A4988 VS DRV8825[Video]: What are the differences between them?

This A4988 is a carrier board or breakout board for Allegro's A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection. Before using this product, please read the A4988 datasheet (380k pdf). This stepper motor driver allows you to control one bipolar stepper motor with an output current of up to 2 A per coil (see the Power Dissipation Considerations section below for more information).

Because DRV8825 is a carrier board or breakout board for TI's DRV8825 stepper motor driver, we recommend that you read the datasheet carefully before using it. This stepper motor driver allows you to control one bipolar stepper motor with an output current of up to 2.2 amps per coil (see the Power Dissipation Considerations section below for more information).

A4988 Pinout

DRV8825 Pinout

A4988 Features

• Simple step and direction control interface

• Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step

• Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates

• Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay)

• Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection

• Short-to-ground and shorted-load protection (this feature is not available on the A4983)

DRV8825 Features

• Simple step and direction control interface

• Six different step resolutions: full-step, half-step, 1/4-step, 1/8-step, 1/16-step, and 1/32-step

• Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates

• Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay)

• 45 V maximum supply voltage

• Built-in regulator (no external logic voltage supply needed)

• Can interface directly with 3.3 V and 5 V systems

• Over-temperature thermal shutdown, over-current shutdown, and under-voltage lockout

• Short-to-ground and shorted-load protection

• 4-layer, 2 oz copper PCB for improved heat dissipation

• Exposed solderable ground pad below the driver IC on the bottom of the PCB

• Module size, pinout, and interface match those of our A4988 stepper motor driver carriers in most respects (see the bottom of this page for more information)

A4988 block Diagram

DRV8825 Block Diagram

A4988 Schematic Diagram

DRV8825 Schematic Diagram

A4988 Control inputs:

Each pulse to the STEP input causes the stepper motor to move one micro-step in the direction indicated by the DIR pin. You should not leave the STEP or DIR pins floating in your application because they are not internally pulled to any certain voltage. DIR can be connected straight to VCC or GND if you only want rotation in one direction. RST, SLP, and EN are the three inputs used to regulate the chip's various power states. Check the datasheet for further information on these power states. Please notice that the RST pin is floating; if not in use, connect it to the neighboring SLP pin on the PCB to bring it high. If you are not using the pin, you can connect it to the adjacent SLP pin on the PCB to bring it high and enable the board.

DRV8825 Control inputs:

RESET, SLEEP, and ENBL are the three inputs that govern the chip's power states. See the datasheet for further information on these power states. The SLEEP pin is pulled low with an internal 1M pull-down resistor, while the RESET and ENBL pins are pulled low using internal 100k pull-down resistors. Both of these pins must be high to enable the driver (they can be directly linked to a logic "high" voltage between 2.2 and 5.25 V, or they can be dynamically regulated via connections to digital outputs of an MCU). The default state of the ENBL pin is to enable the driver, so this pin can be left disconnected.

A4988 Using the driver

DRV8825 Using the driver

A4988 Applications

• The A4988 is a bipolar stepper motor micro-stepping driver with a built-in translator for simple operation. This implies we can control the stepper motor with just two pins from our controller, one for rotation direction and the other for steps.

DRV8825 Applications

• Automatic Teller Machines

• Money Handling Machines

• Video Security Cameras

• Printers

• Scanners

• Office Automation Machines

• Gaming Machines

• Factory Automation

• Robotics

• The pin used to supply logic voltage to the A4988 is used as the DRV8825’s FAULT output since the DRV8825 does not require a logic supply (and the A4988 does not have a fault output). Note that it is safe to connect the FAULT pin directly to a logic supply (there is a 1.5k resistor between the IC output and the pin to protect it), so the DRV8825 module can be used in systems designed for the A4988 that route logic power to this pin.

• The SLEEP pin on the DRV8825 is not pulled up by default like it is on the A4988, but the carrier board does connect it to the FAULT pin through a 10k resistor. Therefore, systems intended for the A4988 that route logic power to the FAULT pin will effectively have a 10k pull-up on the SLEEP pin. (This 10k resistor is not present on the initial (md20a) version of the DRV8825 carrier.)

• The current limit potentiometer is in a different location.

• The relationship between the current limit setting and the reference pin voltage is different.

• The DRV8825 offers 1/32-step microstepping; the A4988 only goes down to 1/16-step.

• The mode selection pin inputs corresponding to 1/16-step on the A4988 result in 1/32-step micro stepping on the DRV8825. For all other microstepping resolutions, the step selection table is the same for both the DRV8825 and the A4988.

• The timing requirements for minimum pulse durations on the STEP pin are different for the two drivers. With the DRV8825, the high and low STEP pulses must each be at least 1.9 us; they can be as short as 1 us when using the A4988.

• The DRV8825 has a higher maximum supply voltage than the A4988 (45 V vs 35 V), which means the DRV8825 can be used more safely at higher voltages and is less susceptible to damage from LC voltage spikes.

• The DRV8825 can deliver more current than the A4988 without any additional cooling (based on our full-step tests: 1.5 A per coil for the DRV8825 vs 1.2 A per coil for the A4988 Black Edition and 1 A per coil for the original A4988 carrier).

• The DRV8825 uses a different naming convention for the stepper motor outputs, but they are functionally the same as the corresponding pins on the A4988 carrier, so the same connections to both drivers result in the same stepper motor behavior. On both boards, the first part of the label identifies the coil (so you have coils “A” and “B” on the DRV8825 and coils “1” and “2” on the A4988).

• For those with color-sensitive applications, note that the DRV8825 carrier is purple.

There are many differences between the A4988 and DRV8825. The DRV8825 offers 1/32-step micro stepping, while the A4988 only goes down to 1/16-step. And The DRV8825 has a greater maximum supply voltage (45 V vs. 35 V), making it safer to operate at higher voltages and less prone to LC voltage spike damage. Additionally, Without any additional cooling, the DRV8825 can deliver greater current than the A4988 (based on our full-step tests: 1.5 A per coil for the DRV8825 vs 1.2 A per coil for the A4988 Black Edition and 1 A per coil for the original A4988 carrier). Because the DRV8825 carrier is so similar to our A4988 carriers, the A4988's minimum connection diagram can also be used to connect the DRV8825 to a microcontroller. 

• A4988 Datasheet

• DRV8825 Datasheet

A4988 Package information

DRV8825 Package information

Allegro MicroSystems, LLC is a market leader in high-performance semiconductor development, manufacturing, and marketing. Allegro's cutting-edge solutions cater to high-growth applications in the automotive industry, as well as office automation, and industrial, and consumer/communications solutions. Allegro has design, application, and sales support centers all throughout the world, with its headquarters in Worcester, Massachusetts (USA).