I have PIC18F45K20 which idealy needs 3.3V and i need to power it by 4x 1.5V alkaline battery that's 6V input voltage.
I used zener voltage regulator as shown here:
Vz = 3.3V and I used 25 Ohm resistor in serie with diode.
And i get output voltage of 4.3V!!!
How is it possible? Did i make a mstake somewhere?
However, although 68 mA may be above the current specfied with nominal zener voltage of 3.3 V. You have to review the datasheet, manufacturers are using quite different values.
I think, it's a bad idea to use a zener regulator with batteries, beacuse it considerably reduces their lifetime. An integrated 3.3V voltage regulator would be much better, consuming only a small quiescent current and the current actually required by the load. For highest efficiency, a switch mode converter will be recommended, but I guess, it's not reasonable in your case.
It's even worse, you don't just lose the voltage, but also additional current to operate the zener regulator. But I think that a linear regulator will be appropriate for most designs with moderate current demand, e.g. up to 50 mA. A switch mode supply can however raise the efficiency from 55% to 80-95%, depending on the switcher perfomance.
Why reinvent the wheel, a simple regulator like LM1117 will have better regulation, takes less space and as a bonus you get current limiting and thermal protection
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