BQ25756: ADC read issue when charge termination done

Hi,

What gives you the indication that the ADC freezes after charge termination? The voltage should be stagnant and there should be no current in the system in termination.

Best,
Michael

Hello Michael,
The values VAC, VBAT, IAC and IBAT doesnot change , when read the register always shows the same constant value when the controller enters charge termination.
e.g lets say VAC= 17V when the controller terminates the charging then if we read the VAC register it always gives back 17V even if we vary the input voltage.

Hello,

That is odd. I have just verified in the lab on the EVM that the ADC can read different voltage levels on the input while in termination. What is the REGN voltage while this issue occurs?

Best,
Michael

Hello Michael,

Thankyou for your response, thats quite strange I also checked on 3 boards but the result was same. The REGN voltage is 5V and also when the battery voltage drops below recharge threshold it starts charging and the ADC reading gets back to normal.

That is interesting behavior. What happens if you disable the ADC and then enable it again while in termination?

Disabling and reenabling the ADC has no effect it shows the same result.

Are you able to provide a schematic of the portions of your design pertaining to the BQ25756?

yes sure, i have attached the schematics of the controller part. Also to avoid your confusion regarding the schematics, the resistor R26 at the CE pin is not populated, since this was designed for host controlled application. And for the DRV supply external 7V is supplied hence only R20 is populated. Also the pullup resistors for the interrupt lines and I2C lines are at the MCU section.CHG CTRLR.pdf

Thanks for providing that information. I do not see anything on the schematic that might cause issues on the ADC.

Has this issue been replicated on any other boards? Does the ADC work in one-shot conversion?