How to identify pin 1 on SOT-23 - Electronic Circuits Projects Diagrams Free

Pommie · 30th August 2008, 02:01 PM

I have some 10f200s in SOT-23 and they are so tiny I cannot identify pin 1 by normal methods. There does not appear to be a dot or notch in the package and even with my big magnifier I cannot read the writing. So, what I have done is use my meter on diode test mode and with the red lead on (assumed Vss) pin 2 I get a forward voltage on all the port pins of around 0.5V. With the black lead on pin 5 (Vdd) I get a reading on all port pins except MCLR. I have therefore concluded that I have indeed identified pin 1.

However, this is obviously not the way it's done and I suspect that the way they are arranged in the packaging would identify pin 1. So, what is the normal way to identify pin 1 on an SOT-23 device?

Mike.

ericgibbs · 30th August 2008, 02:05 PM

Quote:

Originally Posted by Pommie

I have some 10f200s in SOT-23 and they are so tiny I cannot identify pin 1 by normal methods. There does not appear to be a dot or notch in the package and even with my big magnifier I cannot read the writing. So, what I have done is use my meter on diode test mode and with the red lead on (assumed Vss) pin 2 I get a forward voltage on all the port pins of around 0.5V. With the black lead on pin 5 (Vdd) I get a reading on all port pins except MCLR. I have therefore concluded that I have indeed identified pin 1.

However, this is obviously not the way it's done and I suspect that the way they are arranged in the packaging would identify pin 1. So, what is the normal way to identify pin 1 on an SOT-23 device?

Mike.

Hi Mike,
Is this any help.

EDIT:
Found this, the pins are not symmetrical from the ends of ic.

Pommie · 30th August 2008, 02:09 PM

Hi Eric,

Thanks for trying but unfortunately the 10f200s have all six pins present and so are perfectly symmetrical. I guess from your diagram that the code would be SOT-23-6.

Mike.

ericgibbs · 30th August 2008, 02:14 PM

Quote:

Originally Posted by Pommie

Hi Eric,

Thanks for trying but unfortunately the 10f200s have all six pins present and so are perfectly symmetrical. I guess from your diagram that the code would be SOT-23-6.

Mike.

hi,
Look at my edit.

Pommie · 30th August 2008, 03:41 PM

I think that is just the way it's been drawn in the datasheet. If you look at the actual dimensioned drawing around page 83 they are actually symmetrical.

Having now worked out the full ident is SOT-23-6 I found this which suggest the package is the key. I can't however work out which side of the packaging I'm looking at.

Mike.

ericgibbs · 30th August 2008, 03:46 PM

Quote:

Originally Posted by Pommie

I think that is just the way it's been drawn in the datasheet. If you look at the actual dimensioned drawing around page 83 they are actually symmetrical.

Having now worked out the full ident is SOT-23-6 I found this which suggest the package is the key. I can't however work out which side of the packaging I'm looking at.

Mike.

hi,
As you say it looks as though the 'tape dispenser' is the key to the orientation.

Thats a bummer.

ericgibbs · 30th August 2008, 04:19 PM

hi Mike,
Been searching around, all I can find is a reference to a laser mark near pin #1.

mvs sarma · 30th August 2008, 07:55 PM

this is what i found on Microchip DS41239A of 2004 and 10f200 datasheet page 78.
I found the lettering style also on page 77, and obviously pin 1 is bottom left

eng1 · 31st August 2008, 07:37 AM

I used some devices of the PIC10F family in the SOT-23 package, mainly PIC10F202s and PIC10F222s. They are marked with a 4-character label as shown by the datasheets - as mentioned in previous posts. There is a very small dot printed below the label that identifies pin 1.

kjennejohn · 31st August 2008, 08:56 AM

Some SOT packages have a bevel on the pin 1 edge. That is, a bevel where the top surface meets the side. If you have this, hold the chip up with the top towards you, the bevel to your left, and pin 1 is the topmost pin on the left.

Hope that helps.
kenjj

Diver300 · 31st August 2008, 09:42 AM

I am surprised that the combined expertise here hasn't come up with the direct solution.

Connect a supply limited to a few mA and 5 V or less to pins 1 and 4. I know that you don't know which is which at the moment.

The power supply pins are pins 2 and 5. Vdd (pin5) will be the one that is more positive when the supply is connected to pins 1 and 4.

