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Original question:

SN74LVT8996: SN74LVT8996

SN74LVT8996: TRST Input

Jon Key
Intellectual 920 points
Part Number: SN74LVT8996
Other Parts Discussed in Thread: UCD9090-Q1, UCD9090, ,

Hello,

My customer is using SN74LVT8996-EP in a design with the UCD9090-Q1 as the JTAG device. The UCD9090 calls for a 10kOhm external pull down on the /TRST line, but the default state of the SN74LVT8996-EP is to buffer /TRST high (due to the internal pull up on /PTRST).

Is it recommended to place an external pull down on /PTRST to meet the requirements of UCD9090 when there is no JTAG communication taking place? If so, what value should the /PTRST pull down be?

Thanks,

Jon

  • 0
    TI__Guru* 96842 points

    Is it recommended to place an external pull down on /PTRST to meet the requirements of UCD9090 when there is no JTAG communication taking place? If so, what value should the /PTRST pull down be?

    Hi Jon,

    I'm afraid I don't know the requirements for the UCD9090 - you indicated this question is about the SN74LVT8996, so the system sent the question to me.

    I can tell you that you can put a pull-down on the /PTRST pin of the SN74LVT8996 as long as it is 10kohm or smaller. The weak internal pull-up is listed as somewhere between 125kohm and 450kohm (3.6V/30uA to 3.6V/8uA).