Mosfet Driver Chip - Electronic Circuits Projects Diagrams Free

2camjohn · 8th January 2005, 02:59 PM

I have just changed from using power transistors to those Fet chip thingies, specifically the TC4427 dual mosfet chip.

Before I start designing my circuits I just want to check with you good people that I have the right idea when wiring it up.

Below is how I plan to wire each mosfet...

Will this work?
Am I missing anything?
Do I need to account for back EMF, or is it done on the chip?

Thanks
John

Styx · 8th January 2005, 03:08 PM

err correct me if I am wrong But are you trying to use this TC4427 to drive the motor?

The TC4427 is a MOSFET driver. Ie the output of which you connect to a power MOSFET. This ensures that there is a low-impedance gate-voltage source to the MOSFET Gate.

I suppose you could use it to source 1.5A to the Motor. BUT this has been specially designed to provide pulses to 1.5A to the gate of a MOSFET not continuos load. It doesnt even state any continuos load conditions

williB · 8th January 2005, 03:34 PM

http://ww1.microchip.com/downloads/e...tes/00799b.pdf

John , this is a typical configuration for the TC4427 from the microchip site..

Russlk · 8th January 2005, 10:30 PM

The power dissipation rating of the Pdip is 0.73 watt, the output resistance is 7 ohms (typical). 7*1.5=10.5 watts. The chip would smoke in a fraction of a second.

2camjohn · 8th January 2005, 10:52 PM

Right,

Im am trying to drive a solenoid and a small motor with this mosfet chip.

ops:

The current drawn is under 1amp.

I didnt know I needed a mosfet aswell that kind of defeats the purpose!:?

I thought this would be simpler than using transistors with the extra circuitry.

Anyone know of a chip like this one that will do the job??

Thanks
John

Oznog · 9th January 2005, 08:04 AM

Quote:

Originally Posted by 2camjohn

I didnt know I needed a mosfet aswell that kind of defeats the purpose!:?

I thought this would be simpler than using transistors with the extra circuitry.

Anyone know of a chip like this one that will do the job??

You generally do not need a MOSFET driver at all for this circuit.

The PIC will output 5V (assuming you have a 5V Vdd). Most MOSFETs will drive 1 amp fine with this Vgs, although the rdsOn may be a bit high. Check your spec sheet for the MOSFET you have. Many MOSFETs are designed with a lower threshold so they turn on very strongly at 5V or even 3V, these are termed "logic level MOSFETs".

MOSFET drivers are a special purpose kind of thing. Generally we just hook up the MOSFET directly.

2camjohn · 9th January 2005, 01:21 PM

Thankyou,

It seems I have misunderstood what the chip is for.
I thought it was a chip with mosfets on it, not a chip to operate mosfets.

Can you buy a dil chip with a couple of mosfets on it, with the protection diode and stuff?

thanks
John

2camjohn · 9th January 2005, 03:09 PM

Here is the website where I got the idea to use these chips.
http://www.robotroom.com/HBridge.html

I know not to believe everything I read on the internet, but the guys site has loads of good info on it. Should someone contact him and tell him his idea is wrong???

Is it definately a bad idea to use this chip to power a small motor and a solenoid.
The circuit runs of a 6V battery which is only rated to 1A, so with a heatsink it wouldnt fry the chip??? Would it???

williB · 9th January 2005, 03:40 PM

david cook has a Warning posted on his site ..
it reads
Direct motor driving with this chip is only possible for motors that draw less than 100 mA (4427) to 150 mA (4424) under load.
so he is talking very small motors i suppose..

2camjohn · 9th January 2005, 03:57 PM

Thanks

Can somebody suggest a couple of mosfet that will drive my <1A motor and solenoid but does not take up loads of room like my huge TO220 mosfets do?

Thanks
John

Russlk · 9th January 2005, 04:35 PM

Agood way to find parts like that is DigiKey website (www.digikey.com). If you put a keyword in the search, like "mosfet", it will give you a selection of parameters. Choose one at a time until you get the part you want. I found a N-channel good for 1.2 amps in SOT-89 package: ZXMN6A07Z.

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8th January 2005, 03:08 PM	(permalink)
Styx	err correct me if I am wrong But are you trying to use this TC4427 to drive the motor? The TC4427 is a MOSFET driver. Ie the output of which you connect to a power MOSFET. This ensures that there is a low-impedance gate-voltage source to the MOSFET Gate. I suppose you could use it to source 1.5A to the Motor. BUT this has been specially designed to provide pulses to 1.5A to the gate of a MOSFET not continuos load. It doesnt even state any continuos load conditions

8th January 2005, 10:30 PM	(permalink)
Russlk	The power dissipation rating of the Pdip is 0.73 watt, the output resistance is 7 ohms (typical). 7*1.5=10.5 watts. The chip would smoke in a fraction of a second. __________________ see my website: www.geocities.com/russlk

8th January 2005, 10:52 PM	(permalink)
2camjohn	Right, Im am trying to drive a solenoid and a small motor with this mosfet chip.ops: The current drawn is under 1amp. I didnt know I needed a mosfet aswell that kind of defeats the purpose!:? I thought this would be simpler than using transistors with the extra circuitry. Anyone know of a chip like this one that will do the job?? Thanks John __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

9th January 2005, 01:21 PM	(permalink)
2camjohn	Thankyou, It seems I have misunderstood what the chip is for. I thought it was a chip with mosfets on it, not a chip to operate mosfets. Can you buy a dil chip with a couple of mosfets on it, with the protection diode and stuff? thanks John __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

9th January 2005, 03:09 PM	(permalink)
2camjohn	Here is the website where I got the idea to use these chips. http://www.robotroom.com/HBridge.html I know not to believe everything I read on the internet, but the guys site has loads of good info on it. Should someone contact him and tell him his idea is wrong??? Is it definately a bad idea to use this chip to power a small motor and a solenoid. The circuit runs of a 6V battery which is only rated to 1A, so with a heatsink it wouldnt fry the chip??? Would it??? __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

9th January 2005, 03:40 PM	(permalink)
williB	david cook has a Warning posted on his site .. it reads Direct motor driving with this chip is only possible for motors that draw less than 100 mA (4427) to 150 mA (4424) under load. so he is talking very small motors i suppose..

9th January 2005, 03:57 PM	(permalink)
2camjohn	Thanks Can somebody suggest a couple of mosfet that will drive my <1A motor and solenoid but does not take up loads of room like my huge TO220 mosfets do? Thanks John __________________ The first rule of mstechca club is do not talk about mstechca club. http://www.electro-tech-online.com/s...induser&u=1245

9th January 2005, 04:35 PM	(permalink)
Russlk	Agood way to find parts like that is DigiKey website (www.digikey.com). If you put a keyword in the search, like "mosfet", it will give you a selection of parameters. Choose one at a time until you get the part you want. I found a N-channel good for 1.2 amps in SOT-89 package: ZXMN6A07Z. __________________ see my website: www.geocities.com/russlk