Hello, everyone. My name is Vashist Bist, and I will be presenting Competitive Advantages of TI Multi-Channel Half-Bridge Drivers, which is DRV89XX-Q1 Family in Automotive HVAC Damper Applications. This training is focused on the automotive heating, ventilation, and air conditioning. That is, HVAC damper motor application.

There has been a trend of increasing number of motors in a vehicle for enhancing the user comfort. Automotive HVAC system plays a significant role in enhancing the user experience in terms of comfort, performance, and cost. Damper servo assembly is the backbone of the automotive HVAC system which controls the airflow in a vehicle. This training presents the TI's Automotive Multi-Channel Brush DC Motor Driver Family, that is DRV89XX-Q1, which can drive multiple HVAC damper servo motors.

This device family comes with 4, 6, 8, 10 and 12 half-bridges. This family is an automotive AEC-Q100 qualified, and supports Grade-1 temperature classification for automotive applications. The device family has very optimized voltage and current ranges with easy configurability, and detailed diagnostics troubleshooting. The device consists of enhanced integrated protection features such as under-voltage lockout, over-voltage protection, power-on reset, over-current protection, open load detection, and over-temperature warning and thermal shutdown to protect against any unwanted scenario. The device family shows a clear and distinctive advantage over the current solutions in the market.

In this training, we will understand the automotive HVAC system with focus on the key requirements of the automotive HVAC damper, and how it gets implemented in its actual system product. We will also talk in brief about the key specifications, key features, and differentiation of the DRV89XX-Q1 family and the comparison of the multi-channel family with the competitors. This training starts with the understanding of automotive HVAC system. In this, we will understand the car climate control system and the usage of damper motor for climate control. We will then present the DRV89XX-Q1 family, and understand the key specification, device feature, functionality, and protection. This will be followed by the competitive advantages, and concludes with the adjacent application of automotive side mirrors.

Now, let's start with the automotive HVAC system. Automotive HVAC system comprises of various subsystems such as the power supply, compressor controller, blower motor driver, defrost driver, damper motor driver, current monitors, temperature sensors, and the communication interface. The power supply unit takes care of any unwanted spikes and surges in the battery voltage due to load dump or current conditions. This unit also generates the power supply for the digital controller and low voltage circuitry. The whole air conditioning unit is controlled by a central microcontroller, which is connected to the Body Control Module, BCM, by the CAN bus.

Multiple temperature sensors are placed inside the cabin depending upon the zones of the HVAC system. The air conditioning compressor is the heart of the HVAC system. The low pressure refrigerant enters into the compressor to become a high pressure and a high temperature refrigerant. The evaporator and condenser work together and connect through an expansion valve which controls the temperature. Heat is transferred from a low temperature region to a high temperature region due to the pressure difference. This whole process is known as the refrigeration cycle. Blower motor fan controls the fresh air circulation control, the airflow control, and the temperature.

The refrigeration unit is also coupled with many ducts through which air is transferred to the cabin. Damper motor controls the airflow inside the cabin. These damper motors are primarily the brush DC motors which are used for mixing the warm and cold air for temperature control. There are low current motors which peak is generally lower than 500 milliamps and are driven with full bridge driver.

This section explains the DRV89XX-Q1 family to understand the key specifications, device features, functionality, and the protection. DRV89XX-Q1 family of devices is an automotive grade AEC-Q100 qualified devices which supports Grade-1 temperature conditions. This family of multi-channel devices is available in four channel, six channel, eight channel, 10 channel, and 12 channels. The device family is designed to operate from 4.5 volt to 32 volt with a load dump support of 40 volt. Each half bridge is designed to carry RMS current of 1 ampere, and power pins, supply, and ground can carry RMS current of 3 amperes.

The on state resistance of half bridges is 1.5 ohms at room temperature. This device is controlled and configured with a 16 bit 5 megahertz SPI interface which can also support daisy chain operation for connecting multiple such devices. The device offers a low sleep current of less than 3 microamps. It is also equipped with four PWM modes with four internal PWM generators which support 8 bit duty resolution and four frequency options of 80 Hertz, 100 Hertz, 200 Hertz, and 2 kilohertz. The device comes with numerous protection schemes such as the supply under voltage, supply over voltage protection, logic supply power on reset, over current protection on each FET, open load detection on each FET, and thermal warning and shut down.

The primary application of this device family is the automotive HVAC damper motors, and alternatively it can also be used in automotive side mirror control and automotive ambient lighting applications.

