TPS25751: Negotiation method after POR when not using EEPROM

Hi Masashi,

Masashi Mineda said:

If the USB Type-C AC adapter is connected to the USB Type-C connector when the battery is at its lower operating limit voltage and cannot be used, will negotiation be possible normally?

When the battery voltage falls below the lower operating voltage limit, no voltage will be applied to PPHV, PP5V, and VIN_3V3 of TPS25751.

In that state, the TPS25751 should not start.

When the TPS25751 does is not powered through VIN3V3, it can be powered from the Type-C port and VBUS pin in "dead battery mode". The PD controller will boot in dead battery in one of three configurations depending on the ADCIN config. Each configuration will be able to negotiate the most basic type-C default contract. (5V contract). Unlike hte other two, "Negotiate High Voltage" will also attempt to negotiate a PD contract up to 20-V.

In this state, the TPS25751 will start and LDO3V3 will be generated from VBUS. In addition, if you boot like this, a "Dead Battery Flag" is set in the TPS25751 fw which indicates we were brought up in "dead battery" and are being powered off of the Type-C port.

Masashi Mineda said:

Even if a USB Type-C AC adapter is connected, I believe that negotiation will not start because EEPROM cannot be read after POR.

The Dead Battery Configurations are in ROM, so will still operate even if there is no EEPROM in your system. If there was a programmed EEPROM, dead battery will power LDO3V3, which would power the EEPROM and the PD controller would attempt to load a configuration from it on power up in dead battery.

The expected use of dead battery modes is a temporary mode that allows either the EEPROM or MCU to be powered in order to load a config. In SafeMode and AlwaysEnableSink, the PD controller will load into "PTCH" mode, and waits in this mode for an image from and MCU or EEPROM to be loaded. In NegotiateHighVoltage, the TPS25751 goes to "APP" mode but it is expected that once an MCU is ready to load an image, the MCU will put the TPS25751 back into "PTCH" mode and load the fw image.

Masashi Mineda said:

After the USB Type-C AC adapter is connected, will we be using 4CC commands to configure TPS25751 and BQ25792, followed by SSrC commands for negotiation?

I'm assuming you are talking about PBMx 4CC commands to load a fw image?

If the TPS25751 boots in dead battery, the dead battery flag will be raised and it will not be able to source. To enable sourcing, you will need to clear the Dead battery flag using the "DBFg" 4CC command once the system has enough power to source properly. Only then will you able to use the SSrC command properly to negotiate a source contract.

Thanks and Regards,

Chris