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TPS2663: Prevent a turn off at short interruptions of power supply at IN-pin

Carsten Clauss
Prodigy 60 points
Part Number: TPS2663

Hello,

I would like to prevent a turn off in case off short interruptions of the power supply at the IN pin, because I try to prevent the turn-on-delay after.

I can´t buffer the output voltage, but I can buffer the IN_SYS voltage and UVLO pin. Unfortunately the TPS26635 is still swichting off although there is no UVLO or reverse current.

Is it possible to prevent a turnoff by buffering Vin_sys ? 

  • 0
    TI__Expert 5575 points

    Hi Carsten

    TPS2663x has PGTH input which can be used to enable fast turn on when there is transient at the input. During a system fault recovery (example: OVP high to low or UVLO low to high) when the internal FET gate control is enabled, the device samples the PGTH  pin information and decides whether to turn ON the FET with fast slew rate or follow usual dVdT mode based on the sampled V(PGTH) information. 

    We have documented test result for +/-500V EFT pulses in applications section of device datasheet (Figure 50 and 51)

    Can you share more details about your test conditions. It will be great if you can share schematic portion showing TPS26635 configuration.

    I would like to know following in order to understand your use case

    1. Input voltage and input capacitor

    2. Output load current and output capacitor

    3. PGTH and dVdT pin status

    4. Device current limit 

    5. Transient voltage duration and amplitude at the input

    Thanks & Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Prodigy 60 points

    Hello Abhijeet,

     

    my target is a immediately turn on of the TPS26635 when the input voltage supply turns back after a short voltage interruption.

    To answer your questions:

    1. Input voltage and input capacitor -> 19V 1uF

    2. Output load current and output capacitor -> 750mA (Resistor 25 Ohm) 1uF

    3. PGTH and dVdT pin status -> PGTH is connected to IN_SYS (buffered). dVdT = 2nF

    4. Device current limit -> 2A

    5. Transient voltage duration and amplitude at the input -> The Supply voltage is pulled down to 0V for 100us

     

    I use the TPS26630-33EVM evaluation board with the following changes:

    Overview

    Detail view

    CH1 = IN (5V/DIV)

    CH2 = Power Supply [Source Q1] (5V/DIV)

    CH3 = IN_SYS = PGTH (5V/DIV)

    CH4 = OUT (5V/DIV)

     

    I don´t understand why the TPS26635 is switching off:

    -          IN_SYS is all the time >5V

    -          IN_SYS is all the time >OUT

    -          UVLO is all the time much higher than 1,2V

    -          SHDN is all the time much higher than 0,8V

    -          PGTH is all the time much higher than 1,2V

     

    What else can switch off the TPS26635 ?

    Is it possible that it switch off, when Vin is much higher than OUT ?

     

    Best regards

    Carsten

  • 0 in reply to Carsten Clauss
    TI__Expert 5575 points

    Hi Carsten

    Thanks for sharing the information. As we are discussing this query offline i am closing this thread.

    Thanks & Regards

    Abhijeet