TPS563208: EN pin without 0.1uf cap will have ringing

Penn Zhang

Part Number: TPS563208

Hello,

Thanks for your attention.

We have seen if we didn't put 0.1uf cap near EN pin of TPS563208, when pull up voltage(12V) rise from 0V, the EN will have ringing as figure below, if the 12V rail is not rise start from 0V, the EN pin will not have this ringing.

From the datasheet, I see this EN pin is a digital input, it should not cause this different, I'm concerning about the 12V rail have this ringing when power up from 0V, but this is hard to explain why the 0.1uf cap will works for EN ringing.

May I know your idea about this case? thanks.

Penn

over 4 years ago

0 Penn Zhang over 4 years ago

TI__Intellectual 1180 points

Add more,

We can see the 12V green waveform is more smooth, only have one drop during the EN ringing.

The schematic is as below

0 Ryan Hu (BSR-MV) over 4 years ago in reply to Penn Zhang

TI__Expert 4035 points

Hi Penn,

What's the relationship between the 1V8 and the 2V5? 1V8 is the TPS563208's output, what's the 2V5? The ringing on EN maybe is coupled by noise. You can double check it with setting the channel's bandwidth at 20MHz and zoom in the ringing waveform to see the ringing frequency.

As for the voltage drop on VIN, maybe you can check if there is loading added at the DCDC output at that moment.

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TPS563208: EN pin without 0.1uf cap will have ringing