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TLV809: TLV809K33 reset function abnormal

Feng bin Su
Expert 8760 points
Part Number: TLV809
Other Parts Discussed in Thread: TLV803E

Hi team,

My customer has an issue with the TLV809K33DBVR RESET pin toggle which cannot pull up to high state properly when VDD higher than threshold. The figure below is our system connection.

Customer has tried to remove the 0Ohm which connect to 30-50KOhm at the below of circuit then the TLV809K33DBVR RESET pin can work normally.

The abnormal waveform is as below figure. The reset IC has abnormal behavior: Keep toggle every 200ms.

I have found the e2e as below which is similar as the customer result. Would you think it is the same case? Thanks.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/942659/tlv809-tlv809k33-can-t-work-normally?tisearch=e2e-sitesearch&keymatch=TLV809#

  • +1
    TI__Guru 56345 points

    Hi Ben,

    The issue is the TLV809 consumes about 11uA around where the release threshold voltage (~3V).  Once the output is not asserted anymore, the effective impedance of the system changes.  The schematic shows R514 and R516 is in parallel with R520 and R1151 when the output is asserted (low).  The reason is because TLV809 has a push-pull output stage.  When VDD surpasses the release threshold voltage, the output is pulled high momentarily, the 11uA of current is now flowing through R514 (effective impedance of the system is now only R514 and R516) and causing the voltage at "VDD" of the part to drop below the threshold voltage of the TLV809K33DBVR and the output asserts (low) again.

    My suggestion is to use the TLV803E which has an Iq of 250nA (typ) and is an open drain device.  Having an open drain device does not cause the system impedance to change (I believe) and should solve the customer's issue.   

    Ben

  • 0 in reply to Ben C
    TI__Guru 56345 points

    Hi Ben,

    Are there any updates?

    Ben

  • 0 in reply to Ben C
    TI__Expert 8760 points

    Hi Ben,

    Thanks. It should isolate the issue. We are applying the sample TLV803E for verifying it now.

  • 0 in reply to Feng bin Su
    TI__Guru 56345 points

    Hi Ben,

    Thanks for the update!  Keep posted with your results.  Please start a new thread.  I will close this one.

    Ben