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BQ24780S: Configuration (now testing with EVM) with 12Vin, 12Vout and 12V lead battery

Daniel Rebollo
Expert 1205 points
Part Number: BQ24780S
Other Parts Discussed in Thread: BQ25703A

Hi,

Im testing the BQ24780S EVM and seeing the datasheets looks like it is able to do this but I can't obtain any good result...

I've changed the resistor divider of ACDET to obtain 2.5V with 12V at input, but this is not enough... ACOK needs also VCC>BAT so I think I can't get 12Vout with 12Vin and 12V battery.. but maybe there is a way to solve this like changing the battery to a 9V battery, the problem is that I cant get 12V at output, only Vin or Vbat when Vin is off. Seems like no converter is running, but the charge inhibit (0x12[0]) is 0 and ChargeCurrent (0x14), ChargeVoltage(0x15) and InputCurrent(0x3F) are loaded.

Can help me anybody? 

Thanks a lot

  • 0
    TI__Guru 56650 points
    You are right. bq24780S is a buck charger. The input voltage has to be higher than the output voltage. So, you cannot use 12V source to charge 12V battery. But, you can charge a 9V battery.

    Now, it is good time to have a solution for 12V source to charger 12V battery. TI just released bq25703A buck boost charger. It can meet your requirement.