Help Identify another Fan Control IC

[Harimake]

I just ran into another fan control circuit I don't recognize.
It's a 5V DC fan, but it gets +12v DC power from the positive leg of the power supply.
Looks like the ground is going through an IC of some sort. I have two units with different markings for the IC: JC1A or I(or J or L)1A
SOT-23 package.

Pin 1 of the IC goes into a GPIO pin on the PSOC4 over a 2.2k 1% resistor.
Pin 2 goes to a PSOC4 VSS.
Pin 3 connects to the fan motor and a 100uF 25V radial capacitor.

The fan only turns on when I apply heat to the SOT-23 IC (or in that general area). And when it does, I only see about 3V on the fan power pins, which is normal.

My initial thought was that it's just a simple fet and they control voltage to the fan with a PWM from the PSOC4.
But it doesn't seem to be the case as the fan only turns on when the heat is applied to the IC. Which makes me think that it might be a thermistor circuit of some kind.

Please point me in the right direction. Thank you!

[fzabkar]

I would think that a P-channel MOSFET or PNP transistor would be a likely fit, although capacitor C1 seems to contradict this.

[Harimake]

C1 throws me off also. When I measure voltages on a working unit, I get about 3V across the fan pins and about 9 volts across C1. When the fan is off, I get 12v across C1 and 0v across the fan.
What about an NPN darlington transistor being the mystery sot-23? then the 2.2k resistor directly to the base makes more sense.

[abdulbadii]

Sure there's no R or thermistor etc. around low side, as it'd apply 12V on 5V M ?

[fzabkar]

If the transistor is being PWM-ed, then it would need to discharge the relatively massive capacitor every time it was switched on.

That said, I can't see the component as being a linear regulator, as it would need to dissipate 3 times as much power as the fan (9V versus 3V).