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BQ25120 power up status

Warwick Freeman
Prodigy 70 points
Other Parts Discussed in Thread: CC2640, BQ25121, BQ25120

I want to use the BQ25120 or BQ25121 in a system with a CC2640.  I am trying to work out if I need a pull up on the CD line so that the device will power up correctly.  As I understand it from the datasheet if there is no VIN and CD is low (default state due to pull down) and the processor pin is tristate before its programmed then the device will be in Hi-Z state.  The data sheet says that in Hi-Z state "the SYS output is powered by BAT".  Does that mean that the DC/DC converter is working and the SYS output will be regulated to 1.8V (or 2.5V if using the 25121)?

  • 0
    TI__Expert 4600 points

    Yes, the /CD pin does not affect the output of the buck.  The /CD pin is used to control charging when VIN is present, and to enable/disable the I2C interface when battery only is present.  The default is to have /CD low, so the part is in the lowest Iq state when battery only is present, and must be pulled high to communicate to the device with battery only.  When VIN is present, /CD low allows the part to charge the battery, and pulling /CD high will disable charge.  When VIN is present, I2C is always enabled.