I am trying to build something that uses a digital switching mechanism, but
I believe the 4053 I am currently using is blowing me out of the water with
it's 120 ohm "on" resistance. Is there a sub for this part with little or
no "on" resistance? I found a referrence on the net to an unnamed Analog
Devices part with a mere .4 ohms "on" resistance. I guess I could work with
an analog switch instead of a digital, but how do I find this part?

Many thanks,

Dave

Dave wrote:
> I am trying to build something that uses a digital switching mechanism, but
> I believe the 4053 I am currently using is blowing me out of the water with
> it's 120 ohm "on" resistance. Is there a sub for this part with little or
> no "on" resistance? I found a referrence on the net to an unnamed Analog
> Devices part with a mere .4 ohms "on" resistance. I guess I could work with
> an analog switch instead of a digital, but how do I find this part?

You have lots of choices, and analog switches are fine
possibilities. The main concern that limits your choices is
the power supply voltage you are using.

For example, if you are using a 5 volt supply you might be
able to make use of the version of the 4053 in the 74HC
family. Though from its maximum resistance, that may be
what you have already tried (though I generally assume that
a 4000 number implied the CD series).
http://www.fairchildsemi.com/ds/MM%2FMM74HC4053.pdf

What part are you using now, and what power supply and
signal range do you need?
--
Regards,

John Popelish

"John Popelish" <jpopelish@rica.net> wrote in message
news:ubmdnScz4KV8_xXanZ2dnUVZ_v-hnZ2d@comcast.com...
> Dave wrote:
>> I am trying to build something that uses a digital switching mechanism,
>> but I believe the 4053 I am currently using is blowing me out of the
>> water with it's 120 ohm "on" resistance. Is there a sub for this part
>> with little or no "on" resistance? I found a referrence on the net to an
>> unnamed Analog Devices part with a mere .4 ohms "on" resistance. I guess
>> I could work with an analog switch instead of a digital, but how do I
>> find this part?
>
> You have lots of choices, and analog switches are fine possibilities. The
> main concern that limits your choices is the power supply voltage you are
> using.
>
> For example, if you are using a 5 volt supply you might be able to make
> use of the version of the 4053 in the 74HC family. Though from its
> maximum resistance, that may be what you have already tried (though I
> generally assume that a 4000 number implied the CD series).
> http://www.fairchildsemi.com/ds/MM%2FMM74HC4053.pdf
>
> What part are you using now, and what power supply and signal range do you
> need?
> --
> Regards,
>
> John Popelish

Well hello John,

Thank you for the reply. And your assumption would be correct, I am using
the CD4053. For a power supply I am using a 9V battery, and would like to
continue with either that or perhaps something with AA batteries. From a
brief glance at the datasheet you so kindly gave me the link for, I am
thinking that perhaps a +5V regulator and a -5V regulator would be in order
.. The 30 ohm "on" resistance (I think that's what I saw) sounds a lot
better than what I am currently dealing with. You don't know of anything
even lower, do you?

Oh, and for signal range I am using the complementary Q and not-Q outputs
from a 4027 JK flip-flop. Nothing too extreme there. I believe that is
just +5V and ground.

Thank you again for the reply. I am planning a trip to the parts depot Sat.
AM, and your info is most welcome.

Dave

On Fri, 11 Jan 2008 23:43:51 -0600, "Dave" <db5151@hotmail.com> wrote:

>I am trying to build something that uses a digital switching mechanism, but
>I believe the 4053 I am currently using is blowing me out of the water with
>it's 120 ohm "on" resistance. Is there a sub for this part with little or
>no "on" resistance? I found a referrence on the net to an unnamed Analog
>Devices part with a mere .4 ohms "on" resistance. I guess I could work with
>an analog switch instead of a digital, but how do I find this part?
>
>Many thanks,
>
>Dave
>

What exactly are you trying to do? Often it is much simpler
to redesign the circuit so the "on" resistance is not an issue.
"On" resistance tends to be nonlinear, so if you are putting
any kind of a signal through it, you can have problems.
The solution typically involves buffering the switch output
with a high input impedance op-amp using (say) 100k to ground.
So the switch is the top leg in a voltage divider and 100k is
the bottom, meaning there is not much voltage across the
switch itself.

Best regards,





Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
http://www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!

