analog failures

I can't imagine why a Schmitt trigger should be on every clock, SPI in particular. The designer should be able to design the board so there isn't crap on the clock edges. I don't see the big deal with SPI. I've had a lot more trouble with I2C than I have with SPI but I've abused it more, too.

The sales rep just told me they're shipping me something like ten reels of opamp samples (singles and quads in three power/noise tradeoffs). They were tired of sampling cut tapes, I guess. ;-) Really nice opamps at an excellent price. ADI and TI say they want the business but won't come close on price. Now that they own Atmel, I do a lot of business with them.

Uh, because Schimtt triggers only deal with noise at the transition voltage and no one cares about the *exact* state of the MOSI or MISO signal when it is transitioning. If you think you need Schmitt triggers on the non-clock lines you aren't designing correctly and they won't help you anyway.

If you come out of a wimpy ARM pin, and run the SPI clock all over a multilayer board, to multiple targets, the edges will get slow. Slow edges splayed all around a board are very noise sensitive. Schmitts fix that, and let you run the SPI clock at a frequency that's compatible with all that capacitive loading, traces and chips combined.

Noise on \CS is well avoided, too.

SPI is nice because you can stuff it into and out of RS-422 transceivers, effortlessly.

That can take care of a lot of ills.

But still, woe be unto he who skips EMI filtering and ESD protection on signal/data pins that leave the board (and sometimes, even those within). :-)

I hate I2C because its impedance is non-constant and flow is bidirectional. You can buy extender and interface chips, but you can't simply add a logic gate or something. It's a huge ecosystem of special-purpose parts, most of them NXP (of course!).

I'd been told to take I2C off the board, on a few occasions. Always with much protest, from me, of course. I try to filter/protect it as well as I can, but it's always the first to fail when the EM starts flyin'.

(But the worst I've been forced to implement was USB through unshielded cables. Yeah. That didn't last long. After testing, all cables and connectors became shielded, at great expense to the customer's unit cost.)

Tim

Do it. Have one of those script kiddies in your basement* write one over the weekend. Stick ads on it, it'll pay for itself!

(*I know, they moved out, and you moved out too for that matter. Just making reference to that.)

Tim

LT, too.\

The one time I was forced into it (the board and system were already designed - I just had to ae it work), I used an LT I2C accelerator. Worked like a champ.

Let the customer supply the cables. ;-)

With all this consolidation going on I sure hope we'll see some fresh players barging into the market. Else it's going to be like with the airlines or the old Missy Bells who almost got their monopoly back. Choices go down, prices go up.

With switcher chips and similar things I am seeing Chinese companies showing up, and not with copied designs but their own. I hope our semiconductor players see that.

Many reasons. In micro-power systems it's a given because any fraction of a microsecond spent in transition or multiple transitions will result in increased power consumption. The other effect is that multiple triggering of the input threshold on a line that digital guys consider "unimportant" can blow EMC.

Sometimes it's fun to design micro-power. Now how can we shave off two more microamps?

Slow edges use a lot more power in conventional gates, than in schmitts. So schmitts can save power on ce and MOSI too.

If there is someone out there who'd like to code and run a few web sites, a student maybe, I could pay them a modest stipend and share any ad revenue.

I have too many ideas and too little time.

Yup, cross currents. Often I wish digital designers would have at least a slight interest in analog to see some of these effects.

My funniest experience was over 20 years ago. I was tasked with a large mixed-signal design. The original one was way too digital, noisy and they used power-hungry programmable logic just about everywhere. After I was done and it was integrated into their system an engineer turned it on ... click ... zzzzt .. zzzzt .. zzt ... BEEEP ... ka-clack. Now what? Turned out we had dropped below the minimum power consumption for their massive SMPS and it kept tripping off.

If you had let off this statement on some of the newfangled social media your inbox would be flooded by Tuesday morning.

Same here. I don't want to turn into a nerd but have time for some volunteering and sports activities which is why I ditch some ideas.

I want someone who understands a little about electricity.

OK, you can be a guest columnist.

Schmitt trigger inputs don't "fix" noise. They may mask the problem if it is not so severe. I don't recall ever seeing an edge so degraded by loading that it started having noise problems. Your problem isn't the lack of Schmitt trigger inputs, your problem is excessive loading on a clock line. Add some clock buffers.

Only if CS is an edge triggered signal. Fix your noise problem and you don't need to worry about the lack of built in Schmitt trigger inputs.

Coding isn't the issue, the planning, designing and upkeep is the problem.

Sure they do.

It's often got nothing to do with how it is triggered. I had cases where fast logic input stages did a little tarantella dance every time a signal change logic level. Just for a few hundred nsec. That did not upset the functionality of the system but was enough to fail EMC. The initial reaction of the guys was like yours in this thread: "You've got to be kidding!". Except I wasn't kidding. This is one of the reasons why I never travel to an EMC problem case without the near-field probe kit. With that you can narrow it down to the offending chip, sometimes even to the trace.

Yup.

• They had to find real jobs. They returned what money that was left, to the investors. I thought that was good.

We are just at the start of moving the company, working with architects and contractors and electricians. It's going to take a while. It's going to be fun, eventually.

This was a family furniture business, and everybody was ready to retire. We were bidding against Uber, who had more money, but the Marco brothers wanted to lease to a San Francisco family business, so we got it.