TPS53515: TPS53515 WEBENCH stability

Connie Lu1

Intellectual 2080 points

Part Number: TPS53515

Hi Experts,

My customer has to reduce inductor and increase capacitor values significantly to meet a fast transient requirement of <=5mV over/undershoot at 8A/us from 0.4A-2A on WEBENCH. Are these passive values still able to achieve stability? I couldn't find loop analysis feature for this device on WEBENCH.

Any guidance would be appreciated.

Thanks,

Connie

over 3 years ago

0 Connie Lu1 over 3 years ago

TI__Intellectual 2080 points

Looks like the picture didn't go through.

See attachment.

Thanks,

Connie

0 Gerold Dhanabalan - Online Design Tools over 3 years ago in reply to Connie Lu1

TI__Genius 14455 points

Hi Connie

The TPS53515 is DCAP3 and we dont have a closed loop bode plot model for this architecture yet. You can get some sense of stability by doing a transient response and ensuring that ringing, settling time etc. is within bounds and use that as a checkpoint for stability.

Regards,

Gerold

0 Connie Lu1 over 3 years ago in reply to Gerold Dhanabalan - Online Design Tools

TI__Intellectual 2080 points

Hi Gerold,

The transient response on WEBENCH looks fine, no ringing.

However, the Fp is close to 7kHz with switching frequency of 1MHz. It is not close to the high frequency zero. Is this okay? Or the only way to tell is to test the part with bode plot?

Thanks,

Connie

0 Connie Lu1 over 3 years ago in reply to Connie Lu1

TI__Intellectual 2080 points

0 Gerold Dhanabalan - Online Design Tools over 3 years ago in reply to Connie Lu1

TI__Genius 14455 points

The zero helps to cancel one of the poles in the LC double pole. So 7KHz LC double and zero of 12KHz seem pretty close, although I would prefer to have the zero lower than LC double poled. Also, when calculating the LC double pole, include the worst case tolerance as well. If the pole moves very close, then I would recommend going with a lower L to move the LC double pole out.

Regards,

Gerold

0 Connie Lu1 over 3 years ago in reply to Gerold Dhanabalan - Online Design Tools

TI__Intellectual 2080 points

Thank you Gerold!

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TPS53515: TPS53515 WEBENCH stability