DIYbanter - View Single Post - troubleshooting method for micro-controller board ?

Eeyore

wrote:

Eeyore wriote:
"robb" wrote :

so i tested by connecting 5V/1A DC source between Vin and
GND-Pin3 and i checked the voltage with DVM between Vout and
GND-Pin3 and i was getting 3.47 V

Pointless. It won't operate correctly with only 5V in.

Agreed.

A linear voltage regulator has to have several volts more on the
input than the output to function correctly.

Some need 1-2V more, others around 1/2V (I think I've seen
LDOs down to 0.2V dropout [i.e. Vout-Vin]).

Sure, I was generalising somewhat for brevity.

As you say the value may vavy from several hundred millivolts for true LDO types
to as much as 3V in rare cases. 2V is typically a safe value to ensure correct
operation.

Graham