Dave wrote:
> "John Popelish" <jpopelish@rica.net> wrote in message
> news:ubmdnScz4KV8_xXanZ2dnUVZ_v-hnZ2d@comcast.com...
>> Dave wrote:
>>> I am trying to build something that uses a digital switching mechanism,
>>> but I believe the 4053 I am currently using is blowing me out of the
>>> water with it's 120 ohm "on" resistance. Is there a sub for this part
>>> with little or no "on" resistance? I found a referrence on the net to an
>>> unnamed Analog Devices part with a mere .4 ohms "on" resistance. I guess
>>> I could work with an analog switch instead of a digital, but how do I
>>> find this part?
>> You have lots of choices, and analog switches are fine possibilities. The
>> main concern that limits your choices is the power supply voltage you are
>> using.
>>
>> For example, if you are using a 5 volt supply you might be able to make
>> use of the version of the 4053 in the 74HC family. Though from its
>> maximum resistance, that may be what you have already tried (though I
>> generally assume that a 4000 number implied the CD series).
>> http://www.fairchildsemi.com/ds/MM%2FMM74HC4053.pdf
>>
>> What part are you using now, and what power supply and signal range do you
>> need?
>> --
>> Regards,
>>
>> John Popelish
>
> Well hello John,
>
> Thank you for the reply. And your assumption would be correct, I am using
> the CD4053. For a power supply I am using a 9V battery, and would like to
> continue with either that or perhaps something with AA batteries. From a
> brief glance at the datasheet you so kindly gave me the link for, I am
> thinking that perhaps a +5V regulator and a -5V regulator would be in order
> . The 30 ohm "on" resistance (I think that's what I saw) sounds a lot
> better than what I am currently dealing with. You don't know of anything
> even lower, do you?
>
> Oh, and for signal range I am using the complementary Q and not-Q outputs
> from a 4027 JK flip-flop. Nothing too extreme there. I believe that is
> just +5V and ground.
>
> Thank you again for the reply. I am planning a trip to the parts depot Sat.
> AM, and your info is most welcome.

If your signal swings only between +5 and zero, then you
also only need a switch supply with that range.

However, if your signal is truly digital, why not use gating
instead of a switch? That way, the gate reproduces the
logic signal with its output, instead of passing it through
resistance.

This one has 4 selectors (similar to analog switches, but
makes logical copies of one or the other logical inputs),
but all 4 selectors are switched by a single input:
http://focus.ti.com/lit/ds/symlink/sn74hc158.pdf

--
Regards,

John Popelish

On Sat, 12 Jan 2008 02:53:29 -0600, "Dave" <db5151@hotmail.com> wrote:

>
>"John Popelish" <jpopelish@rica.net> wrote in message
>news:ubmdnScz4KV8_xXanZ2dnUVZ_v-hnZ2d@comcast.com...
>> Dave wrote:
>>> I am trying to build something that uses a digital switching mechanism,
>>> but I believe the 4053 I am currently using is blowing me out of the
>>> water with it's 120 ohm "on" resistance. Is there a sub for this part
>>> with little or no "on" resistance? I found a referrence on the net to an
>>> unnamed Analog Devices part with a mere .4 ohms "on" resistance. I guess
>>> I could work with an analog switch instead of a digital, but how do I
>>> find this part?
>>
>> You have lots of choices, and analog switches are fine possibilities. The
>> main concern that limits your choices is the power supply voltage you are
>> using.
>>
>> For example, if you are using a 5 volt supply you might be able to make
>> use of the version of the 4053 in the 74HC family. Though from its
>> maximum resistance, that may be what you have already tried (though I
>> generally assume that a 4000 number implied the CD series).
>> http://www.fairchildsemi.com/ds/MM%2FMM74HC4053.pdf
>>
>> What part are you using now, and what power supply and signal range do you
>> need?
>> --
>> Regards,
>>
>> John Popelish
>
>Well hello John,
>
>Thank you for the reply. And your assumption would be correct, I am using
>the CD4053. For a power supply I am using a 9V battery, and would like to
>continue with either that or perhaps something with AA batteries. From a
>brief glance at the datasheet you so kindly gave me the link for, I am
>thinking that perhaps a +5V regulator and a -5V regulator would be in order
>. The 30 ohm "on" resistance (I think that's what I saw) sounds a lot
>better than what I am currently dealing with. You don't know of anything
>even lower, do you?
>
>Oh, and for signal range I am using the complementary Q and not-Q outputs
>from a 4027 JK flip-flop. Nothing too extreme there. I believe that is
>just +5V and ground.


