Discussion:
voltage regulator
(too old to reply)
RHRRC
2006-08-11 18:36:05 UTC
Permalink
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.

Any suggestions to avoid a phlethora of protection components?
PeteS
2006-08-11 18:47:14 UTC
Permalink
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Depends where in the automotive environment you are.

If you are behind some of the switched power systems, you won't have to
worry about load dump _too_ much. If you're on the battery side, you
have to take that (and a lot of other things) very seriously. (Things
like E-marking, for instance).

All the usual suspects make supposedly 'load-dump protected'
regulators, but I have my doubts.

I don't have a list handy (not currently at the office) but for a
parametric search use a minimum of 30V Vin (a 24V vehicle has a typical
run voltage of about 27.5V). If it's rated higher, all the better.

Input protection can be pretty simple if you get a 40V device; use a 32
- 36V transorb (or one designed for automotive load dump such as the
SM8S series), an electrolytic for energy storage (rated at 63V should
be fine behind a protector) and a ceramic or two for high frequency
noise.

The only extra component I see there is the input protector - hardly a
'plethora' of protection components.

Cheers

PeteS
RHRRC
2006-08-11 21:52:41 UTC
Permalink
Post by PeteS
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Depends where in the automotive environment you are.
If you are behind some of the switched power systems, you won't have to
worry about load dump _too_ much. If you're on the battery side, you
have to take that (and a lot of other things) very seriously. (Things
like E-marking, for instance).
All the usual suspects make supposedly 'load-dump protected'
regulators, but I have my doubts.
I don't have a list handy (not currently at the office) but for a
parametric search use a minimum of 30V Vin (a 24V vehicle has a typical
run voltage of about 27.5V). If it's rated higher, all the better.
Input protection can be pretty simple if you get a 40V device; use a 32
- 36V transorb (or one designed for automotive load dump such as the
SM8S series), an electrolytic for energy storage (rated at 63V should
be fine behind a protector) and a ceramic or two for high frequency
noise.
The only extra component I see there is the input protector - hardly a
'plethora' of protection components.
Cheers
PeteS
Thanks for the response.
The problem is with a single SAD , say a 5KW device, with a nominal
clamping voltage of 33V, a classIII surge will limit at around 80V. A
30V part is *very* close to the limits for a 24V automotive system and
may not be within accepted limit extremes. Two or three parallel 1K5W
devices could keep this down to ~60V.
I am trying to avoid an inductor varistor resistor transorb capacitor
diode 60V regulator set up as I am running out of volts at the 12V end!

35 to 40V devices are fine in 12v systems with straightforward
protection. Problem is in 24V systems, which are 'harsher' than 2x 12v
systems, 70 to 80V devices would be necessary for similar protection to
be adequate.
Such dedicated auto devices were once available, typically with 100V
input, reverse, and load dump protection, but they now seem no more -
or at least I cant find one. Everyone uses switchers but this app
cannot do so at this time.

It is an 'e' product: there is no 'E' applicable
PeteS
2006-08-12 16:23:21 UTC
Permalink
Post by RHRRC
Post by PeteS
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Depends where in the automotive environment you are.
If you are behind some of the switched power systems, you won't have to
worry about load dump _too_ much. If you're on the battery side, you
have to take that (and a lot of other things) very seriously. (Things
like E-marking, for instance).
All the usual suspects make supposedly 'load-dump protected'
regulators, but I have my doubts.
I don't have a list handy (not currently at the office) but for a
parametric search use a minimum of 30V Vin (a 24V vehicle has a typical
run voltage of about 27.5V). If it's rated higher, all the better.
Input protection can be pretty simple if you get a 40V device; use a 32
- 36V transorb (or one designed for automotive load dump such as the
SM8S series), an electrolytic for energy storage (rated at 63V should
be fine behind a protector) and a ceramic or two for high frequency
noise.
The only extra component I see there is the input protector - hardly a
'plethora' of protection components.
Cheers
PeteS
Thanks for the response.
The problem is with a single SAD , say a 5KW device, with a nominal
clamping voltage of 33V, a classIII surge will limit at around 80V. A
30V part is *very* close to the limits for a 24V automotive system and
may not be within accepted limit extremes. Two or three parallel 1K5W
devices could keep this down to ~60V.
I am trying to avoid an inductor varistor resistor transorb capacitor
diode 60V regulator set up as I am running out of volts at the 12V end!
35 to 40V devices are fine in 12v systems with straightforward
protection. Problem is in 24V systems, which are 'harsher' than 2x 12v
systems, 70 to 80V devices would be necessary for similar protection to
be adequate.
Such dedicated auto devices were once available, typically with 100V
input, reverse, and load dump protection, but they now seem no more -
or at least I cant find one. Everyone uses switchers but this app
cannot do so at this time.
It is an 'e' product: there is no 'E' applicable
If I were doing something like this, I would use a LM317HV (Vin <= 60V,
Vdo < 2V @ 200mA).
http://www.national.com/pf/LM/LM317HV.html

For front end protection I would use a SM8S33A
(http://www.vishay.com/product?docid=88387&query=SM8S) behind a hash
choke.

I do almost this (60V part behind those two) for an existing automotive
product rated at 10.5V - 36V in (I use a SM8S36, guaranteed maximum
clamp voltage 58.1V). It's possible to add more protection, but I have
not found it necessary.
I did have to be careful of my choke because I have to meet 95/54/EC
(commonly known as E-marking). You may not have to deal with that.

