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BQ34110: Normal mode current consumption

Part Number: BQ34110
Other Parts Discussed in Thread: BQSTUDIO, BQ25713, TPS24720

Hello, per data sheet, the typical consumption (ICC_NORMAL) is 133uA. However, I measured around 1mA. Only when I issued the SET_SNOOZE control (with bqStudio) I got a reduced power consumption of around 170uA. 

Full disclosure: I have a BQ25713 (set to low power mode with bqStudio before taking the measurement above) and a TPS71533 to supply the fuel gauge as the battery pack nominal voltage is 12V (NiMH 10S). The equivalent resistance of the battery measurement circuit (based on the circuit of the data sheet) is 110k, so when active it would draw about 100uA (anyway, I understand it is enabled only when the fuel gauge needs to make a voltage measurement).

So, my question is if the ICC_NORMAL figure in the data sheet is correct. If affirmative, what should I be looking at to understand this extra power consumption.

Thanks in advance.

  • Hello Elder,

    Where are you taking the current measurement? The datasheet value is based only on the current to the gauge, not from the battery. It would be the REGIN node.

    Sincerely,

    Wyatt Keller

  • Hello, Wyatt.

    The milliammeter is in series with the positive pole of the battery. I understand the current is not only of the fuel gauge, there is the standby current of battery charger (low per data sheet), the ground current of the LDO (also a few uA) that supplies the gauge, the e-switches (two TPS24720 that are disabled at the moment I took the measurement). 

    Still, there is the fact the current drops more than 1mA, to the current level I expect when I send the SET_SNOOZE command. I am trying to figure this out to have all bases covered. Wher should I look at?

  • Hello Elder,

    I would measure the current at the REGIN pin to GND. It may be hard to tell with a milliammeter though, is the resolution good enough for micro-amps?

    If the current at REGIN is out of spec then we can look into it further. 1mA is definitely way too high for this gauge.

    Sincerely,

    Wyatt Keller

  • Hi, Wyatt, the resolution of the milliammeter was actually 0.01m. Reading not too different when I swicthed to uA scale, only that scale was 1uA. Yes, I agree, 1mA (ish) seemed high, that is the reason why I am trying to figure this out. Any ideas?

  • Hello Elder,

    The current was 1mA into REGIN? The gauge specification is based only on the current for the gauge, anything else the gauge is driving or on the same power bus could be drawing some of the current.

    Sincerely,

    Wyatt Keller

  • Wyatt,

    No, not measuring into REGIN, I have no easy way to do it. REGIN is connected to the output of the LDO (TPS71533) and it is the only active thing connected to the LDO output..

    As I mentioned before, I placed the meter in series with the positive pole of the battery. With outputs off (i.e., the e-switches disabled), the battery charger set to low power mode, the current consumption was around 1.2mA. When I send the SET_SNOOZE command (using bqStudio) to the fuel gauge, the current dropped to 0.17mA. So I am assuming the 1mA is being drawn by the fuel gauge itself.

  • Hello Elder,

    To confirm the real gauge consumption we would need to verify it's from the REGIN pin. Otherwise the gauge may be driving something else on the PCB that is causing the extra current draw. 1mA is way out of spec and it's most likely not only the gauge drawing the current, it may be something related to the gauge but I'm not sure of the peripheral components.  

    Can you share the schematic?

    Sincerely,

    Wyatt Keller

  • Hi, Wyatt, could you provide an email address I can send the schematic to?

  • Hello Elder,

    I sent you a connection request on the forum to share privately.

    Sincerely,

    Wyatt Keller