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Alternative to inverter and switch using three MOSFETs?

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ulrikp

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Hi,

I need help finding a component which can replace a PMOS and two NMOS transistors. I have a GPRS system which is woken up once a day by an RTC. It is important that the GPRS system switches off completely due to battery issues. When the RTC alarm sets off, VIN is pulled from high to low. I have an inverter consisting of a CMOS pair, and the system is switched on by the second NMOS (shown in image).

For now, I am planning on using two Fairchild transistors but would like to boil down the number of components. My question is, does anyone know of a single component which can replace the three transistors? Or could I possibly set up the inverter/switch system in a better way?

Best regards,
U
83_1267488010.jpg
 

Why wouldn't you connect Vin straight to the last MOSFET .. see attached picture ..
It should work too ..

Rgds,
IanP
 

Depends on VIN and required output high and low signalling levels. Assuming 3.3V logic input and a 5V open drain/pull-up, a
non-inverting level-conversion seems necessary. In this case you can
- replace the first MN by a pull-down resistor
- use an open drain or tri-state output "single gate" logic IC

P.S.: IanP's solution works, if VIN level can be inverted at will. I guess, it can't.
 

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    ulrikp

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Thanks for the replies - I might try the tri-state logic solution! My RTC is a DS1337 in which VIN level cannot be inverted, ie. it goes from 3.3V to 0 when the alarm goes off.

Best regards
 

ulrikp said:
I might try the tri-state logic solution!
Click to expand...
However you decide, I think all you need you can find in a single MC14007UB chip.
 

You might be able to find one of the Rohm "complex" transistors to do the job:

**broken link removed**

Keith.
 

My RTC is a DS1337
Click to expand...
In this case, you don't need a driver. The DS1337 nINT output is open drain and can drive 5V directly without a driver. If the
current capabilty (3 mA) isn't sufficient, you can connect a pnp BJT in common collector configuration as a current booster,
assumed 0.6V voltage drop above ground is allowed for the control input.
 

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