Zener diodes in TO220 or similar?

[Joerg]

Big zeners are rarely used these days, at least by me. Need to dump
several watts this time. Other than the ghastly DO5 "long bolt" style,
are there any in modern heatsink-able packages such as TO220?

 

[Jim Thompson]

Big zeners are rarely used these days, at least by me. Need to dump
several watts this time. Other than the ghastly DO5 "long bolt" style,
are there any in modern heatsink-able packages such as TO220?

Might not it be cheaper to use a dinky zener (or heavens! a TL431) and
a power MOSFET?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food

 

[Joerg]

Might not it be cheaper to use a dinky zener (or heavens! a TL431) and
a power MOSFET?

Cost is not much of a factor (ain't that nice!) but real estate is. Must
be simple, just something that can be bolted on. I don't want to have to
machine down a DO5 package ...

 

[Joerg]

Microsemi.

According to their web site they only have TO3, like this series:

http://www.microsemi.com/datasheets/SA5-15.PDF

Power-wise that would be ok but too fat (yeah, sorry, I should have said
TO-220 or smaller). Can't really machine down a TO3, only DO5 and the
like. We'll do it if needed but it would be a chore.

 

[Spehro Pefhany]

According to their web site they only have TO3, like this series:

http://www.microsemi.com/datasheets/SA5-15.PDF

Power-wise that would be ok but too fat (yeah, sorry, I should have said
TO-220 or smaller). Can't really machine down a TO3, only DO5 and the
like. We'll do it if needed but it would be a chore.

What's wrong with a ~1W zener and a TO-220 BJT?

 

[Rich Grise]

Big zeners are rarely used these days, at least by me. Need to dump
several watts this time. Other than the ghastly DO5 "long bolt" style,
are there any in modern heatsink-able packages such as TO220?

Isn't there some kind of shunt regulator/zener "booster" circuit that uses
a zener and a mongo transistor?

Thanks,
Rich

 

[Joerg]

What's wrong with a ~1W zener and a TO-220 BJT?

One more part

Seriously, there is literally no room, I can barely get a TO-220 with a
crew cut in there.

If there really isn't any TO-220 or similar zener I'll go for a TO-220
FET and a SOD-523 zener on the board since that's only 1.5mm long and
0.7mm in width and height.

 

[Joerg]

Isn't there some kind of shunt regulator/zener "booster" circuit that uses
a zener and a mongo transistor?

Sure, but no space. The other stuff would have to go on a circuit board
which is already full to the brim.

 

[Jim Thompson]

One more part

Seriously, there is literally no room, I can barely get a TO-220 with a
crew cut in there.

If there really isn't any TO-220 or similar zener I'll go for a TO-220
FET and a SOD-523 zener on the board since that's only 1.5mm long and
0.7mm in width and height.

You seem to have an awful lot of "blue-wire" problems ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food

 

[Joerg]

You seem to have an awful lot of "blue-wire" problems ;-)

What's a blue-wire problem?

 

[Jim Thompson]

What's a blue-wire problem?

Patches to fix unanticipated bugs. Called "blue-wire" because it's
common to use blue Teflon jumpers ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine Sometimes I even put it in the food

 

[Joerg]

Patches to fix unanticipated bugs. ...

So, what about anticipated bugs?

... Called "blue-wire" because it's
common to use blue Teflon jumpers ;-)

Ah, yes, got some of that here. But this circuit isn't even done yet so
it can't have no bugs. And the schedule says there better ain't gonna be
no bugs ...

 

[Joerg]

Oops, they used to exist, apparently gone now.

How about a transzorb in an SMB package?

That would be resulting in a loud bang and engine company 89 roaring
down Cameron Park Drive. Under extreme circumstances I'll have to dump
several watts average into this thing.

But I better do it with a FET. Means more parts but then things don't go
obsolete on my client years down the road.

 

[Joerg]

won't it be eaisier to get a controlled voltage with a bjt?

somthing like tip121 with a 0805 zener would fit on the pads/legs of
the transistor

It's not to generate a controlled voltage but to dump unwanted spike
energy. Without creating smoke

But it looks like it will have to be a FET. Machining a DO-5 package to
a smaller size isn't exactly my favorite method.

 

[Joerg]

what voltage ~?

Not sure yet but probably around 70V.

 

[legg]

One more part

Seriously, there is literally no room, I can barely get a TO-220 with a
crew cut in there.

That's TO262, SC83, SOT404 - D2pak for a mosfet.

If there really isn't any TO-220 or similar zener I'll go for a TO-220
FET and a SOD-523 zener on the board since that's only 1.5mm long and
0.7mm in width and height.

Assuming you have somewhere for the heat to go.....

As for real estate, have you considered wave-side smd component use?

RL

 

[Martin Riddle]

Sure, but no space. The other stuff would have to go on a circuit
board which is already full to the brim.

Go vertical, make the vertical board part of the main board panel.
Assemble the board as usual and v-score when you assemble it.

Cheers

 

[E]

Big zeners are rarely used these days, at least by me. Need to dump
several watts this time. Other than the ghastly DO5 "long bolt" style, are
there any in modern heatsink-able packages such as TO220?

DO4 ? (ok, that one is not modern)

 

[Fred Bartoli]

Joerg a écrit :

It's not to generate a controlled voltage but to dump unwanted spike
energy. Without creating smoke

But it looks like it will have to be a FET. Machining a DO-5 package to
a smaller size isn't exactly my favorite method.

Borderline but... using a low voltage avalanche rated mosfet?

 

[Joerg]

a clamped fet like: VNP5N07 ?

Yes, that is the way to do it. But I'll probably leave the zener from
drain to gate on the outside so we aren't restricted to specialty parts.

not sure how well a normal fet would work in avalance

I'd never trust avalanche unless it was fully spec'd in the datasheet ;-)