Hi,

A brief idea of my Handheld reader is:
1)Using P89C66X as a core micro
2)One 16x2 normal character LCD
3)Powered by battery.
4)One push button for scroll down the menus/display
5)Using Philips MFRC500 chip for the mifare interfaces
6)Build in Mifare antenna on the PCB

I'm not very sure about max. current I need. From LCD datasheet the current is 1.0 mA for typical and 2.0 mA for max.

For the micro, the datasheet wrote the max. current is around 63 mA (if using 20 MHz Xtal)


For the MFRC500, the datasheet wrote the max current is 150 mA.


So I beleives the max current that I need for the devices is the highest one, that is 150 mA, right?


But for the battery, I have two option
1)Using normal 9 Volt battery ( PP3 can style)
2)Using two pieces of 3 Volt Lithium Ion Battery (coin size)

If I choose option no. 1) then I will use 1 Amp 5 volt regulator from ON Semiconductor part no MC7805ACD2T.

If I choose option no. 2) then it will directly connect to the circuit without regulator.


p/s: so my FET circuit was correct?


Thanks

Parif