Load dump is not a slow phenomenon (see ISO7637), and this circuit has
been tested thoroughly against it. The product has had zero failures
from > 5k installations due to front end failures.

Cheers

PeteS
RHRRC
2006-08-12 20:05:48 UTC
Permalink
Post by PeteS
Post by RHRRC
Post by PeteS
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Depends where in the automotive environment you are.
If you are behind some of the switched power systems, you won't have to
worry about load dump _too_ much. If you're on the battery side, you
have to take that (and a lot of other things) very seriously. (Things
like E-marking, for instance).
All the usual suspects make supposedly 'load-dump protected'
regulators, but I have my doubts.
I don't have a list handy (not currently at the office) but for a
parametric search use a minimum of 30V Vin (a 24V vehicle has a typical
run voltage of about 27.5V). If it's rated higher, all the better.
Input protection can be pretty simple if you get a 40V device; use a 32
- 36V transorb (or one designed for automotive load dump such as the
SM8S series), an electrolytic for energy storage (rated at 63V should
be fine behind a protector) and a ceramic or two for high frequency
noise.
The only extra component I see there is the input protector - hardly a
'plethora' of protection components.
Cheers
PeteS
Thanks for the response.
The problem is with a single SAD , say a 5KW device, with a nominal
clamping voltage of 33V, a classIII surge will limit at around 80V. A
30V part is *very* close to the limits for a 24V automotive system and
may not be within accepted limit extremes. Two or three parallel 1K5W
devices could keep this down to ~60V.
I am trying to avoid an inductor varistor resistor transorb capacitor
diode 60V regulator set up as I am running out of volts at the 12V end!
35 to 40V devices are fine in 12v systems with straightforward
protection. Problem is in 24V systems, which are 'harsher' than 2x 12v
systems, 70 to 80V devices would be necessary for similar protection to
be adequate.
Such dedicated auto devices were once available, typically with 100V
input, reverse, and load dump protection, but they now seem no more -
or at least I cant find one. Everyone uses switchers but this app
cannot do so at this time.
It is an 'e' product: there is no 'E' applicable
If I were doing something like this, I would use a LM317HV (Vin <= 60V,
http://www.national.com/pf/LM/LM317HV.html
For front end protection I would use a SM8S33A
(http://www.vishay.com/product?docid=88387&query=SM8S) behind a hash
choke.
I do almost this (60V part behind those two) for an existing automotive
product rated at 10.5V - 36V in (I use a SM8S36, guaranteed maximum
clamp voltage 58.1V). It's possible to add more protection, but I have
not found it necessary.
I did have to be careful of my choke because I have to meet 95/54/EC
(commonly known as E-marking). You may not have to deal with that.
Load dump is not a slow phenomenon (see ISO7637), and this circuit has
been tested thoroughly against it. The product has had zero failures
from > 5k installations due to front end failures.
Cheers
PeteS
Thanks for that.
I had come to a similar conclusion but using two 1.5KE - 33's in
parallel.
What was the nature of your problem with the choke ?

Luhan
2006-08-11 19:52:00 UTC
Permalink
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Seems simple enough, LM317 and 2 resistors drawing power off the
accessory circuit.

Luhan
RHRRC
2006-08-11 20:44:24 UTC
Permalink
Post by Luhan
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Seems simple enough, LM317 and 2 resistors drawing power off the
accessory circuit.
Luhan
Would it were only that simple.
The market is littered with the remains of devices that used such
without extensive protection.
I have considered the LM317HV but the protection required is relatively
costly and quite tight as Vin max is (from memory) only about 60V for
the HV and 40V for the standard part.
Rich Grise
2006-08-11 22:36:50 UTC
Permalink
Post by RHRRC
Post by Luhan
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Seems simple enough, LM317 and 2 resistors drawing power off the
accessory circuit.
Would it were only that simple.
The market is littered with the remains of devices that used such
without extensive protection.
I have considered the LM317HV but the protection required is relatively
costly and quite tight as Vin max is (from memory) only about 60V for
the HV and 40V for the standard part.
Use a hash choke and a Transzorb. THat's any ol' choke that'll carry
your current, and a Transzorb is a transient voltage suppressor:
http://www.vishay.com/diodes/protection-tvs-esd/trans-zorb/

I used to use the 1.5KE series, but I'm sure they have even better ones
nowadays. Just pick one whose minimum threshold is above the system
voltage, and you should be good to go.

I do have qualms about the headroom on the LM317, however.

Good Luck!
Rich
Barry Lennox
2006-08-12 00:37:25 UTC
Permalink
Post by RHRRC
Post by Luhan
Post by RHRRC
I am looking for a linear regulator that can be readily set to ~10V for
a 12/24v automotive environment.
Running current ~200mA.
Any suggestions to avoid a phlethora of protection components?
Seems simple enough, LM317 and 2 resistors drawing power off the
accessory circuit.
Luhan
Would it were only that simple.
The market is littered with the remains of devices that used such
without extensive protection.
I have considered the LM317HV but the protection required is relatively
costly and quite tight as Vin max is (from memory) only about 60V for
the HV and 40V for the standard part.
I saw a similar design for an aircraft device (12-28 volts) that used
an active clamp before a simple LDO reg. It used an ON NCP346 voltage
sensor/clamp that can be set very accurately, to turn on a hi-current
FET, IIRC it was one of the Infineon SmartFETs or ProFETS.

Might be more complex than you want though.

Barry Lennox
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