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Original question:

BQ21061EVM: ship mode current on the BQ21061EVM board

BQ21061EVM: Current consumption in sleep mode is high?

Szhau Lai
Prodigy 50 points
Part Number: BQ21061EVM
Other Parts Discussed in Thread: BQ21061

Hi 

I have battery connected to BQ21061 as in the following schematics. When I connect the battery without usb connection. The BQ21061 should be in shipment mode by default and draw nano amp current. However, I get 4.5mA of current and the output VCC is 1.3V. I have the circuit on a custom pcb and it is not possible for me to measure how much current is draw on the rest of the circuit.

When I click the MR button to start it, it goes down to a reasonable level around 300uA. Would you please help me find the possible reason the sleep mode current is so high. 

I've measured my circuit resistance at the battery port without battery connection. The resistance is in >200kOhm range.  

  • 0
    TI__Genius 12135 points

    Hello Szhau,

    In order to get a better idea, I have a few questions about the situation:

    - Can you please provide the battery voltage, PMID voltage, LSLDO voltage, LP voltage, and VUSB voltage for this scenario?

    - Also is there any other rails connected to battery when this occurs or do the other rails on your system draw power from PMID, LSLDO, VDD?

    - Can you attempt I2C transactions with the device, if so, are they successful transactions?

    Based on the 1.3V on VCC/VDD it seems like either the device is not entirely in Shipmode or the rail is being backfed through some circuit on your board, possibly resulting in the increased current consumption.

    Best Regards,

    Juan Ospina

  • 0 in reply to Juan Ospina
    Prodigy 50 points

    Hi Juan

    The battery voltage is 3.8V.

    In my sleep mode. The voltage for PMID=0.28V, LSLDO=0.28V, LP voltage cannot be measured on my customed board. VUSB is not connected to power and is left floating, However, VUSB is connected to microcontroller's usb port, don't know if that can affect. Interesteingly, VUSB=1.3V even without any power connection(I'll check what happen to the microcontroller ).

    No rails is connected to battery. PMID is floating without connection. LDO is connected to passive resistive sensors, and VDD is connected to many active device, including microcontroller. I thought sleep mode should limit the current output to those devices. Why does the power draw of those systems matter in this case?

    About I2c connection, I have a related question. I can only do i2c transaction successfully whey I connect Vin to USB. When I just connect battery without VUSB, I am not able to do i2c transaction in battery active mode. I am using 1.8V( in battery active mode) from the Bq21061 to power the microcontroller. On table 9.5, it says clearly in battery active mode that I can do i2c function  in battery active mode. Please explain where I do wrong. 

    Thanks for help

    Best Regards

    Szhau Lai

     

  • 0 in reply to Szhau Lai
    TI__Genius 12135 points

    Hi Szhau,

    Thank you for the context you've provided. My first instinct as to the potential issue is that there is some backchannel through which the device is drawing power from the battery. When battery is connected, and VIN is not, I am assuming that battery is the only source for power in the system. Is there any other source for power internal or external for the system?

    VDD being at 1.3V indicates to me that, either it is enabled but too much current is being drawn causing voltage to fall (this indicates that we are not in shipmode) or that voltage is being backfed to this line through one of the connections (such as the MCU or I2C lines). Furthermore, VUSB being set to 1.3V as well increases my belief that there is some channel for current in the system outside of the device. This is why I am curious about other connections to the battery or other possible power sources within or outside the system.

    I am curious what your expected load is on VDD. It's important to ensure that consumption is kept below 10 mA of current.

    Szhau Lai said:
    VUSB=1.3V even without any power connection(I'll check what happen to the microcontroller ).

    When you say without any power connection, is battery present in this scenario?

    Szhau Lai said:
    I am not able to do i2c transaction in battery active mode.

    As you mention, I2C transactions should be available in active battery mode. If possible, can you provide waveform captures of attempted I2C transactions on these lines?

    Best Regards,

    Juan Ospina