Absolute maximum voltage -- how long can digital chips stand it?

They were rejected if they failed the high or low VCC tests. That was the whole purpose.

I've never been overly impressed with Intersil as a company. There is certainly no reason for rude support.

I've worked places where getting a $5 PO through channels was a major PITA so I would ask for samples of nearly everything on the board. When I asked Intersil for a sample of a 4000 series CMOS part they responded that they don't sample those parts, they are well understood. I guess the effort on their part to sample the device was more than the effort on my part to get a PO though channels. So I didn't use the part. No big loss on either side.

On the other hand, some sales folks understand the value of getting a part in the door at companies. Some companies make parts available in the schematic capture data base which can make things easier for engineers. This leads to those parts being designed in more often. So getting a part into a prototype can lead to sales even if that project doesn't use it in the end.

Rick

I've always wondered about that relationship, I seem to recall it is based on the Arrhenius equation. The basic Arrhenius equation has two arbitrary constants, one for the activation energy and one for the basic rate. The exponential describes how the rate varies with temperature. I find it odd when equations work out to nice round integers like 2:1 and 10°C. That makes me think this is a vast simplification and is very approximate, mostly used because it is convenient and "close enough".

Anyone know what the basis for this relationship is? I think I looked it up once and didn't find a real basis for it. There is no physical basis for 10°C so I expect it is all very arbitrary and actually varies a lot in the real world. Or is there something basic I am missing?

Rick

You are absolutely right. ISO9000 is more about being able to explain and justify what you are doing rather than making sure you are doing it right. There is lots of benefit in that. I was hired by one company who had hired more engineers in the past year than they had from prior to that. How do the new hires know how the company is to function? I don't recall if engineering was ISO9000, technically they were a DOD outfit and they were just getting their CMMI certification, which is much similar. In many ways CMMI training is a joke. The CMMI instructors know the "rules" for CMMI, but can't tell you anything about how to apply them to your process. In this case we all flailed about and did a lot of talking in circles. The worst part was in the first bid I worked on we were adding time to the schedule to make the CMMI stuff happen and it infuriated the head guy. "If it doesn't save us time and effort, why are we doing it?" That was a valid point so all the scheduled time for doing the CMMI stuff was removed along with a bunch of other fat.

In many ways this company was using the infinite monkey process... but they did manage to get product out the door. Some of the factory people were pretty good, but some of them hated engineers. Too bad, I like working with manufacturing. No point in designing a product only to have it be hard to make.

Rick

Den 03-01-2013 07:19, miso skrev:

Yess ... I once had to write 700 lines of hand-crafted 64-bit assembly JUST to get two blocks of SDRAM connected properly to a PowerQuick CPU.

... The punishment for being so old that I actually have seen stuff like Instruction Sets and knows what the linker really does ;-)

There is some kind of retarded, but fairly complex, "embedded processor"/state machine in each SDRAM device that handles the protocol and the interface (Each SDRAM device can support several different interface protocols - even 8 bit buses. It defaults to 8 bit, which is how one talks to the controller hardware in the beginning).

The ambition of all "dumb" components is to require a 700-page manual!

The P=CfV^2 equation is based on shoveling buckets of charge at a given rate. But the shoot through aka crowbar current will go up with supply voltage. I'm reading Jeff's mind here, assuming that was what he meant.

There is a lot more than just logic to RAM design. PLLs, sense amps etc,so the bucket of charge back of the envelope equation that works for basic logic might not be operable for a DRAM.

Funny, I ordered three sticks of memory from Crucial (Micron) recently

- one dead. I didn't think the 33% fallout, from the horse's mouth, to be very good either.

Shoot-thru looks like another capacitor; also proportional to f (number of transitions) and V^2 (impedance of the output devices).

Also proportional to f and V^2. I don't see a V^3 component yet.

I recently spun a temperature controller design to make a higher-powered unit. It's all coded in 68K assembly, heavily commented, based on code about 12 years old. The changes and rebuild were bog easy. Open the single .MAC file with a text editor, search for the relevant stuff, make changes, change the rev letter, then run GO.BAT to rebuild the rom file.

Imagine trying to reinstall some C-language GUI, reinstall some code repositary thing on a server, recovering everything, and understanding/editing/recompiling a few dozen files 12 years old.