Now, let's see the benefits of that the DRV89XX-Q1 family. The device is well optimized for 12 volt standard automotive battery, and it can also be used for regulated 24 volt rail application. Due to individual FET control, it can easily support control of brush DC stepper motors, and the solar night loads. This device supports an internal charge pump for driving high side and MOSFETs, and therefore doesn't require any extra capacitors, thus offering a reduced BOM cost.

All devices in this family are pin to pin compatible, which gives customers a benefit of developing a scalable PCB platform. This family also provides a better thermal performance with device low Rdson. It also supports a high peak current capacity for in rush current. The input control pins are deduced by driving the output via a SPI control. And it provides a higher system reliability and reduced design complexity with integrated current protection and fault detection features.

This family of multi-channel devices is available in 4 channel, that is DRV8904, 6 channel, which is DRV8906, 8 channel, the DRV8908, 10 channel, the DRV8910, and a 12 channel device, which is DRV8912, and is available in 24 pin HTSSOP package. All devices in this family are pin to pin compatible, which gives customers a benefit of developing a scalable PCB platform.

Now, let's see the application of DRV89XX-Q1 family. The primary application of the DRV89XX-Q1 is driving multiple brush DC damper motor in automotive HVAC application. This application diagram shows multiple motor connected in independent configuration, sequential configuration, and a parallel configuration. The independent configuration is the most commonly used way of connecting multiple brush DC motors. In this configuration, two half bridges are used to connect a single motor. This configuration gives an advantage of true independent control of individual motor. In sequential mode, 11 motors can be connected to a 12 channel device. However, true independent control cannot be achieved. Whereas the parallel type brush DC motor connection is used for driving higher current motors.

The DRV89XX-Q1 family has numerous advantages as compared to comparators. The DRV89XX-Q1 family of devices is well optimized for 12 volt standard automotive battery, and it can also be used for regulated 24 volt DC rail applications. The device family provides an nFAULT pin by which multiple SPI writes can be avoided. This device family is controlled and configured with a 16-bit 5 megahertz SPI interface, which also supports daisy chain operation for connecting multiple devices. It also have provision for negative current detection during the freewheeling operation and synchronous rectification mode during the open load operation. This avoids any false open load detection in this mode, which is a distinctive advantage over other competitors. The device family also supports 2 kilohertz internal PWM generation with option for faster slew rate setting for supporting PWM current chopping operation. And, due to device low on state resistance, that thermal performance is improved as compared to competitors.

In this section, we will cover DRV89XX-Q1 family advantages over competitors in detail. This section will present the negative open load detect advantage, thermal advantage, two kilohertz PWM operation and fault pin operation, and the extended full over voltage protection. The negative open load detection mode allows TI device to avoid any unwanted fault due to reverse current flowing into the FET. Let's take two cases of asynchronous and synchronous rectification. In normal operation, the full bridge is being operated in forward direction, such that the high side FET of out 1 and low side FET of out 2 are conducting.

The high side FET is driven continuously, and low side FET is driven with PWM. In asynchronous rectification as shown in Figure 1, during the PWM off time, due to motor's inductive nature, the body diode of the high side FET of out 2 half bridge starts conducting. Since the high side FET of out 2 half bridge is off, therefore, the open load detection is disabled. Whereas in synchronous rectification mode, as shown in Figure 2, during the PWM off time, the high side FET of out 2 channel is enabled. Due to this, the reverse direction of current, the open load detection comparator sees this current lower than the threshold open load detection current and detects a false open load detect. This type of implementation is common in competitive drivers. However, the DRV89XX-Q1 doesn't show this issue.

These figures show the waveforms of the driver operation with and without negative open load detection enabled. First figure shows that the waveform of false open load detection when the negative current open load detection setting is disabled. As shown in this figure, the high side FET of the out 1 channel is always switched on, and the low side and high side FET of out 2 channel are operating in complementary fashion. In synchronous rectification, the current flows in negative direction from out 2 node to supply, that is vm, which means from FET source to drain, during the high side FET conduction.

Initially, for the first PWM cycle, the open load detection mode is disabled. However, when the open load detection mode is enabled in second PWM cycle, then device registers a false open load detect during the high side FET conduction. The nFAULT pin is pulled low, and both high side and low side FET of out 2 channels are disabled. The body diode of high side FET out 2 conducts to complete the motor current path. This false detection of open load is eliminated by enabling the negative current open load detection setting. As shown in second figure, the negative OLD current setting is enabled for high side FET of out 2 channel. This setting allows the negative current path from source to drain in high side FET. The nFAULT pin is latched high, and out 2 channel is not disabled when the open load setting is enabled in second PWM cycle.

