIN
Micro controller VI/O
GND
-
-
+
IGND
VGND
ZGND
Limp Home for input.svg
Figure 82
Limp Home Scenario
10.2.2
High level input voltage
With an input signal in this region, the digital circuitry will determine the input to be a high logic level and thus will
turn the output ON or keep it ON. The application must ensure that the minimum voltage applied to the input pin
is higher than VIN(H) to guarantee an ON condition. The micro-controller specification usually provides the minimum
output voltage for a logic 1 signal. As an umbrella specification, Infineon considers VIN(H)_MIN = 3.6V. Adding a
resistor RI/O between the micro-controller and the power device is recommended. However, the voltage drop
across this resistor must also be considered in the design. The equivalent circuit is described in Figure 83 where
the VIOMIN value defined by Equation (17) must be guaranteed.
V IOmin = V IN ( H )min + R IO × I INmax + Z GND × I GND
(17)
All parameters are given in the respective datasheets. Please note that the voltage drop caused by the resistor
RI/O severely limits the number of devices which can be driven from one I/O pin of the microcontroller.
VDD
PROFETTM +
RI/O
GPIO
+
IIN
IN
+ Vdrop +
LOGIC
IIN(H)
VIN
Micro controller
VI/O
GND
-
IGND
VGND
ZGND
-
-
Figure 83
+
High level Equivalent Circuit
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The purpose of the IIN(H) current source is to guarantee the device is OFF when the micro controller pin is floating,
(e.g. during reset, un-powered, etc...).
10.2.3
Undefined region
The undefined region contains the switching thresholds for ON and OFF. The exact value VTH where this switching
takes place is unknown and dependant on the device manufacturing process and temperature. To avoid crosstalk and parasitic switching, hysteresis is implemented. This ensures a certain immunity to noise.
This noise immunity can be defined, assuming that the exact turn ON and turn OFF thresholds are known. As an
example, a rising or falling signal with parasitic noise will see several ON / OFF states before going to a stable
state. Figure 84 gives an example of this situation. At turn ON, the parasitic noise is sufficiently intrusive to turn
the device ON and OFF. At turn OFF, the parasitic noise is filtered by the hysteresis circuitry. The bigger the
hysteresis, the higher the immunity to noise, but the difference between VIN(H)_MIN and VIN(L)_MAX also increases,
limiting the application's range. PROFET™ + use a typical hysteresis voltage of 200mV.
VIN
VIN(hysteresis)
VTH
t
ON
Figure 84
OFF
ON
OFF
OFF
parasitic input voltage.vsd
Benefit of the Hysteresis for Immunity to Noise
The hysteresis value is not tested during production, due to the test complexity.
10.2.4
Low level input voltage
With an input signal in this region, the digital circuitry will determine the input to be a low logic level and thus will
turn the output OFF or keep it OFF. The application must ensure that the maximum voltage applied to the input
pin is lower than the VIN(L)max voltage to guarantee an OFF condition. As umbrella specification, Infineon consider
VIN(L)_MAX = 1.1V. Refer to Figure 85 for details.
The equivalent circuit is described in Figure 85 where the VIOmin value defined by Equation (18) must be
guaranteed.
V IOMAX = V IN ( L )MAX + R IO × I INmax + Z GND × I GND
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The Micro Controller Interface
VDD
PROFETTM +
RI/O
GPIO
IIN
IN
LOGIC
+ Vdrop -
+
+
IIN(L)
VIN
Micro controller
GND
VI/O
+
VGND
IGND
ZGND
-
-
Low level input voltage.svg
Figure 85
Low level Equivalent Circuit
10.3
Sense Pin
As described in Chapter 9.1, the current sense function is driven by a current generator. The sense pin is a
combination of two current generators, one for nominal conditions and one for fault conditions. Micro-controllers
measure voltage, not current hence a sense resistor is required. To find the value of the sense resistor RIS, it is
important to know the maximum load current amplitude the system is required to diagnose.
10.3.1
Maximum Load Current
To define the maximum current IL(NOM)_MAX which can flow in the power DMOS, a solution is to define the minimum
PWM duty cycle at the maximum battery voltage. For example, assuming a duty cycle of 8% as a minimum
functionality (as an example for lamp dimming) and a maximum 18V battery voltage, it is equivalent to start the
PWM at a battery voltage of 5V. Determining the lamp resistance at 5V, out of Equation (1), it is possible then to
determine the maximum current which flows at 18V battery voltage. Refer to Figure 86 with a 27W bulb example.
Out of the graph, it is seen the maximum current which can flow in a 27W during a PWM of 8% at 18V is roughly
5A. A system using BTS5045-2EKA to drive 27W bulb should be able to diagnose 5A current. With IL(NOM)_MAX
known, the minimum current ratio, kILIS_MIN at this point can be determined. With this value, the maximum sense
current the PROFET™ + can provide is IIS_MAX is known. All current above this value will be considered as a short
circuit. Taking into account the micro controller supply VDD, the maximum sense resistor is RIS = VDD / IIS_MAX. Refer
to Figure 87 and Table 16.
