MC33926 dual motor driver
Including €0.01 for ecotax
Overview of the MC33926 dual motor driver from Pololu
Characteristics of the MC33926 dual motor driver
This motor driver carries two Freescale's MC33926 H-bridges. You can command independantly two middle-sized DC motors, for example to differential-drive a mobile robot.
The MC33926 dual motor driver from Pololu sends feedback information on the current in each motor as a proportional voltage. It also includes protections against uder-voltage, over-current and over-temperature.
Using PWM frequencies up to 20 kHz allows to eliminate the audible noise of switching transistors.
Advantages of the MC33926 dual motor driver from Pololu
To allow you to drive your motors with the minimal number of cables, the MC33926 dual motor driver has seven default-overriding jumpers so you can link some input directly to VDD (or to the ground for D1 inputs) withjumper and parametrize your motor driver without external cables.
Moreover, the MC33926 dual motor driver from Pololu connects the 'invert', 'slew' and 'enable' inputs of both H-bridges so you can configure both at the same time.
Headers for the MC33926 dual motor driver from Pololu
The MC33926 dual motor driver from Pololu includes a 25-pin straight breakaway male header so you can connect it to perfboards or breadboards and three 2-pin 3.5mm terminal blocks for making simple motor connections.
Using the MC33926 dual motor driver from Pololu
Pinout of the MC33926 dual motor driver
In a typical application, you need five I/O lines to connect each motor driver channel to a microcontroller: the two input lines, IN1 and IN2, for direction control, one of the disable lines, D1 or D2, for PWM speed control, the current sense output, FB, for monitoring motor current draw (connected to an analog-to-digital converter input) and the status flag, SF, for monitoring motor driver errors.
The control lines can be reduced to two pins per channel if PWM signals are applied directly to the two input pins with both disable pins held inactive.
In all cases, the other unused lines must be connected (using for example the jumpers) to enable proper operation. In the typical case where D2 is used for the PWM input, D1 must be held low to prevent it from disabling the motor driver.
The feedback and error flag outputs are optionnal. They are open-drain outputs, so the two status flag can be wired together for applications where I/O pins are scarce and determining which motor driver is experiencing a fault condition is not necessary.
The EN pin disables the motor driver for both motors, putting the H-bridges in a low-current sleep mode (default mode). You should therefore pull this input high before commanding your motors.
Schematic Diagram of the MC33926 dual motor driver
|VIN||HIGH||This is the main 5–28V motor power supply connection, which should typically be made to the larger VIN pad. The smaller VIN pad can be used to distribute the VIN node to the rest of the application circuit. Operation from 5 – 8V reduces maximum current output the device is also protected for transients up to 40V.|
|GND||LOW||Ground connection for logic and motor power supplies.|
|OUT2||HIGH||The motor output pin controlled by IN2.|
|OUT1||HIGH||The motor output pin controlled by IN1.|
|VDD||HIGH||3-5V logic supply connection. This pin is used only for the SF pull-up and default-overriding jumpers in the rare case where none of those features is used, VDD can be left disconnected.|
|IN2||HIGH||The logic input control of OUT2. PWM can be applied to this pin (typically done with both disable lines inactive).|
|IN1||HIGH||The logic input control of OUT1. PWM can be applied to this pin (typically done with both disable lines inactive).|
|PWM/D2||LOW||Inverted disable input: when D2 is low, OUT1 and OUT2 are set to high impedance. A D2 PWM duty cycle of 70% gives a motor duty cycle of 70%. Typically, only one of the two disable pins is used, but the default is for both disable pins to be active.|
|PWM/D1||HIGH||Disable input: when D1 is high, OUT1 and OUT2 are set to high impedance. A D1 PWM duty cycle of 70% gives a motor duty cycle of 30%. Typically, only one of the two disable pins is used, but the default is for both disable pins to be active.|
|SF||HIGH||Status flag output: an over-current (short circuit) or over-temperature event will cause SF to be latched LOW. If either of the disable pins (D1 or D2) are disabling the outputs, SF will also be LOW. Otherwise, this pin is weakly pulled high. This allows the two SF pins on the board to be tied together and connected to a single MCU input.|
|FB||LOW||The FB output provides analog current-sense feedback of approximately 525mV per amp.|
|EN||LOW||Enable input: when EN is LOW, the both motor driver ICs are in a low-current sleep mode.|
|SLEW||LOW||Output slew rate selection input. A logical LOW results in a slow output rise time (1.5μs – 6μs). A logical HIGH selects a fast output rise time (0.2μs – 1.45μs). This pin should be set HIGH for high-frequency (over 10 kHz) PWM. This pin determines the slew rate mode for both motor driver ICs.|
|INV||LOW||A logical high value inverts the meaning of IN1 and IN2 for both motor drivers.|
Protections and over-heating of the MC33926 dual motor driver from Pololu
The MC33926 dual motor driver contains protections against under-voltage, over-current, and over-temperature, that are reported by a low state on the SF pin. To unlatch the status flag pin toggle the D1, D2 , EN or VIN lines.
The carrier board has a reverse-protection MOSFET for added protection to the motor driver chips.
The MC33926 IC can endure a 5A current but over-heat very quickly in these conditons. We recommand to stay with currents under 3A and to add a heat sink if needed.
The motor driver has a feature that allows it to gracefully reduce current as the current exceeds 5A or as the chip temperature approaches its limit. This means that if you push the chip close to its limit, you will see less power to the motor, but it might allow you to avoid a complete shutdown.
Be carefull while manipulation the MC33926 dual motor driver as it can reach a temperature hot enough to burn you before overheating.