Automotive Driver Requirements, Topologies and Applications

Automotive Driver Requirements,
Topologies and Applications
1
Driver Topologies
Low-Side
Powertrain Loads
• Motors
• Solenoids
• Heaters
• Lighting
Pros
• Easy to Drive
Challenges
• No Protection
from shorts to
ground
• Inductive Energy
• Parasitics
• Reverse Battery
2
VLOAD
High-Side
Body Loads
• Motors
• Solenoids
• Heaters
• Lighting
Pros
• Protection from
shorts to ground
Challenges
• Less Easy to Drive
• Inductive Energy
• Negative Clamp
• ESD Protection
• Reverse Battery
VLOAD
VLOAD
Driver Topologies
Half-Bridge
Powertrain or Body
Pros
• Hs or LS Drive
Challenges
• Inductive Energy
• Parasitics
• Reverse Battery
3
Full-Bridge
Powertrain or Body
Pros
• Hs or LS Drive
• Bi-Directional
Challenges
• Inductive Energy
• Parasitics
• PWM Losses
from drops in HS
and LS & nonoverlap concerns
• Reverse Battery
VLOAD
VLOAD
or GND
ON Semiconductor Automotive Driver Part Selection
Drivers connect to loads directly,
while pre-drivers are intended to drive discrete FETs which drive loads.
Note the
higher
current
ratings for
the drivers,
except for
the highspeed predriver which
is high
current.
4
Load & Driver Spectrum
Percent of Loads
65%
31%
4%
Occasionally
Motor drivers > 10A
High Penetration
Ease of Use
Standard
Standard
Standard
Smart
Smart
Smart
Drivers
Some Drivers
Hybrid
(Multi-die Package)
MOSFET
Integrated
Highly
Integrated
Pre Drivers
+ MOSFETs
0
Pre Drivers
+ MOSFETs
5
20
Load Current
5
Pre Drivers
+ MOSFETs
Deciding on your Driver
• Evaluate your current level as per the chart on the previous page.
– This will result in your choice of a driver, pre-driver, or hybrid
solution.
• Do you need to be able to survive fault conditions?
– A no here will add a discrete solution as a possibility.
• Investigate what happens during faults and the implications on
your system.
– This will result in your decision of a high-side or low-side driver.
• What are your requirements for reporting faults?
– This will result in your choice of a SmartFET or SPI
controllable driver.
6
Evaluating Faults - Short to Ground
High-Side Driver
Low-Side Driver
•Load is continuously on during
an output short to ground
•Output Driver is shorted to
ground. Requires protection for
the output driver.
Vload
Vload
Zload
Zload
Shorts to ground are more likely to
occur than shorts to battery due to
the abundance of sheet metal from
the automobile.
7
Evaluating Faults - Short to Supply
Low-Side Driver
•Output Driver is shorted to
supply. Requires protection for
the output driver.
Vload
Zload
8
High-Side Driver
•Load is continuously on during
an output short to ground
Vload
Zload
Applications
Powertrain
Body
•Historically Low Side Drivers
•Historically High-Side Drivers
•Cheaper (Less Die Area & Easier to Drive)
•Don’t suffer from the effects of
always on when shorted to ground.
9
Driver Loads
• Types of Loads and their special requirements
– Resistive loads.
• No special needs. Only need to evaluate IC Power.
– Relays
• Inductive loads. Need to be concerned about stored energy in the coils.
ICs need protection from high voltage (positive for LS and negative for
HS) caused by inductors turning off.
– Lamps
• Variable resistance. Need to be concerned about in-rush current. Lamp
drivers typically need a blanking time in which to ignore high current
events.
– LED
• Constant current. Need to be concerned about maintaining a constant
current. Some systems require all LEDs in a system to turn off when
one fails (opens). This simulates a bulb and does not allow operation at
minimal illumination.
10
Unprotected Inductive Loads
70 V
peak
https://w05.dealerconnect.chrysler.com/service/mds2002/serviceInfo/en_US/80019913.gif
11
Adding a clamp to the output of your LS Switch
The inductively loaded lowside drive is switched off
causing the voltage on the
output drive pin to spike up.
The spike is clamped here at
44 V.
Output Drive
Control Input
12
High-Side Driver Performance
Concerns:
Repetitive High Power Switching
Clamp Voltage is below ground for HS
switching of inductor.
This is more difficult to the IC
manufacturer for clamping both the Gate
and Source nodes as well as parasitic
suppression in the circuit.
14V
Benefits:
Lower clamp voltage allows faster
Inductive current decay dI V
=
dt
L
Integrated Power
Control Switch
Supplier characterizes performance.
Performance is determined by
technology.
System Level Consideration
Pre-driver / FET Need to match the FET
and Pre-driver performance.
Evaluate FET conduction and switching
losses with the devices energy capability.
13
Transients can cause unforeseen performance
LV NMOS
Tub
D
n
G
S
B
n
epi
p
All transistors are a collection of PN junctions.
Keeping them isolated is the challenge.
The NMOS transistor above shows the parasitic bipolar
devices which are inherently always there.
