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Original question:

BQ24295: Fuel gauge function -Reg

BQ24295: Right for a portable battery powered device? (+ other questions)

Craig Easdale
Expert 2170 points
Part Number: BQ24295

Hello,

I'm exploring the possibility of using the BQ24295 as the battery charger/boost converter combo for a single-cell Li-Ion battery powered device. As far as I understand that is one of it's primary applications, but I wanted to check it meets my criteria/expected operation. 

  • Should charge Li-Ion cell when USB power connected, while also providing a ~5V output to the rest of the system
  • When no USB power is disconnected, the IC should seamlessly switch to provide 5V to the system sourced from the battery

I have a few other more pin-specific questions;

  1. I am a little confused around how to use the OTG pin. Am I correct in thinking this should be pulled high to enable the PMID output when USB power is disconnected? If so, where should this be connected to ensure that process is automatic? SYS? BAT?
  2. Can the thermal resistor connected to the TS pin be an NTC thermistor of a Lithium-ion cell?

Lastly, I was looking to use a fuel-gauge alongside the charger to track battery charge state. Is there anything I shoudl consider if I want to use the BQ27220YZFR between the charger and the battery? It seems this might have it's own connection for an NTC thermistor, should this be used instead of the one on the TS pin mentioned above?

If there are other monolithic parts (around the same combined cost) that do charging, boost, and monitoring then I'd also love to hear about them.

Thanks,

Craig 

  • 0
    TI__Genius 12035 points

    Hi Craig,

    Craig Easdale said:
    • Should charge Li-Ion cell when USB power connected, while also providing a ~5V output to the rest of the system
    • When no USB power is disconnected, the IC should seamlessly switch to provide 5V to the system sourced from the battery

    When powered from a 5V VIN, the same voltage should be available at PMID. Similarly when VIN is not present, PMID can be boosted to 5V while in OTG mode for powering the system.

    Craig Easdale said:
    Is there anything I shoudl consider if I want to use the BQ27220YZFR between the charger and the battery? It seems this might have it's own connection for an NTC thermistor, should this be used instead of the one on the TS pin mentioned above?

    The TS Pin on the Gauge will give you temperature information, however to take action on the charging, you will need to process the information through a host controller and manually change the charger configurations to do so. Connecting the NTC to the charger will allow the charger to take direct action on charging without the need for a host controller, though it may be less flexible in its implementation.

    The two devices should work well for a charger / fuel gauge solution. In terms of more monolithic parts, the BQ2562x family does support charging, boosting, and includes an ADC for monitoring charging characteristics, but fuel gauging would have to be done by a host controller and it may not be as accurate as a dedicated fuel gauge. In terms of pricing this would need to be compared in the TI store or with a sales representative.

    Best Regards,

    Juan Ospina