This figure shows the experimental waveform of the open load detection with negative current detection disabled. The PWM off time is kept lower than the PWM mode open load detection time for first five cycles. As soon as the off time is increased higher than the PWM mode open load detection time, that is around 200 microseconds, that device asserts a fault and the current decays to zero. This figure shows the experimental waveform of the open load detection with negative current detection enabled. In this, the PWM off time is kept higher than the PWM mode open load detection time, that is 200 microseconds, for all cycles. The device doesn't show any open load detection fault, and the nFAULT pin is always clamped high.

This section presents the thermal advantage of the DRV89XX-Q1 device due to better on state device resistance. The DRC89XX-Q1 device on state resistance is 12% lower than the competitor device, which impacts the thermal performance by around 15%. The thermal comparison of the DRV89XX-Q1 device and the competitor device are carried on the TI DRV89XX-Q1 EVM. A common testing condition is taken to ensure that both devices are tested on the similar platform. This test is carried out at an ambient temperature of 25 degrees Celsius with all 12 channels operating in parallel mode. The connection of load is such that all the high side FETs of channel 1, 4, 5, 6, 7, and 9 are on, and low side FETs of channel 2, 3, 8 and 11 and 12 are switched on simultaneously.

A load of 3 amperes is connected to the parallel half bridges, and temperature is measured by the thermal imager. As shown in first figure, the DRV89XX-Q1 device observes a hot spot of 81.2 degrees Celsius, whereas the competitor device shows a hot spot of 95.5 degrees Celsius at similar condition. This clearly indicates a better thermal performance of TI DRV89XX-Q1 device over competitor.

This section presents the 2 kilohertz frequency operation of the DRV89XX-Q1 device. By using the higher frequency operation of motor, the initial in rush current can be limited. This PWM current limit, if carried in the low PWM frequency, can lead to a very high current ripple, audible noise, and motor failing to start. This waveform shows the experimental results of motor starting without using the PWM operation of half bridges. The experiment has been carried out with six half bridges operating in parallel at room temperature. As shown in this figure, the motor takes a huge starting current since the opposing back EMF is very low, and settles to a much lower current value once enough back EMF builds up.

This high in rush current can cause the over current protection to trip and thermal shutdown, which can prevent motor to start at higher ambient temperatures. This waveform shows the experimental results of motor starting with using the 2 kilohertz PWM operation of half bridges. As shown in this figure, the motor in rush starting current is limited due to low average voltage applied across motor. Moreover, the current ripples are reduced due to lower extent from around two amperes to 500 milliamperes.

This section presents the nFAULT pin functionality for the DRV8i9XX-Q1 device. With this hardware interrupt, the user can save repeated SPI leads for checking the device status. This frees up the controller software time and can be used for other tasks. This waveform shows the experimental result of nFAULT triggering during an open load detect. As shown in this figure, as soon as the motor open load is detected, the nFAULT pin goes low, which can be monitored on the GPIO pin of microcontroller.

This section presents the extended over voltage protection of DRV89XX-Q1 device. When this mode is disabled, the over voltage threshold is 20 volts for the nominal 12 volt battery operation. However, when this mode is enabled, the device over voltage threshold limit is extended to 32 volts, which allows the regulated 24 volt battery operation. This waveform shows the experimental results of extended OVP operation, and the device going into shutdown mode as soon as the supply voltage is about 32 volts. As shown in this figure, the nFAULT pin is high during the operation at 24 volts, and goes low as soon as the supply voltage goes higher than 32 volts.

This section presents the applicability of the DRV89XX-Q1 device for the alternate application of automotive side mirror. The DRV89XX-Q1 can be used to control the high current mirror fold motor by paralleling the half bridges. The low current X direction and Y direction motors can be controlled using a single full bridge either in independent mode or sequential mode. This figure shows the system block diagram of the alternate application of DRV89XX-Q1 driving automotive side mirrors. The mirror fold motor is a high current motor which operation is achieved by paralleling the 8 half bridges.

Moreover, the xy direction motors are connected in a sequential fashion considering the fact that either of the horizontal or the vertical adjustment can be done at a time. Two channels are used for the side indicators LEDs, which dimming can be controlled using the 8 bit duty control low frequency PWM signal. Thank you.