On/Off Soft Latching Switch with uC Operating at 3V3

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Hi everyone,

I wanted to share my schematic for on/off soft latching switch used with a uC where the button also serves as an input to the uC and the circuit can be shutoff by the uC:



Datasheets:
DMG9933USD (dual PMOS): https://www.diodes.com/assets/Datasheets/ds32085.pdf
PMV16XNR (single NMOS): https://assets.nexperia.com/documents/data-sheet/PMV16XN.pdf
RS1GTR (diode): http://www.smc-diodes.com/propdf/RS1A-M%20N0988%20REV.A.pdf

As you can see, the power comes from a battery source (~3 to 4.3 V) and the PMOS that controls the power signal will only turn on once the switch button is pushed and the gate of the PMOS (G1) gets grounded. Once the PMOS gate is grounded (or, almost grounded to ~0.6 V due to the diode), the circuit will turn on which will also turn on the DC-DC down converter/buck booster (not shown here) which provides constant 3.3 V. Note that this IC is a single package with both down conversion and boosting capabilities. Since the 3.3 V is now provided for the circuit, the NMOS is turned on and latches the PMOS gate (G1) to ground.

Furthermore, I wanted the button to have multi functioning purpose so the power switch button can also act as an input to the uC. Since the battery power source can go up to 4.3 V, I used another PMOS to provide HIGH/LOW signal to the uC instead of providing HIGH/LOW signal in the same level as the battery because the uC operates at 3.3 V. This is also the reason why the gate of the NMOS is pulled high using 3.3 V instead of battery voltage level since this route has to go to the uC to allow the uC to turn off the circuit whenever required.

The schematic design first started with Dave's video about the simplest soft latching switch () and I became interested in incorporating into my next design with a uC. I browsed around and found this schematic: http://www.instructables.com/id/Soft-Latch-Power-Switch-Ardweeny/. The schematic from Instructables had an extra diode I didn't think was needed and I made changes from using through-hole components to SMD. I also made other changes so that I can use it with a 3.3 V uC.

Any feedback regarding the design would be appreciated!