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