Searching \ for ' 16F84: RA4 as output attached to TTL log' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/ios.htm?key=output
Search entire site for: 'RA4 as output attached to TTL log'.

No exact or substring matches. trying for part
PICList Thread
'[PICLIST] 16F84: RA4 as output attached to TTL log'
2001\01\19@045314 by Jeszs

flavicon
face

Dear piclisters,

I am using RA4 as output pin to attack a TTL chip. Most of the time this pin shall be 0 V.

Since RA4 is open drain output, I need some kind of pull-up circuit.
Frequency is not an issue but could be in the future.
The basic pull-up resistor would be continuously consuming energy and this is what I see 'ugly' in my design.

Could you recomend me alternative solutions for minimum consumption?

Thank you very much in advance!
Ciao

--------------------
Jesús Gonzalo
INSA, Ingeniería y Servicios Aeroespaciales, SA
León (SPAIN)
--------------------


2001\01\19@050011 by Alan B. Pearce

face picon face
>The basic pull-up resistor would be continuously consuming energy and this is
what I see 'ugly' >in my design.

>Could you recomend me alternative solutions for minimum consumption?

Somewhere between 4k7 and 10k should be suitable unless you have a particularly
noisy environment around the track between the two chips. This would give
somewhere between 1ma and 0.5ma current draw when the pin is pulled to ground.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\01\19@062931 by Jinx

face picon face
> Could you recomend me alternative solutions for minimum
> consumption?

How about a low power inverter stage (transistor or gate) between
RA4 and the TTL so you could keep RA4 high

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\01\19@102712 by mike

flavicon
face
On Fri, 19 Jan 2001 11:06:03 +0100, you wrote:

>Dear piclisters,
>
>I am using RA4 as output pin to attack a TTL chip. Most of the time this pin shall be 0 V.
>
>Since RA4 is open drain output, I need some kind of pull-up circuit.
>Frequency is not an issue but could be in the future.
>The basic pull-up resistor would be continuously consuming energy and this is what I see 'ugly' in my design.

>Could you recomend me alternative solutions for minimum consumption?
Using obsolete parts like TTL is uglier - pull-ups are the least of
your power worries.
If using 74HC, you can usually use 100K

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


2001\01\19@151724 by Dwayne Reid

flavicon
face
At 11:06 AM 1/19/01 +0100, Jeszs wrote:
>Dear piclisters,
>
>I am using RA4 as output pin to attack a TTL chip. Most of the time this
>pin shall be 0 V.
>
>Since RA4 is open drain output, I need some kind of pull-up circuit.
>Frequency is not an issue but could be in the future.
>The basic pull-up resistor would be continuously consuming energy and this
>is what I see 'ugly' in my design.

Are you using 'real' TTL?  If so, TTL inputs normally float HI and consume
about 1 mA then pulled LO.  In other words, the current consumption from a
pullup resistor is minor compared to the quiescent current consumed by your
TTL logic.

If you *are* using real TTL, use a pullup resistor of 4.7K - its gonna cost
you 1 mA.  If you are using LS TTL, go to 10K.  If using HC, go to 100K.

dwayne



Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 17 years of Engineering Innovation (1984 - 2001)

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.


More... (looser matching)
- Last day of these posts
- In 2001 , 2002 only
- Today
- New search...