ONSEMI NCV890101

NCV890101
1.2A, 2MHz Automotive
Buck Switching Regulator
The NCV890101 is a fixed−frequency, monolithic, Buck switching
regulator intended for Automotive, battery−connected applications
that must operate with up to a 36V input supply. The regulator is
suitable for systems with low noise and small form factor
requirements often encountered in automotive driver information
systems. The NCV890101 is capable of converting the typical 4.5 V to
18 V automotive input voltage range to outputs as low as 3.3 V at a
constant switching frequency above the sensitive AM band,
eliminating the need for costly filters and EMI countermeasures. Two
pins are provided to synchronize switching to a clock, or to another
NCV890101. The NCV890101 also provides several protection
features expected in Automotive power supply systems such as current
limit, short circuit protection, and thermal shutdown. In addition, the
high switching frequency produces low output voltage ripple even
when using small inductor values and an all−ceramic output filter
capacitor − forming a space−efficient switching regulator solution.
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MARKING DIAGRAM
DFN10
CASE 485C
A
= Assembly Location
L
= Wafer Lot
Y
= Year
W
= Work Week
G
= Pb−Free Device
(*Note: Microdot may be in either location)
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
ORDERING INFORMATION
Internal N−Channel Power Switch
Low VIN Operation Down to 4.5 V
High VIN Operation to 36 V
Withstands Load Dump to 40 V
2 MHz Free−running Switching Frequency
Auto−synchronizes with Other NCV890101 or to an
External Clock
Logic level Enable Input Can be Directly Tied to
Battery
1.4 A (min) Cycle−by−Cycle Peak Current Limit
Short Circuit Protection enhanced by Frequency
Foldback
±1.75% Output Voltage Tolerance
Output Voltage Adjustable Down to 0.8 V
1.4 Millisecond Internal Soft−Start
Thermal Shutdown (TSD)
CDRV
CIN
SYNC
OUT
EN
1 VIN
2 DRV
4 GND
5 EN
• Low Shutdown Current
• Wettable Flanks − DFN
• NCV Prefix for Automotive and Other Applications
•
Requiring Unique Site and Control Change
Requirements; AEC−Q100 Qualified and PPAP
Capable
These Devices are Pb−Free and are RoHS Compliant
Applications
•
•
•
•
L1
SW 10
CBST
DFW
BST 9
3 SYNCO SYNCI 8
See detailed ordering and shipping information in the package
dimensions section on page 14 of this data sheet.
Audio
Infotainment
Safety − Vision Systems
Instrumentation
DBST
NCV890101
VIN
V8901
01
ALYWG
G
SYNC IN
VOUT
COUT
RFB1
FB 7
RFB2
COMP 6
RCOMP
CCOMP
Figure 1. Typical Application
© Semiconductor Components Industries, LLC, 2013
February, 2013 − Rev. 1
1
Publication Order Number:
NCV890101/D
NCV890101
CDRV
VIN
VIN
DBST
L1
SW
VOUT
CIN
3.3 V
Reg
DRV
SYNCO
DFW
BST
Oscillator
PWM
LOGIC
ON
OFF
SYNCI
Sync
Out
In
+
+ S
Sync In
+
−
FB
GND
1.2 A
TSD
+
−
Sync Out
CBST
+
Soft−Start
RESET
COMP
VOLTAGES
MONITORS
RCOMP
Enable
EN
CCOMP
Figure 2. NCV890101 Block Diagram
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2
COUT
NCV890101
MAXIMUM RATINGS
Rating
Symbol
Min/Max Voltage VIN
Max Voltage VIN to SW
Min/Max Voltage SW
Min Voltage SW − 20ns
Value
Unit
−0.3 to 40
V
40
V
−0.7 to 40
V
−3.0
V
Min/Max Voltage BST
−0.3 to 40
Min/Max Voltage BST to SW
−0.3 to 3.6
V
Min/Max Voltage on EN
−0.3 to 40
V
Min/Max Voltage COMP
−0.3 to 2
V
Min/Max Voltage FB
−0.3 to 18
V
Min/Max Voltage SYNCO
−0.3 to 3.6
V
Min/Max Voltage DRV
−0.3 to 3.6
V
−0.3 to 6
V
50
°C/W
Min/Max Voltage SYNCI
Thermal Resistance, 3x3 DFN Junction−to−Ambient*
RqJA
Storage Temperature range
Operating Junction Temperature Range
ESD withstand Voltage
Human Body Model
Machine Model
Charge Device Model
Moisture Sensitivity
Peak Reflow Soldering Temperature
−55 to +150
°C
TJ
−40 to +150
°C
VESD
2.0
200
>1.0
kV
V
kV
MSL
Level 1
260
°C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
*Mounted on 1 sq. in. of a 4−layer PCB with 1 oz. copper thickness.
