NPN output design

LM317 - for 30V you probably want the LM317HV

and for 200mA probably the TO-220 packaged device. If you haven't got room for a big heat sink, you might need the TO-3 packaged version.

Hope this helps

-- Bill Sloman, Nijmegen

--- If you want to design it, then why do you want to buy it ready-made?

And why does it have to be NPN? Try this: (View in Courier)

+30V>----------+-------+ | | [R2] | | E +-----B PNP | C [R3] | | | C | IN>---[R1]---B NPN +--->OUT E | GND>-----------+----------->GND

-- JF

What are the exact requirements? So far, what you describe can be accomplished with 2 part worth less than 2 cents.

--
Yes, I understand, but from his "... able to supply
200mA (up to 30V)."  I took it to mean he was looking for something
able to source 200mA at up to 30V with TTLish input control.

If all he\'s looking for is and open collector sink to 0V, then of
course

                
                     ___ 
                C--->OUT
VIN>---[R1}---B
                E
                |
GND>------------+--->GND

will do.

Perhaps we\'ll find out if/when he posts back. ;)

Sure you're not thinking of the LM195, which is a mask variation of the ubiquitous LM117/317 circuit? But it's been sh*tcanned by National.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

John, it's probably an instrumentation/automation requirement- "NPN output" (implied open-collector) is one kind of standard for digital output, and a high-side driver as above won't work properly unless it's expecting a "PNP", since it will have a pull-up to some external supply voltage.

Of course one could use a n-channel MOSFET rather than an NPN transistor (but a Darlington or Sziklai pair might have too much drop).

If there is a requirement for short-circuit and/or reverse-voltage protection (perhaps implied by the "good/reliable" spec), and transient protection (so that the output could be used to drive a coil and still be "good/reliable)) OTOH, things might get a bit more interesting from a design POV. Also, we would have to consider the drive capability at the input and whether it should be inverted or not.

One way to short-circuit protect such an output would be to measure the Vce drop and remove the drive if it has not dropped to an acceptable value a short time after drive is applied, wait for a fairly long time, then rinse and repeat. An easier way would probably be a polyfuse (and a unidirectional TVS in either case to handle inductive loads) but it wouldn't allow easy fault indication and decent voltage polyfuses tend to be physically large.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

I prefer moving R3 to the NPN's emitter, creating a current-source drive for the PNP, with a defined current that's independent of the supply voltage.

Add one more transistor plus three resistors to implement a foldback current limit to protect the switch in the event of a short. Or simplify your life and use a high-side switch IC incorporating protection, like Infineon's "PROFET" bts409, in a 5-pin TO-220 package, only $2.39 at DigiKey.

?name=BTS409L1E3062AINCT-ND Or the bts611 dual, in stock at D-K, $2.77 each.

These PROFETs include n-channel mosfets, with the gates driven by a charge pump, and Ron = 0.2 ohms. They include a status output signal for faults. They're intended for use up to several amps.

For some reason I can't find either datasheet on Infineon's website, nor strangely, does DigiKey have them. They are current parts, according to their Oct 2006 Automotive Power selection guide. But I'd be happy to email one to anyone who asks.

Oops, I see Infineon just sent out EOL notices for my favorite TO-220 parts, with smt replacements suggested. Sorry, guys, you can't mount a clip-on heatsink on your new parts! Besides, we prototyping guys like leads on our parts! Anyway, folks, plenty are in stock at DigiKey, so get 'em while you can.

BTW, this nasty business of removing datasheets from websites as soon as they're EOL noticed, etc., is one more strong reason you need copies in your own computer - don't depend on the manufacturer!

For 200mA, this'd be better (MOSFET rather than BJT): ___ D--->OUT VIN>---[R1}---G S | GND>------------+--->GND

BTW, Infineon has protected n-channel MOSFETs as well, which they call HITFETs -- what a horrible name! The bts117 is a 0.2-ohm TO-220 package FET that's not EOL. DigiKey has them at $2.45 each, with 30,565 in stock!

Sheesh, 30,565 in stock, that's nearly 34-thousand bucks of inventory at the $1.10444 1k-quantity price.

if that us what you desire, may I suggest you put a shunt resistor on the input of that gate. you don't know what's driving it.

--
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

--
At $2.45 a pop?

What planet are _you_ living on? ;)

--
Sorry, but that\'s not right. This is: (View in Courier)

.                        ___
.                   D--->OUT
.VIN>---[R1]--+---G
.             |K    S
.          [ZENER]  |
.             |     |
.GND>---------+-----+--->GND


With R1 omitted if any kind of speed is needed.