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BQ27Z561: BQ27Z561

lx luo
Prodigy 130 points
Part Number: BQ27Z561

Hello, TI team:

BQ27Z561 has encountered a problem in its application. Please help analyze the cause:
When the cell voltage is higher than 2.5V, all applications are normal;
2. However, when the cell voltage drops to 1.6V, the power consumption of the IC shows abnormal values, such as several hundred microamperes, and slightly smaller ones all have 40-50 microamperes. As shown in the attachment, 5 pieces of data were tested;
3. Until the battery cell voltage drops below 1V, the power consumption becomes normal again.
Can you help me comment on why?

 Thank you！

BQ27Z561自耗电数据20231001.xlsx

  • 0
    TI__Mastermind 27321 points

    Hello,

    Supply current during normal operation has a typical value of 60uA. It looks like the "several hundred microamperes" are only seeing when the device BAT voltage is at 1.6V.

    Do you have any circuit that activates when the BAT voltage drops to 1.6V? Any sort of secondary supply in your design? This is a strange behavior and only happens at a certain voltage. 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 130 points

    Hi Jose Couso,

    Please check the schematic diagram. There is no other active circuit.

    Regards,

    Luo Lixin

  • 0 in reply to lx luo
    TI__Mastermind 27321 points

    Hi Luo Lixin,

    I do not see anything alarming with the BQ27z561 schematic. 

    What is U2?


    How easy can you replicate this? How do you measure the current consumption? 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 130 points

    Hi Jose Couso,

    1. U2 is a MOSFET, The following is the complete circuit diagram，J1 is the output port of the battery pack and nothing is connected.

    2. During the test, R1 is removed, and the cell is disconnected. Adjustable DC power supply is used, and an ammeter is connected to the power supply in series.

    3. Change the voltage of the DC power supply, read the value of the ammeter, and get the test record sheet when the first problem occurs.

    With this information, can we find out why GAS GAUGE consumes so much power?

    Regards,

    Luo Lixin

  • 0 in reply to lx luo
    TI__Mastermind 27321 points

    Hi Luo Lixin,

    I did a quick test and found a similar behavior. See below. 

    Bat voltage Current consumption
    2.6 V 8 uA
    3.6 V 8 uA
    1.7 V 8 uA
    1.6 V 227uA
    1.5 V 3 uA


    It does seems like the device consumes more power when voltage is 1.6V. This seems to be an internal behavior of the IC. 

    Is there a reason why you would operate at this voltage level? 

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 130 points

    Hi Jose Couso,

    We are not applying BQ27z61 to the 1.6V scenario, but we are worried that if the user's system battery is not charged in time after entering the over discharge protection, it is very easy to cause the battery cell to be put dead, and the battery cell is easy to swell after being put dead, which will give the user a bad feeling.
    So, is there any way to improve this phenomenon?

    Regards,

    Luo Lixin

  • 0 in reply to lx luo
    TI__Mastermind 27321 points

    Hi Luo Lixin,

    This is something internal with the IC design. Looks like you might need to control the voltage so that it does not get near 1.6V. 

    Regards,
    Jose Couso