P type Mosfet as a switch for power supply

[robotboy]

Hi,

I want to use a MOSFET to control a 3.3V power supply. Please tell me a SMD part number that can fit my requirement. A small schematic would be very much appreciated.

Thanks in advance!

 

[D.A.(Tony)Stewart]

Any time you need a switch, you need to specify load regulation error such as 2%, 1% or 0.01% which affects output accuracy.
Load regulation also affects ratio of efficiency for switch loss vs load loss, then you need to perform heat calculations.


Next you need to consider faults if short circuited and what protection you have, must protect the switch too before it burns up.

If load is 1A@3.3V a 1% load regulation means the source and switch impedance adds up to 1% of the load or 1% of 3.3 Ohms equiv R.
Now the power supply must have some drop in voltage with rise in current, so determine how much margin you have to load regulation you desire.
If regulator has a load regulation of 0.5% then your switch must be less than 0.5% of max load.
In this example the switch RdsON value would be 0.5% of 3.3 Ohms or 3.3/200=16.5 milliohms

Next you need to specify the control voltage . 3.3? 5? 12V? There are many thresholds from <1 to >2.5 and the RdsON gets lower with higher voltages so they may be rated at 3V, 5V 10V etc. for the promised RdsON switch resistance. Speed is not an issue as well as rated voltage if just switching 3.3V

Big distributor websites and drop down search filters. Learn to use them to choose parts and specify the box for [in stock] and drop down Package for SMT

Mouser.com, Digikey.com etc..... use web search on parameters or from main menu of products... Discrete Semiconductor Products> FETs - Single (34960 items) then use CTRL key + Click or click then select end with shift key + click to select multiple or a range of values in each drop down menu.


Using my above "assumptions" or your missing design Specifications..
I picked range from 8 to 16.5 mOhm ( Click 1st 8 >shift & clicik on last 16.5)
and Mounting Type= "Surface mount"
check box [ ] in stock ( most popular type) and enter Quantity (1) .... 1000? then SEARCH
results can be sorted up down by click { ^ v } on any column

You can even export that page with 500 items on 1 page to excel at the bottom of D-K site search.
Price for 1 ranges from 0.46 to $1
Results matching criteria: 1,912




e.g. https://www.digikey.com/product-sea...onductor-products/fets-single/1376381?stock=1