Any beefy coil driver chips?

Joerg · Aug 1, 2009

Fred said:
Joerg a écrit :

Then it holds, if you're lucky.

But in this case it would cook out. Must ramp down quickly after the
relay is engaged.

Seriously, with a pair of switches you could do that but I just realized
you want hold from brief to, hum, hours...
You could still make your coil supraconducting

Where's your load (coil) attached?

That's still up to me. Luckily ...

If it's to the supply line, then you could use the ubiquitous 3842/45
Enough pins to coax it to do what you need and I've used it in nearly
the same app.

I am still looking at switchers but these are only 1A abs max and the
30V limit is a bit borderline for me. Really nice would be something
from LTC because they provide SPICE models. However, none of their
synchronous bucks seem to go to 40V or so (for safety margin) and
several amps. Unless you use one with external FETs but then I run out
of room.

Martin Riddle · Aug 1, 2009

Joerg said:
Need to drive a >30V (several amps) coil but back off once it's on to
avoid a cook-out. This needs to be PWM'd because the drive electronics
can't get hot at all. So I looked at coil driver chips. DRV103 and the
like. Many can't stomach more than 32V which is borderline for me and
the saturation voltage respectively Rdson values, well, yawn. Nothing
to write home about.

Did I miss a really good chip? Else I'll just roll my own.

Fuel injector driver like a LM1949, obsolete.
Actually I cannot find anything compatible.

Cheers

Joerg · Aug 1, 2009

Martin said:
Fuel injector driver like a LM1949, obsolete.
Actually I cannot find anything compatible.

Yeah, that stuff went mostly custom. Automotive injectors aren't usually
driven that hard either. Here is an interesting FET from that market,
looks like they goofed up the CAD symbol:

http://www.onsemi.com/pub_link/Collateral/MLD1N06CL-D.PDF

Jim Thompson · Aug 1, 2009

Yeah, that stuff went mostly custom. Automotive injectors aren't usually
driven that hard either. Here is an interesting FET from that market,
looks like they goofed up the CAD symbol:

For you amateurs... that's showing the built-in current limiting ;-)

http://www.onsemi.com/pub_link/Collateral/MLD1N06CL-D.PDF

E · Aug 1, 2009

I tried PIC16F684 using following code: (outputs 25 % duty cycle from pin
RA5)
Power up timer was turned off

;config 0x0FD4
include "P16F684.inc"
clrf PORTA
bsf STATUS,0x5 ;bank 1
bcf TRISA,0x5
bcf STATUS,0x5 ;bank 0

silmukka
bsf PORTA,0x5
bcf PORTA,0x5
goto silmukka

end

The led on RA5 pin was first on 14,8 us after power up, so it executes first
instruction about 10 us after power up.

Note power up timer must be off and there is no such option in 10F series.
They take always 18 ms or 1 ms to start. I think cheapest Pic with this
option is 12F609. (it is available as 8-lead DFN package).

E · Aug 1, 2009

Jan Panteltje said:
Yes, short init, very fast

Did you use the 20MHz xtal or the internal osc?

Internal oscillator at default 4 MHz.

Joerg · Aug 1, 2009

Michael said:
How about putting a thermistor in series? The coil energizes, the
thermistor heats up. It's resistance goes up. Problem solved. If it's
mass is small, it cools quickly for the next cycle, yet can be used as
long as needed.

Not enough room. Seriously.

Joerg · Aug 1, 2009

Jim said:
For you amateurs... that's showing the built-in current limiting ;-)

Look again, da picture on page one. In particular at where the subtrate
is connected to

Jim Thompson · Aug 1, 2009

Look again, da picture on page one. In particular at where the subtrate
is connected to

I assume you mean "body"? Artistic license ?

Joerg · Aug 1, 2009

Thanks E, that is very interesting (sorry, I don't know your frist name).

Yes, short init, very fast

Did you use the 20MHz xtal or the internal osc?

There are a few issues though that Joerg would need to look in to.
1) How long will the FLASH last (temp etc).

Yep, stuff like this close to hot relays needs to be mask programmed for
production, but I assume Microchip could do that for the usual (nowadays
steep) fees. So testing with flash could be ok.

2) How reliable does it start up, I have had one case (say in a few hundred),
where my PIC based SWR meter gave wrong ADC readings after startup and subsequently a false
SWR alert (still have a second SWR meter in the transmitter to compare).
Power down and up again on the PIC box fixed it.
So one needs to look at the correct rise times of Vd etc on the PIC to make sure
the program always starts correctly.

