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BQ4050EVM-561: EVM Wake Button

JDJ
Expert 4486 points
Part Number: BQ4050EVM-561

Can you please help me understand the WAKE button down, I see CHG=18.8V and DSG = 5.5V, and I see 7.8V SW with 10k resistor, between 4P and Pack-. How does drawing 7.8V/10k (which looks like a 0.8mA load current) cause the Top side FETs to turn on? 

  • 0
    TI__Mastermind 28590 points

    Hello JDJ,

    Regarding the function of the WAKE button for this EVM, the purpose of it is to bypass the CHG and DSG FETs of the circuit and apply a voltage to the PACK+ pin which in turn is connected to the PACK pin. The device will then sense a voltage greater than the Charger Present Threshold value and wake up the device. This would not effect the gate voltage value of the CHG and DSG FETs in this circuit, hence this should not turn on the FETs.

    Regarding the 18.8V you are seeing at the CHG pin, this is due to the charge pump that drives the gate of the CHG and DSG FETs adding roughly 11.5V to the BAT voltage value. This action is solely to turn on the FETs. The image below describes how the values change when the gates are changed.

    Regards,

    Anthony Baldino