Go Down

Topic: Dual LDO to generate 5V on Arduino UNO (Read 468 times) previous topic - next topic

SteelyD

Sep 26, 2015, 03:11 am Last Edit: Sep 26, 2015, 03:47 am by SteelyD
Does anyone know why two DC-DC converters are used to make 5V from Vin on the Arduino UNO?  I've seen another thread that said it was an "alternate parts" selection (not clear from the schematic), but Vin (which is the net straight after D1) is on two devices.  One is clearly the MC33269 LDO in the ST package, but the other is an 8 pin device labeled 103.  Is that really a second regulator (the MC33269 in the D package)?  What is the point?

aarg

Does anyone know why two DC-DC converters are used to make 5V from Vin on the Arduino UNO?  I've seen another thread that said it was an "alternate parts" selection (not clear from the schematic), but Vin (which is the net straight after D1) is on two devices.  One is clearly the MC33269 LDO in the ST package, but the other is an 8 pin device labeled 103.  Is that really a second regulator (the MC33269 in the D package)?  What is the point?
You mean the 3.3V reg?
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

Wawa

You might be mixing up more than one thing.
There is a 5volt regulator and a 3.3volt regulator.
The 3.3volt regulator on my board is close to the electrolytic caps, and has 5 pins.
There is also an 8-pin LM358 double opamp in that area.
But an 8-pin "103" is likely a 4x10k resistor array.
Leo..

SteelyD

You mean the 3.3V reg?
If you look at the UNO schematic (https://www.arduino.cc/en/uploads/Main/arduino-uno-schematic.pdf), in the upper right there are two regulators between Vin and +5V, that's what I was talking about.  I don't understand the purpose.

I see the 3V3 regulator labeled as U2 on the left-center.  Not talking about that.

CrossRoads

The 2 regulators allow for picking of one or the other, either will fit on the pads on the board.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Go Up