Why not just use an xor gate? Or a true digital mux?

John

On 2008-01-12, Dave <db5151@hotmail.com> wrote:
> I am trying to build something that uses a digital switching mechanism, but
> I believe the 4053 I am currently using is blowing me out of the water with
> it's 120 ohm "on" resistance.

You got other good advice. If you're not sure about the on resistance
as the problem, you could always stack another 4053 on the first one
(piggy-back) and cut Ron in half (at the expense of doubling all the pin
capacitances, but that might not matter to you).

--
Ben Jackson AD7GD
<ben@ben.com>
http://www.ben.com/

"John Popelish" <jpopelish@rica.net> wrote in message
news:cpCdnZ2fobGBbhXanZ2dnUVZ_hWdnZ2d@comcast.com...
> Dave wrote:
>> "John Popelish" <jpopelish@rica.net> wrote in message
>> news:ubmdnScz4KV8_xXanZ2dnUVZ_v-hnZ2d@comcast.com...
>>> Dave wrote:
>>>> I am trying to build something that uses a digital switching mechanism,
>>>> but I believe the 4053 I am currently using is blowing me out of the
>>>> water with it's 120 ohm "on" resistance. Is there a sub for this part
>>>> with little or no "on" resistance? I found a referrence on the net to
>>>> an unnamed Analog Devices part with a mere .4 ohms "on" resistance. I
>>>> guess I could work with an analog switch instead of a digital, but how
>>>> do I find this part?
>>> You have lots of choices, and analog switches are fine possibilities.
>>> The main concern that limits your choices is the power supply voltage
>>> you are using.
>>>
>>> For example, if you are using a 5 volt supply you might be able to make
>>> use of the version of the 4053 in the 74HC family. Though from its
>>> maximum resistance, that may be what you have already tried (though I
>>> generally assume that a 4000 number implied the CD series).
>>> http://www.fairchildsemi.com/ds/MM%2FMM74HC4053.pdf
>>>
>>> What part are you using now, and what power supply and signal range do
>>> you need?
>>> --
>>> Regards,
>>>
>>> John Popelish
>>
>> Well hello John,
>>
>> Thank you for the reply. And your assumption would be correct, I am
>> using the CD4053. For a power supply I am using a 9V battery, and would
>> like to continue with either that or perhaps something with AA batteries.
>> From a brief glance at the datasheet you so kindly gave me the link for,
>> I am thinking that perhaps a +5V regulator and a -5V regulator would be
>> in order . The 30 ohm "on" resistance (I think that's what I saw) sounds
>> a lot better than what I am currently dealing with. You don't know of
>> anything even lower, do you?
>>
>> Oh, and for signal range I am using the complementary Q and not-Q outputs
>> from a 4027 JK flip-flop. Nothing too extreme there. I believe that is
>> just +5V and ground.
>>
>> Thank you again for the reply. I am planning a trip to the parts depot
>> Sat. AM, and your info is most welcome.
>
> If your signal swings only between +5 and zero, then you also only need a
> switch supply with that range.
>
> However, if your signal is truly digital, why not use gating instead of a
> switch? That way, the gate reproduces the logic signal with its output,
> instead of passing it through resistance.
>
> This one has 4 selectors (similar to analog switches, but makes logical
> copies of one or the other logical inputs), but all 4 selectors are
> switched by a single input:
> http://focus.ti.com/lit/ds/symlink/sn74hc158.pdf
>
> --
> Regards,
>
> John Popelish

Hey John,

Not sure what to say. My "signal" (on the Ain/out and the A1/A0 etc.of the
4053) is actually analog (thus my concerns about Ron), and the 74HC4053
(according to that datasheet) requires both a +5V (Vdd) and a -5V (Vee).
And (BTW) what is Vss?

Someone told me that using a 7805 "backwards) to simulate -5V can cause
flaky problems, so I am thinking I need a 7805 *and* a 7905. (Can these
share a common ground?) Or should I use a real powersupply with a 12.6V CT
transformer and associated hardware to provide my voltages?

Sigh Sorry to be so obtuse, but CMOS is still pretty new to me. Hate to
admit it, but it's obvious. I'm not sure what I'm doing, or how I am doing
it.

