TPS2358: Can not enable 12V channel

FRANK1

Expert 8535 points

Part Number: TPS2358

Hi team,

A customer has a hardware issue on TPS2358 design.

How can he turn on the 12v channel?
when he active the 12EN# signal, passx signal do not turn high.

I have limited experience on this device's design.

Can you confirm the following design?

Waiting your clarification for a lot of design experience from you.

Thanks.

Regards,

over 4 years ago

0 Avishek Pal over 4 years ago

TI__Mastermind 38780 points

Hi Frank,

Thanks for reaching out to us. May I know that PG3A# was asserted (means pulled low) before pulling EN12A# low to enable IN12A channel? Because to comply with AdvancedMC requirements, the 12 V channels will not enable unless the associated 3.3 V channel PG# is asserted. In other words, before enabling IN12A channel, OUT3A should be at more than its nominal power good threshold of 2.85 V, Please could you share the following experimental waveforms during enabling the IN12A channel to understand the issue better.

1) PG3A#, IN12A, EN12A#, and PASSA pin voltages.

2) PG3A#, IN12A, EN12A#, and OUT12A pin voltages.

0 FRANK1 over 4 years ago in reply to Avishek Pal

TI__Expert 8535 points

The waveform of each parameter is shown during enabling the IN12A channel in the attachment.

Thank you very much!

OUT12A

OUT3A

IN12A

EN12A

PASSA

PG3A

0 Avishek Pal over 4 years ago in reply to FRANK1

TI__Mastermind 38780 points

Hi Frank,

I think the MOSFET T3 got damaged. Because, why OUT12A is at 8.1 V with IN12A at 12 V when there is no gate signal to the MOSFET. Please could you measure the gate to source, gate to drain, and drain to source impedances of this T3 MOSFET.

0 FRANK1 over 4 years ago in reply to Avishek Pal

TI__Expert 8535 points

Hi Avishek,

Thank you, I will measure it .
If the MOSFET T3 is not broken and there is a active gate signal to the MOSFET , how much voltage should OUT12A be?
Regards,

0 Avishek Pal over 4 years ago in reply to FRANK1

TI__Mastermind 38780 points

Hi Frank,

OUT12A should be same as IN12A, i.e. 12 V.

0 FRANK1 over 4 years ago in reply to Avishek Pal

TI__Expert 8535 points

Hi Avishek,

Because I have two PCBs, the MOSFET T3 in other PCB is good。

In this PCB , when the EN12A# is active, the PASSA# signal of channel 12A still low level。

On the contrary, when the EN12B# is active, the PASSB# signal of channel 12B is high level。

This phenomenon seems to show a fact that both channels can not be opened at the same time.

what i guess is right?

Thank you.

0 Avishek Pal over 4 years ago in reply to FRANK1

TI__Mastermind 38780 points

Hi Frank,

Is this happening for both the boards? Is the customer using both the channels? Please ensure that VDD3A is at 3.3 V. I have sent you friend request. Please accept that. I would like to discuss over WebEx.

+1 Avishek Pal over 4 years ago in reply to Avishek Pal

TI__Mastermind 38780 points

Hi Frank,

As we are communicating through private messaging, I am closing this thread.

0 FRANK1 over 4 years ago in reply to Avishek Pal

TI__Expert 8535 points

Hi Avishek,

you can close this ticket and let us discuss this issue in private.

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TPS2358: Can not enable 12V channel