Methods to Reduce Layout Size and Battery Consumption in Low-Voltage H-Bridge Applications

“For battery-operated and motor-driven systems such as smart locks, video doorbells, gas and water meters, a design focus is to reduce overall power consumption by keeping current consumption low when the motor is not actively driven, so that consumers do not have to change batteries as often . If you are interested in the implementation of these applications, TI has reference designs for IR cut filters for Electronic smart locks and IP network cameras.

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In motor-driven building automation and grid infrastructure applications such as smart meters, smart locks, Internet Protocol (IP) webcams, and video doorbells, there are several ways to design low-voltage systems, as shown in Figure 1.

Figure 1: Battery-Powered Systems: Video Doorbells, Smart Meters, and Electronic Smart Locks

Common challenges when designing motor drive systems for these applications include: meeting the need for durable, resilient, and safe motor operation; shrinking printed circuit board (PCB) space; and meeting various system requirements. When considering motor driver current consumption, special attention needs to be paid to: integrated circuit (IC) and necessary component board size; design simplicity, flexibility and scalability to meet the needs of multiple platform types.

Reduce power consumption

For battery-operated and motor-driven systems such as smart locks, video doorbells, gas and water meters, a design focus is to reduce overall power consumption by keeping current consumption low when the motor is not actively driven, so that consumers do not have to change batteries as often . If you are interested in the implementation of these applications, TI has reference designs for IR cut filters for electronic smart locks and IP network cameras.

Below we will compare two methods of reducing the power consumption of the H-bridge when not driving the motor using the following devices:

Discrete load switches between the battery and motor drive circuits to connect or remove power;

Devices such as TI’s DRV8210 have a dedicated low-power sleep mode with a typical sleep current of 37nA.

Compared to the first device, the second device reduces PCB space by up to 50% and removes power dissipating components when connecting the H-bridge power supply. See Figure 2.

Figure 2: (a) Simple implementation of H-bridge with low-power sleep using external cutoff switch; (b) TI DRV8210 with auto-sleep mode

Reduce PCB and Motor Drive Subsystem Size

Modern smart meters and other low-voltage motor drive applications are becoming more advanced, integrating sensing, wireless and wired communications, power management, and many other modules, as shown in Figure 3.

Figure 3: Reference Design for a Rotary Water Meter

The sheer number of these modules means that it must be ensured that subsystems such as motor drives and surrounding components use as little PCB space as possible. Figure 4 shows a commonly used discrete H-bridge implementation for driving a low-voltage brushed DC motor. However, this H-bridge does not have some necessary functions such as overcurrent protection, undervoltage lockout, thermal shutdown and dead-time control, which requires additional firmware and hardware work.

Figure 4: Discrete implementation of H-bridge and circuitry around the base; PCB area is 16mm x 25mm or 400mm²

Compared to discrete implementations, motor drivers such as the DRV8220 (which have a 4mm package size)²or 1.92mm²) can reduce PCB space by 93% or more, as shown in Figure 5. Check out the technical document “Discrete or Integrated, Not That Risky” to learn more about how our motor drivers reduce board space and component count. Additionally, all TI brushed DC motor drivers, including the DRV8220, offer integrated dead-time control and protection against overtemperature, undervoltage lockout, and overcurrent events, reducing the need for additional components, further reducing PCB space.

Figure 5: DRV8220DSG integrated motor driver layout; PCB area is 4.5mm x 4.4mm, or 19.8mm²

Design flexibility, simplicity, reusability and scalability

Many applications in building automation, grid infrastructure, and personal electronics have multiple platforms with different system requirements. Take, for example, a smart hygiene device company that designs soap dispensers, automatic toilets, tissue dispensers, and similar applications, as shown in Figure 6. These applications require different types of automated loads: bidirectional brushed DC motors for dispensing valves, lock-on solenoids for flush dosing valves, and unidirectional brushed DC motors for tissue dispensing.

Figure 6: Common motor-driven smart sanitary equipment applications

Ideally, you would have a flexible solution for all of these scenarios, but it often takes a lot of time and effort to find discrete components or ICs that support pin compatibility across voltage and current ranges. Achieving this simplicity, scalability and interface flexibility enables the use of the same or similar drivers to drive different motors, relays, solenoids and other types of loads. In addition, the reusability of the design is also taken into account, resulting in a significant reduction in time-to-market. See Section 9 of the DRV8210 datasheet for more details on how the DRV8210 motor driver family can help achieve these benefits.

As described in this article, numerous low-voltage and battery-powered platforms in building automation and grid infrastructure applications require motor drives that are flexible, scalable, and easy to design. At the same time, these motor drive systems must provide a robust low-power sleep mode to maximize battery run time and occupy only a small area of ​​the PCB to leave enough space for other system components. Check out Low-Voltage H-Bridge Motor Drivers to learn more about how TI achieves the advantages of small size, low power consumption and design scalability.