Why does that work? Well by choosing pins 1 and 4 we have two I/O lines that are clamped to Vdd and Vss with diodes. Section 12 of the data sheets says that there a clamp diodes and you mustn't put more than 20 mA through them.

That gives you a bridge rectifier, with GP0 and GP2 as the AC connections, Vdd as the +ve and Vss as the negative. The small current will be rectified and will appear on Vdd and Vss.

hantto · 31st August 2008, 10:22 AM

It's small, but it can be seen. (bad camera)

mvs sarma · 31st August 2008, 11:38 AM

Quote:

Originally Posted by hantto

It's small, but it can be seen. (bad camera)

please see whether the dot is not the one marked with yellow line, just above pin1

Pommie · 31st August 2008, 12:10 PM

Believe me, the dot is not there or (quite likely) my eyesight can't see it. I have a 4" diameter desk magnifier with circular fluorescent and I can't see any dot or read any numbers.

Tomorrow I will take a picture.

Mike.

ericgibbs · 31st August 2008, 12:26 PM

Quote:

Originally Posted by Diver300

I am surprised that the combined expertise here hasn't come up with the direct solution.

Hi Diver,
As I read Mikes first post, he had already done that.

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30th August 2008, 02:01 PM	(permalink)
Pommie	How to identify pin 1 on SOT-23 I have some 10f200s in SOT-23 and they are so tiny I cannot identify pin 1 by normal methods. There does not appear to be a dot or notch in the package and even with my big magnifier I cannot read the writing. So, what I have done is use my meter on diode test mode and with the red lead on (assumed Vss) pin 2 I get a forward voltage on all the port pins of around 0.5V. With the black lead on pin 5 (Vdd) I get a reading on all port pins except MCLR. I have therefore concluded that I have indeed identified pin 1. However, this is obviously not the way it's done and I suspect that the way they are arranged in the packaging would identify pin 1. So, what is the normal way to identify pin 1 on an SOT-23 device? Mike.

30th August 2008, 02:09 PM	(permalink)
Pommie	Hi Eric, Thanks for trying but unfortunately the 10f200s have all six pins present and so are perfectly symmetrical. I guess from your diagram that the code would be SOT-23-6. Mike.

30th August 2008, 03:41 PM	(permalink)
Pommie	I think that is just the way it's been drawn in the datasheet. If you look at the actual dimensioned drawing around page 83 they are actually symmetrical. Having now worked out the full ident is SOT-23-6 I found this which suggest the package is the key. I can't however work out which side of the packaging I'm looking at. Mike.

30th August 2008, 04:19 PM	(permalink)
ericgibbs	hi Mike, Been searching around, all I can find is a reference to a laser mark near pin #1. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

31st August 2008, 07:37 AM	(permalink)
eng1	I used some devices of the PIC10F family in the SOT-23 package, mainly PIC10F202s and PIC10F222s. They are marked with a 4-character label as shown by the datasheets - as mentioned in previous posts. There is a very small dot printed below the label that identifies pin 1. Last edited by eng1; 31st August 2008 at 07:38 AM.

31st August 2008, 08:56 AM	(permalink)
kjennejohn	Some SOT packages have a bevel on the pin 1 edge. That is, a bevel where the top surface meets the side. If you have this, hold the chip up with the top towards you, the bevel to your left, and pin 1 is the topmost pin on the left. Hope that helps. kenjj

31st August 2008, 09:42 AM	(permalink)
Diver300	I am surprised that the combined expertise here hasn't come up with the direct solution. Connect a supply limited to a few mA and 5 V or less to pins 1 and 4. I know that you don't know which is which at the moment. The power supply pins are pins 2 and 5. Vdd (pin5) will be the one that is more positive when the supply is connected to pins 1 and 4. Why does that work? Well by choosing pins 1 and 4 we have two I/O lines that are clamped to Vdd and Vss with diodes. Section 12 of the data sheets says that there a clamp diodes and you mustn't put more than 20 mA through them. That gives you a bridge rectifier, with GP0 and GP2 as the AC connections, Vdd as the +ve and Vss as the negative. The small current will be rectified and will appear on Vdd and Vss.

31st August 2008, 12:10 PM	(permalink)
Pommie	Believe me, the dot is not there or (quite likely) my eyesight can't see it. I have a 4" diameter desk magnifier with circular fluorescent and I can't see any dot or read any numbers. Tomorrow I will take a picture. Mike.