I have a PCB in production which uses a TPL5111 to flash an LED about every 2.5 seconds. Each flash is about 5mS long and the LED uses about 13mA during that time, so the average current draw due to the LED is about 26uA. The AP7381-50SA-7 voltage regulator has a quiescent current of about 2.4uA. The typical current draw of the TPL5111 at 0.035uA is insignificant. Most PCBs with this circuit pull about 30uA, which gives good battery life. Unfortunately, I discovered that some TPL5111 chips draw far more current, from 1200uA to over 4000uA, which reduces the battery life by 100x or so. I'm sure it is the timer chip that is the problem, based on the problem following the chip when I swap them between boards.
I have three boards built in early 2020 which work as expected, and 18 recent boards which are also OK. I have five sample boards from various PCB batches from the timeframe in between, of which four draw too much current (1200uA, 1200uA, 2230uA and 4000uA). All of the chips are marked ZFVX on top. I pulled a few chips off of the boards to check the marking on the bottom. So far the ones marked 84H have all been good. Of those marked 87N, two have been bad and one good.
I'll be able to test a new batch of PCBs soon and can provide more test results then, but in the meantime I would be interested in any suggestions about what the cause might be, things I should test, problems in the design, or anything else which might lead to identifying the cause.
If the schematic below isn't visible, it can also be found here.
Thanks,
Steve