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DRV8833: output disabled above 6.5 volts

martin fernandez1
Prodigy 20 points
Part Number: DRV8833

Hello,

this has got me stumped. I'm using the 8833PWP. Connected to 2 brushed motors and layed out as described in the data sheet. All works as expected when VM is below 6.5 volts. Above this voltage nothing at all.

Is seems above 6.5 volts (VM) the motor output pins are not driven at all. Evem thoug the fault pin is not triggered. I have sleep conencted to my VDD (3.3 volts). 

I'm using zero ohms for the sense resistor. PWM frequency is 20KHz. Sleep is connected directly to VDD (3.3volts). Should I connect sleep to VM via a resistor?

Cheers

  • 0
    TI__Guru 56650 points

    Matin,

    DRV8833  chopping current is calculated in Equation 1. Ichop= 200mV/sense resistor.

    If you use zero ohms for the sense resistor, DRV8833 could put the input voltage to the output. When the input voltage gets higher, the output current gets higher. That current may trigger the Overcurrent protection.


    If this analog current limit persists for longer than the OCP deglitch time, all FETs in the H-bridge will be disabled and the nFAULT pin will be driven low. The driver will be re-enabled after the OCP retry period (tOCP) has passed. nFAULT becomes high again at this time.

    Please send me the waveform on nFault pin voltage; VM voltage; output voltage. If you have a current probe, please send me the output current also. What is the DC motor winding resistance?