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BQ25180: Use of Ship and Shutdown modes

Ben Bristow
Prodigy 20 points
Part Number: BQ25180


We are using BQ25180 to manage a small backup battery in a product. During manufacture we set the battery to a low power mode to minimise cell discharge in transit.

We know we have the option to use Ship mode with a slightly higher quiescent current but don't need functionality beyond Shutdown mode as our recovery mechanism is restoring VIN.

In s/w we use the (15nA) Shutdown mode which, based on measurement, appears to operate successfully.

We don't remove power immediately after setting shutdown (this occurs ~3s later). We do re-write parameters to the device on power up.

We have seen some rare scenarios where the device seems to be in an indeterminate state when powered. In this case, the battery is not charging until we force shutdown mode and restart.

Is there any kind of timing requirement around Shutdown (or Ship) mode being set?

Is there anything we should be aware of in the device operation or startup sequence that might cause data to be corrupted? 

Related to this, for the hardware reset sequence (data sheet 8.3.10) is there a reliable way to identify that the reset process has completed before we apply any of our own register configurations to the device?   

 

  • 0
    TI__Genius 10040 points

    Hi Ben,

    Thanks for reaching out. I'm reviewing this and will follow up tomorrow, 11/6.

    Best regards,

    Alec

  • 0
    TI__Genius 10040 points

    Hi Ben,

    There shouldn't be any issues with waiting 3s before removing power to enter shutdown mode.

    Is the device able to communicate via I2C while in this indeterminate state? Are you able to confirm that the registers are written as intended after exiting shutdown mode?

    The device is effectively off during the hardware reset so it will NACK, but you can wait for the Autowake timer duration + about 5ms before attempting to communicate with the device.

    Best regards,

    Alec

  • 0
    Prodigy 20 points

    Hi Alec,

    No, the device won't communicate, a power cycle is required to force a reset.

    Other devices on the same bus are OK.

    Stephen (s/w team) commented: "I had assumed that this behaviour was because we were trying to talk to the charger while it is still going through the hw reset sequence, so I added some more delay to our startup sequence.  So it is like this:

    1. Send shutdown request to BQ
    2. Remove Power
    3. Wait <2s
    4. Reapply power
    5. Our micro powers on
    6. Software does this:
      1. Wait 2s for BQ to go through a hardware reset after coming from ship mode
      2. Send HW reset request
      3. Wait 2s for *our* reset to complete
      4. Configure device as desired.

     And yet this still fails.  At 6b we find the backup charger device is noncommunicative.  The main charger can be communicated with (so it isn’t a bus problem). I’ve extended the delays out to 5s and see the same.(If we have a longer delay (at stage 3. Above) then there is no issue.  The system starts up, can talk to charger and finds it has come out of shutdown as if it were reset.) I think this device can get itself into a bad state, and only a power cycle (VIN cycle) fixes it.

    We'll check on autowake as suggested.

  • 0 in reply to Ben Bristow
    TI__Genius 10040 points

    Hi Ben,

    Please let me know what you find with the autowake timer. The autowake timer duration is adjustable in REG0x8[bits 4-3] and is 1s by default.

    Does the issue still occur if you wait longer after the hardware reset?

    Best regards,

    Alec

  • 0 in reply to Alec Lehman
    Prodigy 10 points

    Hello Alec,

    Stephen here - Ben's software colleague.

    We leave the autowake timer at the default 1s.

    The full device register set before we go into shutdown mode is:

    MUGA>i2c read 1 0 16
    Device=1, MemAddress=0, Result=16 (ok)
    0x61 0x00 0x00 0x28 0x8E 0x5C 0xC3 0x83
    0x48 0x20 0x0D 0x0C 0x10 0xFF 0xFF 0xFF

    where you can see that 

    • TMR_ILIM [0x08] = 0x48 => AUTOWAKE=1 => 1s
    • SHIP_RST [0x09] = 0x20 => EN_RST_SHIP=1 => "2b01 = Enable shutdown mode with wake on adapter insert only"

    I then do the following:

    1. remove power from our device
    2. wait <2s
    3. reapply power to our device
    4. wait 5s (longer than autowake time)
    5. attempt to communicate with the BQ25180.

    I get no acknowledgement on I2C from the BQ25180 on I2C at any point after this.  It requires a further cycle of VIN before it will communicate.  I can talk to other devices on the same I2C bus.

  • 0 in reply to Stephen Parker
    TI__Genius 10040 points

    Hi Stephen,

    Thanks for sharing the register settings. This definitely sounds unexpected. The device should be able to communicate 5s after waking up from shutdown mode.

    How many units are you seeing this behavior on? And for the units where this happens, does it happen every time or just sometimes?

    When power is reapplied to exit shutdown mode, does the SYS rail come up or does it stay low? If you're able to communicate with other devices on the I2C bus, I'd imagine it comes up? This would help confirm whether the device is actually exiting shutdown mode.

    Also, just to confirm, this behavior only involves shutdown mode, right? You mentioned a hardware reset, but that was just to try and get the device to communicate?

    Best regards,

    Alec