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TL1963A-Q1: TL1963AQKTTRQ1: 1.8Vout shoots up to 2V and linearly drop to 1.82V in 100uSec

Chandan Kumar1
Prodigy 50 points
Part Number: TL1963A-Q1

Hi,

I have used LDO P/N TL1963AQKTTRQ1 in one of my design for 5V to 1.8V step down.

Design details:

Vin: 4.5V to 5.5V

Vout (expected): 1.8V @500mA

ADJ pin resistors: R2: 1.96k Ohms, R1: 4.02k Ohms

While probing the Vout, I observed that at soon as the 5V input turns up, Vout of  TL1963AQKTTRQ1 shoots up to 2V and linearly drops to 1.82V in 100uSec.

This is an issue as the devices I have connected at Vout has absolute maximum rating of 1.89V, thus getting damaged because of initial voltage overshoot.

Kindly suggest if there is any issue in my design and resolution to fix this problem, if any.

Attached snapshot of my design and DSO snap for 1.8V overshoot.

Best Regards,

Chandan Kumar

  • 0
    TI__Prodigy 515 points

    Hello Chandan:

    Your schematic looks good. The VIH  for SHDN pin is 2V minimum (I see the net name EN_1V8, is it intended for 1.8V?).   To further reduce the overshoot during startup, you can increase your output capacitor. Reducing the input slew rate with a larger capacitor also helps.  Can you replace C103 with 10uF, total 20uF output capacitor and measure the overshoot and let me know your result?

    Regards,

    Min Hudgins

  • 0 in reply to Min Hudgins
    TI__Mastermind 23361 points

    Hi Chandan,

    It has been more than 10 days without a reply. We assume the issue has been resolved, if this is not the case, please feel free to post new reply. 

    Regards,
    Jason