I face a need to create a 3.3V pull-up voltage from a 5V supply, but I'm not sure which is the best method to use. The reason I need specifically 3.3V for a pull-up is because I'm "tapping in" to a momentary push-button on another device so I can detect when it has been pressed. The other device runs on 3.3V. But, the other device is not always powered (it is switched under my control), so I need to provide my own pull-up voltage for the button during that time. The only load on the 3.3V will be when the momentary button is pressed, so at most perhaps 10 mA.
Should I use a zener to regulate 3.3V, or a linear regulator?
If I use something like a BZX84 or BZT52, I see that I'll need to provide approx. 5 mA current through it to properly regulate to 3.3V, so I figure a 330 ohm current-limiting resistor should work. One thing I've noted about a zener though is that it will fall out of regulation while the button is pressed, because current will be being diverted through the button and its pull-up resistor (say, 1K) to ground. But then does that even matter? As far as I can see, when the zener current drops, the regulated voltage drops; but all I'm concerned about (and the whole reason for this) is that when the button is off the pull-up voltage doesn't exceed 3.3V, which I don't think it can.
The downside I can see to the linear regulator is it needs more supporting passives - i.e. a couple of caps on the input and output - versus the single current-limiting resistor for a zener diode.
Any advice on which I should use?