RECOMMENDED OPERATING CONDITIONS:
Rating
VIN Range
Ambient Temperature Range
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3
Value
Unit
4.5 to 36
V
−40 to 105
°C
NCV890101
VIN
1
10
SW
DRV
2
9
BST
SYNCO
3
8
SYNCI
GND
4
7
FB
EN
5
6
COMP
(Top View)
Figure 3. Pin Connections
PIN FUNCTION DESCRIPTIONS
Pin No.
Symbol
Description
1
VIN
Input voltage from battery. Place an input filter capacitor in close proximity to this pin.
2
DRV
Output voltage to provide a regulated voltage to the Power Switch gate driver.
3
SYNCO
4
GND
5
EN
6
COMP
Synchronization output. Turn−on of the Power Switch causes the SYNCO signal to fall. SYNCO rises
half a switching period later. Connecting to the SYNCI pin of another NCV890101 causes them to switch
out−of−phase
Battery return, and output voltage ground reference.
This TTL compatible Enable input allows the direct connection of Battery as the enable signal. Grounding
this input stops switching and reduces quiescent current draw to a minimum.
Error Amplifier output, for tailoring transient response with external compensation components.
7
FB
Feedback input pin to program output voltage, and detect pre−charged or shorted output conditions.
8
SYNCI
Synchronization input. Connecting an external clock to the SYNCI pin synchronizes switching to the
rising edge of the SYNCI voltage.
9
BST
Bootstrap input provides drive voltage higher than VIN to the N−channel Power Switch for optimum
switch RDS(on) and highest efficiency.
10
SW
Switching node of the Regulator. Connect the output inductor and cathode of the freewheeling diode to
this pin.
Exposed
Pad
Connect to Pin 4 (electrical ground) and to a low thermal resistance path to the ambient temperature
environment.
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NCV890101
ELECTRICAL CHARACTERISTICS (VIN = 4.5 V to 28 V, VEN = 5 V, VBST = VSW + 3.0 V, CDRV = 0.1 mF, Min/Max values are valid
for the temperature range −40°C ≤ TJ ≤ 150°C unless noted otherwise, and are guaranteed by test, design or statistical correlation.)
Symbol
Conditions
Max
Unit
Quiescent Current, shutdown
IqSD
VIN = 13.2 V, VEN = 0 V, TJ = 25°C
5
mA
Quiescent Current, enabled
IqEN
VIN = 13.2 V
3
mA
UVLO Start Threshold
VUVLSTT
VIN rising
4.1
4.5
V
UVLO Stop Threshold
VUVLSTP
VIN falling
3.9
4.4
V
UVLO Hysteresis
VUVLOHY
0.1
0.2
V
Logic Low
VENLO
0.8
Logic High
VENHI
Parameter
Min
Typ
QUIESCENT CURRENT
UNDERVOLTAGE LOCKOUT − VIN (UVLO)
ENABLE (EN)
Input Current
IEN
8
tSS
0.8
V
2
V
30
mA
1.4
2.0
ms
0.8
0.814
V
1
mA
SOFT−START (SS)
Soft−Start Completion Time
VOLTAGE REFERENCE
FB Pin Voltage during regulation
VFBR
COMP shorted to FB
0.786
IFBBIAS
VFB = 0.8 V
0.25
gm
VCOMP = 1.3 V
4.5 V < VIN < 18 V
20 V < VIN < 28 V
0.6
0.3
ERROR AMPLIFIER
FB Bias Current
Transconductance
gm(HV)
Output Resistance
COMP Source Current Limit
ROUT
1
0.5
1.5
0.75
1.4
ISOURCE
VFB = 0.63 V, VCOMP = 1.3 V
4.5 V < VIN < 18 V
20 V < VIN < 28 V
75
40
COMP Sink Current Limit
ISINK
VFB = 0.97 V, VCOMP = 1.3 V
4.5 V < VIN < 18 V
20 V < VIN < 28 V
75
40
Minimum COMP voltage
VCMPMIN
VFB = 0.97 V
0.2
FSW
FSW(HV)
