I am busy developing a low power sensor circuit using a barebone UNO and the nano timer TPL5110 but seem to be having a big problem. I have 2x18650 lithium batteries connected to a TPL5110 which will turn on +- every hour, provide power to the buck/boost controller (i have tried 2 different models with the same result) and in turn provide power to the UNO and sensors then read sensor data and based on the result perform a few different functions and the UNO will signal the TPL5110 to turn off. In theory this should be a very easy project, however the LED on the TPL5110 simply flickers when powered on, and only produces 1.5V on the DRV pin. After some investigation and connecting the circuit to my lab power supply, if you slowly increase the voltage on the power supply from 0V to about 3V, the circuit starts working and the LED on the TPL5110 remains on, but if you turn off the power supply and turn it back on again the LED just blinks and you only have 1.5V on the DRV pin again.
I have no idea why this is happening and would like some guidance on this if possible.
You need to draw the circuit and show it to us, far too confusing otherwise.
For instance you say "I have 2x18650 lithium batteries connected to a TPL5110" which to many of us would imply you have a supply of 2 x 4.1V = 8.2V connected to a device that has a Vmax of 5.5V, which is not good.
If that is how you have it connected, a circuit diagram would make it clear.
The sensors require 5V. I have tried testing them with 4.2 from a fully charged 18650 cell and they don't work well. The Vin on the sensors is 4.5min and 5.5max.
U1 is the MT3608 buck/boost converter and U5 and U6 are PNP mosfets to turn the sensors on and off.
The battery provides power to the TPL5110, when the TPL5110 turns on (every 2 hours) power will be sent to the buck/boost via the DRV pin on the TPL5110 until the Uno signals the TPL5110 to turn off again. This is an ideal circuit for me as i don't need the circuit to do anything during the 2 hours that it is off. The idle current of the TPL5110 is only 35nA as opposed to the idle current of the buck/boost which is around 1.5mA. This is why I let the TPL5110 control the power from the battery. I hope this makes sense.
The TPL5110 is the breakout from adafruit. The DRV pin on the breakout is powered by a mosfet triggered by the nano timer ic on the breakout board. The strange thing is that when powered from a 5V desktop power supply without the buck/boost module the circuit works 100%. There must be some issue between the TPL5110 and the Buck/Boost. I have put the output of the DRV pin from the TPL5110 breakout board on a scope and it is a very stable supply so i'm not sure what else to try. I have also added smoothing caps before and after the TPL5110 and no difference.
It would help if the schematic labelled the parts appropriatly, there is a world of difference between a TPL5110, which is a Ti sot6 IC, and a breakout board that has a TPL5110 and a pile of other components.
I dont know the Adafruit board, if your having problems with it, perhaps ask them ?
I managed to find a solution. I placed a suitable diode between the DRV pin of the adafruit TPL5110 breakout and the Vin pin of the buck boost. Works a charm. Thanks for your help.