TPS53681: ACLL Range concerns

Evan Zhang

Part Number: TPS53681

Hi expert,

in TPS53681 datasheet, we see ACLL range can start from 0mOhm (P13), however in Fig75,ACLL is suggested to begin from 0.5mOhm.

What would happen if ACLL is lower than 0.5mOhm?

From the control block diagram, 1/ACLL is just used as feedforward, it seems it won't affect stability of the system.

over 5 years ago

0 Rama Pamidi over 5 years ago

TI__Intellectual 1790 points

Hi,

we can use ACLL value lower than 0.5m also. But it's depend on application output inductor and capacitor values. You can find test results of TPS53861web EVM with ACLL=0.25m (https://www.ti.com/lit/ug/sluubp7/sluubp7.pdf?ts=1599454003144&ref_url=https%253A%252F%252Fwww.google.com%252F

schematic to suggest correct ACLL value.

0 Rama Pamidi over 5 years ago in reply to Rama Pamidi

TI__Intellectual 1790 points

Hi,

I don't know, some of the text is missing in my previous reply. so again replied with details.

we can use ACLL value lower than 0.5m also. But it's depend on application output inductor and capacitor values. You can find test results of TPS53861web EVM with ACLL=0.25m. Typically, System bandwidth increases and lower phase margin with reducing ACLL. It may possible to become system unstable with lower ACLL. so please provide your application details and schematics to suggest correct ACLL value.

Thanks.

Regards,

Rama.

0 Evan Zhang over 5 years ago in reply to Rama Pamidi

Prodigy 30 points

Hi Rama,

thanks for your reply quickly.

I just investigate the function of TPS53681, and do some cocept design right now.

and besides,could we set ACLL=0? just because 1/AcLL =∞ if we do.

Much appreciated if can help clear on this.

Best Regards

Evan

0 Rama Pamidi over 5 years ago in reply to Evan Zhang

TI__Intellectual 1790 points

Hi Evan,

No, it is not possible to select ACLL=0. Most of the applications, we suggest minimum ACLL=0.5m. But if output capacitor is higher, we can suggest 0.25m at worst cases.

Please provide your application details.

Thanks.

Regards,

Rama.

0 Evan Zhang over 5 years ago in reply to Rama Pamidi

Prodigy 30 points

Hi Rama,

Much appreciated.

thanks for your explanation, and I just want to know about TI's VRM products.

Best Regards

Evan

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TPS53681: ACLL Range concerns