4.5 < VIN < 18 V
20 V < VIN < 28 V
1.8
0.9
mmho
MW
mA
mA
0.7
V
2.2
1.1
MHz
OSCILLATOR
Frequency
2.0
1.0
VIN FREQUENCY FOLDBACK MONITOR
Frequency Foldback Threshold
VIN rising
VIN falling
VFLDUP
VFLDDN
Frequency Foldback Hysteresis
VFLDHY
VFB = 0.63 V
18.4
18
0.2
1. Not tested in production. Limits are guaranteed by design.
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5
20
19.8
0.3
0.4
V
V
NCV890101
ELECTRICAL CHARACTERISTICS (VIN = 4.5 V to 28 V, VEN = 5 V, VBST = VSW + 3.0 V, CDRV = 0.1 mF, Min/Max values are valid
for the temperature range −40°C ≤ TJ ≤ 150°C unless noted otherwise, and are guaranteed by test, design or statistical correlation.)
Parameter
Symbol
Conditions
Min
SYNCO Output Pulse Duty Ratio
D(SYNC)
CLOAD = 40 pF
40
SYNCO Output Pulse Falltime
tR(SYNC)
CLOAD = 40 pF, 90% to 10%
SYNCO Output Pulse Risetime
tF(SYNC)
CLOAD = 40 pF, 10% to 90%
SYNCI Input Resistance to ground
RH(SYNC)
VSYNCI = 5.0 V
SYNCI Input High Threshold Voltage
VHSYNC
SYNCI Input Low Threshold Voltage
VLSYNC
SYNCI High Pulse Width
tHSYNCI
SYNCI Low Pulse Width
tLSYNCI
Typ
Max
Unit
60
%
SYNCHRONIZATION
4
ns
4
50
ns
200
k
2.0
V
0.8
V
VSYNC > max VHSYNC
40
ns
VSYNC < min VLSYNC
40
ns
External Sync Frequency
FSYNCI
Master Reassertion Time
tI(SYNC)
Time from last rising SYNCI edge
to first un−synchronized turn−on.
1.8
Sramp
Sramp(HV)
4.5 < VIN < 18 V
20 V < VIN < 28 V
2.5
650
MHz
ns
SLOPE COMPENSATION
Ramp Slope (Note 1)
(With respect to switch current)
0.7
0.25
1.3
0.6
A/ms
POWER SWITCH
ON Resistance
RDSON
VBST = VSW + 3.0 V
650
mW
Leakage current VIN to SW
ILKSW
VEN = 0 V, VSW = 0, VIN = 18 V
10
mA
Minimum ON Time
tONMIN
Measured at SW pin
70
ns
Minimum OFF Time
tOFFMIN
Measured at SW pin
At FSW = 2 MHz (normal)
At FSW = 500 kHz (max duty cycle)
45
ns
30
30
50
70
1.4
1.55
1.7
A
400
200
24
500
250
32
600
300
40
kHz
VDRV
3.1
3.3
3.5
V
DRV POR Start Threshold
VDRVSTT
2.7
2.9
3.05
V
DRV POR Stop Threshold
VDRVSTP
2.5
2.8
3.0
V
45
mA
50
mV
PEAK CURRENT LIMIT
Current Limit Threshold
ILIM
SHORT CIRCUIT FREQUENCY FOLDBACK
Lowest Foldback Frequency
Lowest Foldback Frequency − High Vin
Hiccup Mode
FSWAF
FSWAFHV
FSWHIC
VFB = 0 V, 4.5 V < VIN < 18 V
VFB = 0 V, 20 V < VIN < 28 V
VFB = 0 V
GATE VOLTAGE SUPPLY (DRV pin)
Output Voltage
DRV Current Limit
IDRVLIM
VDRV = 0 V
16
OUTPUT PRECHARGE DETECTOR
VSSEN
20
Activation Temperature (Note 1)
TSD
150
190
°C
Hysteresis (Note 1)
THYS
5
20
°C
Threshold Voltage
35
THERMAL SHUTDOWN
1. Not tested in production. Limits are guaranteed by design.
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NCV890101
VIN = 13.2 V
7
6
5
4
3
2
1
0
−50
−25
0
25
50
75
100
125
IqEN. ENABLED QUIESCENT CURRENT
(mA)
8
150
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
−50
25
50
75
100
125
Figure 5. Enabled Quiescent Current vs.
