BQ24074: Are there any issues using the power path from the battery charger going into the BQ27421

Hi Ajay,

The BQ24074 does not have the SYSOFF feature, it has the ITERM pin in its place. The  BQ27421-G1 should be fine with the charger. 

Best Regards,

Anthony Pham

Is there a suggested implementation because currently i am using the ITERM pin to set a termination current.

Thank you,

Ajay

Hi Anthony,

The reason why we ask is because the BQ27421-G1 requires measuring OCV (datasheet page 9, section 8.3) and the charger BQ2407x datasheet says -75/-79 with SYSOFF pin is used with system-side fuel gauge that requires OCV. We like BQ24074 for the wide input range, but it doesn't have SYSOFF.

- If BQ27421-G1 cannot measure OCV (the case with BQ24074), does it still work? What's the trade-off here?

- What's the difference between system-side vs pack-side fuel gauge?

Thanks,

Will

Hi Will,

Do you have a schematic we can review? As long as you have connected the ICs correctly there should be no issues, these parts are compatible with each other. The gauge would go between the charger and battery.

The OCV measurement is taken when the battery is in a relaxed state from the gauge BAT pin. 

System side gauge goes on the main PCB, a pack-side fuel gauge goes inside the battery pack. More info in these threads: e2e.ti.com/.../bq27441-g1-difference-between-system-side-and-pack-side-bq27441-vs-bq27411

Best regards,

Nick

Thanks for the info. Exactly what I need. 

Could we share the schematics in a private msg? As we have a few other questions about the path from battery -> ship mode circuit -> fuel gauge -> charger.