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TPL5111: Timing Accuracy

Victor Aprea
Intellectual 940 points
Part Number: TPL5111

I have configured TPL5111 for 10 minute period according to the datasheet, by installing 127k (1% tolerance) in parallel with 107k (1% tolerance) between pin 3 (DELAY/M_DRV) and GND. I measure with an multimeter the resistance between pin 3 and GND and it reports 57.5k, which is within tolerance of the resistors. I'm not getting very close to 10 minute (i.e 600 second) intervals though. Rather, I'm getting 470 second intervals or (i.e. ~78% of the expected interval). I've got three units all exhibiting the same "running fast" behavior. What might I be missing here?

  • 0
    Intellectual 940 points

    I also have 0.1uF in parallel with those resistors, could that explain it? I will try removing it and report back. 

  • 0 in reply to Victor Aprea
    TI__Mastermind 19780 points

    Hi Victor,

    How are you measuring the tIP you are setting?  Is it from rising edge of DRV to rising edge of next DRV signal?

    I suspect the cap in parallel is a likely cause of the error.  As the TPL5111 initializes, a current is injected into the external resistance and the voltage is sampled by an ADC.  The cap may not be done charging.  I do not have the details on the amount of current at this time.

    Please post the TPL5111 portion of your schematic as well here if the cap doesn't resolve your issue.

    Best Regards,