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UCC3895: Delay AB and CD fail

Chethan hegde
Prodigy 20 points
Part Number: UCC3895

Hi, 

I have set DELAB and DELCD to 220ns and 250ns Respectively in UCC3895. ADS function is turned off. But in two instances, delay time changed to 120ns once and 550ns in another instance. After replacing the IC UCC3895 delay is back to set values. Can you please help me find out, what can cause the Delay functionality to go wrong or fail.

Thanks

  • 0
    TI__Genius 9790 points

    Hi, Chethan

    Delay time is defined by the current of DELAB and DELCD pin, the current is defined by VREF and resistor on DELAB/DELCD. 

    Could you check the bypass cap of VREF pin? The recommended value is not less than 1uF. VREF's  stability is very important. 

    And you need to check the layout of bypass cap of VREF pin, the circuit from VREF to cap to GND should be very short. 

    Yunsheng