TPS25751: Precharge current and old USB protocols

Hi Chen,

Per the PD spec, we cannot have multiple Sink PDOs with the same type and voltage. We can try it in the 751 project, but risk being non-compliant. The PDOs are specific to USB-C PD and are not used in legacy mode.

When you are testing the actual input current, is the attached source capable of 2.4-A? Can you monitor the I2C between the TPS25751 and BQ device to see what current value is written during this time?

Thanks and Regards,

Chris

Hello Chris:

Sure, we can test that. At the meantime, since our design not nailed yet, do you have any other IC options which may meet our requirement?

1. Sink only. Because TPS25750/1 support both sink and source, it is a little bit waste of the IC function.

2. Support USB-C, USB-PD, and can cover most legacy USB port. For all the non-PD/C ports, we only need 5V 500mA input for all of them.

3. Standalone preferred, and can handle "dead battery" properly without MCU.

I think these are not really challenging to meet. If you have any other suggestions, we are open to change the design at this point.

Thank you!

Chen 

Hi Chen,

Potentially TPS25730, but you lose a lot of control and status information. TPS25751 may be the only option here that has the full capabilities. The TPS25730 only has PD support as well and does not support BC1.2. Unfortunately, we may not have an IC that is a good fit for your requirements.

Thanks and Regards,

Chris

Hello Chris:

We tested the BIN file for TPS25751, but seems like no precharging current in the configuration. Could you help to check? The charging data is attached, and the pre-charging voltage threshold is 3V.

Sep-16-2024 Test file.rar

Also, as we reviewing the configuration of the charging system, seems like the charger IC BQ25792 has USB charging function for legacy USB protocols (Pin6 and 7 as D+ and D-). So do you know if we can connect the BQ25792 to the D+ and D- directly and it would handle the legacy USB protocols? We already add the connection and 0ohms resisters for testing purpose.

Thank you!

Chen

Hi Chen,

Is there a tool that I should be opening the .log files in?

If you monitor the I2C on power up, do you not see any I2C writes to register 0x08? I thought we had added this in the past? Could you share the latest .json?

We do not recommend connect the D+/D- lines to the BQ25792 and not to the TPS25751. The issue is that the TPS25751 attempts to control the port and will manage the connection status and update the BQ device based on what it think the port has negotiated. If you move the D+/D- lines from the TPS25751 to the BQ25792 we lose that information.

Thanks and Regards,

Chris

Hello Chris:

You can use excel to open the log file. This is a standard log from BQ40Z50 IC, and you may need to convert the columns to read it clearly.

We are reading the 0x08 register and verify the current. At the meantime, for old USB protocol coverage, is there a register to show if the connection is USB-C/PD? and we can use MCU to read the bit and overwrite the current limit?

Thank you!

Chen

Hi Chen,

You should be able to use the Status register to check the connection.

The connection does not change the current limit.

Thanks and Regards,

Chris