TPS62903-Q1EVM: TPS62993-Q1 Line Regulation Issue

Mayur M Bharadwaj

Intellectual 360 points

Part Number: TPS62903-Q1EVM
Other Parts Discussed in Thread: TPS62993-Q1, TPS62903-Q1

Dear TI team,

We received the TPS62903-Q1 EVM and replaced it with TPS62993-Q1 IC, as it is common.

We are operating with MODE/S-CONF with 11k (1MHz, Auto PWM).

Vout=1.8V

We tried line regulation, and at lower loads (<1A), output was proper. But when load was at 2A & 3A, when input voltage reached ~3V, output started fluctuating. Why is this happening as the device supports 100% duty cycle operation.

Also, output is becoming 0 when input is 2.8V.

I have attached necessary waveforms. I kindly request you to provide your feedback on this issue.

Line Reg @ 3A:

Line Reg@2A:

Line Reg @ 1A:

Issue Part zoomed in @ 3A:

Issue Part zoomed in @ 2A:

6 months ago

0 Shuai Fan 6 months ago

TI__Genius 13031 points

The VIN UVLO of this part is about 2.8V. And I believe the conducting wire also contribute some voltage drop between your power source and EVM.

Shuai

0 Mayur M Bharadwaj 6 months ago in reply to Shuai Fan

Intellectual 360 points

Dear Shuai,

Thanks for the feedback.

But may I know why there are some oscillations observed before the output reaches 0? Why isn't there a smooth cut-off?

+1 Shuai Fan 6 months ago in reply to Mayur M Bharadwaj

TI__Genius 13031 points

Hi Mayur!

I guess it is caused by periodic triggering the UVLO rising and falling threshold and cause the device repeat the start up and shut down actions. The hysteresis is only 130mV.

BTW, may I know more details about this opportunity, like the end equipment, where is the input voltage from and what is the loading?

Shuai

0 Mayur M Bharadwaj 6 months ago in reply to Shuai Fan

Intellectual 360 points

Hello Shuai,

Thanks for feedback. Our max loading can be ~1-2A. Our min input voltage is expected to be 4V, but was performing the line regulation in eval kit, and found this. Hence, just wanted to cross-check.

0 Shuai Fan 6 months ago in reply to Mayur M Bharadwaj

TI__Genius 13031 points

Hi Mayur!

Thanks for your information. Any other questions, pls let us know.

Is the input is from a battery?

Shuai

0 Mayur M Bharadwaj 6 months ago in reply to Shuai Fan

Intellectual 360 points

Hello Shuai,

It has input from Main Battery & Back-Up Battery, both cases the device should support.

0 Shuai Fan 6 months ago in reply to Mayur M Bharadwaj

TI__Genius 13031 points

Thank you!

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TPS62903-Q1EVM: TPS62993-Q1 Line Regulation Issue