using zener diode vs the LM317 in making the voltage regulator for uc

[varunme]

is it using Zener diode or using a LM317 for making a voltage regulator for uc ?

 

[Mehrshad74]

Zener diode:
-low cost
-more loss
-less accuracy
-less stability

lm317:
-more cost
-more accuracy
-more stability

 

[qwertyuiop415263]

Better to use LM7805 regulator to give 5v to microcontroller.Also use decoupling capacitors at input and output.

 

[Ahmmed Razu]

lm7805 is better than all others.as lm317's output voltage is resistance value dependent so if the temperature changes the value of resistance changes as well as output voltage.you should use decoupling capacitor better ceramic which will store lower amount of charge.

 

[RetroTechie]

Well that depends on what type of resistors you use, and for a uc 5V doesn't need to be 5.000V :grin:

With a 7805 you simply need 2 external parts less than with an LM317. And given how cheap + robust 7805 & friends are, there's really no point in using a zener diode as power regulator (very few specialist cases aside maybe). Cooling is also much better & easier.

 

[alexan_e]

With 7805 or LM317 you get short circuit and overheat protection as a bonus (compared to the zener solution)

Alex

 

[varunme]

The 5V uc doesnt be an issue , the 3.3V is the issue , is there a 7805 analogue for the 2V, 2.5V , 3V and 3.3V ?

 

[alexan_e]

2v and 3v are not usual values so you 'll have to use a variable regulator but for 2.5v and 3v3 there are already fixed regulators, for example LM1117 **broken link removed**

Alex

 

[varunme]

is LM1117 , easily available ?

 

[alexan_e]

Yes it is widely available, there are many clones too like AMS1117 or LD1117 or LT1117 etc.
I have used the sot23 packages for my ARM board (3.3v and 1.8v) but there are also TO220 versions available.
I have bought mine from ebay

Alex

 

[mrarslanahmed]

7805 can withstand more change in voltage (dv/dt) as compared to zener