Source for low current zener in China?

Well, Joerg, it looks like you are in a pickle! You mention low zener currents and a tolerance problem. Those two don't generally go well together with zener diodes, which are commonly specified at 20mA. One thing working in your favor, zener diodes in the 5- to 6-volt region have a pretty low zener impedance, which is another way of saying their breakdown voltage doesn't change much with current.

But you are having trouble with zeners voltage rated at 50uA, when used at 200uA. Whew! Just how tight is your spec?

In such a situation, with cheap parts like these, I'd acquire a reel or more and measure a few parts, before throwing the rest into the manufacturing ring. Newark has 15k in stock, $0.045.

How expensive are the CMOS equivalents of the venerable TL431?

...Jim Thompson

Central Semi has a few lines of low current spec zeners.

Hello Win,

Not very tight. The cut-off at end test is 5.1V which is well below the data sheet tolerance band and that band was stated for 50uA. So something seems to be wrong with the lot. I have two inquiries pending. One about whether there is an epidemic problem or whether we can scrounge reels from other places. Or find out which lots would be ok. The other into Vishay which makes almost the same part but where there is a data sheet discrepancy. Figure 7 in there shows the distinct reel or more and measure a few parts, before throwing the rest

Yes, that's what we are doing in parallel.

Hello Jim,

Did that on another design for that client. You have to use the TLV431 because of the low cathode current, plus it adds a couple resistors so it's increasing the cost by a few cents. But on this legacy design from before my time with them they chose to keep the zeners. Which were fine for many years but now they seem to be out of spec, big time. Just baffles me how they could have passed QC in the first place.

Hello Robert,

Yes, they do. CMHZ4626, but non-stock everywhere I checked. I found some others as well but lead times are as high as 18wks and we need them pretty much right now :-(

Hello Spehro,

Could be. However, this manufacturing plant is very professional in their purchasing and I've got photos of the reels. Looks like the normal stuff from ON's Malaysia plant.

Hello Spehro,

I checked the usual suspects but only found SOT23 and other (newer) types of packages. This is a legacy design.

There are some Japanese parts that should be quite available in China, and are spec'd around 3% at 500uA, so they should be pretty tight at

Best regards, Spehro Pefhany

Could be a result of counterfeit parts.

Best regards, Spehro Pefhany

Hello Spehro,

That would be a problem since this is automated assembly. I really was hoping I had an answer from some of the mfgs by now but it seems the care for existing customers (with substantial sales volume) isn't what it used to be. Where are the good old days when it was still Motorola?

There are some in 0.8 x 2.1mm size, but I doubt the leads would reach to your pads.

Best regards, Spehro Pefhany

"Joerg" schreef in bericht news:UNeSg.12213$ snipped-for-privacy@newssvr14.news.prodigy.com...

No care for the existing and substantial customers, no care for the new and small customers... the world is coming to an end.

The bottom line of the delay you experience is that they don't have a solution for you. A "Yes-no problem" answer always arrives quick. For that "No-we're sorry" answer, you always have to wait a bit longer.

Do we have a plan B ?

Hello Frank,

Yes, working on plan B, plan C and plan D :-)

Plan B: CentralSemi has stock of their CMHZ series but the data sheet isn't detailed enough. However, they promised to have an answer this afternoon from Engineering with more data. What the "big players" have to realize is that, typically, after plans B, C and/or D work out the plug gets pulled on them. One of them in your country doesn't even know how much biz they have lost. Water under the bridge though because now they've auctioned most of it off.

"Joerg" schreef in bericht news:kCfSg.12781$ snipped-for-privacy@newssvr14.news.prodigy.com...

I hope plan D are two tickets to Hawaii.

They couldn't care less. Suppliers experiment with their level of service, we search for the cheapest ones around until we get bitten, and hop from one to another after too much frustration. I don't think it will change things a bit.

But then there's always plan D ;)

Hello Frank,

No, it's a blender full of margarita, heavy on the Tequila :-)

Not really, although the pricing has to click, of course. The where many, many times where I found "the" perfect part at Philips or Infineon only to find out that I couldn't get any here in the US. US companies are usually better although TI recently lost a design-in because they failed (after a couple reminders) to furnish more data on the 16bit ADC in the MSP430F2013. I did what I knew would work, designed the whole chebang analog again. Like usual. Once a design is done, it's done. IOW a finished and signed ECO is like a hardened batch of cement. You can't really move it anymore.

About six hours from now it'll be off to plan D...

A quick search of Diodes Incorporated turned up their DDZ9690-7, which seems to be in stock at Digi-Key and Mouser.

Then get a sample of the same part withthe higher current spec and check on the curvetracer. Maybe you will get lucky and find the high current part behaves at the low end. Some parts get a different partnumber if pass into a different bin.

Hello Tony,

Yes, but in the breakdown graphs (fig 4) they have left out that one type, the 9690. Interpolating between the 9688 and 9692 it looks like it becomes rather mushy around 200uA, and even more so at the rated 50uA current level. It doesn't look like a true low current zener.