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Original question:

TPS35-Q1: TPS35AA38AGADDFRQ1

TPS35-Q1: Startup delay configuration for TPS35AA38AGADDFRQ1

Vivek Kalkur
Prodigy 60 points
Part Number: TPS35-Q1


Tool/software:

Hello,

      We have a requirement of 10sec startup delay time and 200-400ms watchdog timeout period in our design. We also need voltage supervision for 3.3V rail. We had contacted one of TI FAE with this requirement and he suggested to use part# TPS35AA38AGADDFRQ1. Below is the circuit diagram for reference. Watchdog timeout period is set around 277ms with capacitor value of 0.056uF. Let me know the way to achieve 10sec startup delay time with below circuit

Regards,

Vivek

  • 0
    TI__Mastermind 20000 points

    Hi Vivek, 

    The TPS35-Q1 has a functionality called on-the-fly-scaling, with this functionality you can implement a multiplier to your watchdog timeout period to scale to a greater value without needing a RESET asserting. This multiplier is configured they SET[0:1] configuration. The TPS35AA38AGADDFRQ1 has a multiplier of 0 when SET0=LOW and 128 when SET0=HIGH. So you can have a pull-up resistor on the SET0 pin to set your watchdog timeout period as 128*.277s = 35.456s at startup, then use a GPIO to pull SET0 LOW when the .277s timeout is needed. 

    Jesse 

  • 0 in reply to Jesse Villanueva
    Prodigy 60 points

    Hi Jesse,

    Unfortunately, we don't have any external GPIO required to pull down SET0 pin after startup. Is there any way to add startup delay of 10 secs without depending on external GPIO control? We actually intended to replace MAX6734A part in our design due to availability issues. We shared the existing circuit as below and your FAE recommended using TPS35AA38AGADDFRQ1 as replacement part.

  • 0 in reply to Vivek Kalkur
    TI__Mastermind 20000 points

    Hi Vivek

    We unfortunately do not have a WD device with a start-up delay of 10s with voltage supervision. Below is a table of parts we have currently released or releasing by the end of the month. 

    Jesse