Something for Joerg, maybe

Wow, that 'typical application' internal schematic is a new low for LTC. What is it, germanium?

Cheers,

Phil Hobbs

Don't have a clue (quite normal).

martin

Thanks, but rather not. Quote "Using series resistance between the power supply and the input of the LT3085 also stabilizes the application. As little as 0.1? to 0.5?, often less, is all that is needed to provide damping in the circuit. If the extra impedance between the power supply and the input is unacceptable, placing the resistors in series with the capacitors will provide damping to prevent the LC resonance from causing full-blown oscillation."

That sounds quite technical :)

martin

I had to try

One day they will make one that you like :)

martin

What's the bet they have a patent pending? :->

Dave.

You don't believe the NPN output transistor symbol?

John

Maybe. But then it should not cost $2 and show zero stock at Digikey ;-)

Possibly someone should teach the movers and shaker in the semi biz to hit the ground running and not come out of the gate too slow.

NPNs are too liberal ...

Bipolar weenies!

John

Can't make the claimed head-room that way ;-)

...Jim Thompson

It can if you pull the base high enough. Which they do.

John

My bad! Didn't read close enough. You _could_ use a charge pump to accomplish such a task.

...Jim Thompson

Ask CA politicians, they'll tell you how to do it without. Well, at least up to now :-(

Charge pumps are so easy to do... I've even utilized them in hearing aids (for the MEMS microphone) and hot-plug circuits.. Could give you LDO without the stability issues, though I'm not sure how well they could respond to transient loads.

...Jim Thompson

LTC.

We recently "invented" the flying-capacitor "isolated" DC power supply, using 300 volt SSRs in a DPDT configuration. They switch slow enough that the spike situation should be pretty good, compared to most dc/dc converters. And no transformers!

It's about time for somebody to make a small laser/pv package as a very quiet isolated power supply.

John

LTC.

I do things that you discrete guys can't easily do... non-overlapping switches at _every_ stage so that I get phenomenal efficiencies... very important in a hearing aid. Of course having VT=0.45V helps a bunch too ;-)

...Jim Thompson

LTC.

Have you seen Jim Williams AN-70 "A Monolithic Switching Regulator with 100uV Output Noise"? He also trades switching speed (and a bit of efficiency) for low noise.

LTC.

I bet you can't plop a 47 uF low-esr polymer aluminum cap inside one of your ICs. Or optoisolate a switch drive!

Most opto ssr's are break-before-make (slow on, faster off) so a non-overlapping flying cap isolator is easy with just any ole square wave drive, 1 kHz ballpark.

John