Junction Temperature
4.5
4.4
4.3
4.2
4.1
4.0
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
150
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
3.7
−50
−25
VFBR. FB REGULATION VOLTAGE (V)
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0
25
50
75
100
125
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
150
Figure 7. UVLO Stop Threshold vs. Junction
Temperature
2.4
−25
150
4.6
Figure 6. UVLO Start Threshold vs. Junction
Temperature
tSS. SOFT−START DURATION (ms)
0
Figure 4. Shutdown Quiescent Current vs.
Junction Temperature
4.6
0.6
−50
−25
TJ. JUNCTION TEMPERATURE (°C)
4.7
3.9
−50
2.6
TJ. JUNCTION TEMPERATURE (°C)
VUVLSTP. UVLO STOP THRESHOLD (V)
VUVLSTT. UVLO START THRESHOLD (V)
IqSD. SHUTDOWN QUIESCENT CURRENT
(mA)
TYPICAL CHARACTERISTICS CURVES
150
0.85
0.84
0.83
0.82
0.81
0.80
0.79
0.78
0.77
0.76
0.75
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
TJ. JUNCTION TEMPERATURE (°C)
Figure 8. Soft−Start Duration vs. Junction
Temperature
Figure 9. FB Regulation Voltage vs. Junction
Temperature
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7
150
NCV890101
TYPICAL CHARACTERISTICS CURVES
100
ISOURCE. ERROR AMPLIFIER
SOURCING CURRENT (mA)
gm. ERROR AMPLIFIER
TRANSCONDUCTANCE (mS)
1.4
1.2
1.0
VIN = 4.5 V
0.8
0.6
VIN = 28 V
0.4
0.2
−50
−25
0
25
50
75
100
125
70
60
50
VIN = 28 V
40
30
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
TJ. JUNCTION TEMPERATURE (°C)
Figure 10. Error Amplifier Transconductance
vs. Junction Temperature
Figure 11. Error Amplifier Max Sourcing
Current vs. Junction Temperature
FSW. OSCILLATOR FREQENCY (MHz)
90
VIN = 4.5 V
80
70
60
50
VIN = 28 V
40
30
20
−50
−25
0
25
50
75
100
125
150
VIN = 13.2 V
2.0
1.8
1.6
1.4
1.2
VIN = 28 V
1.0
0.8
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
Figure 12. Error Amplifier Max Sinking Current
vs. Junction Temperature
Figure 13. Oscillator Frequency vs. Junction
Temperature
19.6
56
19.4
55
19.2
VFLDUP
19.0
VFLDDN
18.8
18.6
18.4
18.2
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
150
150
54
53
52
51
50
49
48
−50
Figure 14. Rising Frequency Foldback
Threshold vs. Junction Temperature
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
Figure 15. SYNCO Pulse Duty Ratio vs.
Junction Temperature
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8
150
2.2
TJ. JUNCTION TEMPERATURE (°C)
D(SYNC). SYNCO PULSE DUTY
RATIO (%)
ISINK. ERROR AMPLIFIER SINKING
CURRENT (mA)
VIN = 4.5 V
80
20
−50
150
100
VFLDUP. VFLDDN, FREQ. FOLDBACK
THRESHOLD (V)
90
150
NCV890101
TYPICAL CHARACTERISTICS CURVES
900
RDS(on). POWER SWITCH ON
RESISTANCE (mW)
RH(SYNC). SYNCI INPUT
RESISTANCE (kW)
160
140
120
100
80
60
40
−50
−25
0
25
50
75
100
125
800
700
600
500
400
300
200
100
0
−50
150
−25
TJ. JUNCTION TEMPERATURE (°C)
80
75
75
70
70
65
60
55
50
45
40
−50
−25
0
25
50
75
100
125
150
60
55
50
45
40
35
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
Figure 18. Minimum On Time vs. Junction
Temperature
Figure 19. Minimum Off Time vs. Junction
Temperature
150
600
FSWAF. FOLDBACK MODE
SWITCHING FREQUENCY (kHz)
ILIM. MINIMUM TIME (ns)
65
TJ. JUNCTION TEMPERATURE (°C)
1.70
1.65
1.60
1.55
1.50
1.45
1.40
−50
15 0
Figure 17. Power Switch RDS(on) vs. Junction
Temperature
tOFFMIN. MINIMUM TIME (ns)
tONMIN. MINIMUM TIME (ns)
Figure 16. SYNCI Input Resistance vs.
