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BQ21080: Iq_bat without push button enabled? Better choices?

Mike Ciholas
Prodigy 140 points
Part Number: BQ21080
Other Parts Discussed in Thread: BQ25180, , BQ21040

The current the BQ21080 and similar BQ25180 use when on battery and with no VIN is a bit discouraging to us at about 4 uA, was hoping to be less so we can sleep long periods without battery draw.

The datasheet for the BQ21080 says 4 uA, but with EN_PUSH on, which uses some current into the TS pin thermistor:

(How do you post higher res images?  Yuck)

What current does it use if EN_PUSH is off?  It has to be less given the current running through the batter thermistor.

Are there any better chips than BQ21080 with lower Iq_bat but otherwise functionally similar?

Thanks.

Mike Ciholas

mikec@ciholas.com

Ciholas, Inc.

  • 0
    TI__Mastermind 23220 points

    Hi Mike,

    Is the shutdown mode a viable alternative here instead of the ship mode? The main difference between ship mode and shutdown is that ship mode has the additional exit option of a push button. If you set EN_PUSH to be off, it becomes essentially shutdown mode which has consumptions in the nA range. 

    As for the image, just the preview is pixelated. Once you click to enlarge, it looks fine. 

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 140 points

    I still have to power by device, so shutdown mode is not a viable option.  My goal is to power my device from battery with the BQ21080 (or something lese) taking as little of this as possible.

    I'm considering something like the BQ21040, which has no I2C and thus far less useful, but it has only 1 uA usage form battery.  But the lack of features is impacting what we can do.  Seems like if the BQ21040 could be lower power, the BQ21080 should have been able to do the same.

  • 0 in reply to Mike Ciholas
    TI__Mastermind 23220 points

    Ah I see!

    Apologies on my part, I thought this was asking about ship mode.  Let me go take some measurements with the push button disabled and get back to you. 

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 140 points

    Thanks.

    My application runs at an average current of about 5 uA.  Having 4 uA used by the BQ21080 really affects the battery lifetime dropping it by almost half.  Would like to get it lower or find some other USB, charger, power path chip.

    I started looking at powering directly from the battery and then putting the BQ21080 in shutdown (ship) mode during battery operation, but that causes issues with proper charging of the cell and defeats the power path features of the BQ21080.  I could go to a simple charger like BQ21040, but that loses some control and also has mixed charging and application usage.

    Basically, I want the features of the BQ21080 but with a lot lower Iq_bat.

  • 0 in reply to Mike Ciholas
    TI__Mastermind 23220 points

    Hi Mike,

    Thanks for your patience and you're right that shutdown/ship mode isn't applicable here since you want your SYS voltage to be active. 

    I was able to take some measurements that should help you make your decision. 

    So with EN_PUSH enabled on a device I see about 3.7 uA. As you've mentioned this is because of how the device sources current to detect push button

    With EN_PUSH disabled, I'm able to measure about 2.2 uA on average. 

    Hope this helps!

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 140 points

    2.2 uA providing VSYS is better than 4 uA, but still kind of more than I would hope for.

    Thanks for the measurements.

  • 0 in reply to Mike Ciholas
    TI__Mastermind 23220 points

    I understand, but just curious and for also for our feedback if you're able to share:

    • What's your battery capacity?
    • What's your product application?
    • What is your system that is consuming 5 uA?

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 140 points

    > What's your battery capacity?

    About 0.5 WH.

    > What's your product application?

    Low power radio beacon.

    > What is your system that is consuming 5 uA?

    Low duty cycle operation, spends vast majority of the time inactive.

  • 0 in reply to Mike Ciholas
    TI__Mastermind 23220 points

    Hi Mike,

    Awesome stuff. Thanks a bunch for sharing. Feel free to come back if there are any other questions regarding the BQ21080.

    Best Regards,

    Anthony Pham