What formulas do I need to use to design a voltage regulator circuit for a zigbee radio?

I've written the code for my zigbee radios, but now I face the obstacle of getting them onto a carrier board to allow access to VCC, GND, TX, RX via a 4 wire connector.

The supply voltage is 3.712 DC and the module takes 2.1 to 3.6 volts.

I know I need to use a voltage regulator suited for this input/output voltage and that there needs to be capacitors on both sides, but I haven't been able to find a formula to figure it out.

• Google for a 3.3V low drop out regulator. A typical circuit will be in the data sheet. If you are using Arduino, use the 3.3V pin to power it. – geometrikal Mar 29 '13 at 5:06

One Option...

The LM317T is a great place to start as it is basically indestructible and stable in the face of almost anything a student or hobbyist might do to it.

The part I recommended is the TO-220 packaged version. It's big and easy to clip or solder to.

Design Data

If you follow my link and click on "Documents" in the left-hand menu-bar you'll have instant access to all the datasheets and related documentation. On page 9 of the datasheet there is a whole section discussing tuning (set resistors and input/output capacitors).

If the voltage is already regulated (to four significant figures: 3.712. Really?), and the module needs anywhere from 2.1 to 3.6, the upper end is just a fraction of a volt away. You can drop about 0.3V with a Schottky diode in series, and you're in range.

• @Justin -- In my answer, you asked for a regulator, so I gave you a regulator, but this is probably a good way to go especially since all the major "ZigBee" (really IEEE 802.15.4) radios have built in regulators and run the analog at 1.8V internally, so the noise created by the diode won't matter. There are some problems with this approach that you'll have to watch-out for. If you post a system-level schematic we can help you avoid them. – DrFriedParts Mar 29 '13 at 5:37
• Unfortunately, I don't have a oscillator and I'm not sure if I need one. The radio is being powered by a thermostat. I took my Greenlee CM-450 multimeter, measured the voltage, and saw a constant 3.712 volts from the leads connected to the thermostat board. – Justin Manuel Mar 29 '13 at 14:13
• Also, because of the tight squeeze inside the thermostat, I need to try and stick with SMD components for the carrier board. I've seen another carrier board for the same thermostat use an MCP1703, but I don't know what the capacitor values should be. Thanks for the help guys! – Justin Manuel Mar 29 '13 at 14:15