Best regards,

Dave

"Bob Masta" <NoSpam@daqarta.com> wrote in message
news:4788c3cb.1505893@news.sysmatrix.net...
> On Fri, 11 Jan 2008 23:43:51 -0600, "Dave" <db5151@hotmail.com> wrote:
>
>>I am trying to build something that uses a digital switching mechanism,
>>but
>>I believe the 4053 I am currently using is blowing me out of the water
>>with
>>it's 120 ohm "on" resistance. Is there a sub for this part with little or
>>no "on" resistance? I found a referrence on the net to an unnamed Analog
>>Devices part with a mere .4 ohms "on" resistance. I guess I could work
>>with
>>an analog switch instead of a digital, but how do I find this part?
>>
>>Many thanks,
>>
>>Dave
>>
>
> What exactly are you trying to do? Often it is much simpler
> to redesign the circuit so the "on" resistance is not an issue.
> "On" resistance tends to be nonlinear, so if you are putting
> any kind of a signal through it, you can have problems.
> The solution typically involves buffering the switch output
> with a high input impedance op-amp using (say) 100k to ground.
> So the switch is the top leg in a voltage divider and 100k is
> the bottom, meaning there is not much voltage across the
> switch itself.
>
> Best regards,
>
>
>
>
>
> Bob Masta
>
> DAQARTA v3.50
> Data AcQuisition And Real-Time Analysis
> http://www.daqarta.com
> Scope, Spectrum, Spectrogram, FREE Signal Generator
> Science with your sound card!

Hey, here we go. I may need to hear more about this type of operation.
What is this technique called, and whre can I find more info about it?

Many thanks for the interest,

Dave

"Ben Jackson" <ben@ben.com> wrote in message
news:slrnfoi8dk.tq9.ben@saturn.home.ben.com...
> On 2008-01-12, Dave <db5151@hotmail.com> wrote:
>> I am trying to build something that uses a digital switching mechanism,
>> but
>> I believe the 4053 I am currently using is blowing me out of the water
>> with
>> it's 120 ohm "on" resistance.
>
> You got other good advice. If you're not sure about the on resistance
> as the problem, you could always stack another 4053 on the first one
> (piggy-back) and cut Ron in half (at the expense of doubling all the pin
> capacitances, but that might not matter to you).
>
> --
> Ben Jackson AD7GD
> <ben@ben.com>
> http://www.ben.com/

Thank you for the idea, Ben. I may use that. Thank you very much...

Dave

Dave wrote:

> Not sure what to say. My "signal" (on the Ain/out and the A1/A0 etc.of the
> 4053) is actually analog (thus my concerns about Ron), and the 74HC4053
> (according to that datasheet) requires both a +5V (Vdd) and a -5V (Vee).
> And (BTW) what is Vss?

Vss is the negative logic supply rail. The control logic
operates between Vss and Vdd. The analog signals can swing
between Vee and Vcc, though Vee can be connected to Vss if
the analog signals stay between the logic rails. But
reducing the total difference between Vdd and Vee from 10
volts to 5 volts almost doubles the switch on resistance
(from something like 4o ohms to something like 70 ohms).

> Someone told me that using a 7805 "backwards) to simulate -5V can cause
> flaky problems, so I am thinking I need a 7805 *and* a 7905.

Much better idea.

> (Can these share a common ground?)

Yes.

> Or should I use a real powersupply with a 12.6V CT
> transformer and associated hardware to provide my voltages?

To use a 7805 and a 79o5 to produce positive and negative 5
volt rails, you will need a raw positive and negative 7 to 9
volts, referenced to the same ground. A 12.6 Vct secondary
will produce about positive and negative 8.8 volts, peak,
minus a diode drop or about 8 volts, so it may work fine
with the two regulators.

> Sigh Sorry to be so obtuse, but CMOS is still pretty new to me. Hate to
> admit it, but it's obvious. I'm not sure what I'm doing, or how I am doing
> it.

You are getting there.

