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DRV8908-Q1: DRV8908 OCP thrigger value below the spec marked

lin fusai
Prodigy 40 points
Part Number: DRV8908-Q1

circuit: the out1-3 drive the USS 

1. use the current proble to capture the OUT1 transient  current,  the current value is 424mA

2.the channel output is abnormal

3.the MISO message indicate the OUT1 OCP bit set

  • 0
    TI__Mastermind 23411 points

    Hey Lin,

    What load were you driving?  And did the OCP occur during startup with no acceleration?  I am not familiar with "USS"

    Give me another day to look into this. 

    Regards,

    Jacob

  • 0 in reply to Jacob Thompson
    Prodigy 40 points

    the USS load is 300mA current maximum  value, and the DRV8908 OUT1 support 4*USS ( the maximum value is 300mA*4=1.2A)

  • 0 in reply to lin fusai
    TI__Mastermind 23411 points

    Hey Lin,

    It is not uncommon for startup current to be 4x the rated maximum current.  I recommend implementing an acceleration/ramp of your input to limit the inrush current, start with PWM duty cycle of 1% and increase up to 100% over 500ms for example, see if that solves OCP.  Just this morning I was testing a motor with 500mA current rating and it drew 1.9A on startup without acceleration.  

    Can you take an oscilloscope capture more zoomed in on the current spike? I wonder if spike was larger than 424mA but that's just what the scope captured at this sample rate. 

    Regards,

    Jacob