TPS54620: Need a buck converter with sinking current capability

Hans

Part Number: TPS54620
Other Parts Discussed in Thread: TPS54672, TPS54372, TPS51100, TPS54310, TPS54317

Hello Team,

in order to move the common mode voltage of an ADC I need a virtual ground of 2V. On top of this 2V I need 1.1V@1.8A and 1.9V@1A. The ADC is shown as resistors in the block diagram below.

Can you recommend a solution for this problem, please? I looked at TPS54620 but its Low-side switch sinking current limit is 2.3A typical.

Thanks and Best Regards,

Hans

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

Any possibility you can pre-regulate your 12 V down to 5 V?

0 Hans over 7 years ago in reply to JohnTucker

TI__Genius 12865 points

Hi John,
yes, this is an option!

Thanks and Best Regards,
Hans

0 JohnTucker over 7 years ago in reply to Hans

TI__Guru**** 191445 points

TPS54672 is designed to both sink and source current.

0 JohnTucker over 7 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Do you need any additional assistance? Will TPS54672 work for you?

0 Hans over 7 years ago in reply to JohnTucker

TI__Genius 12865 points

Hi John,
I ordered an EVM and will try it out.

Thanks and Best Regards,
Hans

0 JohnTucker over 7 years ago in reply to Hans

TI__Guru**** 191445 points

OK, I will close this thread.

0 Hans over 7 years ago in reply to JohnTucker

TI__Genius 12865 points

Hello John,

I did some tests and it worked. But I need 2V as reference and the maximum output of the TPS54372 is limited to 1/2 of the reference which is 1.75V max. correct?

Any idea how to get to 2V, please?

Thanks and Best Regards,

Hans

0 JohnTucker over 7 years ago in reply to Hans

TI__Guru**** 191445 points

Hans,

You should be able to set VSENSE and REFIN up to 4 V. If you are using the EVM, just apply 4 V to J2 VDDQ connector to get 2 V output. I'm not sure why there ius a 1.75 V max listed in the users guide. It was published in 2002, 16 years ago, so I doubt anyone would remember it. Giv it a try and let me know if it works.

0 Hans over 7 years ago in reply to JohnTucker

TI__Genius 12865 points

Hello John,

according data sheet, page 11, you cannot apply 4V to REFIN:
The REFIN pin provides an input for a user supplied tracking voltage. Typically this input is one half of VDDQ. The input range for this external reference is 0.2 V to 1.75 V. Above this level, the internal bandgap reference overrides the externally supplied reference voltage.

I tried it but the max. VTTQ I get get is around 1V.

It looks we have no solution to generate 2V and sink 3A. I checked TPS51100 but its VDDQSNS is also limited to 3.6V which limits the output to 1.8V.

Thanks and Best Regards,

Hans

0 JohnTucker over 7 years ago in reply to Hans

TI__Guru**** 191445 points

Hans,

Maybe we have been over thinking this. The TPS54372 EVM design connects Vout directly to VSENSE without a feed back divider. The best approach I think would be to use TPS54310 (or TPS54317 if you prefer a QFN package). You can use the internal reference and a FB divider to set 2 V output. The difference between TP54310 and TPS54372 is just the external tracking function required for DDR termination. Both will sink current. Let me know if that will work for you.