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Re: Any beefy coil driver chips?
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Actually I must ramp the coil current to the hilt the instant the rail
comes up. In cases like this the rail is the switched line and also the
only power source. Wanting an extra DC power line to come in is almost
like renting a backhoe and starting to trench :-)


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I have to go through their stuff one more time, maybe they really have
something useful. Usually Supertex comes to the rescue in such cases but
not this time. They have only the HV9901 and it wouldn't buy me that
much in space savings versus discretes. OTOH, cost is not the driving
factor on this design, within reason, meaning no chip design. Ain't that
nice for a change?

Sometimes I envy guys like Jim but I had that luxury only twice: You
shop around for HV processes and then piece it all together on your
computation machine. After I did a design on a 60V process I was so spoiled.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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HV ASIC processes are not cost-effective.  You're better off using a
low voltage process plus discretes... unless you're the government and
only size matters ;-)

It's probably been close to 20 years since I last used a 30V process
(not counting specialty processes with HV open drain or collector
devices... like the DMOS processes now available).

                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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[...]

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This was 1997/98: 60V Delco process, grand total with masks, first
silicon, my flights, but without my engineering time somewhere around
$120k. However, I realize that NRE has gone up quite a bit since then.

When we fired it up for the first time lo and behold it worked. A major
pool party over here was called for and held, booze and food provided by
yours truly.

Man, I wish I could get such a deal just one more time :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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Richard Davis?

                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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Doesn't ring a bell but it's over 10 years now.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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spoiled.
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Last I heard he was running the ASIC group at DELCO.  He was one of my
young bucks when I was at Motorola ;-)

                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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spoiled.
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Ok, then I probably do not know him. We did not use their design folks,
just the foundry.

Old buck sometimes must see that young buck also make good stuff :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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[snip]
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Of course, I'm an excellent teacher ;-)

                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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 Hah!  No, this isn't a problem.  Use a small mosfet, with Ciss
 no more than 100pF, so the flying cap, Cboot, need not be
 larger than say 470pF.  Use a small cap across the IRS2153
 internal 15V zener, say 2.7nF.  If the input-power resistor is
 680 ohms (nominal 10 to 15mA of current), then the start-up
 time, including charging Cboot, is under about 3us.  This
 means that you can very quickly assert the ON state.

 Hmm, I wonder, might there be any bounce in the 30V
 input drive, better add a diode in series with the 680 ohms.

 Note, you can run the rest of your control circuitry from the
 15V power tap of the 2153 chip.  Hah, a cmos 555 still has
 a chance to play a role, for your 1 to 5ms high-power timing.
 With a diode, its output can hold up the CT pin.

 Well, it's fun to talk about these things.  But if we get down
 to brass tacks, and get serious, I have to say I'm not happy
 with the IRS21531 chip's long 0.6us dead time during PWM.
 While it may be appropriate for a 200 to 600V application,
 it's far too long at low voltages, and means the lower power
 FET's body diode will always be conducting during the dead
 time, with its ugly reverse-recovery-time snap-off issue.  OK,
 add a Schottky diode across the lower mosfet.  That'll fix it.

Re: Any beefy coil driver chips?
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That is a nice trick. It doesn't even have to be that fast. Several ten
usecs for start-up would be ok. Compared to SMPS converters this stuff
is all relaxingly "slow".


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Abs max says 20mA so even at half that value there should be plenty to
spare. For some reason they only give a typical supply current but with
Iq max at 1mA plus whatever the oscillator causes that leaves plenty for
some CMOS logic. Of course they stated the typical current at a highish
timing resistance where you can't get it above 20kHz. If you ever need
something like this with more nifty power supplies the HV9901 has a 2nd
regulator in there that can be set to the levels of modern uC and is
nicely tied to a bandgap reference in there. Only 1mA but that suffices
for a little MSP430 at a low clock speed. But the comparator offset
specs are horrid, I am wondering if they just were ultra-conservative.


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That's a common trick in synchronous bucks but so far I always got away
without the Schottky.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?
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 So, if the two mosfets are in an soic-8 package (lots
 to choose from) you're talking about three 8-pin soic
 packages and a smattering of discrete parts.  A small
 PCB, with two input pins for the coil power signal, and
 two output pins (the two negative IN and OUT pins are
 wired together) for the coil, and you're all set.

Re: Any beefy coil driver chips?
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Getting three SO-8 packages on there will already be a challenge but the
smattering of discretes is what really can do this in. The HV9901 looks
good so far except for the huge offset voltages, of course. The fact
that it doesn't come any smaller than SO-16 isn't exactly helping either.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?
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couldn't you just switch the low side of the coil and not need
really use Cboot ?

snip


-Lasse

Re: Any beefy coil driver chips?
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You can, but it makes current sense a bear. Unless your chip has an
integrated sampling/gating with proper FET spike blanking built in. Some
do but the IRS2153 doesn't.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?


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

Cheers
 



Re: Any beefy coil driver chips?
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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

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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

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                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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Look again, da picture on page one. In particular at where the subtrate
is connected to :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Any beefy coil driver chips?

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I assume you mean "body"?  Artistic license ?:-)

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

                                        ...Jim Thompson
--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Re: Any beefy coil driver chips?
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Yes, body.



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.

--
Regards, Joerg

http://www.analogconsultants.com /

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