MC33926 driver drive/break mode

Hello. I’m using your MC33926 Dual driver. I have a question about PWMing IN1 and IN2 in “dive/brake” mode.
My config of pins:

EN - High
IN1-pwm/??
IN2 - pwm/??
M1D2 ----- High
M1D1 ----- GND
INV - GND

My problem is I have only ONE available pwm channel from my uC. I intent to switch this pwm signal between IN1 and IN2 with a multiplexer. In order this to work I need IN1/IN2 have at LOW state when the other one is pwm-ed, but they are shmitt stiggered to HIGH by design. My question is: how to make IN1/IN2 pull down when not used? Maybe setting INV pin to HIGH should do the trick? Or maybe some pull-down 1M resistor would do ?(but then if the pin will be pwm-ed the resistor could shorten the pwm to the ground?).

Please help:)
Simon

Please help me since it is quite urgent.
Best regards,
Simon

Hello.

I have a simpler suggestion for you. Just connect your PWM to one of the inputs, such as IN1, and connect the other input, IN2, to a digital output from your MCU. When you want to drive in one direction at a given duty cycle, drive IN2 low and use a normal PWM on IN1. When you want to drive in the other direction at a given duty cycle, drive IN2 low and invert your PWM on IN1 (or set the duty cycle to be 100% - desired duty cycle). Does this make sense?

- Ben

Hi,

Please note that if you do what Ben suggests, you will have a high-side brake in one direction and a low-side brake in the other direction. Probably not a problem, but I wanted to point it out anyway.

- Ryan

Thank you for a reply :slight_smile:
I agree your idea is much simplier. How the difference between high-side and low-side breaking would affect my motor? And which braking is better one? (low low or high high as to my understanding…)
Anyway, I’m very happy with this easier solution, thanks a lot :smiley:

From the motor’s perspective, there is functionally no difference between high- and low-side braking. The braking is the result of the two motor leads being shorted together. High-side braking shorts both leads to power while low-side braking shorts both leads to ground.

The main benefit to low-side braking is that it makes it slightly less likely for you to accidentally short power and ground if you’re sloppy with your connections or the way you handle the powered robot. (When you are using low-side braking and the motors are stopped, the motor driver outputs are at ground; when you are using high-side braking, the motor driver outputs are still at VIN, even though the motors aren’t doing anything.)

- Ben

Thank you for a brief explenation of the issue :wink: