Ground Isolation

Ferrites are usually ok in supply rails. Inductors can be a problem during power cycles, can cause a major phut ... *POOF*

I'm wrong, 700kHz is for a square wave. You will need to go much faster to send PWM signal, You need to send your smallest pulse width through. So if you have 256 levels of PWM, then 100kHz*256 * 7 =3D

Interesting how they can't make them beautiful like they used to.

So that's where all the Power PCs went.

What's a "digital phosphor scope"? They have phosphors in the LCD?

No, they simulate the way a phosphor screen looks with DSP techniques. The data bandwidth is so high, they had to use custom chips to do it, not a traditional DSP processor. The first ones were pretty mediocre, the latest ones actually almost fool you into thinking you are looking at a traditional analog scope, sometimes.

Jon

My understanding is that a lot of high-end embedded systems (e.g., laser printers) use them as well, so at least as an architecture they'll probably be around for quite awhile, even if finding a discrete CPU as such will become impossible.

Weird..I just tried to take some pictures of my 7904, but they all come out black and white. Must be a time warp thing going on.

mike

That's probably because you grabbed the Polaroid Land Camera from the trunk of your Studebaker :-)

My dad bought every car that disappeared. Desoto. Packard. Kaiser. Studebaker. I wonder what the cause and effect were there. The last car he had was a Buick.

John

Oh, oh, that doesn't bode well for Buick then. Maybe they'll be larkinized ;-)

There are only a couple of embedded processors with GbE macs on chip, the unobtainable Marvells ARMs and the Freescale PPCs. The Freescales are a lot cheaper than the can't-get-em Marvells, and Freescale has a free RTOS to boot.

John

Intriguing...

I suppose Arm is reapidly becoming the Microsoft of the embedded processor world.

Ever looked at the TI OMAP parts where they meld a (TI) DSP together with an ARM CPU? The parts are quite popular in multimedia-devices, but the whole idea kinda makes me cringe a bit. The approach Analog Devices took with, e.g., their Blackfin line of adding enough instructions to a traditional DSP to make it "C programmer friendly" strikes me as a better approach. My suspicion is that the TI "completely different cores" approach is attractive in that there's no easy way those lousy just-out-of-college kids who can barely program in C can mess up the carefully hand-crafted and finely-tuned algorithms the DSP wizards stick into their piece of the silicon. :-)

---Joel

Yes. And tablets. And maybe desktop one of these days. ARM+Linux could make a couple of people very unhappy.

We usually combine a uP to do management and communications (things like serial i/o, TCP/IP) with an FPGA to do the serious i/o and number cruncing, like 64 channels of ADC+lowpass filtering for example.

John

Hi All,

I am thinking of testing the ferrite bead and see what happens? Please read the original post. Question is H wo should I choose the Ferrite Bead?

Thanks John

How to choose a ferrite bead to go between your two grounds? How much current is flowing? What frequency is offensive.... This is more a matter of rise times rather than repetition(sp) rates. There are two common mixes, (43 and 72? I'm not sure of the numbers or which is the higher frequency) you have to read the spec sheets.

But why not buy a few of each, stick 'em in and see what happens? It's always nice to have a spare ferrites lying around.

And then try soldering your ground planes together. We did this the other day on a board with a long ground return path for the signal. Soldered a piece of copper tape across the ground planes (after scraping off the coating.) right below the signal line. There's traces of the offending crud left but down from 50 mV to

Nah. It's a figure of speech, like a spider spinning a web.

Cheers! Rich

These are the power rails to single chips, and not 100W monsters.

What about those pesky inductors in the power supplies?! ;-)

worse.

Doesn't matter. Every inductor can behave like an ignition coil, and will do so if it's current is abruptly change. Because Monsieur l'Inducteur absolutely hates change when it comes to current :-)

Those are there for energy storage and shuffling purposes, and the EMI ones are rather small. But I have seen designs where they placed large inductors in DC leads, cranked up the lab supply (by nature a slow process), happily saw that the noise problems subsided. Then in the real application there was that pesky power switch and ... *PHUT*

it

worse.

However, E=LI^2/2. No E, no big *phut*.

Hell, I've seen Light Emitting Ferrites, too. ;-) Never did figure out what went wrong. :-(

it

worse.

E is there when VCC is turned on or off. A delta of 5V can easily turn into tens of volts on the other side. And have ...

It wasn't always phut but also pop or bang :-)

Wow! I can't remember that but I have seen ferrite explode.