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BQ24167 Current Consumption Too High

Brandon Cromer
Prodigy 20 points
Other Parts Discussed in Thread: BQ24167

We are currently using a BQ24167 in a design.  From what I can gather from the datasheet, the max battery current when no external power is available is 5uA.  Unfortunately, we're seeing around 30uA.  The only pins that I can imagine would effect this are the IUSB_ lines, but when measured, they are in their intended states to limit the USB current to 500mA.  IUSB2 and IUSB3 are both pulled low with a 150k resistor (and are driven by a GPIO from our processor).  IUSB1 is connected directly to the DRV output.  CE is also pulled low with a 150k resistor  (and connected to a GPIO on our processor).  What am I missing??

  • 0
    Prodigy 20 points

    An additional comment that should be made is that the 30uA is measured on a board with only the BQ24167 (and its supporting components) populated.  

  • 0
    TI__Guru**** 165886 points

    The I(BATLEAK) spec is the only the leakage current from the battery that gets back to either in the IN or USB supply pins.  To measure it, you would place a current meter from one of the those pins to GND.  The 30uA leakage from the BAT pin into the IC is expected.  If you need less leakage you will need to place a series, low leakage PFET in between the BAT pin and battery so that you can completely disconnect the battery from the IC.

  • 0 in reply to Jeff F
    Prodigy 40 points

    I can't have the battery charger, BQ24167, consume 30uA when the battery is connected and Vin and Vusb are 0V.

    Do you have a recommended circuit layout that would cut power from the battery to the battery charger but allow the battery to power the system load? The system load would be attached to the SYS pin.

  • 0 in reply to Brian Acchione
    TI__Guru**** 165886 points

    I suggest a series PFET between BAT and the battery, source tied to battery and gate tied to an NFET with its gate tied to diode OR output of IN and USB.  I also suggest another PFET with source tied to SYS, drain to battery and gate tied directly to diode OR output of IN and USB.  The pull up resistors across the source and gate of each can be sized large enough to reduce the leakage current. 

  • 0 in reply to Jeff F
    Prodigy 40 points

    Would I have to worry about damaging the battery charger chip or it drawing current when the source of the PFET is connected to SYS?

    I'm worried this would end up supplying power to the battery charger through the SYS and SW pins.

    I attached the circuit I was planning to use but I'm concerned about the PFET connected to SYS. I also wasn't sure why the PFET was suggested between the battery and the battery charger. Could you take a look at the attached circuit?

    0045.3704_001.pdf

  • 0 in reply to Brian Acchione
    TI__Guru**** 165886 points

    You will not damage the chip.  We do not spec the current consumption into SYS/SW so that would have to tested but it should be small.  If large, then you would need another FET.

    You will need to isolate the battery from the BAT pin to prevent current flow into BAT pin.  If the battery will be discharged enough so that IN/USB will provide enough drive to an NFET, you could use an NFET; otherwise you will need a PFET.  Keep in mind both NFETs and PFETs have body diodes that allow current flow in the opposite direction of their expected current flow.