Hi teams
My customer encounters some problems with DRV8870. The application details are listed below:( I didn't obtain the schematic from the customer)
Schematic/Configuration: IN+ connected with MCU GPIO and IN- connected to GND. 30Khz Switching frequency with 12V voltage supply.
It means that only two operation status could be achieved: Forward and coast (As the IN- connected to GND and always be logic low level.)
Issue phenomenon: When the PWM duty cycle in IN+ is 50% the motor spin normally but when the duty cycle decrease to 33% the motor stops with obvious vibration. The output voltage waveform is shown below.
My questions:
- Are 30Khz switching frequency is suitable for DRV8870? What factor we should consider during switching frequency selection? (efficiency? motor parameter? )
- For such a design that connects IN- to GND is there any potential risk?