Features and Benefits

Low RDS (on) output; full-step and half-step capability; small package; forward, reverse, and brake modes for DC motors; sleep mode with no current consumption; PWM control up to 250 kHz; cross-current protection; thermal shutdown (TSD).

illustrate

The A3901 is a dual full-bridge motor driver designed for voltage portable applications including bipolar stepper motors or brushed DC motors. The outputs are optimized for low voltage drop, currents up to ± 400mA (± 800mA with outputs in parallel), and an operating voltage range of 2.5 to 5.5 V. Four inputs (IN1 to IN4) can control bipolar stepper motors in full-step or half-step mode, or DC motors in forward, reverse, or brake mode. Inputs can be current or speed PWMed controlled at frequencies up to 250 kHz. Internal protection circuitry includes thermal shutdown (TSD) and crossover (shoot-through) protection.

The A3901 is nominally 3 mm x 3 mm x 0.75 mm high in a 10-lead DFN package with exposed thermal pad (package "EJ"). This small package is lead-free, with a 100 % matte tin-plated lead frame.

Feature performance

Function description

device operation. The A3901 is a dual full bridge low voltage motor driver capable of operating a stepper motor or up to two DC motors. The MOSFET output stage greatly reduces the voltage drop and power dissipation at the output of the A3901 compared to typical bipolar transistor drivers.

Internal circuit protection includes hysteretic thermal shutdown, clamp diodes, and cross-current protection.

The A3901 is designed for portable applications with a typical power-down (sleep mode) current of 50 mA and an operating voltage of 2.5 to 5.5 volts. The A3901 logic inputs are compatible with 3 to 5 volt logic.

The output current can be adjusted by input pulse width modulation (PWM). Full-bridge outputs can be paralleled for higher current applications (see Figure 6).

In the event that the logic supply voltage drops below 2.5V, both the sink and source RDS(on) will increase beyond the specified value. In extreme cases, no power is delivered to the motor. However, the device will not be damaged.

In stepper operation, the device can be driven in full-step or half-step mode. The step mode is set by the signal mode on the INx terminal, as shown in the step timing diagram.

External Pulse Width Modulation. A pulse width modulation input allows adjustment of the output current. Slow decay mode works by holding one input high while PWMing the other input. Keeping one input low and pushing the other in will result in rapid decay. See external PWM diagram.

sleep mode. Pulling all input voltages to 0.5V or less puts the A3901 into sleep mode, during which it typically pulls 50mA.

Thermal shutdown. If the junction temperature reaches 165°C, the A3901 will disable the output. When entering thermal shutdown, the output will re-enable after the junction temperature drops by 15°C.

braking mode. When driving a DC motor, the A3901 will enter braking mode (turn on both receiver drivers) when all inputs INx are logic 1. There is no protection when braking, so care must be taken that peak currents during braking do not exceed the absolute maximum current.