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Title: IC Identification and questions about 74 series logic Post by: Foster on March 04, 2009, 05:28:05 AM ID this IC, it is a 6 pin DIP
lettering on the IC: IL2 W0105H I am thinking optical isolation of some sort. Is the N at the End of the 74 series part number important? EX: 74F07N Title: Re: IC Identification and questions about 74 series logic Post by: KirkLasVegas on March 04, 2009, 12:02:41 PM I would suspect that those numbers are what we called "House numbering". Large customers could get their order of chips labeled anyway they wanted.
6 pin dips were usually an opto-isolater, you might want to remove it from the board and look on the underside of the chip, *sometimes* they have the generic numbers there. Kirk in Las Vegas Title: Re: IC Identification and questions about 74 series logic Post by: Foster on March 04, 2009, 09:23:19 PM Also I am looking for simple schematic software.
I dont need to test the design in software. I am trying to create a schematic from an existing board thats works corectly. The only unknowns will be the various caps on the board. I am not even sure of the type of cap they are no electrolytics. Title: Re: IC Identification and questions about 74 series logic Post by: KirkLasVegas on March 04, 2009, 09:53:15 PM Also I am looking for simple schematic software. I dont need to test the design in software. I am trying to create a schematic from an existing board thats works corectly. The only unknowns will be the various caps on the board. I am not even sure of the type of cap they are no electrolytics. You will find that in 74 type TTL logic that most of the caps are power supply bypass. usually a .01Mfd to a .1Mfd. The value is not critical. other caps you will find are clock timing caps and audio coupling caps.They usually are placed close to the chip and by the power supply rails. These .01 and.1Mfd caps are ceramics and usually NEVER fail. Power supply caps are usually electrolytic and have a "-20/+80" allowance. In other words you can make them 20% smaller or 80% larger and still get the designed results. If it is indeed a "opto" look for a ridge on top of the casing.inside the opto is a LED and a photo-transistor. on a ohm-meter the LED will show a 0.7volt drop when biased. The transistor will look open from emitter/collector. Some of them do indeed have a base lead to the device. They were used a LOT in games to isolate the front door from the MPU/IO boards. Hope this helps... Kirk Title: Re: IC Identification and questions about 74 series logic Post by: Op-Bell on March 04, 2009, 09:57:51 PM IL2, optocoupler, Vishay.
http://www.vishay.com/optocouplers/list/product-83612/ (http://www.vishay.com/optocouplers/list/product-83612/) Title: Re: IC Identification and questions about 74 series logic Post by: Op-Bell on March 04, 2009, 10:19:41 PM Most good schematic capture software is $$$. By good I mean with adequate library support, so you can (for example) call up a 74LS191 and just drop it in. With less-good software, you can spend an awful lot of time drawing each part in the library yourself.
Go a search for schematic capture free; you get a few hits. But beware, most of them aren't really free. For $0 you get a working package, but limited in the number of pins or connections. 200 pins sounds like it will go a long way, but it only covers a few square inches in practice. Here's a really free one, but I haven't tried it - http://tinycad.sourceforge.net/ (http://tinycad.sourceforge.net/) For unlimited complexity, logic circuits only, you could try the FPGA design software like Xilinx - http://www.xilinx.com/ise/logic_design_prod/index.htm (http://www.xilinx.com/ise/logic_design_prod/index.htm) This is for designing chips, not PCBs, but it turns out you can design chips just like PCBs, by dropping standard 74 series logic blocks into the diagram. And these tools are well supported with parts libraries. Not so long ago you had to pay $10k+ for this design software, but now it's a free download. You just have to register to download and suffer having salesmen call you occasionally, but it's no biggie, they don't mind that you're using their software but not buying their chips. Title: Re: IC Identification and questions about 74 series logic Post by: Op-Bell on March 04, 2009, 10:24:03 PM And finally... The 'N' at the end of 7400 numbers is the package code. N means "dual in line" for Texas Instruments. W would be a surface mount of some kind. Codes are different for different manufacturers but N usually means the same thing.
Title: Re: IC Identification and questions about 74 series logic Post by: Foster on March 04, 2009, 10:42:11 PM Thanks Op Bell
Can I substitute a 74LSxx series for a 74Fxx or 74HCxx or 74Nxx series or are the 74LS too slow? Just to get the design done I will probably do the simple schematic version first then use a program that shows the various gates as well. For those that want to know how it works Title: Re: IC Identification and questions about 74 series logic Post by: Op-Bell on March 04, 2009, 11:18:19 PM Can I substitute a 74LSxx series for a 74Fxx or 74HCxx or 74Nxx series or are the 74LS too slow? You have to do some work to determine that. 74LS has typical propagation delay of 10ns, max 20ns. HC is about the same. F series is 2ns typical, 5ns max, so it's significantly faster. Most people wouldn't use an F if they could avoid it, as they take a lot of power and run hot. These days the AHC series is a better choice - cool running CMOS and 3ns propagation delay. You have to analyze the logic to determine whether the speed is important. Often it's not, it's the higher fanout that counts (drives more inputs). I rebuilt an old TTL design recently using HC and AHC CMOS and it staggered me how much faster it was than the original. I could clock it at twice the speed and (it has a video output) get four complete copies of the screen showing at the same time, in a 2x2 square. I had to put extra clocked latches in here and there to slow it down. |