Is there a cheaper TLV431/LMV431?

Few hundred nanoseconds = Dreamer ;-)

You sure do get into CHEAP don't you ?:-)

...Jim Thompson

You must be working for a toy company. They are the only ones I know that care about this kind of niggling cost savings!

Luhan

Sheesh, Hope I never need some "medical electronics" now I know what depths they sink too :-)

martin

Hello Jim,

The TLV431 can pull that off. Look at figures 15 and 16:

At low currents you'll have to give it a little "capacitive english" to get results similar to figure 16.

Hafta, sometimes :-)

Hello Martin,

It was just a general question because I and others run into that a lot. But hey, when you design disposable stuff you have to turn every penny around. After all, it helps keeping a lid on otherwise run-away health care premiums.

A lot of things in med must be disposable. You can't use something like a catheter on the next guy. Then there are the consumer disposables (non-prescription stuff). For regular users it makes a difference whether they pay $9.99 or $10.99 every time. Especially for folks on fixed incomes.

Hello Luhan,

No, disposables mostly. But I would love to design toys.

I have designed a lot of industrial equipment - they only care about how soon it gets done.

I have designed for medical equipment companies - they just dont want unecessary liablility.

I have designed for the toy industry - they are crazy.

Luhan

Are there any transistor pairs or arrays (like the 3046) that are cheap enough to build a bandgap reference? Can you use your BAV99 and calibrate when you do board test?

Hello Luhan,

My clients usually care more about how reliable it is going to be and that preferably nothing will be going obsolete in the next decade. This means you must use low cost mainstream parts. The other parts usually don't live 20 years or more. So, none of those hooty panacea chips here.

I have seen that. However, companies that do not push the envelope typically don't live very long. Except for very large ones but they only keep being a player by regularly buying smaller companies in each segment. Meaning companies that did push the envelope.

If you don't design smarter stuff or lower cost than the competition the competition will have you for lunch. Latest at the next big trade show. Med can be a dog-eat-dog world.

Nah, they are fun. We can learn a lot there.

Anyway, one of my consulting trademarks is that the clients know they'll get close to the best possible deal when the design is done. I won't use a FET where a BJT for three cents less would do. Unless they tell me it's not too important and need it all as fast as possible.

CA3046-BandGap.pdf on the S.E.D/Schematics page of my website, can be scaled way down in current.

...Jim Thompson

Luhan skrev:

Well - we produce pumps and we care about each and every cent (> 1mill quantity/year)

The KA431 is cheaper (beware of the TL1431 which we have had plenty trouble with - prone to oscillations)

Regards

Klaus

Hello Tim,

These became expensive. Digikey wants several Dollars for the 3046 now, guess it's going lalaland. Plus I was looking for something small, SOT23 or so.

Calibration is possible but iffy because cheap uCs normally don't have any temp logging on board. The >1$ versions often do and then it's easy. But most of those have a nice bandgap reference on chip anyway.

It doesn't have to be 1.24V. It just has to be below 2V or so to accomodate the typical two-cell design that must be allowed to function down to less than 2.5V.

Hello Klaus,

Alright, that's my kind of design environment.

It's 2.5V and requires at least 1mA of cathode current. Be careful with these. IIRC Fairchild has rung the obsolescence bell on them.

You could consider a bandgap made using a dual nonmatched transistor (the typical Vbe matching is actually pretty good, IIRC) but there are no guarantees except thermal tracking. Future book price for Rohm UMX3NTR is 3.6 cents in quantity 10 (reels, that is).

Best regards, Spehro Pefhany

What's the story on those KA parts anyway? Was Fairchild just brand-naming them?

Best regards, Spehro Pefhany

Hello Spehro,

Don't know but some of the SOIC seem to remain in production. Also the LM431 in SOT23. Lots of brands of the 431 can be had for around 5c at every street corner. But the guys using TO92 need to probably watch it.

For low power designs there is hardly any way around the TLV/LMV versions and for some reasons those did not enjoy the bargain pricing that they bigger brethren reached. Maybe because the non-economy version is just fine for PC power supplies and thus sells more.

Hello Spehro,

Nice price, although with three resistors you'd be back above 5c. But maybe less than a TLV.

Is the LM10 still being made?

...Jim Thompson

Hello Jim,

Yes, even ROHS compliant versions. But over $1 :-(

You can buy them at Digikey if you need a few.