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BQ24296: Limiting Charge Current

Ryan.Bishop
Expert 3900 points
Part Number: BQ24296
Other Parts Discussed in Thread: BQ24253, BQ24292I, BQ24192I, BQ25606, BQ24266

Hello,

A customer will be using this device in an application where the default charge current of 2.048A is too high. Reading datasheet section 9.3.3.1, it says this default charge current will only be supplied if battery charging is enabled at POR (REG01[5:4] = 01).

So I think we would want charging disabled on power up (REG01[5:4] = 00), but are these registers stored in non-volatile memory? If not, won't REG01[5:4] default to 01 on reset, thus allowing the default charge current to be sourced?

Ultimately, my question is how can I ensure the charger won't source the 2A default charge current in situations like a reset or if the host controller hangs up before it can set the necessary registers.

I hope that was clear, please let me know if you have any questions. Thanks!

-Ryan B 

  • 0
    TI__Mastermind 25800 points

    Hey Ryan, 

    You are correct that charging is on by default in the register setting. And if a total reset occurs, all settings will return to default. However, we also have an active low signal pin called /CE. This pin is a hardware disable of charging. In order to charge, both REG01[5:4] and /CE must be set to enable.

    One option, if your customer will be using a host controller, is to tie /CE to a GPIO that will drive it low until the default charge current setting is changed to <2.048A. If the system hangs and the charger PORs, have that pin automatically pull high until the host restarts. Open-drain outputs are great for this as you can pull-up the pin to a rail.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Expert 3900 points
    Hi Joel,

    Thanks for your quick help! This is a good option if the customer is okay allocating a GPIO to implement this function.

    They are now looking at bq24253 also as an alternative because it's charge current can be set by an external resistor.

    Regards,
    Ryan
  • 0 in reply to Ryan.Bishop
    TI__Mastermind 25800 points

    Hey Ryan,

    You can also take a look at parts like the bq24192i and bq24292i, which have defaults currents @ 1A, which may be more suitable for your customer's needs, if they are still looking for something host controlled.

    Additionally, you may look at the bq25606 as an alternative standalone charger as well as the bq24266, albeit in QFN packages.

    Hope this opens up your options.

    Edit: The bq24261M is another host-controlled charger with charge disabled by default. 



    Regards,
    Joel H