FET driver ENABLE pin for extended control


There was recently some mentioning of EN pin for control purposes on the Github thread.

I just want to clarify something regarding that.

Example :

For stepper control w. 4 pin PWM I am working on a driver w. 4 separate half-bridge drivers, each with a EN (ENABLE) pin.

If for instance we would like to do low side PWM only, with these FET drivers, it will involve using the EN pin, with the MCU to driver PWM signal low. Doing that, will ensure, that the HIGH side never is turned on. All this could enable the use of steppers as power generators, not that it would be especially effective. Is there any other use for it, when driving steppers ?

Another use case is for 3 PWM (BLDC) drivers, where U want to do regen (boost) breaking. Using half-bridge drivers, w. PWM input. Right, that would be a advantage for someone using a stepper driver, like the one im working on, for a 3phase BLDC, if the need for regen arises.

Would you switch the EN pin like that, in the first place ?

Edit: Or you can put a LAPTOP charger to the stepper driver A1A2B1B2 outputs w. a beefy coil, and charge a eBike (52v) battery…

Tell me, HOW is the relationship between input voltage/amp and output voltage/amp?

Hey @Juan-Antonio_Soren_E,

For BLDCs with 6-PWM I have implemented it to the APIs, and for the RP2040 and STM32 MCU types so far. I haven’t tested yet.

But I didn’t implement it to the StepperMotor class, and its not currently supported in 4-PWM mode, as I think we discussed on GitHub (can’t find the link right now).

So I’d say the building blocks for this are in progress, but someone will have to implement it to the StepperMotors and test it out, I don’t really use them…

I think I will sacrifice the TACHO (FAN RPM) input, and just have the PWM output, that leave me with 4 open pins for FET driver Enable pin switching.

Ive put gate resistors on all the high side gates. Maybe I should add those to LOW side as well ?

The thermistor glowing with a green color is placed there to be in contact with a potential heatsink or through some heat_tape.

@runger then maybe for the Dual Core ST MCUs at some point. The feature is not really needed for steppers.


By paralleling the two phases on one suitable coil, the heat is shared between the two bridges. This does need deadtime insertion between the two phases.

Comparing the Portenta H7 size-wise does not really make sense, since the Dual Core STM32H747 is available in a 7X7mm 0.5mm pitch uBall package (The floating MCU below).