Junction Temperature
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
−25
0
25
50
75
100
125
150
VIN = 4.5 V
550
500
450
400
350
300
VIN = 28 V
250
200
−50
−25
0
25
50
75
100
125
150
TJ. JUNCTION TEMPERATURE (°C)
TJ. JUNCTION TEMPERATURE (°C)
Figure 20. Current Limit Threshold vs.
Junction Temperature
Figure 21. Short−Circuit Foldback Frequency
vs. Junction Temperature
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NCV890101
40
3.50
38
3.45
VDRV. DRV VOLTAGE (V)
FSWHC. HICCUP MODE FREUQNCY
(kHz)
TYPICAL CHARACTERISTICS CURVES
36
34
32
30
28
3.35
IDRV = 0 mA
3.30
IDRV = 16 mA
3.25
3.20
3.15
26
24
−50
−25
0
25
50
75
100
125
3.10
−50
150
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
TJ. JUNCTION TEMPERATURE (°C)
Figure 22. Hiccup Mode Switching Frequency
vs. Junction Temperature
Figure 23. DRV Voltage vs. Junction
Temperature
3.1
150
IDRVLIM. DRV CURRENT LIMIT (mA)
30
3.0
2.9
VDRVSTT
2.8
VDRVSTP
2.7
2.6
2.5
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
150
29
28
27
26
25
24
23
22
21
−50
Figure 24. DRV Reset Threshold vs. Junction
Temperature
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
Figure 25. DRV Current Limit vs. Junction
Temperature
55
VSSEN. OUTPUT PRECHARGE
DETECTOR THRESHOLD (V)
VDRVSTT. VDRVSTP, DRV RESET
THRESHOLDS (V)
3.40
50
45
40
35
30
25
20
−50
−25
0
25
50
75
100
125
TJ. JUNCTION TEMPERATURE (°C)
Figure 26. Output Precharge Detector
Threshold vs. Junction Temperature
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10
150
150
NCV890101
GENERAL INFORMATION
INPUT VOLTAGE
inductor current at which the power switch shuts off. The
Current Mode control method employed by the NCV890101
allows the use of a simple, Type II compensation to optimize
the dynamic response according to system requirements.
An Undervoltage Lockout (UVLO) circuit monitors the
input, and inhibits switching and resets the Soft−start circuit
if there is insufficient voltage for proper regulation. The
NCV890101 can regulate a 3.3 V output with input voltages
above 4.5 V and a 5.0 V output with an input above 6.5 V.
The NCV890101 withstands input voltages up to 40 V.
To limit the power lost in generating the drive voltage for
the Power Switch, the switching frequency is reduced by a
factor of 2 when the input voltage exceeds the VIN
Frequency Foldback threshold VFLDUP (see Figure 27).
Frequency reduction is automatically terminated when the
input voltage drops back below the VIN Frequency Foldback
threshold VFLDDN.
SLOPE COMPENSATION
A fixed slope compensation signal is generated internally
and added to the sensed current to avoid increased output
voltage ripple due to bifurcation of inductor ripple current
at duty cycles above 50%. The fixed amplitude of the slope
compensation signal requires the inductor to be greater than
a minimum value, depending on output voltage, in order to
avoid sub−harmonic oscillations. For 3.3 V and 5 V output
voltages, the recommended inductor value is 4.7 mH.
SHORT CIRCUIT FREQUENCY FOLDBACK
Fsw
(MHz)
During severe output overloads or short circuits, the
NCV890101 automatically reduces its switching frequency.
This creates duty cycles small enough to limit the peak
current in the power components, while maintaining the
ability to automatically reestablish the output voltage if the
overload is removed. If the current is still too high after the
switching frequency folds back to 500 kHz, the regulator
enters an auto−recovery burst mode that further reduces the
dissipated power.
2
1
CURRENT LIMITING
4
18 20
36
Due to the ripple on the inductor current, the average
output current of a buck converter is lower than the peak
current setpoint of the regulator. Figure 28 shows − for a
4.7 mH inductor − how the variation of inductor peak current
with input voltage affects the maximum DC current the
NCV890101 can deliver to a load.
