TPS82084: TPS82084 Vout locked at 2.2V when Vin <Vout designed

cyan zhou

Expert 1500 points

Part Number: TPS82084

TPS82084 using as below:Vsys is from Single Battery voltage.

When the input voltage is lower than output voltage required, the TPS82084 Vout will lock at 2.2V.

We haven't find any description about this.

There're only 2 descriptions about the Low voltage output in datasheet, shown as below:

Does this mean: only when the voltage is lower than 2.2V, the output will be turned off. But if 82084 works like this, how can this lock output 2.2V happen like in our design？

Our phenomenon can be reproduced stably now. or is this the intentional design of the chip? Thanks!

over 5 years ago

0 Chris Glaser over 5 years ago

TI__Guru**** 150950 points

Hi Cyan,

I do not understand what 'locked' means. Can you send a waveform of Vin, Vout, EN, and inductor current?

0 Chris Glaser over 5 years ago in reply to Chris Glaser

TI__Guru**** 150950 points

Hi Cyan,

Were you able to resolve this? If not, can you share more information?

0 cyan zhou over 5 years ago in reply to Chris Glaser

Expert 1500 points

when the voltage drop from 3.8V to 3.65V, the output voltage drop and locked to 2.2V, and this can be reproduced;

but if give a lower voltage for 82084 directly, eg 3.54V , there will be a ,3.52V output, not 2.2V.

0 Chris Glaser over 5 years ago in reply to cyan zhou

TI__Guru**** 150950 points

Thank you for the waveform. What is each channel in the circuit?

Does this occur on multiple boards or just on 1 system?

Can you attach a probe to the switching end of the inductor on top of the IC and add this channel to the waveform?

0 Chris Glaser over 5 years ago in reply to Chris Glaser

TI__Guru**** 150950 points

Hi Cyan,

I see there is an email thread in parallel with this E2E thread. I will close this E2E thread and work your specific issue on the email.

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TPS82084: TPS82084 Vout locked at 2.2V when Vin <Vout designed