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bq24400 does not charge

Laura 56109
Prodigy 170 points
Other Parts Discussed in Thread: BQ24400

Hello,

 

I have made the circuit in the datasheet in the figure 8. I have changed the number of batteries in 2 with the resistors R6 undR7= 110k and instead of the Temperature sensor i have a divider network. With this network on, i can measure 1,5V at the Ts pin.

Without Batteries everything is fine. I measure at the RC Oin about 2V and at the Mod Pin some Pulses. If i attach the batteries it does not work as it should. At the RC Pin i measure Pulses every 1,2s with a 3,4V amplitude. At this pin should not be annything else but DC Voltage or sawtooth.The Led is also blinking at 1Hz.

Does anybody has a explanation for this behaviour of the IC?

 

 

Thanks

  • 0
    TI__Mastermind 30990 points

    Hi Laura,

     

    What is your VCC voltage?

    What’s happening with your LED during this time?

     

    If the voltage on the BAT pin is less than the internal threshold, VLBAT, the bq24400 enters the battery conditioning state. This condition indicates the possibility of a defective or shorted battery pack. In an attempt to revive a fully depleted pack, the bq24400 enables the MOD pin to trickle-charge at a rate of once every ~1s.

     

    For the Temperature sensing, if the voltage at the TS pin (VTS) is less 0.225*VCC, the device stops charging.  

     

    Thanks

    -Tahar

  • 0 in reply to Tahar Allag
    Prodigy 170 points

    Hi Tahar,

     

     

    it looks like it was a problem in the Layout design. With a new design where the sense resistor is very close to the IC (Bq24400) and all the wires that have 1A (charging current)  made as short as possible its charging.

     

     

    Thanks a lot,

    Laura