VIN (V)
Figure 27. NCV890101 Switching Frequency
Reduction at High Input Voltage
1.4
ENABLE
MINIMUM CURRENT LIMIT (A)
The NCV890101 is designed to accept either a logic level
signal or battery voltage as an Enable signal. EN low induces
a ’sleep mode’ which shuts off the regulator and minimizes
its supply current to a couple of mA typically (IqSD) by
disabling all functions. Upon enabling, voltage is
established at the DRV pin, followed by a soft−start of the
switching regulator output.
SOFT−START
Upon being enabled or released from a fault condition,
and after the DRV voltage is established, a soft−start circuit
ramps the switching regulator error amplifier reference
voltage to the final value. During soft−start, the average
switching frequency is lower than its normal mode value
(typically 2 MHz) until the output voltage approaches
regulation.
1.3
(3.3 VOUT)
1.2
1.1
(5 VOUT)
1.0
0.9
0.8
0.7
0.6
0
5
10
15
20
25
30
35
40
INPUT VOLTAGE (V)
Figure 28. NCV890101 Load Current Capability
with 4.7 mH Inductor
ERROR AMPLIFIER
The error amplifier is a transconductance type amplifier.
The output voltage of the error amplifier controls the peak
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11
NCV890101
SYNCHRONIZATION
does not arrive at the SYNCI pin within the Master
Reassertion Time, the NCV890101 controls its own
switching frequency, allowing uninterrupted operation in
the event that the clock (or controlling NCV890101) is
turned off.
If internal conditions or excessive input voltage cause an
NCV890101 to fold back its switching frequency, the main
oscillator switching frequency is still derived from the
frequency received at the SYNCI pin. Under these
conditions, the SYNCO pin is held low.
An external pulldown resistor is not required at the
SYNCI pin if it is unconnected.
Two NCV890101 can be synchronized out−of−phase to
one another by connecting the SYNCO pin of one to the
SYNCI pin of the other (Figure 29). Any number of
NCV890101 can also be synchronized to an external clock
(Figure 30). If a part does not have its switching frequency
controlled by the SYNCI input, it drives the SYNCO pin low
when it turns on the power switch, and drives it high half a
switching period later. When the switching frequency is
controlled by the SYNCI input, the SYNCO pin is held low.
Synchronization starts within 2 ms of soft−start completion.
A rising edge at the SYNCI pin causes an NCV890101 to
immediately turn on the power switch. If another rising edge
VIN
CDRV1
CDRV2
DBST2
NCV890101
1 VIN
CIN2
2 DRV
3 SYNCO
4 GND
EN2
L2
SW 10
DBST1
NCV890101
CBST2
BST 9
DFW2
RFB1
SYNCI 8
CIN1
VOUT2
1 VIN
SW 10
CBST
1
2 DRV
COUT2
3 SYNCO
BST 9
FB 7
RFB1
FB 7
COMP 6
5 EN
VOUT1
COUT1
DFW1
SYNCI 8
4 GND
Synchronization
L1
RFB2
RCOMP1
5 EN
RFB2
COMP 6
SYNC MASTER
CCOMP1
RCOMP2
SYNC SLAVE
CCOMP2
Figure 29. NCV890101s Synchronized to Each Other
Master Enabled by Battery
VIN
CDRV1
DBST2
NCV890101
1 VIN
CIN2
2 DRV
3 SYNCO
4 GND
EN2
SW 10
BST 9
DBST1
NCV890101
CDRV
2
L2
CIN1
VOUT2
2 DRV
CBST2
DFW2RFB21
1 VIN
COUT2
3 SYNCO
SYNCI 8
4 GND
FB 7
BST 9
SYNCI 8
DFW1
RFB11
FB 7
COMP 6
5 EN
L1
SW 10
CBST
1
RFB12
RCOMP1
5 EN
COMP 6
RFB22
CCOMP1
RCOMP2
Synchronization
CCOMP2
CLK
Figure 30. Both NCV890101s Synchronized to External Clock
#1 Enabled by Battery
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12
VOUT1
COUT1
NCV890101
BOOTSTRAP
DESIGN METHODOLOGY
At the DRV pin an internal regulator provides a
ground−referenced voltage to an external capacitor (CDRV),
to allow fast recharge of the external bootstrap capacitor
(CBST) used to supply power to the power switch gate driver.