14
Worst Case Parasitics
The worst
situation
outside of
permanent
damage is
for the device
to activate a
latch made
up of a PNP
and an NPN
device.
In a typical
parasitic latch, the
two bipolar
transistors typically
share the N and P
junctions.
Once activated, the
device must be
powered down to
turn off.
P
N
P
N
A PNPN latch
15
Transients can be bad for an integrated circuit
Parasitic
QP
VS
phv
epi
nsd
OUT
n
16
This example shows a parasitic
PNP formed from 2 back to
back diodes impacting the
expected performance of the
driver.
The parasitic PNP shown was
shown to steal drive current
away from the FET causing
significant switching transition
discrepancies with increased
supply voltage.
Other Sources of Parasitic Transistors
HS Recirculation
LS Recirculation
When the LS transistor turns off
When the HS transistor turns off
Other
epi
body
diode
17
IC Solutions for Flyback
•1st diode clamps the output
•2nd diode prevents the gate from
being pulled down by the drain as it
is being turned on.
Output
Turn-on
Control
18
Load Dump
Be aware of conditions during load dump.
The setup at left will experience a load dump
through the inductor (relay) without power
applied to the IC.
The clamp condition of your driver IC may not
clamp at the same voltage under the 2
conditions (powered and unpowered)
depending on the technology used in the IC.
Vpwr
Vreg
VCC
If the output clamp is trimmed and stored in
memory, the clamp voltage will be less than a
powered IC.
GND
19
GND
If you exceed the clamp threshold, current will
flow through the inductor. This will be a high
power event as it occurs at the clamp voltage.
Insuring Robustness
•
Automotive Requirements
– ISO 16750-2 (the International Organization for Standardization), Road
vehicles – Environmental conditions and testing for electrical and electronic
equipment. Part 2: Electrical Loads.
– Our main level of focus:
• Supply Voltages (12 V systems and 24 V systems) (car and truck).
– Rating of Code A = 6 V to 16 V (car), Rating of Code A=10 V to 32 V (truck)
» These are the typical power supply ranges we are expected to perform within.
although recently the low voltage level requirements at the OEM are going lower.
• Jump Start
– 24 V for 60 seconds
» Historically these voltage levels were used by tow vehicles to get vehicles started
which were immobile at the side of the road.
• Slow Decrease and Increase of Supply Voltage
– 0.5 V/minute from 0 V to Vmax and Vmax to 0 V
» All functionality must perform in predictable manner.
• Short Circuit Protection
– Connect all relevant inputs and outputs to Vmax for 60 seconds.
• Short Circuit Protection (Also AEC-Q101 Automotive Electronics Council) SHORT
CIRCUIT RELIABILITY CHARACTERIZATION OF SMART POWER DEVICES FOR 12 V
SYSTEMS
– Rating of Grade A >1,000,000 cycles with 0 fails.
20
Further ISO16750-2 Requirements
Engine Cranking
Voltage can dip down to 4.5 V for >15 msec.
Maintaining operation at this reduced level is frequently being
requested now.
This is the
most difficult
level for
integrated
circuit
compliance.
Head room
issues limit IC
operation.
21
Current surge
from starter
motor starting
Starter
motor
turning
Engine is running &
starter is off.
Industry Guidelines
Repetitive Clamping
Normal operation of a relay driver will activate the clamp to
dissipate energy stored in the inductor. Customer driven
specifications are becoming the norm for this activity. There is no
standard at this time.
The typical specification will be included in the absolute maximum
ratings table of the datasheet.
This is a relatively new test. Some of our older parts will not include
this.
22
Shoot- Through Current
In normal
Potentially destructive
operation, the
events can occur
motor changes
(blue) if:
direction as
1) the bottom driver
the drivers
turns on before the top
switch on and
driver turns off.
off in the
sequence
2) the bottom driver is
such that
not shut off before the
current flows
top driver turns on.
as per the red
and green
Integrated circuits should have specifications which protect for this.
paths.
Also note putting high limits on these parameters can limit switching speed.
23
H-Bridge Turn-Off Current
Current flow in an H-Bridge configuration.
scope capture –current from the power supply VS.
green – normal current flow through the motor.
red – the current wants to continue to flow through the inductance of the motor and finds
a path through the body diode of the top FET. Note the polarity of the current as it goes negative
(out of the IC pin).
I(VS) (50 mA/div)
24
How does this current effect your system?
Amplified
waveform
Turn-off current
from the previous
slide
When the current goes out of the pin, it typically goes to the external
filter capacitor.
The impact on voltage “noise” will be determined by the external
capacitor value.
I = 100 mA, dt = 0.5 usec
dV
I =C
dT
dT
dV = I
C
User define C = 10 uF
Yield dV = 5 mV
25
Power Considerations
In addition to the power dissipated across the FETs
during on time (Rdson*Iload), recirculation currents
must be considered in thermal calculations.
Power is generated when current flows through the
body diodes when energy is released form the coil.
Pre-driver / FET system level consideration
FET and Pre-driver performance should be matched.
