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TPS62810-Q1: Can we use 1K ohm for PG pin pull up ?

PYTsai
Genius 11675 points
Part Number: TPS62810-Q1
Other Parts Discussed in Thread: TLV62569

Hi 

In our application TPS62810-Q1 PG out is connected to the enable pin of 3 pcs of TLV62569. 

We followed the TPS62810-Q1  EVM value 100K ohm and see the PG can not turn on the 3 pcs of TLV62569.

We need to reduce the pull high resistor to 1K ohm for our circuit to work correctly. 

May i check,  Can we use 1K ohm for PG pin pull up ? 

  • 0
    TI__Expert 8420 points

    Hi PYTsai,

    100kohm seems to cause a large voltage drop , which makes the PG voltage of TPS62810 to be lower than V_IH of TLV62569. Therefore TLV62569s do not recognize the PG voltage as being a logic high.

    Could you please share a picture of your test setup and schematic? What are the operating conditions for TPS62810-Q1 and TLV62569?

    Regards

    Sabrina

    PS: This is currently holiday period please allow some delay in answering. 

  • 0 in reply to Sabrina
    TI__Genius 11675 points

    Hi Sabrina,

    Schematics attached as below. The operation condition for TPS62810 is 5V -> 3.3V 2A. TLV62569 3.3V -> 1.8V 1.5A. 

  • 0 in reply to PYTsai
    TI__Expert 8420 points

    Hi PYTsai,

    Thanks for the details.

    Are you connection the three TLV62569 to the single PG of TPS62810? it is not clear to me with this schematic

    In my opinion for these operating conditions, 1 kohm resistor is less. In case PG is low, this could cause a higher current than I_PG(2mA) to flow across the PG switch of TPS62810

    Did you try out connecting with higher values like 4k or 6kohm? do you get the same issue?

    You can find, details on how to calculate the minimum pull up resistor on page 3 of this app note http://www.ti.com/lit/an/slva485/slva485.pdf

    Regards,

    Sabrina

  • 0 in reply to Sabrina
    TI__Expert 5425 points

    Hi PYTsai,

    i don't see a need for using 10k from EN to GND at the EN of the TLV62569 (R985). As I understand it, this is the main reason for having problems with the value of the pull up resistor at PG of TPS62810. Why are you using 10k there? If the circuit above is complete this resistor is not needed at all. PG properly controls the EN at all conditions. 

    Best regards,

    Juergen