Hello,
I designed a new product that will use a single AAA battery cell to generate a 3.0V regulated power rail. This product will send some sensor data over the LoRaWan network and deepsleep the rest of the time.
I use the TPS610985 to generate the 3.0V main power rail as it seems to fullfill my power requirement.
The input voltage is in the 0.8V to 1.5V range and consumption is about 100mA max during Tx transmit. Deepsleep power consumption is about 1µA.
I build 5 prototype board and unfortunately the TPS610985 isn't working on 2 boards.
Input capacitance is 2uF and output capacitance is 41uF (10uF close to the chip with additional decoupling capacitors close to each critical components).
Startup time is about 7ms and input current limitation is set to 2A.
The TPS610985 start the boost converter when output voltage reach 1.8V as expected. I didn't expect this input voltage drop with 2A current limitation.
I measured the output voltage when startup fail. (1st channel - yellow) vs input voltage (2nd channel - blue).
The power supply is locked and the output never reach the expected 3.0V. As output voltage is below 1.8V, the boost converter never turn on.
If I increase the input voltage to about 2.3V, the boost converter will start and I get the 3.0V output voltage as expected. Then it works even if the input voltage is decreased to 1V, but it will fail again if I power cycle the input power supply.
Could you please give me some information about what's going on when the TPS610985 is not able to start ?
Regards
Noel