We are doing a pre-market production run on a design and have had ~12 failures out of the batch of 40 units where the battery charger side of the IC will not fire up. All the devices for this build are from the same batch, marked:
BZF, TI 741, CJGL and purchased from Mouser Electronics.
The device is acting fine as a pass though from Battery or external power, however we get no charge current or charge status indicator output (CHG) when battery and external power is available. When the device is replaced the system charges the battery correctly, an no abnormal conditions are observed (current consumption etc). The test conditions should be identical, same battery etc.
We have been using this part of quite a few designs with >500 units produced by us, and no particular issues with either production failures or units in the field.
Initially I thought It could be one of the following:
- TS sensing, ruled out as
- battery 10k therm can be measured at pin 1 of the BQ24074
- Doesn’t explain why device swapping fixes it
- Power sequencing
- Previous production did not show any faults with same build methods
Any help you could provide would be greatly appreciated.
Below is a snippet from the schematic, the boards are electrically tested for shorts on VBATT, CHG_OUT_3V_TO_4V2, 5V_MAIN before the circuit is tested.
.
