Reply by Steve at fivetrees●February 9, 20062006-02-09
"Tim Wescott" <tim@seemywebsite.com> wrote in message
news:kvydnXn6L9P8s3XenZ2dnUVZ_sKdnZ2d@web-ster.com...
>> You are thinking of "totem-pole" output, which may be performed by
>> either complementary devices (p and n channel) or by configuration
>> (common collector and common emitter circuits hooked together). The
>> choice depends on the available semiconductor process.
>>
>> Push-pull means two unidirectional outputs driving two sections of
>> an output transformer, in such a way that only one driver is
>> operational at at time (class B or C) or partially overlapped
>> (class A). This is a left-over from vacuum tube days, when all
>> devices were effectively n-channel fets.
>>
> Hmm. I always thought that "totem pole" only referred to the stack of
> transistors in a TTL. Now I'm going to have to go look at actual usage,
> 'cause push-pull isn't a bad way to describe what's happening in general.
> Tim Wescott wrote:
>
> ... snip ...
>
>>"Push-pull" (normal output) -- Actively supplies current from VCC
>>to pull the voltage up, and pulls current to VEE to pull the
>>voltage down. In CMOS this means it has a P-type transistor to
>>VCC and an N-type transistor to VEE.
>
>
> You are thinking of "totem-pole" output, which may be performed by
> either complementary devices (p and n channel) or by configuration
> (common collector and common emitter circuits hooked together).
> The choice depends on the available semiconductor process.
>
> Push-pull means two unidirectional outputs driving two sections of
> an output transformer, in such a way that only one driver is
> operational at at time (class B or C) or partially overlapped
> (class A). This is a left-over from vacuum tube days, when all
> devices were effectively n-channel fets.
>
> Open-collector (or open drain) circuits are normally used to
> perform "wired or", which is better termed "wired and" for the
> usual positive logic.
>
Hmm. I always thought that "totem pole" only referred to the stack of
transistors in a TTL. Now I'm going to have to go look at actual usage,
'cause push-pull isn't a bad way to describe what's happening in general.
Maybe if we all just started to use the term it'll be adopted, since
there aren't that many transformer finals out there to make things
ambiguous.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply by CBFalconer●February 6, 20062006-02-06
Tim Wescott wrote:
>
... snip ...
>
> "Push-pull" (normal output) -- Actively supplies current from VCC
> to pull the voltage up, and pulls current to VEE to pull the
> voltage down. In CMOS this means it has a P-type transistor to
> VCC and an N-type transistor to VEE.
You are thinking of "totem-pole" output, which may be performed by
either complementary devices (p and n channel) or by configuration
(common collector and common emitter circuits hooked together).
The choice depends on the available semiconductor process.
Push-pull means two unidirectional outputs driving two sections of
an output transformer, in such a way that only one driver is
operational at at time (class B or C) or partially overlapped
(class A). This is a left-over from vacuum tube days, when all
devices were effectively n-channel fets.
Open-collector (or open drain) circuits are normally used to
perform "wired or", which is better termed "wired and" for the
usual positive logic.
--
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Reply by Tim Wescott●February 6, 20062006-02-06
Antti Keskinen wrote:
> Hello !
>
> Can anyone direct me to a good guide which explains the differences between
> "common" microcontroller pin types, such as "open-drain" or "push-pull" etc
> ?
>
> The reason I'm asking this is that I'm trying to connect a TEA5768HL's
> SWPORT1 to a C8051F320's input port pin and I'm not sure how I should do it
> to make sure it works correctly. I've contacted Philips asking them the same
> question, but while they're able to help me with this specific issue, I
> would like to understand what it's all about so I don't have to ask again
> when I move on to another product or project.
>
> Greetings,
> Antti Keskinen
>
>
Any good book that explains digital logic should do this. I would
imagine it's in the ARRL handbook or "The Art of Electronics" by
Horowitz & Hill (I'm not sure, though).
Here's a quick guide, though:
"Push-pull" (normal output) -- Actively supplies current from VCC to
pull the voltage up, and pulls current to VEE to pull the voltage down.
In CMOS this means it has a P-type transistor to VCC and an N-type
transistor to VEE.
"Open-drain" (or open collector) -- Has a transistor to ground, either
N-type MOS or NPN in TTL.
"Tri-state" -- Has pull-up and pull-down transistors, with a control
line to turn both off. Hence, three states -- high voltage, low voltage
or high impedance (to let other devices drive the line).
In addition to this you need to pay attention to old-style TTL logic
interfaced to CMOS: a 5V TTL part is only guaranteed to drive about 2.7V
or so as a "high", which is less than what 5V CMOS is guaranteed to
respond to. If you want to interface TTL to CMOS you have to use
special CMOS parts with a lower threshold. Ditto for interfacing parts
with a 3.3V VSS to parts with a 5V VSS.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Reply by Antti Keskinen●February 6, 20062006-02-06
Hello !
Can anyone direct me to a good guide which explains the differences between
"common" microcontroller pin types, such as "open-drain" or "push-pull" etc
?
The reason I'm asking this is that I'm trying to connect a TEA5768HL's
SWPORT1 to a C8051F320's input port pin and I'm not sure how I should do it
to make sure it works correctly. I've contacted Philips asking them the same
question, but while they're able to help me with this specific issue, I
would like to understand what it's all about so I don't have to ask again
when I move on to another product or project.
Greetings,
Antti Keskinen