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'[PIC]: how about a 3-pin PIC chip??'
2002\08\15@080529 by Roman Black

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Has anyone else ever desired a 3-pin PIC, or
better still, ever seen/used a 3-pin micro??

I'm imagining something the size of a TO-92 (small
plastic transistor) or 3-pin SMT device, with
2 power pins and a single I/O pin.

A simple pullup resistor on the I/O pin would allow
it to transmit and receive digital at the same time
on the one pin, so it could drive a constant PWM
signal out (to operate a motor or SMPS etc), and
at the same time receive serial in from any source.

Internally it should have a precise osc with on-chip
resonator so it can be used as a programmable
real-time clock, or a timed controller system.
And some internal eeprom... How much was it again
to get a batch of custom chips made?? :o)
-Roman

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2002\08\15@083023 by Alan B. Pearce

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>Has anyone else ever desired a 3-pin PIC, or
>better still, ever seen/used a 3-pin micro??
>
>I'm imagining something the size of a TO-92 (small
>plastic transistor) or 3-pin SMT device, with
>2 power pins and a single I/O pin.

Is this not a description of a Dallas 1-wire device? I would have thought
the RTC devices and the like would be 3-wire micro's :)))

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2002\08\15@083224 by Quentin

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What about the Dallas I-button? Been a while since I checked (and then not
so well) but I seem to thing there is a Java thingy.

Quentin
spam_OUTqscTakeThisOuTspamiptech.co.za
http://www.iptech.co.za

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2002\08\15@112043 by Mike Singer

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Roman,
what is the motivation of the posting?
Have you limited PCB area, or you just don't want
to mess with extra pins?
If dimensions are critical: you may use chips in
new ultra small packages(japanese microcontrollers,
if available).

Mike.

Roman Black wrote:
{Quote hidden}

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2002\08\15@113609 by =?iso-8859-1?Q?F=E1bio_Pereira?=

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The only problem will be design a reliable programming protocol to use just
one pin !!!! hehe

Fabio

{Original Message removed}

2002\08\15@115127 by Spehro Pefhany

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At 06:24 PM 8/15/02 +0300, you wrote:
>  Roman,
>  what is the motivation of the posting?
>Have you limited PCB area, or you just don't want
>to mess with extra pins?
>If dimensions are critical: you may use chips in
>new ultra small packages(japanese microcontrollers,
>if available).

Not just the Japanese, see National Semiconductor's
COP series and Cygnal's 11-pin 8051.

Eg. COP8SAA7 4.5 x 5.5mm 28 pins
(16-pin SOIC version is about 75 cents/1k)
Or a 44 pin 6mm x 6mm..

Or.. C8051F301 3mm x 3mm 11 pins
(has 8K of flash on chip, an internal oscillator that
is accurate enough for serial comms, runs at 25MIPS)
Digikey wants about $4-5 for these in 100's

The problem with the 3-pin package is figuring out how to multiplex power
and ground. ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
.....speffKILLspamspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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2002\08\15@122029 by mike

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Maybe a SOT23-6 would be a nice compromise - if TI can get a 16
delta-sigma ADC into one I'm sure a PIC would fit... but PLEASE PLEASE
lets have a brownout on board (and a proper low-power one, not the
power hogs on the current PICs that makes them often unuseable...) the
lack of one is a major pain on the 12Cxxx parts.

On Thu, 15 Aug 2002 18:24:17 +0300, you wrote:

{Quote hidden}

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2002\08\15@122040 by mike

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..and of course the Fairchild ACE, in an 8 pin TSOP

On Thu, 15 Aug 2002 11:55:19 -0400, you wrote:

{Quote hidden}

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2002\08\15@134356 by Brendan Moran

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> Roman,
>  what is the motivation of the posting?
> Have you limited PCB area, or you just don't want
> to mess with extra pins?
> If dimensions are critical: you may use chips in
> new ultra small packages(japanese microcontrollers,
> if available).
>

There's a 10-pin 8051 that takes 3x3mm of boardspace....

- --Brendan

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2002\08\15@153644 by Peter L. Peres

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On Thu, 15 Aug 2002, Roman Black wrote:

>Has anyone else ever desired a 3-pin PIC, or
>better still, ever seen/used a 3-pin micro??

Well, if you cut off all the pins excepting the power pins and a single
gpio pin on any pic then you have a 3-pin pic. If it's a SMD one it'd be
small, too.

