This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25155: Issue reading DeviceID from register 0x6F when VIN is removed

Part Number: BQ25155


We are currently experiencing an issue in which the BQ25155 does not properly respond to a request for I2C register 0x6F. Normally, the device responds with 0x35. However, when VIN is applied for a brief moment to bring the device out of ship mode, then quickly removed, we notice the device responds with the value of 0x19 at reg 0x6F. The 0x19 response is confirmed with external scope sniffer decode as well.

This issue seems very similar to BQ25155: I2C reading operation problem

This issue is deterministic and can be replicated with the following steps:

  1. Put the BQ25155 in to shipmode
  2. Apply 5V to VIN for a brief moment to bring the device out of shipmode
  3. Wait for a short time (20 secs)
  4. Apply 1.8V to VIO
  5. Apply pull up to VIO on SCL and SCA
  6. Wait 100ms
  7. Apply pull up to VIO on /LP
  8. Wait 2ms
  9. Request reg 0x6F
  10. Read 0x19

When VIN is steadily applied and never removed in step #2 above, then 0x35 is read from reg 0x6F in step #10.

We have duplicated this issue across several duplicate devices. We have not yet reduced the issue to a minimum necessary circuit yet, but I am sure we will get there eventually.

I just wanted to reach out and see if there were any thoughts on why we might be seeing this or published part errata that we could download.

Thank you,


  • Issue Resolved.  Our jig was adding just enough additional capacitance to cause a bit to not be registered.  Issue can be resolve by either decreasing the pull up resistance for SDA or removing the device from the Jig.

    Sorry for the confusion.