TPS65982: Current Sensing using ADCs 4cc command with 5mohm

Hi Onawa-san,

The current formula does not rely on the sense resistor as a variable. Once you have set the correct value in your configuration, the ADC should read the correct value. Here is the formula:

IsenseACC is equal to 5 from the 82 Datasheet:

Thank you,

Eric

Hi Eric-san,

Did you really check it before?
I have been able to reproduce it using our EVM.

Could you try it with our EVM on your side also?

[Experimental setup]

① TPS65981_HD3SS460_DRP_Source_Advanced_v3_10.tpl
② TPS65981_HD3SS460_DRP_Sink_Advanced_v3_10.tpl
Active Source : 20V@3A
Power path : PP_Ext
Rsense bit in System config reg was set to 5mohm
I used TPS65981EVM because 5mohm sense resister is mounted as default.

[Result]

The ADC data were almost 150% far from expected current as below.
I also did other voltage condition, 5V, 9V and 15V. And It showed the same trend at all voltages.
If the formula you indicated is correct, there should be any bugs in FW.

Example:

When Eload sinking 3A, the ADC was showing 1.82 A.

Regards,

Takashi Onawa

Hi Onawa-san,

If you select the 10mohm Rsense value, does the current reading change?

Thank you,
Eric

Hi Eric-san,

I got almost same result with 10mohm Rsense value.
In other word, Despite changing the setting of Rsense to 10mohm, ADC current was almost the same result as at 5 mohm setting.

How was your side's result?

Regards,
Takashi Onawa

Hi Onawa-san,

I am seeing the current value change when I change from 5mOhm to 10mOhm using the ADCs command on I_PP_EXT. I am using a constant resistive load to draw the same current through VBUS in both test cases. Are you using the latest FW on the TPS65981?
I used a DFP template and set the PP_EXT as the only enable power path.

Thank you,
Eric

Hi Eric-san,

OK, I understood that you could saw the change on ADC value. I can't not reproduce it because I don't have any Available TPS65982EVM. Anyway It's good news for me.

Could you take data(Actual Drawing current vs ADC value) as I showed above and plot it on the graph?
If it is working properly, the ADC value should be twice the value of Actual Drawing Current.

By the way, which version did you use in your evaluation? I was using ver3.10 for the evaluation and I believe this is the latest one.

Regards,

Takashi Onawa

Hi Eric-san,

How long does it take to get the data?

Regards,
Takashi Onawa

Hi Eric-san,

Am I making sense to you?

Experimental Setup

My customer would like you to double check ;

1. Accuracy of actual ADC on TPS65982EVM
2. Whether 5mohm Rsense function works properly or not

So, Could you take data(Actual Drawing current vs ADC value) as I showed above and plot it on the graph setting 5mohm Rsense under 10 mohm actual sense resister?
If it is working properly, the ADC value should be twice the value of Actual Drawing Current.

Regards,

Takashi Onawa

Hi Eric-san,

OK. I will close this thread once.

Regards,
Takashi Onawa