SO14 package at 154C/W? Really?

We actually have a CT scanner for this up in Poughkeepsie. Takes a pretty long time when there are high atomic weight metals in the way, so iiuc it's used for sample testing and failure analysis--hopefully the failures happen during qualification and not in the field!

Cheers,

Phil Hobbs

PSU

mW.

seems

significant

they're not

Yet the

So it's all load related. Why not buffer the outputs with a couple of discretes (or one if it's only unipolar ?). Is it that tight for space ?

Graham

PSU

mW.

seems

significant

they're not

Yet the

discretes (or one if

In this case that means 30 more parts to place, versus 12 if I just use single opamps.

Last case was in 2007.

I am self-employed and most of my clients farm out assembly.

Sometimes you've got no choice, like where there are 400+ contacts. But I try to stay away from such monster chips in my designs. I find that gull-wing contacts take flexing and G-force in the most graceful manner.

I don't know if you've worked in hi-rel design: System goes onto a launch pad, lifted x feet, dropped, crashes onto concret surface, lifted x feet again, and so on. Once in a while someone pours on another layer of concrete because the previous surface has hammered itself farther into the ground. After a while they protrude into the soil like stalactites.

Nice to hear that you found a solution. But I'm astonished that the medical authorities are satisfied with with you just using the data sheet values without any evidence that the manufacturer has really tested them for the parts delivered to you. In other areas considered critical for human life, the authorities would never accept using just data sheet values from the manufacturer but rather require detailed procurement specifications clearly showing which parameters are tested.

It would be interesting to hear about the rules used for designing medical equipment (to see if you can rely on these devices if you end up in a hospital :-) )

This is not a life support application. In life support apps you basically have to make your own parts. One company even ran their own foundry (no, I am not kidding).

In (most) non life support apps you can use datasheet values but you cannot use the typical values. Not the graphs, just the hard min-max data in the tables, that's it. One reason why I never use LDOs because they only give a typical stability range graph. That doesn't fly.

At the end of the day the hazard analysis will tell the story. Along the lines of "If opamp U31 fails what effects will there be, what are the likely consequences and what will mitigate these effects?"

Whether a mfg tests or not that says nothing about whether that part will fail on December 23 or not.

What's your impression so far with respect to BGA versus PQFP and others?

Depends on the customers. Remember that ad picture in EE Design or something where a missile test went wrong, big fire ball, little arrow points to small black box up in the air, all dinged up? "This is one of our power supply modules and afterwards it still worked!"

I don't know--we basically don't use any packages with leads!

I can tell you that 32x148 pin surface mount connectors are hard to use.

Cheers,

Phil Hobbs

Not jtag. I was thinking of programming the fpga to put a weak pullup on all pins. Then pull a pin low and turn it loose and see how long it takes to go high. An unsoldered pin will have very little capacitance, so will go high pretty fast. Done right, this could catch all opens and shorts on all the i/o pins, without the need for jtag gadgets on the other ends.

Essentially none of the things we connect to fpga's have jtag of their own.

Maybe so.

John

I bought an anodizing kit from Caswell.. hopefully sometime in the next year I'll get around to trying it out.

Justifiable!

Cool. Best regards, Spehro Pefhany

Yeah, it used to be that "you can't base a company on a product", which meant that you had to have a grand scheme and a product line with critical mass to reach a market. Now, one person, with one good home-brew product, an assembly line in a garage or a big closet, and a decent web site, can get started and sell and grow. And a small company, using mostly free press releases and a keyword-loaded web site, can be as visible in some specialties as Tek or Agilent. The levelling power of the search engine is astounding.

John

What the heck do you use for a mating connector?

A male version surface-mounted on the backplane. ;) That's the standard backplane connector for the current P- and Z-series machines. Half of the pins are grounds, so for signals it's only 16x148. There's a _big_ preload put on it before reflow. (Yes, I realize that this is a ridiculous connector. That's one reason we're trying to move towards optical interconnection.)

It's been quite educational working in the packaging research area, even though I don't personally do any significant amount of electrical packaging work. You pick up stuff by osmosis and from people's talks.

Cheers,

Phil Hobbs

It sounds like the wrong place, in the system, to interconnect.

RL

Electronics is 50% packaging.

John

Nope, just a really big system. The on-board bandwidth is 5 or 10 times higher--we could use twice that much off-board bandwidth.

Cheers,

Phil Hobbs

RL

Either way, it sounds like a good reason to create a ZIF connector with wiping action. 4736 pins at even 0.05 oz insertion force is no joke. And move the power to another connector. 2368 signals is a lot of signals, even if half of them are power (leaving 1184 signals).