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BQ24253: How to set charge current to 1A with no NTC input coming from the battery pack

Vijay Gandhi1
Prodigy 70 points
Part Number: BQ24253

Hi, We are using BQ24253RGET charger chip in a wearable application. We used exactly same circuit as that of BQ24250EVM.

We use 5V/2A input adapter and 2000mAh battery. VDPM is set to 4.48V. USB D+/D- are not used.

Even though we set maximum charging current as 1A, by setting R-ILIM to 267 ohms and R-ISET to 249 ohm; we see that the battery charges with 0.54A maximum both on our application as well as on the 24250EVM.

Note that our battery pack doesn't have temperature/NTC input coming to the TS pin of the charger chip 24253. Currently the TS pin is configured with two 20K resistors divider network from LDO supply to GND(same as on the EVM). I tried setting the jumper JP4 to "var" position and adjusting the POT on TS pin, but the charging current doesn't seem to increase beyond 0.54A.

Can you please let me know how I can charge with 1A current? What changes do I need to make to the circuit?

Thanks in advance.
Vijay

  • 0
    TI__Guru**** 165786 points
    Vijay,

    If you tie D+=D- then set EN2=0 and EN1=1 and apply power, do you still get only 0.54A? If so, what is the voltage at the IN and BAT pins?
  • 0 in reply to Jeff F
    Prodigy 70 points

    Jeff,

    Thanks, it works. Once I shorted D+, D- pins, it is charging at full current.

    Currently I left D+ and D- pins of 24253 unconnected to uUSB port.

    We only have one uUSB port which we use for programming the controller as well as for charging.

    So, can I connect D+ and D- lines from the uUSB port to D+ and D- of both the controller and BQ24253 ?

    Regards,

    Vijay

  • 0 in reply to Vijay Gandhi1
    TI__Guru**** 165786 points

    Vijay,

    You can connect the USB D+/D- to the bq24253 and controller.  The bq24253 will only use the lines for the first 1.5s at power up.  Keep in mind that if the port is only an SDP port, for example, the input current limit will be limited to 100mA but you toggle the ENx lines. In addition, when an SDP port is detected, charging is only allowed for the first 45 minutes if the battery <=3.6V and not allowed at all if the battery is >3.6V, per the original USB BC 1.2x spec. Also, the bq24253 does not consistently recognize CDP ports.