Pololu G2 High-Power Motor Driver 24v13

The Pololu G2 high-power motor driver is a discrete MOSFET H-bridge designed to drive large brushed DC motors. The H-bridge is made up of one N-channel MOSFET per leg; the rest of the board contains the circuitry to take user inputs and control the MOSFETs. The absolute maximum voltage for this motor driver is 40 V, and higher voltages can permanently destroy the motor driver. Under normal operating conditions, ripple voltage on the supply line can raise the maximum voltage to more than the average or intended voltage, so a safe maximum voltage is approximately 34 V.

The versatility of this driver makes it suitable for a large range of currents and voltages: it can deliver up to 13 A of continuous current with a board size of only 1.3? × 0.8? and no required heat sink. The module offers a simple interface that requires as few as two I/O lines while still allowing for your choice of sign-magnitude or locked-antiphase operation. A current sense output gives an indicator of motor current, and the driver can limit the motor current to a configurable threshold. The power supply inputs feature reverse-voltage protection, while integrated detection of various fault conditions helps protect against other common causes of catastrophic failure; however, please note that the board does not include over-temperature protection.

Features

• Operating voltage: 6.5 V to 40 V (absolute maximum)

• Output current: 13 A continuous

• Inputs compatible with 1.8 V, 3.3 V, and 5 V logic

• PWM operation up to 100 kHz

• Current sense output proportional to motor current (approx. 40 mV/A; only active while H-bridge is driving)

• Active current limiting (chopping) with default threshold of 30 A (can be adjusted lower)

• Reverse-voltage protection

• Undervoltage shutdown

• Short circuit protection

General specifications

Dimensions

Using the motor driver

Connections

The motor and motor power connections are on one side of the board, and the control connections (1.8 V to 5 V logic) are on the other side. The motor supply should be capable of supplying high current. There are two options for making the high-power connections (VIN, OUTA, OUTB, GND): large holes spaced 5 mm apart, which are compatible with the included terminal blocks, and pairs of 0.1?-spaced holes that can be used with perfboards, breadboards, and 0.1? connectors.

For good performance, it is very important to install a large capacitor across the motor supply and ground close to the motor driver. We generally recommend using a capacitor of at least a few hundred ?F and rated well above the maximum supply voltage; the required capacitance will be greater if the power supply is poor or far (more than about a foot) from the driver, and it will also depend on other factors like motor characteristics and applied PWM frequency. A through-hole capacitor can be installed directly on the board in the holes labeled '+' and '?' (connected to VM and GND, respectively). The driver includes an on-board 100 µF capacitor, which might be sufficient for brief tests and limited low-power operation, but adding a bigger capacitor is strongly recommended for most applications.

The logic connections are designed to interface with 1.8 V to 5 V systems (5.5 V max). By default, the driver is in a low-power sleep mode; the SLP pin should be driven or tied to a logic high voltage in order to enable the driver. In a typical configuration, only two other pins are required: PWM and DIR.

Pinout

With the PWM pin held low, both motor outputs will be held low (a brake operation). With PWM high, the motor outputs will be driven according to the DIR input. This allows two modes of operation: sign-magnitude, in which the PWM duty cycle controls the speed of the motor and DIR controls the direction, and locked-antiphase, in which a pulse-width-modulated signal is applied to the DIR pin with PWM held high.

In locked-antiphase operation, a low duty cycle drives the motor in one direction, and a high duty cycle drives the motor in the other direction; a 50% duty cycle turns the motor off. A successful locked-antiphase implementation depends on the motor inductance and switching frequency smoothing out the current (e.g. making the current zero in the 50% duty cycle case), so a high PWM frequency might be required.

PWM frequency

The motor driver supports PWM frequencies as high as 100 kHz, but note that switching losses in the driver will be proportional to the PWM frequency. Typically, around 20 kHz is a good choice for sign-magnitude operation since it is high enough to be ultrasonic, which results in quieter operation.

A pulse on the PWM pin must be high for a minimum duration of approximately 0.5 µs before the outputs turn on for the corresponding duration (any shorter input pulse does not produce a change on the outputs), so low duty cycles become unavailable at high frequencies. For example, at 100 kHz, the pulse period is 10 µs, and the minimum non-zero duty cycle achievable is 0.5/10, or 5%.