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PICList Thread
'[PIC:] 18F452 / 18LF452'
2004\04\13@091326 by Wouter van Ooijen

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My supplier states a lead time on 18F452's is a few weeks, but 18LF452's
are in stock. As far as I can see from the datasheet an 18LF is the same
or better compared to an 18F. It this correct? Is this generally true
for all PICs?

Wouter van Ooijen

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2004\04\13@093141 by Brian Clewer

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Wouter wrote:

> My supplier states a lead time on 18F452's is a few weeks, but 18LF452's
> are in stock. As far as I can see from the datasheet an 18LF is the same
> or better compared to an 18F. It this correct?

Better.  The LF enables you to operate down to a voltage of 2V, thus drawing
less power.


>Is this generally true
> for all PICs?

Yes.

Brian.

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2004\04\13@093349 by Jan-Erik Soderholm

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Wouter van Ooijen wrote :

> As far as I can see from the datasheet an 18LF
> is the same or better compared to an 18F. It this
> correct?
>
> Wouter van Ooijen

Hi.
The only paramater I've found that points a lower/worse spec
for th LF parts, is in table 17-1 on page 186 (DS39564B).
As I read it, you must run the LF parts at a lower speed if using
the ADC. Or did I miss-read the table ?

Jan-Erik.

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2004\04\13@094559 by Ehlers Riaan

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The 18LF452 is the low voltage version for the 18F452.

P263 in datasheet:
PIC18F452  operates between 4.2V and 5.5V
PIC18LF452 operates between 2V and 5.5V

I think you are correct. You can run both from 5V, but only the 18LF can run from 3V.
I use the 18F452. Very nice chip.

Thanx
Riaan

{Original Message removed}

2004\04\13@095014 by Wouter van Ooijen

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> The only paramater I've found that points a lower/worse spec
> for th LF parts, is in table 17-1 on page 186 (DS39564B).

As I read it you are correct: in this aspect the LF version seems to
have a lower spec than the F version.

Wouter van Ooijen

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2004\04\13@095842 by Jan-Erik Soderholm

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Riaan wrote :

> The 18LF452 is the low voltage version for the 18F452.

Brian wrote :

> Better.  The LF enables you to operate down to a voltage of 2V, thus drawing
> less power.


C'mon guys !
I'm sure Wouter knows what the "L" in "LF" stands for ! :-) :-)
I don't think  *that* was what he was asking about...

And besides...

Brian wrote :

> > > Is this generally true for all PICs?
> Yes.

Well, yes and no.
There are "F" PIC's that runs from 2.0 V also (with no LF part at all).

Jan-Erik.

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2004\04\13@100644 by hael Rigby-Jones

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>-----Original Message-----
>From: Wouter van Ooijen [spam_OUTwouterTakeThisOuTspamVOTI.NL]
>Sent: 13 April 2004 14:50
>To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
>Subject: Re: [PIC:] 18F452 / 18LF452
>
>
>> The only paramater I've found that points a lower/worse spec
>for th LF
>> parts, is in table 17-1 on page 186 (DS39564B).
>
>As I read it you are correct: in this aspect the LF version
>seems to have a lower spec than the F version.
>
>Wouter van Ooijen

I asked my FAE about this sometime ago, and ISTR the specs are exactly the
same on the F and LF when operating at 5volts, but the spec's had to be
relaxed for working at low voltages, (i.e. if you stick to the conditions
shown for the F part in the table, the LF should meet those specs when run
at 5 volts).

Regards

Mike




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2004\04\13@104857 by Hulatt, Jon

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>
> I asked my FAE about this sometime ago, and ISTR the specs
> are exactly the same on the F and LF when operating at
> 5volts, but the spec's had to be relaxed for working at low
> voltages, (i.e. if you stick to the conditions shown for the
> F part in the table, the LF should meet those specs when run
> at 5 volts).
>

Do we therefore think it likely that the ~LF parts are not physically
different to the ~F parts, but just turn out to be the best of the bunch?

A la Intel testing cpus and speed grading accordingly?

It's an out of interest thing; please noone jump on my back saying I
shouldn't run a pic out of spec etc etc. :)


Jon

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2004\04\13@110652 by hael Rigby-Jones

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{Quote hidden}

Very probably.  I have (accidently) run non-LF parts at 3.3volts with no
problems at all. YYMV etc.

Regards

Mike




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2004\04\13@141856 by Rfiles

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Some time ago i made a built a project that i saw in a website, it was a
frequency meter (pic16f876). I did try with an F and a LF part and with a LF
part i could only measure ~25Mhz max and with a F i could measure ~50MHz,
Later i check the datasheet and i found that the timer (that the pic used to
make the measurement) could only read max at 25ns (LF part) and 10ns (F
part). And there are some other timings that the LF part is slower.

Regards,
Ricardo Reis

-----Mensagem original-----
De: pic microcontroller discussion list [@spam@PICLISTKILLspamspamMITVMA.MIT.EDU] Em
nome de Wouter van Ooijen
Enviada: terça-feira, 13 de Abril de 2004 14:14
Para: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
Assunto: [PIC:] 18F452 / 18LF452

My supplier states a lead time on 18F452's is a few weeks, but 18LF452's are
in stock. As far as I can see from the datasheet an 18LF is the same or
better compared to an 18F. It this correct? Is this generally true for all
PICs?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development,
PICmicro products

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See http://www.piclist.com/#archives for details.

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2004\04\13@153206 by Jason Harper

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Jon wrote:
> Do we therefore think it likely that the ~LF parts are not physically
> different to the ~F parts, but just turn out to be the best of the bunch?

VERY likely.  Consider the 16LF parts, which have a rather useless brownout
detector - its threshhold is still 4.x volts, appropriate only for use from
a 5V supply.
       Jason Harper

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2004\04\15@163415 by Jesse Lackey

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I have had some problems with 'F' parts @ 3.3V, erratic programming
failures, but they ran fine.  Circuit cellar 2002 had a smartmedia
article that ran an 'F' @ 3.3V, the author said nothing about how this
is contrary to datasheet spec.  Personally I spend the extra $1 for the LF.

J

Michael Rigby-Jones wrote:
>>{Original Message removed}

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