Other Parts Discussed in Thread: DRV8884, DRV8885, DRV8886,
Dear Sir,
We have used stepper motor driver IC DRV8884 since long time. It works perfect in production.
We are using stepper motor at 12V / 300mA per winding.
But, unfortunately due to unavailability of stock of DRV8884,DRV8885,DRV8886, we have to change the IC & have to find alternative of DRV8884.
We have found DRV8428, which can be fitted with our criteria.
We have designed one prototype of DRV8428. Design specification is as below:
1) Enable & Sleep pin always logic high by MCU(3.3V). currently we have disabled sleep mode & Enable MOSFETs.
2) input step frequency at STEP pin 800Hz(square wave pulse train). DIR pin is logic high OR low by MCU. (3.3V / 0V, both has been tested)
3)VM = 12V with all necessary capacitor (200uF // 10nF)
4)PGND / GND / Thermal Pad - all are grounded.
5) DVDD = we get 5V output from IC which is perfect as per design.
6) VREF = by using resistor devider network(8200 ohm & 1800 ohm) & DVDD of IC, we have set 0.9V which is also perfect as per design.(for 300mA, Vref should be 0.9V as per equation given in datasheet)
7) Microstepping Pin = M1 logic high (3.3V) & M0 logic low (1/4 Microstepping)
8) Decay = 0 = Smart Tune
Now Queries are as below:
1) Microstepping Pin M0 : It is TRI-LEVEL input pin.
This pin is internally pulled down in the IC. We are able to make it logic high OR logic low by MCU.
but how to make it High - Z mode?
If we left it open or floating, it is measured as logic low because of internal pull down resistor. If we measure voltage then we get 0V.
2) Main issue is We do not get pulses on A1, A2, B2. these 3 pins remains at 12V.
only B1 gets the pulses.
I have checked this with & without connecting Stepper motor. but both time result is same. only B1 gets pulses & all others remains at 12V.
I have tested this with DRV8884 with & without connecting Stepper motor., All terminals (A1,A2,B1,B2) gets pulses perfectly both times.
So, I am confused now, what could be the problem so that only one terminal gets pulses, all other remains at 12V. this is strange. isn't it?
Please help me to sort out my queries.
Regards,
Jigar