TUSB4041I: Capacitor Values with DC BIAS

Tsubasa Yagi

Part Number: TUSB4041I

Tool/software:

Hello, I'm trying to choose the capacitors. To choose the capactor value, should I consider DC vias capacitance value?
Some capactor values are written on "10.1 TUSB4041 Power Supply", "10.2 Downstream Port Power" and "11.1.1 Placement of datasheet".
And I wonder if I should follow the value as they are written or I should consider DC bias capacitance at the voltage.

eg. 1uF for VDD33 power supply, is it better to choose GRM155R61E225KE11D (2.2uF, 1.630uF at 3.3V) instead of GRM155R61E105KA12D (1uF, 0.628uF at 3.3V)?

over 1 year ago

0 Brian Zhou over 1 year ago

TI__Guru**** 154650 points

Hi Tsubasa:

You don't need to follow the value as written in datasheet but should be close.

The VBUS of each downstream port requires a large-bulk capacitor of 22 µF or larger.

All power rails require a 10-µF capacitor or 1-µF capacitors.

Place a 0.1-µF capacitor as close as possible on each VDD and VDD33 power pin.

Best

Brian

0 Tsubasa Yagi over 1 year ago in reply to Brian Zhou

Prodigy 20 points

Brian Zhou said:
You don't need to follow the value as written in datasheet but should be close.

Do you mean the value should be close to the one with consideration of DC bias or without?
Because the effect of DC bias is not so small (-42% at 3.3V) on some capacitors.

+1 Brian Zhou over 1 year ago in reply to Tsubasa Yagi

TI__Guru**** 154650 points

These big value capacitors are not used for DC bias, it's just for stability and noise immunity. so the value should be close to the one without consideration of DC bias .

Best

Brian

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TUSB4041I: Capacitor Values with DC BIAS