If the voltage at the DRV pin goes below the DRV UVLO
Threshold VDRVSTP, switching is inhibited and the
Soft−start circuit is reset, until the DRV pin voltage goes
back up above VDRVSTT.
In order for the bootstrap capacitor to stay charged, the
Switch node needs to be pulled down to ground regularly. In
very light load condition, the NCV890101 skips switching
cycles to ensure the output voltage stays regulated. When the
skip cycle repetition frequency gets too low, the bootstrap
voltage collapses and the regulator stops switching.
Practically, this means that the NCV890101 needs a
minimum load to operate correctly: to cover all conditions
of input voltage and temperature, this minimum load is 8
mA.
The NCV890101 being a fixed−frequency regulator with
the switching element integrated, is optimized for one value
of inductor. This value is set to 4.7 mH, and the slope
compensation is adjusted for this inductor. The only
components left to be designed are the input and output
capacitor and the freewheeling diode.
Output capacitor:
The minimum output capacitor value can be calculated
based on the specification for output voltage ripple:
C OUT min +
DI L
8 @ DV OUT @ F SW
(eq. 1)
With
− DIL the inductor ripple current:
ǒ
V OUT @ 1 *
DI L +
OUTPUT PRECHARGE DETECTION
V
Ǔ
OUT
V
IN
(eq. 2)
L @ F SW
− DVOUT the desired voltage ripple.
However, the ESR of the output capacitor also contributes
to the output voltage ripple, so to comply with the
requirement, the ESR cannot exceed RESRmax:
Prior to Soft−start, the FB pin is monitored to ensure the
SW voltage is low enough to have charged the external
bootstrap capacitor (CBST). If the FB pin is higher than
VSSEN, restart is delayed until the output has discharged.
R ESR max +
THERMAL SHUTDOWN
A thermal shutdown circuit inhibits switching, resets the
Soft−start circuit, and removes DRV voltage if internal
temperature exceeds a safe level. Switching is automatically
restored when temperature returns to a safe level.
DV OUT @ L @ F SW
ǒ
V OUT 1 *
V
Ǔ
OUT
V
IN
(eq. 3)
Finally, the output capacitor must be able to sustain the ac
current (or RMS ripple current):
MINIMUM DROPOUT VOLTAGE
I OUTac +
When operating at low input voltages, two parameters
play a major role in imposing a minimum voltage drop
across the regulator: the minimum off time (that sets the
maximum duty cycle), and the on state resistance.
When operating in continuous conduction mode (CCM),
the output voltage is equal to the input voltage multiplied by
the duty ratio. Because the NCV890101 needs a sufficient
bootstrap voltage to operate, its duty cycle cannot be 100%:
it needs a minimum off time (tOFFmin) to periodically re−fuel
the bootstrap capacitor CBST. This imposes a maximum duty
ratio DMAX = 1 − tOFFmin.FSW(min), with the switching
frequency being folded back down to FSW(min) = 500 kHz to
keep regulating at the lowest input voltage possible.
The drop due to the on−state resistance is simply the
voltage drop across the Switch resistance RDSON at the
given output current: VSWdrop = IOUT.RDSon.
Which leads to the maximum output voltage in low Vin
condition: VOUT = DMAX.VIN(min) − VSWdrop
DI L
2 Ǹ3
(eq. 4)
Typically, with the recommended 4.7 mH inductor, two
ceramic capacitors of 10 mF each in parallel give very good
results.
Freewheeling diode:
The diode must be chosen according to its maximum
current and voltage ratings, and to thermal considerations.
As far as max ratings are concerned, the maximum reverse
voltage the diode sees is the maximum input voltage (with
some margin in case of ringing on the Switch node), and the
maximum forward current the peak current limit of the
NCV890101, ILIM.
The power dissipated in the diode is PDloss:
ǒ
P Dloss + I OUT @ 1 *
Ǔ
V OUT
V IN
@ V F ) I DRMS @ R D (eq. 5)
with:
− IOUT the average (dc) output current
− VF the forward voltage of the diode
− IDRMS the RMS current in the diode:
EXPOSED PAD
The exposed pad (EPAD) on the back of the package must
be electrically connected to the electrical ground (GND pin)
for proper, noise−free operation.