I got into the temperature controller business because the previous vendor lost some files or something, or somebody quit maybe, and they couldn't make any firmware changes that the customer wanted.

Or 1400, for a small uP.

--

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

Oops. I goofed. Even using just the voltage increase, 1.975V is about a 73% increase in dissipation.

There's no mind left to read. It's been a busy and rough holiday season for me. I was thinking in terms of a simple resistor model for the RAM current and nothing very sophisticated. KRW is correct. I double counted the dissipation increase.

If all else fails, there's always the data sheet. This looks typical: Top of the bullet list shows: VDD=VDDQ=1.5V +/- 0.075V which is +/- 5%. Running it at 1.975V is +32%. I don't think the manufacturer is going to guarantee their specs at +32% overvoltage.

Looking at the above device data sheet at: on Pg 11 shows: Stresses greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

In other words, the manufacturer thinks it's a bad idea. This section is mostly concerned with voltage tracking between Vdd and Vddq, but probably could apply to any overvoltage.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I've been getting great support from their FAE. The bad news is that it's been needed and there isn't much to back it up. There is a 70% chance that we're going to dump their four-phase boost regulator.

We've been getting more samples for our prototypes than my last job used in most production runs. Intersil isn't an exception; 100 of the above regulator chipsets and a few hundred LDOs. We have no problems ordering parts but often they're only available in full reels. It's easier to just ask for samples. I don't do it for passives (though our purchasing group will) because I try to make sure they're all on reels. Passives in cut tape is a PITA and beggars can't be choosers.

I've never used a schematic symbol the manufacturer has provided. They're ugly (though ours are worse, now). OTOH, I can't figure out why companies like XFMRS doesn't have 3D models for their parts, particularly ones like Ethernet connectors.

I worked for an electronic manufacturer in the 90s that went ISO9000 while I was there... We had documents for production to refer to (before and after ISO), but they didn't refer to them much before or after ISO and didn't seem to do what they were supposed to do. My impression is that ISO9000 doesn't mean squat. It didn't help production but we got stuff out the door with or without ISO.

boB

It is pretty fuzzy. The failure rate goes up as something like exp(Ea/KT), where Ea (activation energy) varies from maybe 0.4 to over 1 ev for various failure mechanisms. Google for more gory details.

It make take a 25C increase to double the failure rate for some parts. The 10C thing is a rough guess. Anyhow, cooler is better, and PCB layout has a lot to do with cooling.

Most ICs are astoundingly reliable if they aren't connected to the outside world.

--

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

If the value of shoot through was independent of supply voltage, then yeah, you could estimate it as PWM. The the spike level isn't directly related to V^2 but rather (V-Vt)^2. based on the C T Sah equations.

The Intersil of today hardly relates to your grandfather's Intersil. Look at the history:

------------------------------------------------------

One of the first semiconductor companies in Silicon Valley, Intersil was founded in 1967 by Jean Hoerni to produce digital watches. When microprocessors emerged in the 1970s, Intersil participated with its

12-bit IM6100, which was the first microprocessor produced in CMOS technology and emulated the DEC PDP-8 instruction set. Two Different Owners

Intersil was acquired by General Electric in 1980. RCA?s semiconductor division was also acquired by GE, and the two companies were combined with GE?s own semiconductor operations.

In 1988, GE?s semiconductor business was acquired by Harris Corporation. The product lines of Intersil, RCA and GE were combined with those of Harris and Radiation, Inc. (previously acquired by Harris). In 1999, Harris spun-off its entire semiconductor division, and Intersil was re-born as an independent company. In early 2000, Intersil went public in what was then the largest semiconductor IPO in US history.

-------------------------------------------

I'm not saying they are good, but they have little relevance to the Intersil of yesteryear. Missing from the Intersil history page is the revolt of engineers when GE took over. They formed a few start ups in the valley, with Maxim being the better known of them.

others do, and I'm actually trying to talk them out of it.

Overclocking a PC is not electronics. Those RAMs are not supposed to last while properly designed devices are.

It's from physical chemistry, was discovered long before electronics, and works just fine.

Joe Gwinn

Keep stretching. I'm sure you can move the goalposts further than that.

The certification certainly doesn't mean anything. Like many of these things, ISO9000 is just a set of tools. You can use them to build a quality system or you can wallpaper a turd with the certificates. Mostly, I see the latter.