Hello, I am designing a battery-powered device with ultra low power requirements. The TPS610986DSER step-up is utilized for generating digital 3.3V supply from 2x alkaline or lithium AA cells i.e. the overall input voltage range comprises 2.4-3.6V. In normal operation, approx 100uA is driven form the batteries, however, a mode with temporarily larger current consumption of about 40mA exists. The switch in TPS610986DSER is not utilized and analog 3V supply is generated by another stand-alone LDO set behind the step-up. My problem is that at lower battery voltages, the TPS610986DSER will not properly boot, driving hundreds of mA from batteries while generating less than 1V at output. It seems that any not-as-large resistance (e.g. a PTC fuse or Schottky diode) between battery pole and TPS610986DSER input causes voltage drop at switch-on, which prevents reaching step-up input voltage for proper booting. The problem is also always present when a mA-meter is inserted into the battery circuit (the mA-meter is also equipped with a fuse in its inner circuitry).
I wonder if this problem is known for you and what solution would you suggest. Particularly fatal is the fact that such device can be drawing 300mA from battery without informing the user - power to uC is not present, there is no power good flag etc. A device which shall work for years will be useless in couple of hours!
