The only supply
VM is the only supply the board has, and the chip builds its own internal supply out of it. Both edges of the 2.7 to 10.8 V window catch people, and a nominal 12 V pack is past the top one before you plug it in.
One pin, and one rail behind it
There is no logic supply on this board. VM feeds the motors and the chip's own internal supply, which is the reason the pinout has no 3.3 V input.
VM arrives at the power terminal across the top, VM on the right under the + and GND on the left under the −, or at pin 2 of the control header. They are the same net. Use one.
The bottom edge takes the logic with it
The operating range starts at 2.7 V. Below that nothing is promised, and by 2.6 V at the latest, with VM falling, the undervoltage lockout switches off every circuit in the chip and resets its logic. It comes back when VM rises again.
The symptom is a board that ignores good signals while your microcontroller, on its own regulator, carries on sending them. It reads as a dead driver or a wiring mistake, and it is usually a flat pack, or a pack pulled down by the motor it is powering.
Between 2.7 and 5 V the part works, but its switches have more resistance and the datasheet's current rating falls, so a motor gets less than the same motor at 5 V would.
The top edge is closer than the label
10.8 V is the top of the operating range. 11.8 V is the absolute maximum, which is not a performance limit but the point past which the part may be damaged.
A nominal 12 V pack is not 12 V. Three lithium cells fresh off the charger are 12.6 V, over the absolute maximum with nothing connected. Eight NiMH cells are 9.6 V nominal and around 11 V straight off the charger, which is over the operating range.
Two supplies that fit comfortably are a two-cell lithium pack at 7.4 V (8.4 V charged) and four alkaline cells at 6 V. With the sense resistors at 0 Ω, VM also sets the current in a stepper coil, so which one is right depends on the motor. That is the last article in this book.
Grounds have to meet
The control header's GND and the power terminal's GND are the same net, and both have to be common with your microcontroller's ground. A logic high is a voltage relative to a ground both ends agree on; without a shared return, the signals your board sends are not the signals the driver sees.
When it does not work
Check VM at the board before anything else. Below 2.7 V the part is out of specification, and by 2.6 V (VM falling) its undervoltage lockout has switched off every circuit in the chip, while your microcontroller, on its own regulator, carries on sending signals.
A bench supply holds its voltage and a battery does not. Motor inrush pulls a pack down for a moment, and if that dip reaches the lockout the chip resets in the middle of your ramp. Measure VM at the board under load, not at the battery at rest.
10.8 V is the top of the operating range and 11.8 V is the absolute maximum, past which TI says the part may be permanently damaged. Three lithium cells fresh off the charger are 12.6 V, so the pack is over the absolute maximum before the motor has drawn a single amp.
Eight pins on the control header, and how many of them you actually have to connect. Here is what each one is for and which ones you can leave alone.
Wire it to your board →Edit this page — content/books/drv8833/the-only-supply.mdx
Questions about this product
See what other owners have asked, and read their solutions.
DRV8833 Dual Motor Driver
Loading discussions…
Discuss this article
Ask about this page. The answer stays here, on the page it belongs to, for whoever hits the same wall next.