SSZT337 February 2020 DRV8904-Q1 , DRV8906-Q1 , DRV8908-Q1 , DRV8910-Q1 , DRV8912-Q1
Hector Hernandez Luque
Automotive heating, ventilation and air-conditioning systems (HVAC) systems contain multiple flaps, each driven by a corresponding motor. Integrated, multichannel motor drivers give designers the ability to drive multiple motors independently in both directions. Having the ability to drive all motors (also known as flap actuators) from a single device saves not only board space but also cost, albeit introducing challenges.
One design challenge when integrating multiple half bridges in one device is how to handle the thermals of the integrated field-effect transistors (FETs) in the operating ambient temperature range. Driving multiple motors with the least amount of pulse width modulation (PWM) signals is a complex task. There are cases where one of these multichannel devices is not enough to drive all of the HVAC system flaps, and multiple device communication setups are required.
Another design challenge is how to control the movement speed of the flap loads. This speed control is typically achieved using a pulse-width modulation (PWM) drive, which requires the generation of PWM signals within the device.
To solve these challenges, TI created the integrated, multichannel DRV8912-Q1 motor-driver family. These drivers can drive up to six motors simultaneously in both directions or up to 11 motors separately in a single integrated circuit. Figure 1 shows the pinout of the device, highlighting its integration of 12 half-bridge outputs, the use of Serial Peripheral Interface (SPI) communication and no PWM input pins.
Drive more motors with fewer brushed-DC drivers | |
![]() |
Reduce design time and increase reliability in your automotive HVAC design with the DRV8912-Q1 family of scalable, multi-channel brushed-DC motor drivers with advanced diagnostics. |
Thermal management, which is managing the die temperature of the device, is one of the biggest challenges with integrated multi-half-bridge drivers. Figure 2 shows the low drain-to-source on-state resistance (RDS[on]) of the integrated FETs in the DRV8912-Q1 motor-driver family across an ambient temperature (TA) and with an operating voltage range from 4.5 V to 32 V. The ability to drive multiple loads while keeping the die temperature below 150°C is essential for a multi-half-bridge device in HVAC systems.
For cars that have multiple HVAC zones and options, there could be a need for multiple devices to drive a large number of flap actuators. This does not mean that you need to increase the number of microcontrollers in your design, however, as the DRV8912-Q1 family does daisy-chain in SPI-based communication. As shown in Figure 3, one microcontroller is a master communication device, and multiple drivers are slaves using a single SPI communication. This feature of the motor driver reduces hardware expenses and overall system size.
Speed control is a benefit of using PWM control in HVAC systems. The motor drivers in the DRV8912-Q1 family have four integrated PWM generators. These generators enable the configuration of duty cycle and frequency, as well as PWM generator assignments to one or more channels. For example, you can assign one PWM generator to half bridges 1, 3, 5 and 6, while assigning a second PWM generator to half bridges 2 and 4. This setup enables you to drive up to two groups of loads with two PWM generators.
Open-load detection (OLD) is a diagnostic feature that determines whether or not there is an open electrical circuit between the HVAC control module and the flap motor. In HVAC systems, disconnected load detection is challenging because the current required to drive the motor changes when the airflow changes. These current changes can cause false open-load faults.
The DRV8912-Q1 motor driver family provides four types of OLD diagnostics to meet HVAC load disconnection diagnostic needs:
HVAC systems vary in complexity and automation level, depending on vehicle class. The DRV8912-Q1 family is pin-to-pin compatible between all devices. With low RDS(on) for thermal performance, SPI daisy-chaining, internal PWM generation and unique open-load detection, the benefits of the DRV8912-Q1 device family for HVAC systems are numerous.
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS” AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you permission to use these resources only for development of an application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either on ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2024, Texas Instruments Incorporated