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I have been looking about (on the web and printed catalogs) attempting to replace a part that is now discontinued.

The experience has been part success - and part failure. A part is available to use if I update a board design to use a different package - but not a drop in replacement.

And so, I inquire - what is a the process or technique individuals in the electrical engineering field apply when they must replace/update a part/design with either of the following criteria:

  1. Equivalent replacement (you want to keep the same design or minimize changes to that design, e.g.; a discontinued part burned out - drop-in replacement).
  2. Complete redesign (you have a design that uses older parts - thru-hole components, etc - and you want to update that design with smd parts, but some of your old parts are discontinued and no obvious replacement part is available).

For reference, the part I am looking into is the M54564P/FP - I am thinking the A2982 is a good candidate - but it requires updating my board design and so, not a drop-in replacement. Any tips?

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  • \$\begingroup\$ I'll put this here - since I do not want to add this as an answer; For point 2 - I have been finding a few ways to narrow parts down: In general - you will, more than likely, already know what you want that part to do - so when searching distributors and you come across a potential part - take the manufacturer's part number and search their database - e.g.: TI will sometimes recommend an improved part for your design if you wish. Now you have two parts to consider. For example: An ULN2003A can be replaced with a TPL7407L - pin by pin. \$\endgroup\$ – avluis Aug 6 '15 at 9:36
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I'll tackle point 1 with your specific use case in mind: a solution could be to design a small daughterboard on which to fit the new part with possible ancillary components. That little board would have two strips of pin headers dimensioned in the right way to be plugged in the socket of the old part. If the old part is not socketed, careful desoldering would be done and the header from the daughterboard soldered in their place.

Of course this assumes that:

  1. there is enough space once the old part is removed; but in your case since the new part is SMD you have some headroom, especially if the daugherboard has 4 layers, so that routing the new part pins to connect to the old part's holes would be easier.

  2. parasitics are not a problem because you keep the operating frequency sufficiently low. The daughterboard will introduce more stray capacitance and inductance relative to a setup where the part is soldered in the right place.

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  • \$\begingroup\$ That's actually a pretty good idea - I have been seeing parts like these more often as well. \$\endgroup\$ – avluis Aug 3 '15 at 9:44
  • \$\begingroup\$ Yep, but keep in mind that those are adapters for breadboards, so they don't help you reroute pins. The new part could have a very different pinout (I didn't check the datasheet thoroughly), so it may be that you have to design a custom one. But since they are transistor arrays, this shouldn't be terribly difficult (probably a simple 2 layer board could do). \$\endgroup\$ – Lorenzo Donati -- Codidact.com Aug 3 '15 at 9:48
  • \$\begingroup\$ Thanks for bringing that up as well - completely missed that if the part is not pin compatible, then a daughterboard is a must. \$\endgroup\$ – avluis Aug 3 '15 at 9:50

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