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bq24105/bq24115 Interchangability

Greg Houlette
Prodigy 30 points
Other Parts Discussed in Thread: BQ24105, BQ24115

I have an existing desgn built around the bq24105 and I'd like to add microprocessor control (for many reasons).

The bq24115 appears to be a near perfect alternative, but I noticed that it doesn't have a STAT2 pin.

Is there an alternative method for the IC to report:

Battery absent
Overvoltage

  • 0
    TI__Genius 13700 points

    Hello Greg,

    What sort of functionality are you hoping to gain by migrating from the BQ24105 to the BQ24115? I ask because outside of being able to externally control when the charger is a precharge or fast charge there is little additional control added to the 115 over the 105. Both devices have their precharge, fast charge, and termination currents are set in the same way between the two devices with resistors connected to ISET1 & ISET2.

    So it looks like with the migration you will gain a precharge/fast charge control but without the STAT2 pin the information to differentiate between charge complete and some fault scenarios indicated by STAT2 is not possible with the device alone.

  • 0 in reply to Ryan May
    Prodigy 30 points

    My application is the charging to 50% SOC (for long term storage) of a 6.8Ah Li-Ion battery.  In an attempt to optimize the operation on a battery by battery basis, I have an external current shunt amplifier (LTC6102) which allows me to monitor current flow in addition to the battery voltage in real-time.  So, technically, I already have a method to detect Battery Absence and Overvoltage (and Overcurrent as well).  Being able to dynamically change the Pre-charge to Fast Charge transition point (and also the Termination on the tail-end) may help me get a better outcome over a wider variety of battery conditions.  And there is a price point to all this, such that I really do want the bq241xx to assist in managing the CC to CV portion of the charge profile.  It's a bit more than just strapping for 4.2V @ 1.33A/133mA.

    Back to my original question, it seems your answer is NO.

  • 0 in reply to Greg Houlette
    TI__Genius 13700 points

    Hello Greg,

    Unfortunately with switching devices you will lose the distinction of the battery state/fault condition information from the STAT2 pin.

    I am not sure what you mean by the last two sentences. The BQ24115 will manage the CC and CV control needed for the battery charge profile. Also the CMOD pin only provides you with the ability to switch between precharge and fast charge. This will not allow you to control charging termination since it is set by the ISET2 resistor.

  • 0 in reply to Ryan May
    Prodigy 30 points

    It's simple, I can Terminate the charge with the ~CE pin control when I've determined that the battery has taken enough to meet the 50% mark (somewhere between 600mA and 400mA level).  I can still use the recommended Precharge level set by the ISET2 resistor while controlling the actual vLOW transition point (based upon the battery's response and other factors).  So, in effect, I can control the Precharge to Fast-charge transition point (via CMODE) and the Charge Termination point (via ~CE).  All this may seem unecessary to you, but I DO have my reasons for it.

  • 0 in reply to Greg Houlette
    TI__Genius 13700 points

    Hello Greg,

    Sounds like you have this system planned out to use a number of features of this device to your advantage.

    Let me know if you have any other questions otherwise it looks like you have a handle on exactly what you want to do and how to accomplish it.