Texas Instruments’ DRV8801 is a tiny H-bridge motor driver IC that can be used for bidirectional control of a single brushed DC motor at 8 V to 36 V. It can supply up to about 1 A continuously and can tolerate peak currents up to 2.8 A for a few seconds, making it a good choice for small motors that run on a wide range of voltages. Since this board is a carrier for the DRV8801, we recommend careful reading of the DRV8801 datasheet (1MB pdf). The board ships populated with all of its SMD components, including the DRV8801.
In a typical application, power connections are made on one side of the board and control connections are made on the other. Aside from motor and power connections, the only required pins are DIR and PWM (called PHASE and ENABLE in the DRV8801 datasheet, respectively). A PWM signal can be applied to the PWM/ENABLE pin to achieve variable speed control in the direction determined by the state of the DIR/PHASE pin. The carrier board pulls PWM low by default, so the driver is only enabled when this pin is supplied with a high signal. The DIR pin does not have a defined default state, which means outputs could behave erratically if the DIR pin is left disconnected while the PWM pin is high.
The BRAKE pin determines whether the motor brakes or coasts when PWM pin is low (this pin is called MODE1 in the DRV8801 datasheet). The carrier board pulls it high, which corresponds to braking (both motor outputs are shorted together through ground). Setting the BRAKE pin low sets the outputs to coast whenever the PWM pin is low (both motor outputs are off). We generally recommend leaving this high while supplying a PWM signal to the PWM pin to get drive-brake (or “slow-decay”) operation, as this typically provides a more linear relationship between PWM duty cycle and motor speed than drive-coast (or “fast-decay”), and it can result in better performance at low duty cycles. The following truth table shows how the PWM, DIR, and BRAKE pins affect the driver outputs:
|DRV8801 Truth Table|
|PWM||1||1||PWM (H/L)||L||forward/brake at speed PWM %|
|PWM||0||1||L||PWM (H/L)||reverse/brake at speed PWM %|
|L||X||1||L||L||brake low (outputs shorted to ground)|
|PWM||1||0||PWM (H/OPEN)||PWM (L/OPEN)||forward/coast at speed PWM %|
|PWM||0||0||PWM (L/OPEN)||PWM (H/OPEN)||reverse/coast at speed PWM %|
|L||X||0||OPEN||OPEN||coast (outputs off)|
Note: When braking, the driver brakes low because the DRV8801’s MODE2 pin is pulled low on the carrier board. The MODE2 pin is not exposed to the user.
The SLEEP pin is pulled high on the board through a 10k resistor and can be left disconnected if you do not want to use the low-power sleep mode of the DRV8801.
The FAULT pin is an open-drain output that is driven low by the chip whenever an over-current, over-temperature, or under-voltage condition occurs. The carrier board includes a pull-up resistor on this pin, so no external pull-up is necessary. Note that the FAULT pin is a status-only signal that does not affect device functionality, so a low FAULT signal does not necessarily mean the driver outputs are disabled. For example, the driver will start operating normally once the motor supply voltage is above 8 V, but the FAULT output will be low until the motor supply voltage reaches approximately 12 V. Please see the datasheet for more information about how the DRV8801 responds to and reports faults.
The CS pin outputs an analog voltage proportional to the motor current (approximately 500 mV per A).