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TPS22918: PCB Design and Value Selection

Trung Nguyen90
Prodigy 20 points
Part Number: TPS22918

I have a design using TPS22918. I looked at the datasheet but not fully understand the value selection. 

http://www.ti.com/lit/ds/symlink/tps22918.pdf

That's why I follow the Design Reference on the Datasheet.

My Design: 

Vin = 3.3V

Load Current = 400 mA

Page 17 recommend Cin > Cout 10 times.

That's why I choose Cin= 10uF and CL = 1uF

CT=1000pF

I have Rext =330 Ohm between Vout and QOD (1ms fall time)

And the weird thing here on Page 18 when testing the QOD functionality.

Some tests used Cin = 1uF and CL = 10 uF which opposite with recommendation on Page 17.

Please recommend if those values are good enough for my design.

Thank you very much

  • 0
    TI__Genius 15760 points

    Hi Trung,

    All of your component values should not cause any problems for your design. Having a 10:1 capacitor ratio is still the recommendation, but because your load is light (400mA) the design would still work with a 1:1 ration if desired (1uF CIN, 1uF COUT). The reason we don't recommend CIN < COUT under all circumstances is just in case the input voltage suddenly drops in your application. If this is the case, then the output may decay slower than the input, and that could cause reverse current from VOUT to VIN.

    In short, no issues with your current setup.

    Thanks,

    Alek Kaknevicius