TB67S279FTG Mode Select Line toasted?

Other Hardware Motors, Mechanics, Power and CNC
1

Hello all :slight_smile:

I'm trying to build a rotary table using a bipolar stepper with a phase resistance of1.6 Ohms and phase current of 1.7 Amps, using a QT Py and a TB67S279FTG driver (TB67S249FTG Stepper Motor Driver Compact Carrier - Opencircuit).
After some try and error i have it working, all seems fine, just with a single problem:

The driver has three input pins for choosing the step resolution, DM0, DM1 and DM2. Apparantly, Pin DM2 is faulty and I am not able to pick every available Resolution since it won't recognize high input and is thus stuck on low. E.g. wenn I want full step, the driver goes into standby. As is, only 1/16, 1/2(b), 1/2(a) steps are available...

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Is there a way to confirm that the DM2 line is toast? E.g. by measuring with a Multimeter?

2

Page 5 of the datasheet shows DMODE2 pulled to ground with a 100K pulldown resistor, check resistance of pin to ground with Ohmeter.
https://opencircuit.shop/resources/file/ff121666d22c39cd411a7d643f25c6c382300706466/TB67S249FTG-datasheet.pdf

1 Like
3

It measures 8 MegaOhms, so seems like it is in fact toast.
Thanks for the pointer to the specsheat! Could have known better and try to look it up in there from the beginning. :+1:

4

Actually that might not prove anything, on-chip resistances are implemented as
FETs of special geometry, so if the chip is measured powered down, the resistance will not be enabled.

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