TPS25751: Charging current seems to be limited

Hi Dave, 

I have a couple follow-up questions to help with debugging:

1. What did you use to test on the source side (provider)? Does it have PD capabilities to source 60W or greater? 

2. If the far-end device/charger you use is capable of PD, can you capture PD logs (CC traffic)? This will allow us to see if the PD negotiation was successful and which PDO/contract was negotiated. 

3. What did you set for Q12 (INDPM) and Q13 (VINDPM)? Based on the questionnaire selection here this will impact the input voltage/current limit configured from the PD to the BQ which can impact the charge current. You can also provide the JSON file for us to review. 

4. Do you have any scope capture of the I2C traffic between the PD and the BQ? 

Thanks and Regards,
Raymond Lin

Hi Raymond,

Raymond Lin said:

1. What did you use to test on the source side (provider)? Does it have PD capabilities to source 60W or greater? 

The USB Type-C adapter I use to test is HP TPN-CA06. It can source maximum 65W (PDO: 20V==3.25A).

Raymond Lin said:

2. If the far-end device/charger you use is capable of PD, can you capture PD logs (CC traffic)? This will allow us to see if the PD negotiation was successful and which PDO/contract was negotiated. 

I attach the PD log files in *.csv and *.ccgx3 formats. My PD analyzer is Infineon CY4500. If you would like to read the *.ccgx3 file, you can download the utility at the following URL:

https://softwaretools.infineon.com/tools/com.ifx.tb.tool.ezpdprotocolanalyzer

This is the version banner of the PD analyzer I'm using.

The below archive includes the PD logs.

tps25751_drp_60w_0729.zip

Raymond Lin said:

3. What did you set for Q12 (INDPM) and Q13 (VINDPM)? Based on the questionnaire selection here this will impact the input voltage/current limit configured from the PD to the BQ which can impact the charge current. You can also provide the JSON file for us to review. 

I set 0% for INDPM, and 5% above for VINDPM.

Raymond Lin said:

4. Do you have any scope capture of the I2C traffic between the PD and the BQ? 

Yes. I attach a screenshot of the I2C scope captured log below. The recorded time range is from the time the Type-C charger is connected to the completion of the negotiation.

Thanks.

Best regards,

Dave

Hi Dave, 

Thank you for providing the logs, I'll look into this and provide feedback by mid-week. 

Thanks and Regards,

Raymond Lin

Hi Dave, 

In the original query you posted:

Wei-Ting Huang said:

However, after actual measurement, no matter how much power the battery has, the maximum charging current is only about 2.67A~2.70A. This is still a little bit far away from the charging current (2.944A) we set on USBCPD_ACT. How can we increase the charging current closer to our set value? What other configurations do we need to set?

Are you measuring the current draw on the BQ and battery side or PD and BQ side (PPHV pin of TPS25751)? The I2C log/screenshot you previously attached doesn't seem to align with PD sink events (i.e. PD writing to reg 0x06 and 0x08 of BQ to configure VINDPM/IINDPM). 

Thanks and Regards,
Raymond Lin

Hi Raymond,

Raymond Lin said:

Are you measuring the current draw on the BQ and battery side or PD and BQ side (PPHV pin of TPS25751)?

I'm measuring the current draw on the BQ and battery side.

Raymond Lin said:

The I2C log/screenshot you previously attached doesn't seem to align with PD sink events (i.e. PD writing to reg 0x06 and 0x08 of BQ to configure VINDPM/IINDPM). 

I captured the I2C log of the entire process when I connected the PD charger. Is there any problem with these logs? Do you need me to provide you with more information?

Thanks.

Dave

Hi Dave, 

Apologies for the confusion, I was checking the I2C log against BQ25756 register mapping and not BQ25713. The I2C log does show TPS25751 configuring BQ25713 to the correct charge voltage/current to 19.2V/2.944A.

The PD log also shows we've requested 20V/3A from the source but the current draw from the connector (VBUS) to PD is relatively low (not sure if the PD analyzer is accurate on the current draw). 

What is the measured voltage/current on the VBUS side of TPS25751 as well as the source (charger) end? If the VBUS voltage is dropping too much the charger might be limiting its output current to prevent browning out. 

Thanks and Regards,

Raymond Lin

Hi Raymond,

These are the voltage and current values ​​I measured on each side.

VBUS sode: 19.77V/1.14A

PD and BQ side: 7.80V/2.67A

BQ and Battery side: 7.62V/2.63A

Thanks.

Dave

Hi Dave, 

How is the PD and BQ side voltage/current different from VBUS side? Did you measure the voltage/current from TPS25751 PPHV pin to BQ25713 VBUS pin or somewhere else? Connector (USB Type-C port) VBUS to TPS25751 VBUS and TPS25751 PPHV to BQ25713 VBUS should have the same voltage/current reading. 

Looking at the values you provided, it seems the system is only drawing up to 1.14A (~22W) on the port side and between "PD to BQ" and "BQ to Battery" the power consumption is around ~20W. 

From PD (TPS25751) perspective it seems like everything is set up correctly, I'll forward this thread to the BQ support team for more support on BQ25713. 

Thanks and Regards,

Raymond Lin

Hello Dave,

Can you provide all of the register data for the BQ25713?

Best Regards,

Christian.