ahmedragia21

audioguru ,Try a few hundred of them and pick the most sensitive one.

i think this is not a good engineering soultion

Nigel Goodwin

Easy answer, dump the crap Atmel and move to a PIC!

I'm also amazed to hear how poor the Atmel is.

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ahmedragia21

Nigel, how its different between sourcing current and sinking , is that not happens in the same transistor output pin ? In other words, why at VOH it sources so little current at uA and VOL ( sink) it sinks 1.3 mA .. ?

I wonder also about blinking an LED . According to the specs it only sink 1.3mA or so so i cant interface even an LED to it ?? or we read the specs wrong ?

BeeBop

I was looking for a description of the pins (data sheets for better parts include a circuit diagram of the ports) in the data sheet I have locally, but couldn't find it! That diagram would explain why the chip can sink more than it can source...

I would agree!

However, I had to go looking at data sheets after reading this thread.

Yes, it looks like most of the 8051 -52 atmel chips don't give much for drive, but some of the smaller x2051 x4051 can sink 10 mA, and can source peanuts, like the OP's chip.

To be fair, though, the AVR is much better, and close to the pic sink or source 20 mA per pin. Some AVRs provide up to 400 mA total, but most are like the pic: 200 mA total.

I had a hard time finding what I wanted in the Atmel data sheets, and much prefer Microchip data sheets. (Some posters were recently whining about microchip data sheets, I think they should give these a go!)

audioguru

The PIC is made with high speed Cmos the same as in 74HCxx logic ICs. An output has a max allowed sink or source current of 25mA and can fry the IC with a typical unlimited current of about 60mA.

Maybe the Amtel is made with antique MOS.

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Uncle $crooge

Roff

Oops! Too much wine, I guess!

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Ron

Roff

Do you have access to a 2N7000? You can use one as a level shifter, or buffer, to drive either the TIP120 or the IRF540.

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Ron

colin mac

A logic N-mosfet turns on fully at 5V?
So why not use one of those?

ahmedragia21

I've a question , regarding to the datasheet it cant source more than 60uA , is this means i should use a transistor which its base has a min for e.g 120uA to saturate ?

Roff, sorry we dont have this transistor at the egyptian market

audioguru

No, you need a transistor that saturates with a base current of only 60uA.Then the transistor's output current is only 1.2mA. It can drive a transistor that saturates with an output current of 24mA that can drive a darlington transistor.

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Uncle $crooge

Roff

Read my previous posts. I already suggested that. He says he doesn't have access to the one I suggested. It is likely that he will not have access to any you could suggest.

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Ron

Roff

Since 89S52 is a CMOS part, its outputs should swing rail-to-rail with no load (the datasheet says 0.9*Vcc @ 10uA source current). The sink capability is 1.6mA at 0.45V, so you should be able to use a PNP as as a buffer. See below.

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Ron

Hero999

A typical IRF540 will pass 20A with the gate at 5V so I don't think he'll have any problem with it passing 3A, even with a bleow average MOSFET.
http://www.irf.com/product-info/data...ta/irf540n.pdf

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Mikebits

What ever happened to VN10K's. I always found them to make great switches.

Roff

Ahmedragia21, how many of these are you going to build? A good engineering solution is not required for a one-off. If you are going into manufacturing, then your concern is valid. However, if you are going into manufacturing, you shouldn't be concerned about your inability to find a local source.

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Ron