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High Side Driver

How clever of you, to change the supply voltage to 12, to conceal from us that the actual voltage is 3.8.

Well done!

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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Reply to
John Larkin
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Of course! I have to leave some tidbit for you to whine about. Otherwise your sycophants will realize you're an idiot, and we can't have that... at least not quite yet >:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

You said, "L = R^2 * C gets you in the ballpark"... please give supporting evidence for that asinine conclusion. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

So, how did you calculate the R and L values? I assume you did it twice, once for 12 volts and once for 3.8.

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John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

Think about it JOHN! Fundamentals! Sheeeesh!

I'm sorry! I apologize! You're a victim of your Tulane kindergarten education. My sincere apologies >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

OK, you can't do it.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

That's just matching the L/R and RC time constants. That's the ballpark L to shunt peak a video amp or suchlike circuit. Overshoots a tad, actually, but it's a reasonable starting point for things like this.

The problem here is that the mosfet is not a simple capacitor. You could futz with Qg and the approximate threshold voltage, but this is easier to just simulate and tweak. Actually, I'd have overkilled on stored energy in the L and used a s-g zener to define the gate voltage. That's safer in the long term.

Or, actually, I'd first look for a suitable low-threshold p-fet and get rid of all those drive parts.

So, how did you calculate it?

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

You're BS-ing. You don't know what's going on... like we already didn't know that you didn't.... >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

Doesn't the magic smoke come out if there's even a tiny bit of current leakage draining away the voltage that L1 transferred to MN1's base? Or if the control signal to MN2 has a bit of a bounce? At least in your slightly obfuscated circuit, that would leave MN1 pumping out about 2 times its rated wattage.

PSpice needs a "circuit board in the tropics" mode.

Reply to
Kevin McMurtrie

Thanks, I had to save it before I could right click. I looks much better using Adobe than it does Foxit Reader. Anyone else have a problem seeing the lines... hmm, now after saving the file and opening it with Foxit, the schematic looks better with Foxit than Adobe. Any time I want to view Jim's schematics, I'll save it first. I think that was the solution. Mikek

Reply to
amdx

For this application the drive is repetitive at ~2kHz square-wave. Think of it as a one-cycle boost: When MN2 turns off, 0.5*L*I^2 gets transferred to 0.5*C*V^2, turning on MN1. When MN2 turns back on, the L is recharged and the gate of MN1 is discharged.

Except for "tropics" mode ;-) I believe it will hold up for significantly lower rep-rates.

The link now includes a complete .CIR file suitable to run directly in LTspice. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

You could've just said "the driver FET is more than fast enough for turn-off time not to matter."

Indeed. Just calculate the inductor energy, and the voltage that creates on discharge. You could've said that too rather than playing with everyone.

Again, you could've said "It's an integrated device that's not likely to change, but changing the limiting resistor changes the FET gate voltage, if ever required."

A zener would be better. Then you can over-fill the inductor, creating plenty of margin, and the zener clamping swamps any device dependencies.

Cheers, James Arthur

Reply to
dagmargoodboat

It's even more "fundamental" than that... Freshman EE: the current in an inductor cannot instantaneously be changed; the voltage on a capacitor cannot instantaneously be changed.

Shots were fired without fact... a constant annoyance here.

Nope. It's a discrete device on a PCB.

Yes. But note that, if the driven MOSFET has a 2:1 spread of CGS from part-to-part, that amounts to +/-20% tolerance on the gate voltage, easily accommodated in the initial design calculations.

Quoting that pompous S.E.D sage J.Larkin, "It's an unnecessary component" >:-}

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

Speaking of unnecessary components... upon imposing a 10ns max time-step I found that the improvement in gate drive due to D1 is so miniscule as to not be cost effective. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

In other words, you are designing this by simulation, not calculation.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

John, Why don't you grow up? I calculated. Period >:-}

I thought the diode necessary to avoid loss of energy in the series resistor. Turned out, in my particular case, that the loss is miniscule. I would expect higher power applications to need the diode. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

Speaking of "calculation", John Larkin's L = R^2 * C "calculation" is totally out-to-lunch or inane or insane... take your pick >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

Not believable. Show us your math.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

Hey, John... Nobody, but nobody cares what you believe >:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142   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.
Reply to
Jim Thompson

Given a charging RC, you can add an inductor in series with the R to speed up the rise.

L = K * R^2 * C

where K around 0.5ish is near critical damping, K=1 overshoots a bit. It's a handy starting point for simulation. That ROT is in the RadLab books.

Show us your calculations.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators
Reply to
John Larkin

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