How to measure VRF using 'via' on drv8834

i’ve read this advice from Derrill in post

how do you ‘measure VREF at the via’ ?

i see the ‘through hole’ (which i guess is ‘via’) which on my DRV8834 is above the trim pot, and i have a multimeter.
is there some kind of special probe i need to have ?
or do i solder something there ?

i’m assuming the ground probe would be placed on the ground rail for the driver power.

once i have the correct multimeter placement i assume i just ‘run’ the driver with motor attached and take a reading, then use the formula (Current Limit = VREF × 2) and adjust the pot until i get what i need. right ?



You’re definitely on the right track. The via you see between the potentiometer and the IC is the best place to measure VREF, that formula for the desired voltage is correct, and the potentiometer will allow you to adjust it. There is a tinned solder pad at the via, which should provide a good contact if you stick the point of a standard multimeter probe into the hole. The measurement will be most accurate if the ground probe is placed on the ground at the carrier board, though other nearby grounds should give a fairly accurate result.

The voltage for the current calculation can be measured accurately with the motor disconnected. It is better to leave it disconnected while adjusting the current in this manner to avoid accidentally creating a situation where the motor is driven with more current than desired.


got it!

thanks, nathan.