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'supply voltage for 16f84?'
1998\11\01@223428 by Andrew John Thoms

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the datasheet states that the 16f84 has a wide operating range 2.0v to
6.0v (page 1) and also that the voltage on vdd with respect to vss can be
as large as 7.5v (page 73)

does this mean that I can power it from a 7.2v battery with no regulation
as thechip can handle that voltage at its supply, or do I need to regulate
to below 6v?

I have also experienced problems in the past when the battery voltage
dropped to  about 3.5v, the chip ceased to function. has anyone got any
ideas?

Thanks

Andrew

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1998\11\02@002413 by James Cameron

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Andrew John Thoms wrote:
> Does this mean that I can power it from a 7.2v battery with no
> regulation as the chip can handle that voltage at its supply,
> or do I need to regulate to below 6v?

Regulate.

(a) 7.2 volt battery rarely is.  Measure it fresh, and you may find it
sitting at 1.6 x 5 = 8.0 volts, depending on the chemistry.

(b) the chip is warranted to handle up to 6v continuously, and
presumably up to 7.5v intermittently, presumably because of how it is
constructed, and how their tests came out.

Every limit can be broken, but for how long?  If it fails at 6v then you
have a case to seek compensation, but if it fails at 9v and isn't rated
for it, then you buy a new one yourself.

--
James Cameron                                      (spam_OUTcameronTakeThisOuTspamstl.dec.com)

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Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1998\11\02@162904 by Russell McMahon

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I think you will find that the 2 volt spec only applies to the LP
part - even though it says "2 to 6 volt operation" elsewhere on the
data sheet.

I also think 7.2v is the "maximum allowable rating" and not an
operational one (see where it is in data sheet - I may be wrong). If
so, operation at this level MAY be possible but is not advisable. An
LM2936 5v regulator is somewhat dearer than the normal 78L05 but has
low dropout (<0.5 volt) and has a quiescent current of a few 10's of
microamps. It 's what I use for this sort of application if component
cost is not absolutely critical.


Russell McMahon.

From: Andrew John Thoms <.....ajthomsKILLspamspam@spam@PROGSOC.UTS.EDU.AU>
>6.0v (page 1) and also that the voltage on vdd with respect to vss
can be
>as large as 7.5v (page 73)
>does this mean that I can power it from a 7.2v battery with no
regulation
>as thechip can handle that voltage at its supply, or do I need to
regulate
>to below 6v?

1998\11\02@224334 by James Cameron

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Russell McMahon wrote:
> I think you will find that the 2 volt spec only applies to the LP
> part - even though it says "2 to 6 volt operation" elsewhere on the
> data sheet.

I agree.  I was reading the data sheet over breakfast this morning and
found the table of voltage limits according to which oscillator
configuration and which chip was being used.

16F84 shows up as 4.5 to 5.5 volts for most common oscillator
configurations.

So I'm not surprised if it works down to 3.5 volts.  Andrew was just
lucky, I guess.  ;-)

--
James Cameron                                      (cameronspamKILLspamstl.dec.com)

OpenVMS, Linux, Firewalls, Software Engineering, CGI, HTTP, X, C, FORTH,
COBOL, BASIC, DCL, csh, bash, ksh, sh, Electronics, Microcontrollers,
Disability Engineering, Netrek, Bicycles, Pedant, Farming, Home Control,
Remote Area Power, Greek Scholar, Tenor Vocalist, Church Sound, Husband.

"Specialisation is for insects." -- Robert Heinlein.

1998\11\13@173150 by John Payson

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Russell McMahon wrote:
> I think you will find that the 2 volt spec only applies to the LP
> part - even though it says "2 to 6 volt operation" elsewhere on the
> data sheet.

|I agree.  I was reading the data sheet over breakfast this morning and
|found the table of voltage limits according to which oscillator
|configuration and which chip was being used.

On the other hand, I was testing to see just how far down
the thing could go in LP mode; it kept running even down to
a volt, and dropping it down to 0.7 caused it to stop run-
ing but didn't disrupt its operation (raising VDD allowed it
to resume).  I would not rely upon this in any sort of design,
but it was IMHO kinda impressive.

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