TPS54122: TPS54122 EVM Core Supply Voltage DC/DC Drop Voltage

Gerald Choi

Part Number: TPS54122

Hi Non-Isoloage DC/DC team

We tested SW output and LDO output for really load test on TPS54122-EVM as a chart below

I searhed LDO Dropout Voltage on datasheet, However I can't search SW Output Dropout Voltage on datasheet

SW Output [1.2V]		LDO Output [3.3V]
1.1947		3.3186
A	V	A	V
0.1	1.1910	0.1	3.2888
0.5	1.1760	0.5	3.2800
1.0	1.1579	1.0	3.2686
1.5	1.1406	1.5	3.2572
2.0	1.1243	2.0	3.2464
2.5	1.1077	2.5	3.2345
3.0	1.0907	3.0	3.2200

Can I get Product test value? And, Are you okay our result test Value?

We think that Droput voltage so big on SW output drop voltage.

Best Regards

Gerald Choi.

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

I am not sure at all what you are asking about. Are you testing for load regulation ( Vout vs Iout) or some other test. Can you post your input voltage and schematic?

0 Gerald Choi over 7 years ago in reply to JohnTucker

Expert 1400 points

Hi John

Thanks for your reply

- Vin : 5V

- LDO Vout : 3.3V / 3A

- Step down Vout : 1.2V / 3A

0 JohnTucker over 7 years ago in reply to Gerald Choi

TI__Guru**** 191445 points

What you are really inquiring about then is load regulation not low headroom drop out. 5 V input is more than enough input voltage for 1.2 V output. I do not see anything that immediately jumps out from your schematic. How are you measuring the output voltage? It may be a measurement issue or possibly poor PCB layout. Your regulation should be much tighter than what you report.

0 Gerald Choi over 7 years ago in reply to JohnTucker

Expert 1400 points

Hi John
Thanks your reply.

We tested on TPS54122 EVM board by current loader. And as a above SW-OUT measured Drop Voltage on EVM Board
Are you think that wrong drop voltage measurement?

Best Regards
Gerald Choi.

0 JohnTucker over 7 years ago in reply to Gerald Choi

TI__Guru**** 191445 points

Yes, the voltage should only vary by less than 1 %. Probably a lot less than 1% variance. I notice that for some reason, there is no published data for it. But I have measured the load regulation for many, many dc/dc converters similar to this. They always have very tight regulation performance if measured correctly.

0 JohnTucker over 7 years ago in reply to JohnTucker

TI__Guru**** 191445 points

I checked the regulation for the switcher portion. It varies less than +/- 0.2 % from 0 to 3 A.

0 Sanghee Byun over 7 years ago in reply to JohnTucker

Prodigy 50 points

Dear. John Tucker

I attached the Test Report about TPS54122.

Please check the File.

TPS54122 Test_170330.pptx

0 JohnTucker over 7 years ago in reply to Sanghee Byun

TI__Guru**** 191445 points

You cannot measure the output voltage at your electronic load. The connecting wires have resistance that causes an IR drop. You need to measure Vout directly at the EVM output with a separate meter.

Power management

Power management forum

TPS54122: TPS54122 EVM Core Supply Voltage DC/DC Drop Voltage