Checked a few micro-power shunt references this morning. The ROHS compliant versions of the LM385 were called "mature" on the Arrow web site and that word always makes my neck hairs stand up. Could this mean it's headed for lalaland? If so, which micro-power shunt refs are engineers using instead these days? The TLV431 is kind of out in my case, too much cathode current.
-- Regards, Joerg http://www.analogconsultants.com
Digikey has 0.6uA listed for the cathode current for digi#296-18865-1-ND it's a TL431BCDBR Or just type in TL431 as a keyword..Looks like there's versions that need an idle Ic up to 1mA..
Also..as an alternative...I think I saw a micropower op amp with a built in reference IC that can be turned into a shunt reg.. Can't remember the IC #... But I recall finding similar IC's that had a flea power op amp but then the fk'n build in reference was just a hog.
I just took a quick peek at this voltage reference ISL60002.. It's not a shunt reg... just a Vref that draws 400nA... Take it as a clue that there's gotta be something much "lighter" than the TL431. Maybe make a shunt reg with a flea reference + flea op amp + mosfet?
D from BC
A lot of the info in those tables isn't correct. The lowest cathode current version of the 431 I have ever seen is 50uA. But down there the selection of vendors shrinks and it consequently begins to become expensive, meaning >15c. The run-of-the-mills TL431 varieties are between 400uA and 1mA min.
There are some boutique chips like that. Unfortunately they also carry boutique price tags :-(
-- Regards, Joerg http://www.analogconsultants.com
I use LM4040, but its 60 uA min vs the 10-20u of your 385. The SC70 package is nice, though .
National's site shows 385 in full production for all its variants, maybe its not doomed...
Steve
Yup..that ISL60002 is about $8.00CAD!!! But I mentioned it as a benchmark example.
Is anyone going to tell Digikey than the TL431 tables are wrong??? They should have a reward program where customers get a credit for reporting errors.. A free bag of flea power shunt regulators for every reported error! :)
D from BC
The LM385 is a "High Side Adjustable Current Reference" vs. the TL431 family which has a low side reference. Is there any other HSACRs with low Ik beside the LM385 in a SMD? The LM385 do not come in SMD so they probably will be phased out. Regards, Harry
-- National\'s web site says all versions are in full production, TI\'s says they\'re active, and ON semi has zillions of \'em so probably not to worry for a while.
It does come in SOT-23 and also TSSOP. LM385M3X-1.2 would be the SOT-23 version from National, for example.
-- Regards, Joerg http://www.analogconsultants.com
Yes, they list them as active. I am just wondering why Arrow calls them "mature". Usually that isn't a good sign. Also, I've had instances in the past, like with a log amp chip, where there was full production indication and then suddenly poof. As if someone had turned the lights off. The purchasing manager came down the hallway, all red in the face.
I have used the LM4040 on the design that I am wrapping up right now but on this next one 60uA would be too much. That low power requirement bites everywhere. For example, I'd really like to use a chunk of a LP339 as a linear amp but there isn't much info around to calculate the loop stabilization. Just hanging 1uF at the output is kind of crude and won't work here anyway.
-- Regards, Joerg http://www.analogconsultants.com
Why doesn't the adjustable version come in SOT-23?
robert
Joerg, Where did you find the adjustable LM385 in a SOT-23 pack??
The adjustable only comes in SOIC, AFAIK. That would be LM385BM. Digikey has some but they are kind of pricey.
-- Regards, Joerg http://www.analogconsultants.com
No idea. Maybe the die area is too large but I can't really imagine that on a 20uA device. It does come in SOIC though.
-- Regards, Joerg http://www.analogconsultants.com
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