Pololu VNH5019 for DC Motor with Driver Carrier

Overview

This module is a compact breakout board for ST’s high-power VNH5019 motor driver IC, a fully integrated H-bridge that can be used for bidirectional speed control of a single brushed DC motor. The basic operation of the driver is summarized below, but we also recommend careful reading of the VNH5019 datasheet (475k pdf) before using this product. The board incorporates most of the components of the typical application diagram on page 14 of the VNH5019 datasheet, including pull-up and current-limiting resistors and a FET for reverse battery protection. It ships fully populated with its SMD components, including the VNH5019, as shown in the product picture.

Features

• Operating voltage: 5.5 - 24 V¹

• Output current: 12 A continuous (30 maximum)

• 3V-compatible inputs

• PWM operation up to 20 kHz, which is ultrasonic and allows for quieter motor operation

• Current sense output proportional to motor current (approx. 140 mV/A; only active while H-bridge is driving)

• Motor indicator LEDs (indicates what the outputs are doing even when no motor is connected)

• Robust:

○ Reverse-voltage protection to -16 V

○Can survive input voltages up to 41 V

○Undervoltage and overvoltage shutdown

○High-side and low-side thermal shutdown

○Short-to-ground and short-to-Vcc protection

VNH5019 motor driver carrier, bottom view with dimensions.

¹ While the overvoltage protection typically kicks in at 27 V, it can trigger at voltages as low as 24 V, so we do not recommend using this motor driver with 24 V batteries, which significantly exceed 24 V when fully charged.

Using the Motor Driver

The motor and motor power connections are on one side of the board and the control connections are on the other side. The motor power supply connects to the large VIN and GND pins; it should be between 5.5 and 24 V and have the ability to deliver the potentially high currents the motor will require. The logic power supply (typically 2.5 - 5 V) connects to the small VDD and GND pads on the control side of the board and is used to power the internal pull-ups on the ENA and ENB enable lines. Any control input voltage above 2.1 V is guaranteed to be high, so this driver can be directly interfaced into both 3.3 and 5 V systems.

The following diagram shows the minimum connections required for interfacing this motor driver with a microcontroller:

Minimal wiring diagram for connecting a microcontroller to a VNH5019 motor driver carrier.

In this configuration, motor direction is determined by the states of the INA and INB pins and motor speed is controlled by the duty cycle of a PWM signal supplied to the driver’s PWM pin. The PWM pin is pulled low on the board, so the motor driver outputs are effectively disabled by default; the INA and INB pins are floating (they are not pulled to any particular default voltage). See the truth tables in the VNH5019A-E datasheet for more information on how the INA, INB, and PWM pins affect the driver outputs, OUTA and OUTB. Note that it is also possible to save a microcontroller I/O line by directly PWMing the INA and INB pins while holding the PWM pin high (e.g. by connecting it directly to VDD), but the trade-off is that this only works at low frequencies (a few hundred Hertz or less).

This board features motor indicator LEDs that can be used to test that motor driver outputs are working as expected before actually connecting a motor (this can be especially helpful in detecting problems due to insufficient power supplies). The LED brightness with increase with motor speed, and the LED color changes with direction.

Pinout

Schematic Diagram

Schematic diagram for the Pololu VNH5019 motor driver carrier.

This schematic is also available as a downloadable pdf: VNH5019 carrier schematic (34k pdf).

Current sensing

The current sense output is approximately 140 mV/A. Note that the output is only active while the H-bridge is driving; it is inactive (low) when the driver is coasting (motor outputs are high impedance) or braking. During the coast portion of the drive/coast cycle, current will continue to circulate through the motor, but the voltage on the FB pin will not accurately reflect the motor current.

Real-world power dissipation consideration

The motor driver IC has a maximum continuous current rating of 30 A. However, the chips by themselves will overheat at lower currents (see the table above for typical values). The actual current you can deliver will depend on how well you can keep the motor driver cool. The carrier’s printed circuit board is designed to draw heat out of the motor driver chips, but performance can be improved by adding a heat sink. In our tests, we were able to deliver short durations (on the order of milliseconds) of 30 A and several seconds of 20 A without overheating. At 6 A, the chip gets just barely noticeably warm to the touch. For high-current installations, the motor and power supply wires should also be soldered directly instead of going through the supplied terminal blocks, which are rated for up to 16 A.

This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it.

Many motor controllers or speed controllers can have peak current ratings that are substantially higher than the continuous current rating; this is not the case with these motor drivers, which have a 30 A continuous rating and over-current protection that can kick in as low as 30 A (50 A typical). Therefore, the stall current of your motor should not be more than 30 A. (Even if you expect to run at a much lower average current, the motor can still draw short bursts of high currents, such as when it is starting, if special steps are not taken.)

Specifications

Dimensions

General specifications

Notes:

1 Without included headers. The height applies to boards manufactured after December 2014; before this, the electrolytic capacitor was 0.07" taller, making the board height 0.37".
2 Without included headers.
3 Not recommended for use with 24V batteries.
4 To -16 V. Connecting supplies over 16 V in reverse can damage the motor driver.

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