TPS548A20: RF resistor setting

tateo yamashiro

Part Number: TPS548A20
Other Parts Discussed in Thread: TPS53515

Hi,

We got a question from customer about TPS548A20.
Could you help us?

[Question]
They consider to set RF resistor refer to EVM manual "6.1 switching frequency selection".

- If we achive resistor divider ratio, can we use any other value for Rrf_h and Rrf_l?
- How much is the allowable range of the resistor divider ratio? If they want to set 500kHz, how much is the range of the resistor ratio?

Best Regards,
tateo

over 8 years ago

0 JohnTucker over 8 years ago

TI__Guru**** 191445 points

I do not understand your question. The divider ratios are as stated. Can you elaborate?

0 tateo yamashiro over 8 years ago in reply to JohnTucker

Guru 10890 points

Thank you for your reply.

They should use their standard parts. So they should choice different resistor value from the recommended Rrf_h and Rrf_l.
Can they set the switching frequency with different resistor value from the recommended Rrh_h and Rrf_l? Especially they want to know allowable range of the resistor divider ratio.

Best Regards,
tateo

0 JohnTucker over 8 years ago in reply to tateo yamashiro

TI__Guru**** 191445 points

The required resistors for each setting is clearly listed in the datasheet. Why would you want to use different values?

0 tateo yamashiro over 8 years ago in reply to JohnTucker

Guru 10890 points

The recommended resistor value is not listed in their standard parts list. They consider to select the resistor from their list.

Best Regards,
tateo

0 Sepeedah Zadeh over 8 years ago in reply to JohnTucker

TI__Expert 3100 points

Hi John,

I came across the same problem actually. The main problem is the data sheet is missing the formula of how the resistor divider ratio is calculated, which seems to be this based on the TPS53515 datasheet:

Thanks,

Sepeedah

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TPS548A20: RF resistor setting