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TPS7A8300: TPS7A8300 EN deglitch filter

Neo.Wang
Intellectual 870 points
Part Number: TPS7A8300

Hi TI experts,

In our design, there is an uncontrollable high pulse (3.3V) applied to EN pin before normal power up sequence starts.

The pulse width is about ~10ns. Is there any deglitch filter inside TPS7A8300 EN pin which can filter this pulse? Will this pulse trigger TPS7A830 operating?

Thanks

Neo

  • 0
    TI__Expert 5370 points

    Hi Neo,

    According to the datasheet section 8.1.1.1 Enable (EN) and Undervoltage Lockout (UVLO), "The TPS7A8300 only turns on when both EN and UVLO are above the respective voltage thresholds." This means that VEN, VIN, and VBIAS (if used) will have to be above their respective UVLO thresholds in order for the device to enable.

    To determine if this 3.3V pulse will cause TPS7A830 to enable, can you help send a schematic that shows TPS7A8300 and surrounding connections? Of particular interest is if the bias pin is being used and if the IN and EN pins are tied together or supplied separately.

    I will also be checking in parallel with my team to see if there is any type of deglitch filter that might result in the ~10ns pulse of 3.3V on the EN pin to be filtered out.

    Regards,

    Kelsey

  • 0 in reply to Kelsey Farr
    Intellectual 870 points

    Hi Kelsey,

    Attached the schematic, the bias is not used. 

    In this design, VIN (3.3V_AUX) comes up firstly then followed by a 10ns pulse on EN pin. We used separated VIN and EN connection.

    Please help check on this. 

    Thanks

    Neo

  • 0 in reply to Neo.Wang
    TI__Expert 5370 points

    Hi Neo,

    Thanks for sending! I checked with our design team, and their feedback was that if the 3.3V pulse on the EN pin is only ~10ns, the device will not have time to start regulating before the pulse ends. This is true regardless of whether VIN and VEN voltages both exceed the respective UVLO thresholds. So, it is not expected for the pulse to trigger TPS7A8300 operating.

    I also reviewed the schematic, and everything looks good. The one thing you could do if desired is remove the capacitor on the BIAS pin if this functionality is not used, as this will not impact functionality of the device. BIAS can be left floating if not used. I think the "NONE" marking might indicate that this cap won't be populated, but I wanted to mention it just in case.

    Regards,

    Kelsey

  • 0 in reply to Kelsey Farr
    Intellectual 870 points

    Hi Kelsey,

    Thanks for confirmation.

    Yes, "NONE" in schematic means this cap won't be populated.

    Thanks.