Confirm Cross-over delay times and Gate drive
currents complement External Gate Capacitance.
1
26
Smart Drivers and Drivers with SPI fault Reporting
Smart Drivers, such as the NCV8401, NCV8402, and NCV8403 offer 3
features over a discrete component.
1) Current Limit
2) Thermal Shutdown
3) Voltage Clamping
(These are manufactrered on our HDPlus technology.)
(A fabrication technology developed for high power with added analog functionality.)
SPI Drivers, such as the NCV7703, NCV7708A, NCV7512, NCV7513A, and
NCV7515 offer the same feature set as the Smart Drivers with the added
capability of offering logic fault reporting for
1) Over load conditions
2) Under load conditions.
3) Thermal issues.
4) Power supply status (under voltage and over voltage).
(These are manufactured on our Powersense and IxTyy processes).
(A fabriacation technology developed for logic with added power capability).
27
Smart Drivers vs SPI Communication
Examples of a Smart Driver (NCV8401)
and an IC with SPI Communication (NCV7703).
The Smart Driver is much simpler (similar to a
discrete component) as compared to a device with
SPI Communication.
28
SPI Communication
There are 4 logic pins associated with SPI (serial peripheral communication)
1) Chip Select Bar (CSB)
2) Serial Input (SI)
3) Serial Clock (SCLK)
4) Serial Output (SO)
Input Pins – CSB, SI, SCLK
Output Pin - SO
29
SPI Operation
1) SPI operation is activated by
CSB going low.
CSB
SI
SCLK
SO
a) This can mean an
operation is being input to
the IC or information fault
information is being
requested on SO (or
both).
2) A command signal is input
(clocked in) into the SI port.
b) Note we are addressing
the 3rd bit with a one.
3) Fault and state information is
output of the SO pin.
Note the 3rd and 15th bit is high (to be used on the next slide)
30
SPI Table
The left column is the Input
Data (SI)
The right column is the
Output Data (SO)
1) OUTH1 is told to turn
on.
2) OUTH1 turns on.
3) There is an under load
condition present.
31
Deciphering the SPI information
SI - This SPI frame is telling OUTH1
to turn on.
SO – This is reporting OUTH1 is on
(OUTH1) and is in an underload
(ULD) condition.
32
ON Semiconductor Automotive Driver Portfolio
Drivers
33
Pre-Drivers
NCV7708A
Double Hex Driver
34
microprocessor
NCV7708A Applications
OUTLH1
M
Right Temperature
OUTLH2
M
Defroster
OUTLH3
M
Left Temperature
CSB
SI
SO
OUTLH4
M
Floor and Ventilation
SCLK
OUTLH5
M
Recirculation Shutter
OUTLH6
HVAC systems
heating, ventilating, and air
conditioning
NCV7708A
The primary application for this device is for HVAC
systems to control DC motors to guide air flow through
out the automobile. The other motor in the system (the
blower motor) is typically controlled with a high-side
switch.
35
NCV7708A Applications
OUTH1
OUTL1
Secondary applications
allow the device to drive
any combination of loads
OUTH2
OUTL2
OUTH3
• Motor
OUTL3
OUTH4
M
OUTL4
M
• Inductive (relays)
• Resistive
OUTH5
microprocessor
M
CSB
SI
SO
OUTL5
SCLK
OUTH6
OUTL6
NCV7708A
36
• Lamp
NCV1413 Darlington
Transistor Array
Internal flyback
clamps on each
output for
inductive loads
37
NCV7702 Dual H-Bridge
Bipolar devices also can report diagnostic data. The
Status pins here report diagnostic information.
38
NCV7703 Triple Half
Bridge Driver
Typical Application is for
automotive side-view mirror
control
39
NCV7703 Mirror Adjust and Fold Application
microprocessor
U1
OUT1
M
CSB
SI
SO
OUT2
SCLK
OUT3
NCV7703
U2
OUT1
X-Y mirror adjust
M
CSB
SI
SO
OUT2
SCLK
OUT3
NCV7703
40
M
Mirror fold
This design can be used
for high end applications
with x-y mirror adjust and
mirror fold applications
using two NCV7703
devices (U1&U2) populated
on the PC board.
For low end applications,
with only x-y mirror adjust,
the same PC board can be
used by simply not
populating (U2) the 2nd
NCV7703 device.
AMIS-39100 Octal High-Side Driver
High-Side Drivers require a charge pump to provide a sufficient voltage in which to drive the output.
41
NCV75xx Series (NCV7512/13A/17)
Quad/HexLow-Side Pre-Driver
NCV7512 – Four Low-Side Drivers
NCV7513A – Six Low-Side Drivers
NCV7517 – Improved NCV7513A
(blanking timer modifications and
Higher gate drive capability)
42
NCV33152 Dual High Speed MOSFET Driver
43
For More Information
•
View the extensive portfolio of power management products from ON
Semiconductor at www.onsemi.com
•
View reference designs, design notes, and other material supporting
automotive applications at www.onsemi.com/automotive
44
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