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BQ25606: Boost operation of the BQ25606.

KIM Andy
Expert 2530 points
Part Number: BQ25606


Hi
My client is using BQ25606.
  There are two questions regarding the Boost operation of the BQ25606.
1. If there is no adapter and the battery is present, does the battery operate when it falls below a certain voltage and is below the output voltage?
If so, is it possible to keep the output voltage constant?

2. If there is only battery and there is no battery, output voltage will be up down at regular intervals. Can this phenomenon be improved by adjusting the resistance of both ends of the TS pin? At present, the thermistor is not used, but the resistance of the lower end of the TS is increased.

  • 0
    TI__Genius 11850 points

    Hi,

    1) If OTG is enabled and only the battery is connected, then VBAT must be above 3 V to support OTG mode, as shown in the EC table below. In OTG mode, the BQ25606 will maintain 5.15 V at VBUS, and VSYS will be equal to VBAT minus the voltage drop across the BATFET. Please see Section 8.3.3 in the datasheet for more details about OTG mode operation.

    2) I'm assuming you mean there is only an adapter connected, but no battery? The VSYS oscillation you're describing is because no battery is connected, so there is only a small capacitor storing the voltage on VBAT. This capacitor charges and discharges quickly, which causes the BQ25606 to continuously enter termination and re-charge cycles. VSYS will oscillate from about 3.7 V to 4.2 V.

    There are a few solutions for this:

    1) Pull the /CE pin high to disable charging.

    2) Use the TS pin. The BQ25606 was designed assuming that, without a battery, the TS pin would fault and disable charge. Pulling the TS pin voltage high/low to force a battery COLD/HOT state disables charging. However, this solution requires that you use a thermistor so that the TS voltage when the battery is connected is different from the TS voltage when the battery is disconnected.

    Best regards,

    Angelo