BQ35100: Power management forum

Hello Jimi,

Is the gauge showing that with no current flowing there's 1020mA flowing? Were the other calibrations successful (temperature and voltage)? Also make sure to reset the device once you have programmed the ChemID and completed the calibration.

Sincerely,

Wyatt Keller

Hi Eric,

Yes, gauge was in AAC mode and [GA] bit was set.

-Jimi

Hi Wyatt,

The behavior is gauge reported 1020mA but actually 1000mA flowing, before and after current calibration.

Temperature calibration is also unsuccessful as current calibration, reported temperature is still the same. 

We don't pop components for external voltage measurement so it always shows "Calibration cell voltage is out of range" after voltage calibration.

Here is how I did current calibration:

1.  Send command GAUGE_START

2. Send command UNSEAL_FULL_ACCESS

3. Send command CAL_TOGGLE

4. Current Calibration -1000mA

5.  Send command RESET

Before we clarified calibration process, due to project schedule, can you help to provide golden file after current calibration?

The calibration value will be 1000mA/1020mA=0.98 and base file is default bq35100 firmware.

Please help on this. Thanks. 

-Jimi

Jimi,

Prior to sending the Reset command please read the datamemory and see if the CC Gain and Capacity gain values changed at all

Thanks,

Eric Vos

Hi Eric,

Prior to sending Reset command, still no values change in Data section at all.

-Jimi

-Jimi

Jimi,

Does a red error message show up at the bottom left corner of bqStudio? 

Thanks,

Eric Vos

Hi Eric,

After taking an average from 30 units and using that to program the rest of the units, the production units have <2% error with system current 100mA but about 1x% error with 10mA. Below are my questions.

1. How much current accuracy would you expect when using this method of calibration?

2. As you know we only write fix CC Gain/Delta that obtained from 1000mA loading calibration.

With this method, if 10mA accuracy would be affected by CC Gain/Delta modification?

3. Below figure I(err) from datasheet shows reported current has few mA errors in low current. If this data is from gauge default parameters or after normal calibration process?

-Jimi

Hello Jimi,

The current accuracy is based on the ADC range for SRP and SRN, also the temperature coefficient and size of the sense resistor. Was the error resolved with your system?

I believe the error measurements are after the calibration, but I can check and get back to you.

Sincerely,

Wyatt Keller

Hi Wyatt,

Thanks for your reply. To better check current reading accuracy, we'll set up as below to isolate system current  from gauge current sense and provide independent current source for current sense.

Do you think this setup is valid to verify current reading accuracy?

And we noticed EOS Gauge Load Current to compensate current reading. Would you suggest how we can use it with current accuracy checking as above? 

-Jimi

Hi Wyatt,

So with this setup, to compare with the real current, we need to add 0.035mA (35 is default value EOS gauge load current, Unit is 0.01mA) to gauge current reading?

-Jimi

Hi Wyatt,

Thanks for your confirmation. 

As you may know we average 30pcs PCBA fuel gauge current reading and obtain new CC Gain and CC Delta from averaged golden sample.

Thus we'd like to know what is the current reading accuracy BEFORE current calibration from 0mA~1000mA.

It will be helpful if temperature coefficient is also considered.  

Thanks.

-Jimi

Hi Wyatt,

As above mentioned, could you confirm the figure 3. current error measurements are after the calibration? Thanks.

-Jimi