--
Regards,

John Popelish

"John Popelish" <jpopelish@rica.net> wrote in message
news:WZydnX0zuasOARfanZ2dnUVZ_hKdnZ2d@comcast.com...
> Dave wrote:
>
>> Not sure what to say. My "signal" (on the Ain/out and the A1/A0 etc.of
>> the 4053) is actually analog (thus my concerns about Ron), and the
>> 74HC4053 (according to that datasheet) requires both a +5V (Vdd) and
>> a -5V (Vee). And (BTW) what is Vss?
>
> Vss is the negative logic supply rail. The control logic operates between
> Vss and Vdd. The analog signals can swing between Vee and Vcc, though Vee
> can be connected to Vss if the analog signals stay between the logic
> rails. But reducing the total difference between Vdd and Vee from 10
> volts to 5 volts almost doubles the switch on resistance (from something
> like 4o ohms to something like 70 ohms).
>
>> Someone told me that using a 7805 "backwards) to simulate -5V can cause
>> flaky problems, so I am thinking I need a 7805 *and* a 7905.
>
> Much better idea.
>
>> (Can these share a common ground?)
>
> Yes.
>
>> Or should I use a real powersupply with a 12.6V CT transformer and
>> associated hardware to provide my voltages?
>
> To use a 7805 and a 79o5 to produce positive and negative 5 volt rails,
> you will need a raw positive and negative 7 to 9 volts, referenced to the
> same ground. A 12.6 Vct secondary will produce about positive and
> negative 8.8 volts, peak, minus a diode drop or about 8 volts, so it may
> work fine with the two regulators.
>
>> Sigh Sorry to be so obtuse, but CMOS is still pretty new to me. Hate to
>> admit it, but it's obvious. I'm not sure what I'm doing, or how I am
>> doing it.
>
> You are getting there.
>
> --
> Regards,
>
> John Popelish

Okay, one more stupid question. Do you think I could run both the 7805 and
the 7905 off of the same 9V battery? Probably wouldn't last long if I did,
though. Still... I have to ask.

Thank you for your help. It is appreciated.

Regards,

Dave

Dave wrote:

> Okay, one more stupid question. Do you think I could run both the 7805 and
> the 7905 off of the same 9V battery? Probably wouldn't last long if I did,
> though. Still... I have to ask.

Can't do it. you would need two in a stack, with the center
point as ground, and the two ends as plus and minus 9 volts
as inputs to the regulators. That would run for a few hours.


--
Regards,

John Popelish

On Sun, 13 Jan 2008 13:35:25 -0600, "Dave" <db5151@hotmail.com> wrote:

>
>"Bob Masta" <NoSpam@daqarta.com> wrote in message
>news:4788c3cb.1505893@news.sysmatrix.net...
>> On Fri, 11 Jan 2008 23:43:51 -0600, "Dave" <db5151@hotmail.com> wrote:
>>
>>>I am trying to build something that uses a digital switching mechanism,
>>>but
>>>I believe the 4053 I am currently using is blowing me out of the water
>>>with
>>>it's 120 ohm "on" resistance. Is there a sub for this part with little or
>>>no "on" resistance? I found a referrence on the net to an unnamed Analog
>>>Devices part with a mere .4 ohms "on" resistance. I guess I could work
>>>with
>>>an analog switch instead of a digital, but how do I find this part?
>>>
>>>Many thanks,
>>>
>>>Dave
>>>
>>
>> What exactly are you trying to do? Often it is much simpler
>> to redesign the circuit so the "on" resistance is not an issue.
>> "On" resistance tends to be nonlinear, so if you are putting
>> any kind of a signal through it, you can have problems.
>> The solution typically involves buffering the switch output
>> with a high input impedance op-amp using (say) 100k to ground.
>> So the switch is the top leg in a voltage divider and 100k is
>> the bottom, meaning there is not much voltage across the
>> switch itself.
>>
>> Best regards,
>>
>>
>>
>>
>>
>> Bob Masta
>>
>> DAQARTA v3.50
>> Data AcQuisition And Real-Time Analysis
>> http://www.daqarta.com
>> Scope, Spectrum, Spectrogram, FREE Signal Generator
>> Science with your sound card!
>
>Hey, here we go. I may need to hear more about this type of operation.
>What is this technique called, and whre can I find more info about it?
>
>Many thanks for the interest,
>
>Dave

I don't know of a specific name, it's just one of the ways to deal
with nonlinear analog switches. If you will explain what it is you
are trying to do, we can probably give more specific advice.

BTW, in answer to your question about running positive and negative
regulators off one 9V battery, you may not need any regulator at all,
just a "ground splitter". This is a non-inverting op-amp buffer whose
positive input is tied to a voltage divider that provides 4.5V from
the 9V battery. The output of the amp (which is also connected to
the inverting input to make it a buffer) drives the circuit ground.
If your ground current needs are not too high, this may be all you
need, or else you may need some output transistors to provide some
extra current capability.

The above won't be regulated, but CMOS doesn't care about that as
long as the voltage is in a (fairly wide) useable range.

Best regards,



Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
http://www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!