Scenario:
I have a design for a low power device which uses 3x 1.5V (so 4.5V) AA batteries to be powered. On 99% of the time that it is running, it draws around only 1mA current. For the 1%,it can draw up to 200mA of current thanks to a vibration motor. I have noticed that my battery voltage drops during this time. The way the motor is controlled is done by a microcontroller. I have also noticed that the microcontroller resets itself as the motor tries to start spinning. It seems to be caused by the voltage drop on the cells.
I have decided to add a coin cell battery as a supplementary voltage source so that the microcontroller will not reset during this time. I tried to use a MOSFET for this circuit so that the ground of the coin cell can be connected to it and prevent the coin cell powering the microcontroller by itself when the cells are not present. However, I seem to have misunderstood how a MOSFET works in this case and wired it incorrectly where no current would flow at all from the main cells to the microcontroller. In this case, it seems the coin cell is always trying to power the device all the time.
Some info:
R19 is 15ohm resistor
VMAIN is 4.5V from 3 cells
Q5 is a BSS214NWH6327XTSA1
B1 is a CR2032MFRRV
What do I need to change for this? I just want the AA batteries to be the main voltage source, and the coin cell will only power the microcontroller (to prevent a reset) when the voltage on the cells drop to some threshold (lower than the coin cell?). Is this possible?
I have a design for a low power device which uses 3x 1.5V (so 4.5V) AA batteries to be powered. On 99% of the time that it is running, it draws around only 1mA current. For the 1%,it can draw up to 200mA of current thanks to a vibration motor. I have noticed that my battery voltage drops during this time. The way the motor is controlled is done by a microcontroller. I have also noticed that the microcontroller resets itself as the motor tries to start spinning. It seems to be caused by the voltage drop on the cells.
I have decided to add a coin cell battery as a supplementary voltage source so that the microcontroller will not reset during this time. I tried to use a MOSFET for this circuit so that the ground of the coin cell can be connected to it and prevent the coin cell powering the microcontroller by itself when the cells are not present. However, I seem to have misunderstood how a MOSFET works in this case and wired it incorrectly where no current would flow at all from the main cells to the microcontroller. In this case, it seems the coin cell is always trying to power the device all the time.
Some info:
R19 is 15ohm resistor
VMAIN is 4.5V from 3 cells
Q5 is a BSS214NWH6327XTSA1
B1 is a CR2032MFRRV
What do I need to change for this? I just want the AA batteries to be the main voltage source, and the coin cell will only power the microcontroller (to prevent a reset) when the voltage on the cells drop to some threshold (lower than the coin cell?). Is this possible?