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Is the 4066 suitable for power switching?

Hi, I'm using a 4066 quad switch to turn on and off 2 devices, an oscillator and a smart card, both of which accept 3.3V. I'm wondering if the 4066 is capable of driving enough current, because my voltages seem to drop on the output side even though oscillators/smart cards don't really draw much power.

I measured the various pins on the 4066. My control signals are 3.3V, and the inputs are also 3.3V, but the output to the osc is only

2.9-3.0V while the output to the smart card is only ~2.8V. When I remove the smart card the output jumps back to 3.3V. What's wrong here?

Thanks!

Reply to
galapogos
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galapogos a écrit :

RDSon. Read the datasheet. There are specialized power supply switches and the 4066 isn't one at all.

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Thanks,
Fred.
Reply to
Fred Bartoli

The 4066 has a series resistance which might be why your having problems. Maybe you could try some transistors on the output.

Regards

AJ

Reply to
AJ

Thanks. I read the datasheet but no Ron was given for 3.3V. I guess I can extrapolate that from the 5V figures. Anyway, are there any generic switches that work for power switching? I don't expect anything more than 60mA.

Reply to
galapogos

If you're switching a 3.3V rail with a 3.3V signal and all grounds are common you can just use a PMOS FET. It's basically what you'd be getting from a specialized switch, and it's (probably) cheaper and (maybe) smaller.

If you can stand a bit of drop (less than 0.2V) you could use a PNP transistor. Zetex has some low VCEsat devices in NPNs and may have them in PNPs as well -- but why not use a FET?

You could also consider a 74ACT4066, or just a 74ACTxx buffer ('06?). These will have lower on resistances than a plain old 4066, and may be enough.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

yep, but if uve only used one of the switches maybe putting them all in parallel might give you a bit more voltage.

Colin =^.^=

Reply to
colin

ll.

Hi,

I tried using a 2N930 NPN transistor with the collector wired to the oscillator ground, the emitter wired to ground, and the base wired to the control output signal from my MCU gpio pin, with a 1K series resistor. However, the io pin voltage seems to be ~3.15V no matter what I drive it with my application, and the base voltage is ~0.7V. VCE is always close to 0V, which means the oscillator is always getting full Vcc. What am I doing wrong here?

Reply to
galapogos

classic part for this is something like the FDG6324 or FDG6323

David

Reply to
David Collier

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