Any beefy coil driver chips?

Bingo!

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With a well placed shorted turn you may even slow down the arrival enough without having to change the drive current...

--
Thanks,
Fred.

I did that in the '60's. After one week of continuous cycle testing the mechanics changed enough that they didn't match the driving curve and it all fried.

...Jim Thompson

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| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
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 I love to cook with wine     Sometimes I even put it in the food

have it=20

anywhere?

=20

That would be rather a strange thing. CDs are block coded to 2048 byte blocks (before/after error correction stuff). The first level on encoding reed-soloman cross interleave for about 30% overhead, then

8-14 (EFM) modulation plus 3 merging bits for over 100% overhead. So a 2 KiB block of data has about 6 KiB on disc.

.

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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.

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".

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.

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

--
Regards, Joerg

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st.

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tage

that

M.

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couldn't you just switch the low side of the coil and not need really use Cboot ?

snip

-Lasse

st.

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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.

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.

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Regards, Joerg

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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

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:

go=20

so=20

too.

=20

pump.

I cannot get it below two timers and a gate plus drive for the switch (3 gates in parallel?). I would use old CD4000B cmos. 10 or 12 volt internal rail R and zener. Hefty mosfet and a freewheeling diode.

:

datasheets=20

=20

normally executing.

there too.

internal osc.,

valid.

before

uS if

in about 400 us,

too...

This also gets into the question of how fast the clock oscillator starts. If it takes a millisecond to start you are toast.

executing.

too.

osc.,

400 us,

Internal RC clock oscillator- no external parts and it will start in the order of one cycle (microseconds). Not as accurate as a crystal or resonator, but zero components/zero added cost and would probably be the most accurate part of the subsystem (factory calibrated).

Best regards, Spehro Pefhany

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can you do a two windining coil relay? or is quantity too low?

No, they'd have me flogged if I suggested that :-)

Anyhow, I am pretty much done. Discrete transistor-level solution, the usual. Meaning the prototype experiments will be fun, SC75 packages,

0402 or maybe even 0201. Drop a part and you'll never find it back. So here I am, my eyes getting older and the parts on my designs becoming smaller and smaller.

That's where I envy guys like Jim. Their IC mask geometries are also becoming smaller but on the screen it always remains the same, or they can even buy a larger monitor when getting older. They never have to solder the stuff.

--
Regards, Joerg

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That is why I got a 47x boom microscope.

I have no problem seeing the components :)

I have one of those 20x Veho USB microscopes. But for work at clients I still have to get some software loaded that can turn its big LEDs off so the fan of the laptop doesn't always come on. It's one of those almost mil-spec laptops and its fan can literally blow SC75 transistor off the table.

And easy on the coffee :-)

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Nah, just make a little ski jump air deflector out of a coffee can lid (droop it with a heat gun to make it bend). Stick it under the edge lf the laptop when needed, roll it up in your briefcase when not needed.

Cheers

Phil Hobbs

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