Slashdot Mirror

You children have obviously not had the pleasure of experiencing latch-up in a CMOS circuit. Fairchild's early versions of their 74AC/ACT logic family was especially prone to this; all it took was to bounce a scope probe off the wrong thing to include a power glitch and set them off!! Smoke, fire, and the laughs of unsympathetic colleagues!!

A 7805 voltage regulator in TO-220 package (which appears to be what was used) can deliver, at most, 1 amp. At 5 volts, that's 5 watts max being delivered to the CPUs. And that's when the 7805 has a good heat sink. The 7805, when fed by 12V, must itself dissipate 7 watts as heat. See here. This was rigged.

>well, this just shows how little you know on the subject.

See, this just shows how stupidly pompously arrogant you are.

>Sorry, its TRANSISTORS that can't handle the current.

Oh. I guess that explains this then, right?

Since you probably can't read the datasheet, I'll let you in on what's important:

Collector Current (DC) = 25 A

That's just a cheapo $3 part. Imagine what a $30 part can do!

>Furthermore, EVERY high powered TV and Radio station you've ever heard of uses tubes for output amplification. So, take 700 WLW in cincinnati, outputting half a million watts. Thats all tubes.

Watts != current!

We learned this in GRADE 10 PHYSICS, for Christs' sakes!

Question: How many amps of current exit a small power generation station supplying 10 grids through high voltage mains (250,000 volts is typical)? The station is generating, oh, let's say 1,000,000 watts.

Let's do the math (why do I have to explain this again?)

P = I * V
I = P / V
I = 1,000,000 / 250,000
I = 4 amps.

But, why, you'll ask, does a power station do that?

Take a look at this AWG chart. Note how the wire is rated as ohms per feet.

Play about with those numbers in ohms law for a while.

Ahhhh. The answer hits you like a tonne of bricks.

So...

Tubes = High Voltage
Transistors = High Current

Now. Speakers = High Conductivity. That means high currents if you want to drive them with lots of power.

You do the math.

Impedance matching transformers? YUCK! Why the hell would you want to further distort the sound? At least transistor based amps can direct drive your speakers. The last thing I dealt with that used impedance matching transformers was a PA system, and it sounded worse than a drive thru speaker.

...you should check to see if you actually know what you are talking about

I generally do. Maybe you should do the same.

EL and Cold Cathode Flourescent Lamps (CCFL's) aren't usually used in cellphones. LED technology is generally preferred. They use DC power with an operating voltage of about 3v or so. They are also cheaper than inverter+CCFL/EL and use less power, and they don't whine when powered on (my phone certainly doesn't whine). Here is an example of a typical backlight LED (a blue one used in a typical monochrome cellphone display). Colour phones of course use while LEDs which do consume a bit more power but not dramatically so.

Even so, CCFL's do need AC voltage, but the conversion circuitry is generally low power and sealed within the display unit--in other words not an explosion hazard. Operating current is 5 mA. Even if you were to bust open the display unit and have it remain functional, operating voltage wouldn't exceed 1000V. Keep in mind that this is all tightly sealed inside a unit with the LCD. The external power connectors on the backlight/LCD unit are typically 3.3V or 5V DC in your cellphone or PDA.

Regardless of the display type, power-wise they consume milliwatts to a watt or so. The dome light in your car probably uses more power than that. Regardless of voltage or frequency, they wouldn't cause an explosion or really even injure you.

Of course the clock generator that this guy is ripping out with a hack saw is in the couple of hundred megahertz range, with crystal accuracy.

Sure, this is the 300th post or something, but in case the author reads them all:

Fairchild Semiconductor is an excellant employer of interns.

Arithmetic Controller The ACE1101 (Arithmetic Controller Engine) family of microcontrollers is a dedicated programmable monolithic inte-grated circuit for applications requiring high performance, low power, and small size. It is a fully static part fabricated using CMOS technology. The ACE1101 product family has an 8-bit microcontroller core, 64 bytes of RAM, 64 bytes of data EEPROM and 1K bytes of code EEPROM. Its on-chip peripherals include a multi-function 16-bit timer, watchdog/idle timer, and programmable under-voltage detection circuitry. On-chip clock and reset functions reduce the number of required external components. The ACE1101 product family is available in 8-pin TSSOP, 8-pin DIP and 14-pin DIP packages.

