TPS25750: Dead-battery start-up condition

Koshi Ninomiya

Part Number: TPS25750

Dear team,

My customer is considering to use TPS25750D as USB PD3.0 100W/20V/5A Sink controller. Their product does not have a battery. So, the TPS25750D need to start up from the dead-battery/no-battery condition. The TPS25750 datasheet describes in the following sections.
9.3.2 Power Management
9.3.4.4 Dead Battery Advertisement
I understand that the TPS25750 is powered from the VBUS input with the higher voltage during the dead-battery start-up condition and until the dead-battery flag is cleared.

After the dead-battery flag is cleared, VIN_3V3 of the TPS25750D should be powered from application.
Q1: Can they use a LDO (TLV709A33DBVR) which regulates 3.3V for VIN_3V3 of the TPS25750D from VBUS (5.0V - 20V)?

When the TPS25750D is used for Sink only operation,
Q2: Can PP5V pin and VBUS pin of the TPS25750D be set open? These pins must be floated?

I look forward to your advice.
Thank you.

Best Regards,

Koshi Ninomiya

over 1 year ago

0 Christopher Lim1 over 1 year ago

TI__Mastermind 37855 points

Hi Koshi,

Why do they need to clear the dead battery flag?

Koshi Ninomiya said:
After the dead-battery flag is cleared, VIN_3V3 of the TPS25750D should be powered from application.
Q1: Can they use a LDO (TLV709A33DBVR) which regulates 3.3V for VIN_3V3 of the TPS25750D from VBUS (5.0V - 20V)?

Yes, that should work as long as VBUS stays up.

Koshi Ninomiya said:
Q2: Can PP5V pin and VBUS pin of the TPS25750D be set open? These pins must be floated?

I'm not sure what you mean here. Are open and floating the same?

If you are doing sink only, you should follow this FAQ. PP5V get grounded and VBUS is connector to a Capacitor to ground.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/988215/faq-tps25750-how-do-i-create-a-sink-only-usb-c-pd-port-to-replace-a-legacy-barrel-jack-connector?tisearch=e2e-sitesearch&keymatch=tps25750#

Thanks and Regards,

Chris

0 Koshi Ninomiya over 1 year ago in reply to Christopher Lim1

TI__Expert 5465 points

Hi Chris-san,

Thank you for your reply. I will follow the FAQ.

About the dead battery flag, can the TPS25750D operate sink only mode without clearing the dead battery flag?
If it is Yes, do the TPS25750D regulate LDO_3V3 from VBUS (5.0V - 20V) continuously?
In this case, the power dissipation of internal LDO from VBUS to LDO_3V3 has no problem?

Best Regards,

Koshi Ninomiya

+1 Christopher Lim1 over 1 year ago in reply to Koshi Ninomiya

TI__Mastermind 37855 points

Hi Ninomiya-san,

Koshi Ninomiya said:
About the dead battery flag, can the TPS25750D operate sink only mode without clearing the dead battery flag?

Yes, you should be safe to operate sink only without clearing the dead battery flag. The dead battery flag mainly prevents some source behaviors as it assumes you are VBUS powered.

Koshi Ninomiya said:
If it is Yes, do the TPS25750D regulate LDO_3V3 from VBUS (5.0V - 20V) continuously?
In this case, the power dissipation of internal LDO from VBUS to LDO_3V3 has no problem?

Yes, LDO3V3 will regulate as long as VBUS is there.

There are limits to the current LDO_3V3 can provide, but as long as you stay under those limits, power dissipation should not be a problem.

Thanks and Regards,

Chris

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TPS25750: Dead-battery start-up condition