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13
NCV890101
I DRMS +
Ǹ
ǒ
(1 * D) I OUT 2 )
DI L
12
Ǔ
For example, using a 4.7 mH input capacitor, it is easy to
calculate that an inductor of 200 nH will ensure that the
input filter has a cut−off frequency below 200 kHz (low
enough to attenuate the 2 MHz ripple).
2
(eq. 6)
− RD the dynamic resistance of the diode (extracted from
the V/I curve of the diode in its datasheet).
Then, knowing the thermal resistance of the package and
the amount of heatsinking on the PCB, the temperature rise
corresponding to this power dissipation can be estimated.
PCB LAYOUT RECOMMENDATION
As with any switching power supplies, there are some
guidelines to follow to optimize the layout of the printed
circuit board for the NCV890101. However, because of the
high switching frequency extra care has to be taken.
− Minimize the area of the power current loops:
♦ Input capacitor ³ NCV890101 switch ³ Inductor
³ output capacitor ³ return through Ground
♦ Freewheeling diode ³ inductor ³ Output capacitor
³ return through ground
− Minimize the length of high impedance signals, and
route them far away from the power loops:
♦ Feedback trace
♦ Comp trace
Input capacitor:
The input capacitor must sustain the RMS input ripple
current IINac:
I INac +
DI L
2
ǸD3
(eq. 7)
It can be designed in combination with an inductor to build
an input filter to filter out the ripple current in the source, in
order to reduce EMI conducted emissions.
ORDERING INFORMATION
Device
NCV890101MWTXG
Package
Shipping†
DFN10 with wettable flanks
(Pb−Free)
3000 / Tape & Reel
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
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14
NCV890101
PACKAGE DIMENSIONS
DFN10, 3x3, 0.5P
CASE 485C
ISSUE B
D
PIN 1
REFERENCE
2X
0.15 C
2X
EDGE OF PACKAGE
A
B
ÇÇÇ
ÇÇÇ
ÇÇÇ
ÇÇÇ
L1
E
DETAIL A
Bottom View
(Optional)
MOLD CMPD
0.15 C
0.10 C
(A3)
A1
A
10X
SIDE VIEW
A1
D2
10X
L
1
DIM
A
A1
A3
b
D
D2
E
E2
e
K
L
L1
MILLIMETERS
MIN
MAX
0.80
1.00
0.00
0.05
0.20 REF
0.18
0.30
3.00 BSC
2.40
2.60
3.00 BSC
1.70
1.90
0.50 BSC
0.19 TYP
0.35
0.45
0.00
0.03
SOLDERING FOOTPRINT*
5
2.6016
E2
K
10
10X
1.8508
2.1746
6
3.3048
b
0.10 C A B
0.05 C
C
DETAIL A
e
A3
DETAIL B
Side View
(Optional)
SEATING
PLANE
0.08 C
10X
ÉÉÉ
ÉÉÉ
EXPOSED Cu
TOP VIEW
DETAIL B
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ASME Y14.5M, 1994.
2. CONTROLLING DIMENSION: MILLIMETERS.
3. DIMENSION b APPLIES TO PLATED
TERMINAL AND IS MEASURED BETWEEN
0.25 AND 0.30 MM FROM TERMINAL.
4. COPLANARITY APPLIES TO THE EXPOSED
PAD AS WELL AS THE TERMINALS.
5. TERMINAL b MAY HAVE MOLD COMPOUND
MATERIAL ALONG SIDE EDGE. MOLD
FLASHING MAY NOT EXCEED 30 MICRONS
ONTO BOTTOM SURFACE OF TERMINAL b.
6. DETAILS A AND B SHOW OPTIONAL VIEWS
FOR END OF TERMINAL LEAD AT EDGE OF
PACKAGE.
BOTTOM VIEW
NOTE 3
10X
0.5651
10X
0.5000 PITCH
0.3008
DIMENSIONS: MILLIMETERS
*For additional information on our Pb−Free strategy and soldering
details, please download the ON Semiconductor Soldering and
Mounting Techniques Reference Manual, SOLDERRM/D.
ON Semiconductor and
are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks,
copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC
reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any
particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without
limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications
and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technical experts. SCILLC
does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where
personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and
its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly,
any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture
of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
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NCV890101/D