TPS25750: Dead battery startup

Jan Van Bogaert

Part Number: TPS25750

Hi.

I am a bit confused on the dead battery behavior of the TPS25750.

In section 9.3.4.4 of the specification it is stated that "TPS25750 hardware is configured to present this Rd during a dead-battery or no-battery condition" .

Is this statement always valid or only in NegiotateHighVoltage mode?

I think that in SafeMode the Rd is not present on the CC pins, and therefor the system remains without power when plugged into a USB-C adaptor with PD support.

Is this assumption correct? Do I have to reconfigure my design to use NegiotateHighVoltage mode and is SafeMode useless for supporting dead batteries?

over 1 year ago

0 Christian Moyer over 1 year ago

TI__Mastermind 33051 points

Hello Jan,

Please refer to section 9.4.1 of the datasheet:

The USB PD is disabled, until a configuration is loaded onto the PD device.

Jan Van Bogaert said:
Is this assumption correct? Do I have to reconfigure my design to use NegiotateHighVoltage mode

Yes, If you do not plan on loading a configuration on to the device before the sink path is enable.

Best Regards,

Christian.

0 Jan Van Bogaert over 1 year ago in reply to Christian Moyer

Prodigy 80 points

How can I load the configuration when the battery is dead and the sink path is not enabled? Does the TPS25750 gets power from the CC lines in that case? Assuming the TPS is powered form CC. can I use the LDO of the TPS to power my processor?

0 Christian Moyer over 1 year ago in reply to Jan Van Bogaert

TI__Mastermind 33051 points

Hello Jan,

Jan Van Bogaert said:
How can I load the configuration when the battery is dead and the sink path is not enabled?

The TPS25750 can draw power from VBUS to power the PD device, even if the sink path is not enabled.

Jan Van Bogaert said:
can I use the LDO of the TPS to power my processor?

Yes.

Best Regards,

Christian.

0 Jan Van Bogaert over 1 year ago in reply to Christian Moyer

Prodigy 80 points

In order to power from VBUS, Rd must be present. So how does the TPS25750 decide on the activating Rd on the CC lines if it has no power?

Is activating Rd not the same as enabling the sink path?

0 Christian Moyer over 1 year ago in reply to Jan Van Bogaert

TI__Mastermind 33051 points

Hello Jan,

Jan Van Bogaert said:
Is activating Rd not the same as enabling the sink path?

The TPS25750 hardware is configured to present RD during a dead-battery condition.

Best Regards,

Christian

0 Jan Van Bogaert over 1 year ago in reply to Christian Moyer

Prodigy 80 points

This brings me back to my original question: is this also in case when the device was configured in safe mode?

My testing shows that it is not.

+1 Christian Moyer over 1 year ago in reply to Jan Van Bogaert

TI__Mastermind 33051 points

Hello Jan,

Jan Van Bogaert said:
SafeMode useless for supporting dead batteries?

No, I ran a test with the TPS25750 EVM in safe mode and in dead battery mode and the PD device had power.

I have a few questions:

Are you using the TPS25750 EVM or your own design?

If you are using your own design can you provide your schematic: my email is C-moyer@ti.com.

How are you determining that RD is not present?

Are you using an EEPROM?

Best Regards,

Christian.

0 Jan Van Bogaert over 1 year ago in reply to Christian Moyer

Prodigy 80 points

OK, it turns out that CC1 and CC2 are not properly connected on my board. When I fixed this, I get the voltage delivered from the power supply.

Thank you for all your help.

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TPS25750: Dead battery startup