voltage regulators

[lrjaj0000]

Hi
can someone tell me how works voltage regulator? and why you need MOSFET??

 

[4pyros]

What is that from?

 

[ronsimpson]

I believe the MOSFETs job is reverse battery protection.

 

[Dragon Tamer]

Not sure what the regulation voltage is for the IRU1205 because the variant isn't specified in the schematic.

The variation is as follows:
IRU1205CL= Adjustable
IRU1205-18CL= 1.8V
IRU1205-25CL= 2.5V
IRU1205-28CL= 2.8V
IRU1205-30CL= 3.0V
IRU1205-33CL= 3.3V
IRU1205-36CL= 3.6V

The drop out voltage is between 10mV and 400mV depending on the amount of current you are drawing.

Pin 1 is the input voltage (max of 10V)
Pin 2 is the ground pin
Pin 3 is the enable pin
Pin 4 is the adj/Cbp - either the voltage adjust pin for variable regulator version, or the bypass capacitor for all other versions
Pin 5 is the output

Here is the link to the data sheet:
http://www.datasheetcatalog.org/datasheets2/41/41896_1.pdf

I'm going to agree with ronsimpson on the MOSFET, I'ts probably there to protect the battery although a regular diode could have done that job just as well. I thing the MOSFET is a redundancy and unless the designer intended to use it to shutdown the circuit, you can probably get away with not using it.

 

[ronsimpson]

A diode has 0.7 (or 0.4) volts loss. When power is coming from a 6V (or 3V) coin cell this is major.
The MOSFET can have very little voltage loss.

 

[Dragon Tamer]

Depending on the load, I was assuming an unknown load and a signifigant input voltage in which case a didode may be more appropriate.