BQ76952: Command for full reset BQ7695202 and Current accuracy

Hello Gaurav,

You can perform a FULL RESET by using the RESET() command. The following FAQ will be useful:

• How do I RESET the BQ769x2 device?

Your CC Gain seems to be incorrect. The equation from the TRM is to use 7.5684 / (Rsense in mOhm), this is mentioned in Section 4.12 Current Calibration of the TRM.

Assuming a 1-mOhm sense resistor, CC Gain = 7.5684. Using an on-line 32-bit IEEE-754 calculator, I find that 7.5684 translates to 0x40F23055. Capacity Gain (As you pointed out) then is CC Gain * 298261.6178, which translate to 0x4A09C74D.

Your current CC Gain value translates to 0.742 in decimal form, this would correspond to a sense resistor of ~10.2-mOhms.

Best Regards,

Luis Hernandez Salomon

Hi Luis,

Luis H. S. said:

Assuming a 1-mOhm sense resistor, CC Gain = 7.5684. Using an on-line 32-bit IEEE-754 calculator, I find that 7.5684 translates to 0x40F23055. Capacity Gain (As you pointed out) then is CC Gain * 298261.6178, which translate to 0x4A09C74D.

After configuring these values in code, current read on Multimeter is 5.6A but in our code (debugger) I got 66.7A

please suggest the procedure how to improve the current calibration.

Hello Gaurav,

Can you provide more detail on what you are programming? Did you read back to ensure that it was properly programmed? I've already explained how to adjust for the current sense, so it would not be so inaccurate. 

Can you please share a logic analyzer capture of what you are writing to the device? Is your sense resistor 1-mOhm?

This E2E shows an example of how to correctly program this:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1346253/bq76952-problems-programming-calibration-current-cc-gain-register

Best Regards,

Luis Hernandez Salomon

Hi Luis,

We don't have logic analyzer. Tomorrow I will check the set value and read from BQ studio and reply the same.

Hello Gaurav,

Thanks! Do let me know what that says.

Best Regards,

Luis Hernandez Salomon

Hi Luis,

I checked the above values with BQ Studio in the attached image. In this the current is shown in multimeter is 5.6 A but, in our code, (during debugging) it's 56A.

I also set the values (7.5684/10) with BQ Studio in the attached image. With this value the current is shown in multimeter is 5.6A but, in our code, (during debugging) it's 6.4A. which is not much accurate as expected.

Hello Gaurav,

That is very strange. Again, what is your sense resistor value? Is it actually 10-mOhms?

What I would recommend here is to follow the steps in Section 2.6 Current Calibration of the BQ769x2 Calibration and OTP Programming Guide. Typically it is enough to follow the steps in the TRM, but for this case I would recommend to go a step further.

Best Regards,

Luis Hernandez Salomon

Hi Luis,

Luis H. S. said:

That is very strange. Again, what is your sense resistor value? Is it actually 10-mOhms?

1mOhm sense resistor 

Luis H. S. said:

What I would recommend here is to follow the steps

Ok I will check and follow the steps for calibration.

• If the RST_SHUT pin is asserted while the device is updating something in RAM, the RAM integrity check could fail and trigger a full RAM RESET.

How can I know that RAM is updating after full RAM RESET.

Hello Gaurav,

Ok, I hope this type of calibration may be more helpful for you.

I don't believe there is a good way to know if something is being updated in the RAM. If a FULL reset were to happen, the Battery Status[POR] bit would be set.

Best Regards,

Luis Hernandez Salomon