TPS65137AS: Shuts down

Serguei Antonov

Prodigy 10 points

Part Number: TPS65137AS

Dear Experts,

We are using TPS65137AS to provide power to a 1.9" AMOLED display based on RM67162.

Here is a schematic:

And the PCB layout:

If the display is not connected then everything seems to be fine (CH1 - OUTP, CH2 - OUTN):

However when the display is connected this happens:

This waveform shows the input +3.3V and OUTN:

I have tried the following:

1. Changing input and output capacitors (C20, C21, C26) to 4.7uF. The result is the same.

2. Changing input and output capacitors to 22uF. The result is the same.

The display does not require a lot of current as the dev board I have uses BV6802 DC/DC converter that is rated for 100mA only.

I don't understand why TPS65137AS shuts down.

Could anyone suggest a solution to the problem?

Thank you.

Best Regards,

Serge.

over 1 year ago

0 Patrick Yao over 1 year ago

TI__Mastermind 34640 points

Hi Serge,

The ELVSS seems only ramp down to ~-4V, but the default should be -4.9V, so have you re-programmed the ELVSS? And the trace width of ELVDD and ELVSS are better to be much wider.

Patrick

0 Serguei Antonov over 1 year ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

Thank you for your reply.

If the display is not connected then the ELVSS does go down to ~ -4.9V:

However if the display is connected the voltage goes down to only ~ 4.0V:

Do you think the traces as they are right now (8mil) can cause the shutdown?

Best Regards,

Serge.

0 Patrick Yao over 1 year ago in reply to Serguei Antonov

TI__Mastermind 34640 points

Hi Serge,

This IC integrates a short-circuit protection which detects the VNEG gets about 420mV above the programmed value for more than 3ms. So I think the wrong VNEG cause the IC shutdown.

May I know if display disconnected, will VPOS and VNEG ramping successfully and IC continuous work? Your waveform seems only captured the start-up period.

Patrick

0 Serguei Antonov over 1 year ago in reply to Patrick Yao

Prodigy 10 points

Hello Patrick,

If the display not connected then both VPOS and VNEG stay continuously at the correct levels (+4.6V and -4.9V respectively).

Best Regards,

Serge.

0 Patrick Yao over 1 year ago in reply to Serguei Antonov

TI__Mastermind 34640 points

Hi Serge,

Could you please measure the voltage drop on the 8mil trace? And have you checked whether the display will force the VNEG to ~-4V?

Patrick

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TPS65137AS: Shuts down