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Original question:

TPS22810: Question about QOD Fall time design requirements in TPS22810's datasheet

TPS22810: doesn't need output bypass capacitor?

Seokmin Hong
Intellectual 485 points
Part Number: TPS22810

I have 2 questions using TPS22810.

TPS22810 uses CL value for the QOD.

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And this is placed in the Vout.

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Normally, when using any ic, I learned there needed to be bypass capacitor to reduce noise. Value about 0.1uF.

1. If I use CL capacitor, does CL capacitor acts as bypass capacitor?

2. Cin's recommended value is 1uF in the datasheet. And there also says Cin to CL ratio is 10 : 1 is good for inrush.

But If I use Cl value about 10uF, or 22uF, then this makes C in value to 100uF . Isn't this too big?

In the datasheet page 20, there are some measurement graphs  and it used Cin 1uF and CL for 10uF.

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Will there be any side effect? In this case Cin to Cl ratio is 1:10 backwards to recommended 10:1 Value.

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.AND Can I put Vin and En together? Vin is 12V.  (Datasheet says like below, 1.8V, 3.3V, 5V can be directly driven. there is no other comments about 12V or others.)

  • 0
    TI__Prodigy 240 points

    Hi Seokmin,

    Thank you for your questions about TPS22810!

    1. Yes, both the input capacitor, CIN, and load capacitor, CL, reduce AC noise in the DC power supply signal by acting as bypass capacitors.
    2. The 10:1 capacitor ratio is a recommendation that reduces the effects of inrush current. When switching heavy loads, a CIN that is 10 times the CL reduces the effects of inrush current and causes less of a voltage dip in VIN when the device is switched on. However, the 10:1 ratio is a recommendation and not a necessity in order to ensure proper device functioning. A lower ratio (such as 1:1) can be used. A 1:1 ratio may cause a slight dip on VIN upon turnon due to inrush current; however this is not a major concern for the device functionality.
    3. Yes, you can tie VIN and EN together to 12V since 12V is well within the -0.3V - 20V EN/UVLO voltage range. However, to ensure proper timing characteristics, VIN must be applied before EN is toggled high.

    Best regards,

    Rachel Richardson

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