Note that the PROFET™ + current sense range is limited by the maximum current the P channel MOSFET can
provide. Refer to Figure 66. Table 17 summurizes the maximum load currents PROFET™ + devices can
diagnose.
Table 16
Optimized RIS calculation example
20mΩ
30mΩ
45mΩ
90mΩ
120mΩ 180mΩ
Load planned
(W)
2x27+5 2x21
27+5
21
2x5
1x5
Load current
max (A)
11
8
8.6
4.0
1.9
0.8
1870
1305
1305
480
480
1.2
0.8
1.6
1.2
2.9
kILIS mini 2610
RIS (kΩ) 1.2
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15 App. Note
The Micro Controller Interface
6
5,5
Lamp current in dimming
Lamp current in power limitation
Lamp current in DC
5
Load current (A)
4,5
4
3,5
3
2,5
2
1,5
1
2
4
6
10
12
14
16
Battery Voltage (V)
r
Figure 86
8
18
maximum load current . vsd
Maximum Current with 8% PWM Function of the Battery Voltage. 27W Lamp
16
I sense all max
I sense max I fault min
14
I sense typical
Sense Current IIS (mA)
I sense min I fault max
12
I sense all min
10
8
6
4
2
0
0
20
40
60
Load Current I L (A)
80
Figure 87
Sense Current Function of the Load Current with BTS5020-2EKA
Table 17
PROFET™ +s Maximum Diagnosable Current
20mΩ
30mΩ
45mΩ
90mΩ
100
current sense current .vsd
120mΩ 180mΩ
Target Load 2x27W 2x27W 27W 21W 2x5W 5W
+5W Maximum current 11A 8.6A 5A 4.3A 1.8A 0.9A
with 8% PWM k ratio typical 3000 2150 1500 1500 550 550
ILIS
Diagnosable load 15A 11A 8A 8A 2.8A 2.8A
current I LMAX Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
The Micro Controller Interface
10.3.2
Minimum Load Current
The minimum load current the PROFET™ + devices will experience is the open load. As described in Chapter 6.3
and Chapter 9.6.3, in that case, the minimum current IIS(OL) shall be too small to be detectable by the RIS defined
in Chapter 10.3.1. In such a case, the usage of an additional sense resistor RIS_LOWLOAD and a switch has to be
considered. Figure 88 sketches the circuitry to be employed. A suggested value for RIS_LOWLOAD is 10kΩ.
+
VS
VDD
PROFETTM +
+
Micro controller
IS
IIS
A/D
+
+
RA/D
VS
VDD
RIS
VA/D
RIS_LOWLOAD
VIS
I/O
-
-
low high load current switch.svg
Figure 88
Low Load Current Detection Circuitry
10.3.3
Sense Pin Voltage
The sense pin has no particular clamping structure, except the ESD structure, referenced to VS. It means if no
external limitation is applied, VIS can go up to VS. Refer to Figure 89. To protect the micro controller, a serial
resistor is necessary, as a minimum. In that case, the micro controller protection diode will limit the voltage while
the serial resistor will limit the current.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15 App. Note
The Micro Controller Interface
+
VS
IIS_LIN
IIS_FAULT
VDD
+
VS
µC
IS
VDiode
IA/D
A/D
VA/D
RA/D
-
+
VDD
IIS
+
+
+
RIS
VA/D
VIS
-
-
-
sense for the baleze single.svg
Figure 89
Current Sense Circuitry and Minimum Protection Circuitry
It is also possible to use a Zener diode to clamp against over voltage. This improves the over voltage robustness
of the system. Refer to Figure 90. The IA/D is dramatically reduced and most of the voltage is clamped by the Zener
diode. RSENSE is necessary to protect the sense structure from destructive power dissipation under normal
conditions and from reverse polarity.
+
VS
IIS_LIN
IIS_FAULT
VDD
VS
+
µC
IS
VDiode
VDD
-
+
VA/D
+
IA/D
-
RA/D
A/D
+
IZ
+
VA/D
VZ
VSENSE
RSENSE
+
RIS
-
-
IIS
+
-
VIS
-
sense for the baleze single improved.svg
Figure 90
Current Sense Circuitry with Improved Protection Circuitry
It is important to notice the power in the sense circuitry (IIS_LIN; IIS_FAULT) is not negligible, thus the VIS should not
be limited, either by too low sense resistor, either by Zenering.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
PROFET™ + Scalability
11
PROFET™ + Scalability
PROFET™ + belongs to a family. Every electrical parameter is scaled around the RDS(ON) value. The RDS(ON) value
scales mainly kILIS ratio, EAS capability and IL(SC) current limitation. All other parameters are identical!
11.1
High Ohmic Family
Table 18 summarizes the difference between the high ohmic PROFET™ +.
