Is the 4066 suitable for power switching?

[galapogos]

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!

 

[Fred Bartoli]

galapogos a écrit :

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!

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

 

[AJ]

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!

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

Regards


AJ

 

[Eeyore]

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?

The transmission gates have an ON resistance you'll find in the data sheet.

Graham

 

[galapogos]

galapogos a écrit :

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

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.

 

[Tim Wescott]

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.

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

Posting from Google? See http://cfaj.freeshell.org/google/

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

 

[colin]

"Fred Bartoli"

galapogos a écrit :

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

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

Colin =^.^=

 

[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

Posting from Google? See http://cfaj.freeshell.org/google/

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

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?

 

[David Collier]

*Subject:* Is the 4066 suitable for power switching?
*From:* "galapogos" <[email protected]>
*Date:* 8 Nov 2006 01:22:23 -0800

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?

classic part for this is something like the FDG6324 or FDG6323

David