Peter

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2002\08\16@040845 by Michael Rigby-Jones

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> -----Original Message-----
> From: Roman Black [SMTP:.....fastvidKILLspamspam.....EZY.NET.AU]
> Sent: Thursday, August 15, 2002 1:02 PM
> To:   EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
> Subject:      [PIC]:  how about a 3-pin PIC chip??
>
> Has anyone else ever desired a 3-pin PIC, or
> better still, ever seen/used a 3-pin micro??
>
> I'm imagining something the size of a TO-92 (small
> plastic transistor) or 3-pin SMT device, with
> 2 power pins and a single I/O pin.
>
> A simple pullup resistor on the I/O pin would allow
> it to transmit and receive digital at the same time
> on the one pin, so it could drive a constant PWM
> signal out (to operate a motor or SMPS etc), and
> at the same time receive serial in from any source.
>
So tell me again how it drives out PWM at the same time as receiving a
serial bit stream? :o)

> Internally it should have a precise osc with on-chip
> resonator so it can be used as a programmable
> real-time clock, or a timed controller system.
> And some internal eeprom... How much was it again
> to get a batch of custom chips made?? :o)
> -Roman
>
It would also have to have a one wire programming protocol, and no reset pin
(internal programmable brownout?).  I belive EEPROM cells are quite large,
so combined with the PIC itself I suspect that fitting it into a SOT23 style
package might be a challenge.

Regards

Mike

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2002\08\17@120410 by Roman Black

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Quentin wrote:
>
> What about the Dallas I-button? Been a while since I checked (and then not
> so well) but I seem to thing there is a Java thingy.


Thanks Quentin! That is a pretty cool gizmo. :o)
the link: (2-wire micro)
http://www.ibutton.com/ibuttons/index.html
-Roman

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2002\08\17@120620 by Roman Black

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Michael Rigby-Jones wrote:
{Quote hidden}

Sure, it's easy if the incoming serial signal is
significantly faster or slower than the PWM signal.
A resistor sets the voltage level on the pin so it can
output a PWM "hi" when the PIC goes hi, then in the
low PWM period the low voltage changes according to the
serial data, which can be detected by the PIC with the
pin configured as an input at that time. Obviously
the change in "low" voltage signal is not enough to
affect the PWM which reads it all as a low.

> It would also have to have a one wire programming protocol, and no reset pin
> (internal programmable brownout?).  I belive EEPROM cells are quite large,
> so combined with the PIC itself I suspect that fitting it into a SOT23 style
> package might be a challenge.

This is a good point. Although I could think up lots
of cool things to make with a 3-pin micro, the actual
construction itself might be difficult, ideally for a
device like this to have real value it *needs* a built
in crystal or other acceptable timing source.

It would be a useful device for sending particular
signals, and yes I have seen the amused comments "cut
some legs off a 12C508" ;o)

I suppose as a PIC "enthusiast" I was intrigued by the
idea of a little 3-legged transistor type device that
had a nice PIC in it... ;o)
-Roman

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2002\08\17@124317 by Roman Black

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Spehro Pefhany wrote:
>
> At 06:24 PM 8/15/02 +0300, you wrote:
> >  Roman,
> >  what is the motivation of the posting?
> >Have you limited PCB area, or you just don't want
> >to mess with extra pins?
> >If dimensions are critical: you may use chips in
> >new ultra small packages(japanese microcontrollers,
> >if available).

I just like the 8-pin PICs, and thought a PIC in
a TO-92 or SOT-23 pack, with inbuilt accurate timer,
would be a cool addition to the PIC family. :o)

> The problem with the 3-pin package is figuring out how to multiplex power
> and ground. ;-)

Ha ha! Don't laugh, I already have a couple of
designs drafted out! :o)

Although the 3-pin micro doesn't need "other" use
of the Vdd or Vss pins they *can* be used for other
things, as would be needed with the i-Button:
http://www.ibutton.com/ibuttons/index.html
-Roman

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2002\08\19@123812 by Mike Singer

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Roman Black wrote:
> Has anyone else ever desired a 3-pin PIC, or
> better still, ever seen/used a 3-pin micro??

If size is critical, maybe our as ever desired PICs
in MicroLeadframe (MLF) packages will match?

Mike.

------------------------------------
From
http://www.electronicstalk.com/news/ari/ari107.html

8 February 2002

Microchip's popular PICmicro OTP and Flash microcontrollers
are now available in space-saving MicroLeadframe (MLF)
packages that are 50% smaller than traditional SSOP
alternatives.
The elimination of conventional side leads and a
near-chip-scale package improves board space efficiency,
making these devices ideal for designs where space is
at a premium.
The MLF package also incorporates ExposedPad technology,
exposing the die paddle that can be soldered directly to
the printed circuit board.
The new package simplifies manufacturing and reduces
thermal limitations.
Die customers will find handling and wire-bonding issues
to be non-existent and mounting and testing are made easier.
The first devices are available in 28-lead 6 x 6mm
packages with a common pitch size of 0.65mm and competitively
priced with typical SOIC devices.
These include four OTP devices (PIC16C62B, PIC16C63A,
PIC16C72A and PIC16C73B) and two Flash devices (PIC16F73
and PIC16F76).
Additional devices in 8-, 20- and 40-lead packages
are planned for later in the year.
Applications include handheld computers, PDAs,
high-frequency wireless handsets, handheld measurement
devices, small toys and various automotive applications,
such as keyless entry or ignition systems.
Microchip offers several development tools that support
the MLF devices.
The AC164031 adapter kit is also available now for the
PICstart Plus and Pro Mate II development kits.

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