8051F020 series, 5V tolerant input schematic?

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You seem to be mainly versed in yourself. Maybe JF will write a poem in your honor.

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have

Please do me the honor of keeping your mouth shut. I have no interest in your opinions.

I can confirm as fact an LT part that simulates nicely, but fails on the PCB, confounding the FAE, and, now, the factory.

NOLA white trash. ...Jim Thompson

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I don't see much of a point in doing that. The switcher can deliver a certain amount of energy per cycle, mainly set per R5 and V2. So for long term sims you could just assume a current source that's curbed when the regulated output voltage is reached.

If you absolutely have to simulate with 4000uF you could set the inductor coupling to k=1 which helps a little, then play with abstol and reltol. But it'll still take forever. 4000uF is huge. Like modeling rear axle shock response for one complete Sahara desert crossing.

The last sentence sums it up what is missing: How many volts above abs max are allowed over how many milliseconds or microseconds? There use to be family specs and stuff like that but not anymore.

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Honor? Among Thompsons?

Likely a bad PCB design. Did you do it?

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With all the cap load that I can stand to sim, it actually bursts. That is probably good in my application.

It does run at about 300 KHz, which isn't what I expected, given the timing resistor. Maybe, with the inductor I have, it's skipping clocks waiting for the current to build up to the peak trip point. OK, go ahead, force me to buy a smaller, cheaper inductor.

Mantis and Metcal next!

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in

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unfortunate

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Nice, hard-working, innocuous people, mostly. JT has bragged about what a vengeful, unforgiving lot the Thompsons are, himself included. Hey, I believe him.

He could actually provide some on-topic content once in a while. Like what part it is and what the problem is.

Hell, you could provide some on-topic content once in a while, instead of just whining about personalities.

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Learn to read... your comprehension is REALLY BAD... "confounding the FAE, and, now, the factory" ...Jim Thompson

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I qualify as "Black Watch" ;-)

Who really gives a f@#$ what Larkin opines? ...Jim Thompson

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And the jerk forced a 10ns max timestep... what did he expect?

Plus... apply Thompson's rule... any simulation which staggers along indicates a bad circuit design. ...Jim Thompson

Just a widdle bitty bit ;-) ...Jim Thompson

That is because the comp node (Vc) initially rails. Once the converter reaches regulations and Vc comes off its peg it goes slightly above

Que quieres decir con eso?

I thought the Mantis is fixed, and the illumination ring gloweth again. I've always liked the tower-look of Metcals but they are just too durn expensive for my taste.

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And you, too.

Who did the PCB? Is it an eval board?

What part is it? What's the problem?

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I'm not sure. The work was done in Auckland, NZ, by my client, not by me, I don't do PCB's, I only do chips... and my 64-channel LED driver is working gorgeously.

FAE == LT Field Application Engineer... he couldn't figure out the problem... it was built exactly to the data sheet. Problem sent off to the factory, who, 4 months later, still haven't resolved the issue.

I was asked to simulate it on LTspice, which I did, and the simulator says it works... actuality says it doesn't.

LTC3853, oscillates/loop-instability; running as 3-phase single-output. ...Jim Thompson

Adding a point... the part is peddled as a 3-output device, but the application note shows 3-phase single-output operation. I suspect this was just thrown onto the data sheet without physical testing, just simulation of a _behavioral_ model >:-} ...Jim Thompson

Those multiphase slope-compensated things are prone to all sorts of loop funnies, including sub-cycle oscillation. Cap ESR matters a lot.

Running at higher frequency sometimes helps.

Is the problem on an eval board, or a new design?

surge or

up

rail

surges

diodes.

Well, Jeorg you could use two stage protection; say 50 ohms then a 5.6 V zener to ground, then another 100 ohms and a 5.1 or even 4.7 volt zener to ground. Either way, you have to decide.

?-)