bq27742 calibration

Hi Onyx

I am using the bq27742-G1 on a portable application

1.- In the post a you mentioned that setting the right chemID, performing the calibration sequence and generating the learning cycle the golden image is done. Does bq27742-G1 need the calibration process for each board? or Do I have to make a calibration average like post b?

a) https://e2e.ti.com/support/power_management/battery_management/f/180/p/472303/1698156#1698156

b) http://e2e.ti.com/support/power_management/battery_management/f/180/t/478040#pi317195filter=all&pi317195scroll=false

2.- You also mentioned 'You can average out the entire calibration parameters. cc offset might refuse to change if you have a different value than what the gauge initially has when programming. Don't be bothered about that, the gauge automatically does that specific calibration.'. This sentence is not clear to me, could you elaborate it more?

3.- We have to  make a plan for mass production, how do you recommend to perform the mass production programming (we have to know if several external programmers are needed)? 

hi Julio

1. It's your choice. Either you calibrate each board for higher measurement accuracy or you carry out the average. The accuracy when the average is done is acceptable.

2. The gauge performs cc offset calibration before going into sleep mode.  When programming your golden gg file you obtain after the averaging the  calibration values, the cc offset value will be retained on each gauge. It likely  wouldn't be  programmed on the gauge. Don't worry about that. Just ensure the other averaged calibration parameters program ok.

3. After you program you have completed a learning cycle after having programmed the chem id and  carried out calibration, use bqstudio to extract a bqfs file. This is a flash stream format file which you can parse on the gauge using your host controller. This is the most common means used by most customers for mass production.

Let me know if you have further questions.

thanks

Onyx

Hi Onyx

Thanks for your answers. I have one more question:
In the TRM section 5.8.1.4 (board offset), the following sentence appears: "The simplified ground circuit design in the fuel gauge requires a separate board offset for each tested device."; could you elaborate more this sentence?

Thanks in advance

Hi Julio,
board offset is different from cc offset. Carrying out board offset calibration is done if your device is measuring current when there is no actual current flow. When you do this calibration, the device makes adjustments to the calibration parameters responsible for that calibration which will be part of what you will be averaging.

thanks
Onyx

Hi Onyx,
We are implementing 1% passive components on our HW and we want to develop a single golden image (no averaging) for all the batch.
1.- Is it possible to do this?
2.- If positive, what is going to happen with the adjustments on the calibration parameters based on the board offset value?

Hi Julio,

You can do the single golden image without calibration and then calibrate each board afterwards OR average calibration parameters of ten calibrated units and incorporate this in your golden image. That way you don't have to do calibration on each board and the results should be ok.

thanks
Onyx

Hi Onyx

Thanks for the answer. One more question:

Only the calibration parameters need to be averaged, or Do I have to average others parameters?

Thanks in advance

Hi Onyx
Could you check the last question? I have to close the golden image and programming on factory plan. I will really appreciate it.
Thanks in advance

Hi Julio,

You do not need to average other data memory parameters when creating your golden file.

Best Regards,
Ben Lough

Hi Ben
Thanks for reply. I will perform the golden image.
Regards

Hi Onyx and Ben

I performed the learning cycle and I have a doubt. I had to make two learning cycles due to the change in the Sense resistor component. At the end of the first learning cycle the Ra_0 register was updated but the Ra_a0x was not; after the second learning cycle I noticed that the R_a0 and the R_a0x registers have the same values.

First learning cycle

Second learning cycle

a) Does it mean that the first learning cycle was not performed properly?

b) If affirmative, the value of the new Ra Table values could be corrupted due to the previous Ra Table values?

Hi Julio,

This is actually ok. The gauge alternates which table is updated (flag 0055 is the newly updated table, flag 0000 is the previously updated table).

Best Regards,
Ben Lough

Hi Ben
Great to know that everithing is ok on the learning cycle. I am finishing the golden image but the way to fill some registers are not detailed in the TRM. Could you make an example to fill the following registers?
1.- SOC Load I
2.- Max DeltaV and Min DeltaV
3.- Max Sim Rate and Min Sim Rate
4.- Ra Maximum Delta -> After the learning cycle, the R_a04 is 146 and then this value is calulated as 22 (146*0.15). Is it correct?
5.- Qmax Maximum Delta Percent
6.- Qmax Upper Bound Percent
7.- Delta V Maximum Delta

Hi Julio.
1. SOC load I should be your typical system current.
2. Keep the default
3. keep the default
4. correct
5. Keep the default
6. Keep the default
7. keep the fefault.

The bq27542 TRM has some additional details for some of these parameters.
thanks
ONyx

Hi Julio
Only the calibration parameters.

thanks
Onyx