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.
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See (from Nagle's teletype hammer driver request)...
If you have trouble understanding it, let me know and I'll hold your hand ;-)
...Jim Thompson
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| James E.Thompson, P.E. | mens |
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| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
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I love to cook with wine Sometimes I even put it in the food
It would be pretty simple to use a power mosfet and a quad-nand-schmitt, HC132 maybe, to make a blipper/PWM driver. Cheap.
John
There are *many* high/low side automotive switches made by Infineon, IRF. They are very robust and protected from anything, and typicaly rated over 48V. However they are slow so the PWM rate can't be higher then several kHz.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Well, I know how to do it in discretes but was hoping there'd be a chip with most of this in there :-)
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Yes, that plus an opamp for the PWM, plus a SVS so the FET doesn't go
*PHUT* when the control voltage is sluggish, numerous resistors, and so on. Stuff kind of adds up and I'm cramped for real estate on this one. Maybe it's time for those SC75 and TSSOP packages again. I hate debugging such small stuf, but I guess man's got to do what man's got to do. Que sera, sera ...-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Those "several" kHz will be a wee problem.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
"High" voltage processes are getting rarer and rarer... they tend NOT to be economical solutions given the quality of discrete power devices.
I just received an RFQ for a TRIAC-uP interface, powered directly from the line. I'll do it with a cheap 5V process and use two discrete TRIAC's.
...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 | |
| Voice:(480)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
One HC132 section will do that.
plus a SVS so the FET doesn't go
What's an SVS?
numerous resistors, and so
One HC132, 2 or 3 Rs, 2 Cs maybe, if I understand what you want to do.
Cheap.
John
Have you looked at CRT vertical deflection (PWM) drivers or are they already too specialized ?
Paul
Seems to me if you could use AC you could just use a triac and skip cycles. I don't know how well they work at these low voltages.
how about a steppermotor driver? something like L6207 or L6506 + fet
-Lasse
On a sunny day (Thu, 30 Jul 2009 20:49:35 -0700) it happened Joerg wrote in :
Since I did the PWM SEPIC with one PIC and one power MOSFET, I would have a go with a PIC and maybe 3 resistors... decoupling cap too. Maybe the PIC can take over functons of other things on the board too. That is usually where the advantage is,
o
Regarding Vladimir's suggestion for Infineon half-bridge drivers, check out their NovalithIC family...
These have lots of integrated goodies, but they are indeed slow. Even the fastest ones are still slow, so watch your switching losses...
--frenchy
With a Schmitt? I haven't gotten that far yet but have done amps with regular CD4000 inverters. Still, that'll be another chip.
Supply voltage supervisor, basically to make sure that there is no gate drive until VDD has reached at least 10V. With some hysteresis on there.
Cheap yes, but eats real estate.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
I had thought about that as well but a uC ain't desired in this situation. Plus needs drivers for the FET gate. Oh well, guess I'll just do it discrete then. My old turf :-)
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They could be ok but they are just about ready to follow the dinosaurs, no market left for them.
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Yes, those would be an option because some have a I-sense line and an enable that I could use for PWM. I am also looking at synchronous buck chips where I can unhook the look. But slim pickens at those voltage levels.
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Forgot to mention one "minor" detail. I also do not have a supply voltage, just the on/off control signal with lots of amps (think industrial control gear). This excludes many uC and also stepper driver chips because they need several msec to boot, reset or prime a charge pump.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On a sunny day (Fri, 31 Jul 2009 06:26:18 -0700) it happened Joerg wrote in :
That is easy to solve, drive the MOSFET gate from the incoming voltage, and while the PIC starts up in *microseconds* have it do the pulldown thing on the gate, As the PIC is high impedance output while not initialized, all you need is a pullup resistor on thte PIC output. You need a resistor to ground otherwise... for the same reason: intintial floating ouput pins.
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