• Fairchild Semi product page
• PDF Datasheet
• Newark product page ($2.47 each)
• Great page on the WebACE server and WebACE II
• Ace resources

Arithmetic Controller The ACE1101 (Arithmetic Controller Engine) family of microcontrollers is a dedicated programmable monolithic inte-grated circuit for applications requiring high performance, low power, and small size. It is a fully static part fabricated using CMOS technology. The ACE1101 product family has an 8-bit microcontroller core, 64 bytes of RAM, 64 bytes of data EEPROM and 1K bytes of code EEPROM. Its on-chip peripherals include a multi-function 16-bit timer, watchdog/idle timer, and programmable under-voltage detection circuitry. On-chip clock and reset functions reduce the number of required external components. The ACE1101 product family is available in 8-pin TSSOP, 8-pin DIP and 14-pin DIP packages.

• Fairchild Semi product page
• PDF Datasheet
• Newark product page ($2.47 each)
• Great page on the WebACE server and WebACE II
• Ace resources

Could it be done with the 64 bytes ram? Maybe. (It's the stack space too remember.) It would be a tight hack. It would also be much easier to keep all the web functions on the external computer and use the microcontroller just to turn on/off the LEDs. So much easier, that I really suspect that we're being hosed about the server really being done on the fly.

Could it be that they've got a midget in the pedestal playing the chess moves, err, another computer doing the web page and using the Fairchild chip as an LED controller?

It's not possible to easily transform DC (increase or decrease voltage).

Do you know what this is?. Of course, lowering DC voltage is more practical than raising it (though recent semiconductor advances are changing this).

It's also interesting that they are doing this in New York. I thought all chip manufacturing was done overseas, where labor is cheaper. Perhaps IBM is getting some sort of government subsidy for creating American jobs. Or maybe New York has a good supply of chipmakers already, so they can find more skilled workers.

>Scientists are detail-oriented by nature, and for them to miss a small detail such as the proper pluralization of a word they use constantly is out-of-character.

Haven't read a DataSheet lately, have you?

Do they still make ISA voltage regulator cards that can reg -12v down to -5v?

• Fairchild
• Micrel
• Microsemi

Don't forget that these are just the transition times for TTL. You also have to hold the signal high or low for a specified time in order to trigger the next logic gate this one is connected to.

You mention the 74LS00 quad-NAND as an example. Don't forget that this chip exists in a number of different logic families. The 74 prefactor means TTL, and the LS means Low-Power Schottkey. There's also 74F and 74HC and others I can't remember right now that might be faster and/or lower power (albeit with somewhat-varying voltage levels).

We don't use TTL in today's computers of course, it's too slow

TTL is a 'slower' logic family because it runs the BJT's (Bipolar Junction Transistors) in saturation. This is good for power requirements (although not as good as CMOS), but it when a transistor is saturated, it takes some time to come out of saturation for the next cycle. THat's the inherent limitation of TTL.

and chips requiring 5V signals produce too much heat for small circuit paths in the chip.

It isn't just the voltage that causes the waste heat, it's the current too. Remember that TTL signals have low current at 5V, and high current at low signal. Look at the datasheet yourself. (This is for 74ALS00, and a 8-pint SOIC surface-mount device, but functionally equivalent to the DIP 74LS00 you most-likely used in your class).

Typical values in the low state are 0.1mA at 0.35 V, for a power of 35 uW. The high state is 3V at 20uA, for a power of 60 uW. So you see it's not just the voltage that causes the heat.

Because the low states use more power, control signals for gates (for instance, hi-Z output control in tri-state chips) use inverse-logic to activate them. Ie, a signal that will be used only occasionaly will typically have a logic-low activate it's function. Saves power in the long run, and seems kind of weird when you design TTL circuits at first.

Now if you want high speed, look at ECL (Emitter-Coupled Logic). This logic family is really fast. unlike TTL, the BJT's are not run in saturation, so they can switch faster. A side effect of this is that the transistors use more power, and hence run hotter. Like most things, it's a tradeoff. The fastest commercially-available logic family I've seen (and used) is ECLinPS (pronounced Eclipse), for ECL-in-PicoSeconds. These chips can run at several GHz! Pretty sweet. Look here for a datasheet for the ECLinPS NAND gate.

Unfortunately, one of the fastest logic companies has gone out of business about 10 years ago, and I've only been able to glimpse some of their datasheets. It was GigaBit Logic, who in the late 80's and early 90's had logic devices that beat the pants off of what we have now, implemented in GaAs (Gallium Arsenide). However, it cost way too much to develop profitably, and sadly the company is gone. Datasheets had devices listed at 10GHz (although I haven't tested any so I can't guarantee how accurate the datasheets are).
__ __ ____ _ ______
\ V .V / _` (_-&#60_-&#60
.\_/\_/\__,_/__/__/