CMOS 4000 series obsolescence
CMOS 4000 series obsolescence
(OP)
I am designing a small digital control circuit using CMOS electronics. The circuit will be used in a consumer product and will be manufactured in quantity of about 10,000 per year. I had originally selected the CD4000 series, then an associate told me that this series is headed for obsolescence in the not-too-distant future, and the 74HC series would be a better choice. I found a couple of items on the Internet that support this statement, but when I check availability from distributors, the CD4000 series is more widely available and considerably less expensive.
The devices I'm considering are:
CD4017, 74HC4017 Johnson decade counters
CD4029, 74HC161 4-bit binary counters
CD4093, 74HC132 quad 2-input NAND gates with Schmitt trigger inputs
CD4585, 74HC85 4-bit magnitude comparators
All distributors I've checked have ALL the 4000 series devices - mostly at dirt cheap prices. I haven't found any one distributor that stocks all the 74HC series devices, and the 74HC series devices I have found cost two or three times as much as the corresponding 4000 series devices.
Manufacturers have not been helpful - they won't give generalizations about an entire series. They will only look up status of individual devices. Texas Instruments tech support says most of the 4000 series devices I'm considering are in full production and recommended for new designs, and some of the 74HC devices I'm considering are "made to order" only.
Can anyone provide a bit of an overview on this issue?
The devices I'm considering are:
CD4017, 74HC4017 Johnson decade counters
CD4029, 74HC161 4-bit binary counters
CD4093, 74HC132 quad 2-input NAND gates with Schmitt trigger inputs
CD4585, 74HC85 4-bit magnitude comparators
All distributors I've checked have ALL the 4000 series devices - mostly at dirt cheap prices. I haven't found any one distributor that stocks all the 74HC series devices, and the 74HC series devices I have found cost two or three times as much as the corresponding 4000 series devices.
Manufacturers have not been helpful - they won't give generalizations about an entire series. They will only look up status of individual devices. Texas Instruments tech support says most of the 4000 series devices I'm considering are in full production and recommended for new designs, and some of the 74HC devices I'm considering are "made to order" only.
Can anyone provide a bit of an overview on this issue?





RE: CMOS 4000 series obsolescence
You have several choices, among them:
> make a lifetime buy now - but have the attendant sunk cost up front
> use the most common and available parts and do nothing until the suppliers ask for lifetime buys
> consider alternate designs that can eliminate these components altogether. 4000 series seems hardly compatible with surface mount that usually required to keep commercial costs down. Are there no other parts such as processors or FPGA's that could incorporate these functions?
TTFN
RE: CMOS 4000 series obsolescence
RE: CMOS 4000 series obsolescence
--
Mike Kirschner
Design Chain Associates, LLC
http://www.designchainassociates.com
RE: CMOS 4000 series obsolescence
I have one product I made in the 70's that used a 1K EPROM. This is all the memory I need. However, today, that is the one part I can no longer buy. I can still buy all the 40000 series logic, I can still buy the op-amps, the 555 and all the passives. I just can't buy the EPROM. Same for all the programmable logic from back then.
4000 series - If it will do the job, go for it.
RE: CMOS 4000 series obsolescence
I recently opened-up my new laptop and found a few 4000 parts - aparently within the battery monitoring circuit.
I would predict the factor that will most likely determine a problem in getting 4000 series parts would be a fast recovery from a recession, and a resulting capacity crunch on semiconductor lines which would displace lower-margin/volume parts such as 4000 devices. In such cases, sourcing the parts may require going to Korean or other far-east semi vendors.
RE: CMOS 4000 series obsolescence
Comcokid makes a great point; once demand exceeds supply these low-margin parts are always the first to go on allocation because wafer, package assembly, and test capacity go to product that has higher margin. When the economy turns expect demand to exceed supply faster than it ever has because this recession has resulted in the dismantling of lots of capacity.
Look at other, more recent logic families if you insist on designing with individual gate-level logic devices and stick to the basics.
--
Mike Kirschner
Design Chain Associates, LLC
http://www.designchainassociates.com
RE: CMOS 4000 series obsolescence
When I worked in the semiconductor industry, we made some metal-gate PMOS devices when the industry was already going to 74FC parts. We subcontracted the wafer fab, test, packaging, etc. The only thing that we did was to put our logo on the parts. We still had a 75% net margin. When we needed more operating margin, we increased the prices or forced last-time buys.
The moral is that you can design with 4000 series parts, but be prepared to pay premium prices relative to the identical function in another technology and be prepared to redesign.
TTFN
RE: CMOS 4000 series obsolescence
As for the 4000 series, these are made by so many different cmpanies, they seem to be the bedrock of semiconductor logic. There have been no changes to speak of in the devices for 2o years and no forseeable changes in the future. They are the B-52 of logic. Built right in the first place and like the B-52 where the grand children of the early crews are flying them now, it is likely our grand children will be designing with the 4000 series.
RE: CMOS 4000 series obsolescence
It is the only standard logic family that can work with power supply voltages up to 18V! All of the others use supply voltages at or below 5V.
So my experience is that if you need the higher supply (and increased noise margins) then the '4000 family can be used, but if you have a system at or below 5V supply, you can protect against possible obsolescence by using a different logic family.
As an aside, I have always found the HEF4xxx parts (originally from Philips and RCA) have more "bullet-proof" front ends than the CD4xxx parts. That is, they are better protected against stray noise spikes. This was very important when I designed equipment for industrial control, as was the increased noise margin when running +15V instead of +5V supply.
RE: CMOS 4000 series obsolescence
--
Mike Kirschner
Design Chain Associates, LLC
http://www.designchainassociates.com
RE: CMOS 4000 series obsolescence
If you can use 5 volts, go to the 74HC series. If you must use the 4000 series, check with the manufacturers of the part to see if it is on phase-out status. Just because it is on the shelf at Digikey and Allied or other distributors does not mean it will be available by the time you get well into production.
RE: CMOS 4000 series obsolescence
Are you going to have other components, too, on the PC board ? Analog ?
<nbucska@pcperipherals.com>
RE: CMOS 4000 series obsolescence
Also, one of the other attractive aspects of 4000 cmos is its essentially ZERO power dissipation when it is not switching. Whether the output level is high or low, as long as you are not attempting to switch the devices at too high a speed (>50 kHz) the power dissipation is miniscule. In fact, you have to be careful to disconnect any powered inputs to a package when the supply is shut off as the powered input can feed a voltage into the gate, up through the input protection diode and out the Vcc supply pin to the rest of your design. The first time this happened to me (1970's) I thought I had invented perpetual energy as I couldn't figure out why my circuit was still working with the power supply turned off!! LOL
In summary, I have been hearing the call of death for 4000 cmos since the 1980's by our own Material Engineering staff. I am sad to say that in these decades of downsizing that the support engineers that warned me against designing with 4000 cmos have been made obsolete by our company while we continue to buy, build and sell equipment into the medical marketplace with the devices. The average lifetime of our products are 10-15 years. And yes, we will continue to soure the very cost effective, readily available 4000 cmos gates.
RE: CMOS 4000 series obsolescence
Mike
--
Mike Kirschner
Design Chain Associates, LLC
http://www.designchainassociates.com