That's the concern. It may work several thousand times and then one fine
day ... *KABLAM*

While it is no problem to devise my own SVS/POR/BOR (I often do that
anyhow because I have learned not to trust many commercial products on
this) there needs to be some guarantee by the mfg such as "If you hold
RST down for xx microseconds after VCC is above x.x volts it'll be all
peaches". That would need to be in the datasheet or some other released
document.

3) The power down of the PIC must be 100% guaranteed, so it is not still running, or erratically
running on low voltage, when the next pulse comes.

The extermal BOR could pull it into reset and hold it there until it's
down to about a volt.

Joerg · Aug 1, 2009

Jim said:
I assume you mean "body"? Artistic license ?

Yes, body.

Did you note the split source? I've done that myself... handy.

Hey, don't skedaddle over to another topic here, the body connection
_is_ wrong. So, I guess your amateur remark was a bit uncalled for

I am not such a fan of split source. Neither of using Rdson to measure
currents. The process tolerances are too large, I like to have my own
sense resistors so I can push the inductances a bit harder without white
knuckles.

Jim Thompson · Aug 1, 2009

Jim said:
Jim said:

Jim Thompson wrote:
[snip]

http://www.onsemi.com/pub_link/Collateral/MLD1N06CL-D.PDF
Look again, da picture on page one. In particular at where the subtrate
is connected to

Click to expand...

I assume you mean "body"? Artistic license ?

Click to expand...

Yes, body.

Did you note the split source? I've done that myself... handy.

Click to expand...

Hey, don't skedaddle over to another topic here, the body connection
_is_ wrong. So, I guess your amateur remark was a bit uncalled for

Perhaps. I thought you were referring to the unusual structure
underneath.

I am not such a fan of split source.

Why? You wouldn't know one if you saw it.

Neither of using Rdson to measure
currents. The process tolerances are too large, I like to have my own
sense resistors so I can push the inductances a bit harder without white
knuckles.

That device doesn't use RDSon...probably SiCr resistance.

I'm yet to see precise specifications for your requirement... just
vagueness.

Do you really want advice, or might we interpret _all_ your requests
as self aggrandizement/advertising ?

Joerg · Aug 1, 2009

Jim said:
Jim said:

Jim Thompson wrote:
[snip]
http://www.onsemi.com/pub_link/Collateral/MLD1N06CL-D.PDF
Look again, da picture on page one. In particular at where the subtrate
is connected to
I assume you mean "body"? Artistic license ?

Click to expand...

Yes, body.

Did you note the split source? I've done that myself... handy.

Click to expand...

Hey, don't skedaddle over to another topic here, the body connection
_is_ wrong. So, I guess your amateur remark was a bit uncalled for

Click to expand...

Perhaps. I thought you were referring to the unusual structure
underneath.

But that's not a goof-up, that's a feature

Why? You wouldn't know one if you saw it.

Rest assured, I am used to fanned emitters from my RF stuff so a
lengthwise structure wouldn't be exactly new either.

That device doesn't use RDSon...probably SiCr resistance.

This one doesn't but many new switcher chips do.

I'm yet to see precise specifications for your requirement... just
vagueness.

What's vague about wanting to ramp up a coil fast, keep it up at rated
current for x msec, ramp it down very fast and keep a hold current?

Do you really want advice, or might we interpret _all_ your requests
as self aggrandizement/advertising ?

Now, now, let's remain professional here, won't we? As can be gleaned
from the subject line all I asked here was if someone knows a decent
modern coil driver chip. How's that in any way aggrandizing? There are
still some around but all old-tech like the L295. Big, fat, not too
great in efficiency.

BTW, I gave the important specs yesterday, quote:

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

.... and "No supply rail". Of course 24V industrial means it should take
40V peaks.

Jim Thompson · Aug 1, 2009

Jim said:
Jim said:

[snip]

Click to expand...

What's vague about wanting to ramp up a coil fast, keep it up at rated
current for x msec, ramp it down very fast and keep a hold current?

Do you really want advice, or might we interpret _all_ your requests
as self aggrandizement/advertising ?

Click to expand...

Now, now, let's remain professional here, won't we? As can be gleaned
from the subject line all I asked here was if someone knows a decent
modern coil driver chip. How's that in any way aggrandizing? There are
still some around but all old-tech like the L295. Big, fat, not too
great in efficiency.

BTW, I gave the important specs yesterday, quote:

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

... and "No supply rail". Of course 24V industrial means it should take
40V peaks.

