Finding an IC chip

  • #1
309
1
I'm designing a simple little circuit board for prototyping purposes (a byte displayer using a pair of 7 segment displays).

Problem is, I can't find a binary->7-segment hex decoder still being made anywhere. I found a couple leads on Google, but Digikey and Mouser showed them as discontinued. I'd prefer a small SMD package (SOIC or TSSOP), since I''d like the board to be as small as possible.

If not, I'm willing to program an http://ca.mouser.com/ProductDetail/Atmel/ATF16LV8C-10XU/?qs=sGAEpiMZZMvwLjDpJZyitOLIDNjXIEtrQxy19NCE7eA%3d" [Broken] to do the job. I have access to a programmer and WinCUPL software, but it only fits DIP packages. How do you program an SOIC or TSSOP without some expensive $85 adapter socket?
 
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Answers and Replies

  • #2
555
9
You could do it in random logic. It doesn't require that many gates.
 
  • #3
309
1
You mean with 7400s, '04s, and whatever?

Unless I did my k-maps wrong or there's some technique I don't know, I'd need 7 OR gates with 3-4 inputs each, and 20 at least 20 AND games with 3-4 inputs each. with the smallest chip size possible, that's a lot of board space with a lot of traces running around. And it's be hell to solder.

And that's just with DCBA inputs; I'm not counting RBI, LT, or CE because I don't really care about those for this application.

Why the hell are the programmers so expensive? I can hardly find any for <$100.

A Parallel in/out EEPROM would work, as log as it wasn't much bigger than necessary (16x8 is all that's needed), cheap enough, easy to program without fancy parts.
 
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  • #4
129
0
small microcontroller?
 
  • #5
863
4
@ Digikey:
296-2079-5-ND
296-3528-1-ND
568-3125-5-ND

All of these are under a dollar, in stock, and have a minimum quantity of 1. Digikey has tons of them - try a search for "BCD-7".
 
  • #6
555
9
You mean with 7400s, '04s, and whatever?

Unless I did my k-maps wrong or there's some technique I don't know, I'd need 7 OR gates with 3-4 inputs each, and 20 at least 20 AND games with 3-4 inputs each. with the smallest chip size possible, that's a lot of board space with a lot of traces running around. And it's be hell to solder.

And that's just with DCBA inputs; I'm not counting RBI, LT, or CE because I don't really care about those for this application.

Why the hell are the programmers so expensive? I can hardly find any for <$100.

A Parallel in/out EEPROM would work, as log as it wasn't much bigger than necessary (16x8 is all that's needed), cheap enough, easy to program without fancy parts.

Or try this:

http://cgi.ebay.com/1-pc-74LS47-BCD-7-Segment-Decoder-DIP-16-pin-IC-/170467158261
 
  • #7
309
1
@ Digikey:
296-2079-5-ND
296-3528-1-ND
568-3125-5-ND

All of these are under a dollar, in stock, and have a minimum quantity of 1. Digikey has tons of them - try a search for "BCD-7".

I already found (and bookmarked) several BCD->7-segment decoders. I've had no trouble finding several different kinds of those. I'm looking for a Hexadecimal->7 segment decoder. I can't find that anywhere.
 
  • #10
555
9
I'm trying to get the haxadecimal to display on one 7-segment, not two. That solution doesn't help.

I think you're misunderstanding me. The circuit in that .gif converts a nybble to BCD. Use two of them to convert your byte. Then concatenate the outputs and send to the BCD-to-7-segment display driver.
 
  • #11
309
1
I think you're misunderstanding me. The circuit in that .gif converts a nybble to BCD. Use two of them to convert your byte. Then concatenate the outputs and send to the BCD-to-7-segment display driver.
At the moment, I'm not looking to convert binary to BCD, thought that's a good backup plan if I can't do what I'm trying to do.

I'm trying to get a display like this:
7-segments_Indicator.gif

And can't find a chip anywhere to do it.
 
  • #12
555
9
At the moment, I'm not looking to convert binary to BCD, thought that's a good backup plan if I can't do what I'm trying to do.

I'm trying to get a display like this:
7-segments_Indicator.gif

And can't find a chip anywhere to do it.

...and the simplest way to do that is a binary ripple counter driving a binary to BCD converter...
 
  • #13
309
1
...and the simplest way to do that is a binary ripple counter driving a binary to BCD converter...
I don't get it. Most of the BCD->7-segment decoders I've found show either gibberish or blanks for anything above 9. How does your scheme let me display A-F?
 
  • #14
555
9
I don't get it. Most of the BCD->7-segment decoders I've found show either gibberish or blanks for anything above 9. How does your scheme let me display A-F?

You may be right. I have only used one 7-segment display and we designed our own decoder (for a lab class) that accepted A-F.

You want the DM9368. It will do the job. There is one here:

http://cgi.ebay.com/DM9368N-Integrated-Circuit-x-1-pieces-DM9368-/150583168277

But you may be able to find it elsewhere, cheaper, if you do some digging.

Good luck.
 
  • #15
309
1
I believe that's one of the chips I came across that's discontinued. $30 is a ridiculous price for a chip as simple as this, and I don't really know where else to look.

For programming a surface-mount PLD, would getting a board like http://www.epboard.com/eproducts/protoadapter.htm" [Broken] and just pressing the IC onto it while it's in the programmer work in a pinch?
 
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  • #16
863
4
I agree, $30 is ridiculous. There are FPGAs that cost around $7 and microcontrollers less than $2. Good luck, sorry I could not be of more help.
 

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