BQ24250 Programming Resistor not working?

Hi,

There are a few things that could limit charge current. Could you please check following?

1. What's your input voltage at IC pin? At higher current, IR drop on wire could be very significant. Actual Vin(seen by BQ24250) could be much lower than adapter nominal value, and force IC into VINDPM. Higher input voltage or short wire will help.

2. What's your R value for ILIM? Can you try to short it to GND. By doing so, it will set input limit to 2A.

3. Can you measure voltage at TS? It should be around half of LDO voltage. You can refer to DS Page 12 for details. Otherwise it will enter regulation.

Best Regards,

Linhong

1.) Voltage at the input is 4.85V

2.) I have a series combination of 100 and 25 ohm resistors connected to ILIM.

3.) The voltage is in fact 4.7V at this node.  Could there be a problem with my resistor values at this node?  I used values as close to those given to my by the excel calculator TI provides.

My mistake...I measured the voltage at the TS pin and it is in fact about half of the LDO voltage.  (I measured the wrong pin before)

With R_ILIM=125ohm, your "nominal" input current limit would be 2.16A = 270/125. Your input voltage is already at lower side, 4.85V. This could be a factor. What if you short it to GND? Will charge current change?

Also what's your battery voltage? If it is too close to VIN, it will also limit the charge current. Can you try on a 3.6V battery, for example?

Thanks.

Linhong

Shorting ISET to ground did not seem to change anything for us.

Battery voltage is approximately 3.6V.

ILIM is shorted to GND nativley in our design.

Also, we are trying to override the external resistor and change register settings to allow for the full charging current, however we are not able to change register 2.  It is stuck at 0xec.

You probably have watchdog enabled. When watchdog expires, it will reset all registers to default. Please refer to Fig. 24 in datasheet.

Regards,

Linhong