Table 18
Difference in High Ohmic Family
Number
Parameter
Symbol
BTS
5020
BTS
5030
BTS
5045
BTS
5090
BTS
5120
BTS
5180
Unit
Overview
Load
PLOAD
2*27+5
2*27
1*27+5
1*27
1*21
2*10
1*10
2*5
1*5
W
Overview
Typical kilis ratio
kILIS
PTOT
EAS
RthJA
RDS(ON)
3000
2150
1500
1500
550
550
-
Inom1
Inom21)
-IL(INV)1)
P_4.1.22
Maximum power
P_4.1.23
Inductive energy
P_4.3.2
Junction to ambient
P_5.5.1
P_5.5.21
On state resistance
P_5.5.2
P_5.5.3
Nominal load current
P_5.5.9
Inverse current
capability
P_5.5.19
1.9
1.9
1.6
1.6
1.4
1.4
W
80
60
40
30
15
10
mJ
33
33
35
35
40
40
K/W
44
20
60
30
90
45
180
90
240
120
360
180
mΩ
7
5
6
4
5
3
3.5
2.5
3
2
2
1.4
A
5
4
3
2.5
2
1.4
A
1
1
0.675
0.675
0.34
0.12
mJ
1
1
0.675
0.675
0.3375
0.12
mJ
P_6.6.4
EON
Switch OFF energy
EOFF
Load current limitation IL5(SC)
50
65
80
36
47
57
25
32
40
20
30
40
9
12
15
8
11
15
A
P_6.6.7
Load current limitation IL28(SC)
25
32
40
18
23
29
12
16
20
10
15
20
4
6
8
2
4
8
A
P_6.6.12
Short circuit average
current after several
minutes of thermal
toggling
8
7
6
6
3.5
3
A
P_7.5.2
Open load threshold in IIS(OL)
ON state
4
5.6
8
8
21
21
µA
P_7.5.9
IL for kILIS1
IL1
0.5
0.5
0.5
0.5
0.25
0.25
A
P_7.5.10
IL for kILIS2
IL2
2
2
1
1
0.5
0.5
A
P_7.5.11
IL for kILIS
IL3
4
4
2
2
1
1
A
P_7.5.12
IL for kILIS4
IL4
7
7
4
4
2
2
A
P_5.5.20
Switch ON energy
IL(RMS)
1) For dual channel only
Application Note
Smart High-Side Switches
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App. Note
Appendix
12
Appendix
12.1
PWM Power Losses Calculations
(19)
P PWM = P RON + P SW
Power losses are splitted in losses during RDS(ON) phases PRON and switching phases PSW.
(20)
2
× t ON × F
P RON = R DSON × I PWM
Power losses in the RDS(ON) phases depends on the PWM frequency F, the time ON tON, the RDS(ON) and the load
current IPWM.
(21)
V PWM 2
d = F × t ON = -----------------2
V BAT
The duty cycle is dependant on the VPWM voltage where PWM starts (usually 13.2V) and the effective battery
voltage VBAT.
(22)
2
I
2
PWM
P RON = R DSON × F × V PWM × --------------- = K 1 ×
2
V BAT
2
I PWM
--------------2
V BAT
Replacing Equation (21) in Equation (20), and defining a constant value K1 to simplify the term.
(23)
V BAT
I PWM = -----------------R LAMP
The load current IPWM is depending on battery voltage VBAT and RLAMP, resistor of the lamp, constant due to PWM.
(24)
2
K1
K 1 × V BAT
P RON = ---------------------------------------- = ------------------ = K2
2
2
2
R LAMP
V BAT × R LAMP
Replacing Equation (23) in Equation (22), and defining a constant value K2 to simplify the term, power losses in
the RDSON phase is constant!
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
Appendix
(25)
1 V BAT I PWM
P SW = 2 × P SWON = 2 × t SWON × --- × --------------- × --------------2
2
2
Switching losses PSW are twice the PSWON (assuming switch ON and OFF is symetric).
(26)
2
V BAT
1
P SW = t SWON × --- × ------------------4 R
LAMP
Replacing Equation (23) in Equation (26)
(27)
2
P SW = K 3 × V BAT
PSW is depeding on the VBAT².
2
P PWM = K 2 + K × V BAT
3
Replacing Equation (24) and Equation (27) in Equation (19)
12.2
Open Load Resistor Calculation
The maximum acceptable value for ROL, (open load pull up resistor) is searched for.
R DIRT
V BAT – 3V < ---------------------------------- × V BAT
R DIRT + R OL
The voltage at the output VOUT should be higher than the highest voltage possible understood as a present load.
This voltage is given by the voltage divider formed by RDIRT and ROL.
V BAT × ( R DIRT + R OL ) – 3V × ( R DIRT + R OL ) < R DIRT × V BAT
Enlarging the equation,
( V BAT – 3V ) × R OL < 3V × R DIRT
Symplifying and bringing ROL on the right hand side.
Application Note
Smart High-Side Switches
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Rev 1.0, 2010­12­15
App. Note
13
Revision History
Table 21
Revision History
Version
Date
1.0
2010.12.15 All First release
Application Note
Smart High-Side Switches
Chapter
Change
80
Rev 1.0, 2010­12­15
Edition 2010­12­15
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2010 Infineon Technologies AG
All Rights Reserved.
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