Joerg · Aug 1, 2009

Jim said:
[...]

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

... and "No supply rail". Of course 24V industrial means it should take
40V peaks.

Click to expand...

Inductance?

"...held there for a msec or so"?? How many "so's"??

Not determined yet, could be 3, 4, 5msec. In a circuit like this it
should not matter, I just make that time selectable with a component
such as R or C. It is something that will most likely have to be changed
later. Usually the allowed tolerance is large. If it had to be under 10%
there would always be the old CD4060 which nowadays even comes in TSSOP.

Jim Thompson · Aug 1, 2009

Jim said:
Jim said:

[...]

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

... and "No supply rail". Of course 24V industrial means it should take
40V peaks.

Click to expand...

Inductance?

"...held there for a msec or so"?? How many "so's"??

Click to expand...

Not determined yet, could be 3, 4, 5msec. In a circuit like this it
should not matter, I just make that time selectable with a component
such as R or C. It is something that will most likely have to be changed
later. Usually the allowed tolerance is large. If it had to be under 10%
there would always be the old CD4060 which nowadays even comes in TSSOP.

Jamie · Aug 1, 2009

Joerg said:
John said:

Jamie wrote:

[...]

Back in the hay days, we used to have dual coil solenoids, one as
the start coil that was in series with a contact on the relay.. It
simply open when pulled in, allowing only the low current coil to
stay energized. But I'm sure this doesn't fit your application.

Not enough room. If that was possible they wouldn't need me

Click to expand...

I think I can do it with one NAND schmitt trigger section, 2 Rs, 2 Cs,
driving a mosfet.

Click to expand...

Seriously, it ain't quite that easy. Just one of the nastier effects:
Such lines can hang, rattle, sizzle, and then you get serious
undervoltage coming in for a while, FET tries its darndest to hang in
there ... *PHUT* ... red lights flash, sirens wail ...

I'm kind of curious as to the type of solenoid coil you're using?

The timing spec's you are spitting out seems a little fast for a
conventional coil? I would think the induction in the coil wouldn't
allow the response times you are dealing with?

Care to tell us the H value of the coil?

Fred Bartoli · Aug 1, 2009

Jim Thompson a écrit :

Jim said:
Jim said:

[...]

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

... and "No supply rail". Of course 24V industrial means it should take
40V peaks.
Inductance?

"...held there for a msec or so"?? How many "so's"??

Click to expand...

Not determined yet, could be 3, 4, 5msec. In a circuit like this it
should not matter, I just make that time selectable with a component
such as R or C. It is something that will most likely have to be changed
later. Usually the allowed tolerance is large. If it had to be under 10%
there would always be the old CD4060 which nowadays even comes in TSSOP.

Click to expand...

Inductance??

...Jim Thompson

voltage*rise_time/current

Jamie · Aug 1, 2009

Joerg said:
Yeah, that stuff went mostly custom. Automotive injectors aren't usually
driven that hard either. Here is an interesting FET from that market,
looks like they goofed up the CAD symbol:

http://www.onsemi.com/pub_link/Collateral/MLD1N06CL-D.PDF

That's an interesting MosFet, Kind of gives me some idea's for it's
use in a project, accept with a higher (A) rating.. Interesting
internal current limiting circuit. Even the Vgs(t) looks inviting!

Does save on part count.

Jim Thompson · Aug 1, 2009

Jim Thompson a écrit :

Jim Thompson wrote:
[...]

"It's not cast in concrete yet but something like 24V industry rail with
tons of noise on there, coil about an ohm so it can ramp up to 3A or so
in a fraction of a msec, then must be held there for a msec or so, then
ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto
the real estate of a postage stamp and dissipate next to nothing, as in
<500mW. If it doesn't it slowly cooks out the relay box, as has happened
on the heat pump controller we had in Europe."

... and "No supply rail". Of course 24V industrial means it should take
40V peaks.
Inductance?

"...held there for a msec or so"?? How many "so's"??

Not determined yet, could be 3, 4, 5msec. In a circuit like this it
should not matter, I just make that time selectable with a component
such as R or C. It is something that will most likely have to be changed
later. Usually the allowed tolerance is large. If it had to be under 10%
there would always be the old CD4060 which nowadays even comes in TSSOP.

Click to expand...

Inductance??

...Jim Thompson

Click to expand...

voltage*rise_time/current

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Any beefy coil driver chips?

Any beefy coil driver chips?

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