(Long day debugging what turned out to be a stupid design error. I hate it when I do that. Need to find some faster comparators!)
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
What comparator?
4 us is pretty pokey, LM339 sort of ancient stuff.What's your input swing range? Need analog precision? I know a trick.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
;-) Some of the micro-power comparators are butt-slow. ...Jim Thompson
-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
MCP6542. I did what I usually do when I make these mistakes: I had selected it for another project with different requirements (it has way low current draw, and for that project the speed wasn't an issue), then I used it in the current project because I'd used it before.
The MCP6562 looks pretty good, at a reasonable price.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
But micro-power, which meant a lot for the circuit for which I originally chose it, but not for the one I put it into this time (I used it because I'd already used it, which led me to not pay much attention to the specs, because hey -- I'd used it. I work at my mistakes!)
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
I've done worse, much worse. Wanna hear about it ?
Thought not.
Love those sot-23 comparators.
--
Thanks,
- Win
See MicrochipComparators.zip on the Device Model & Subcircuits Page of my website for models that match the datasheet pretty closely. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
If you have a drop-in fix for the problem, it's a 2-on-a-scale-of-10 mistake. You can have it fixed tomorrow.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Tell us! Tell us!
--
John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers
jlarkin att highlandtechnology dott com
I've used LMC7211 before, which is on pretty much the same speed node. $0.943 in 100s. Looks like the '6542 is about half the cost, and even less quiescent. But low voltage.
I've also used MCP6561, which is fast like an LM319, but sips only 0.1mA. $0.39/100s.
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
My first circuit board layout job was when I was a TA in high school. I mirrored the IC, so the sophomores had to solder them onto the back side of the board to get it to work.
It was not an isolated incident...
-- www.wescottdesign.com
Through-hole rules.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Yes please. There is always a sharing of successes, but more rarely our mistakes.
OK this is not really a mistake, but one of my longest trouble shooting battles was with a ramp- triangle wave circuit. Current in to a cap with a comparator that switched the sign at top and bottom. (modded from AoE) Anyway all of a sudden I had a bunch where the two sides were wildly different in slope. (currents were in the uA range) I probed here and there, started ripping out pieces of circuit, replacing components..
I finally got to the point were I'd changed everything but this toggle switch, that was used to disable the ramp. Yup, that was the problem.. A whole bunch of toggle switches with a few Meg of resistance between the contacts. (when "open")
George H.
Maybe cheap nylon bodies with ionic contamination?
Nylon is a truly evil material.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Here's my femtoamp parts tester. I used Rat Shack binding posts and eventually discovered that they were leaky. After the whole thing was built, I had to machine the hole in the top for the lexan sheet.
But I've made far worse mistakes than that.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
We somehow messed up the PADS library footprint for the SOT23 decal. Several boards came out with the pinouts wrong. If you are willing to bend the leads up and rotate the part, any SOT23 permutation can be fixed.
I saw a board at a customer site that was a 250 pin FPGA that was laid out wrong. They fixed it with a ball of wires. I wish I had a picture.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
They were "good" C&K toggles. It was the goo they put into them. They got a bad batch or changed formula.. I don't know. It seemed to get a bit worse with heat too. (soldering)
George H.
Some years ago, we got back the first-samples of an ASIC from the fab, nicely packaged in the usual ceramic package. Plugged it in, powered it up carefully, and it got *really* hot.
Turned out the fab had "spun" the dice 180 degrees before bonding them to the pins. Power was going into all the wrong places, and the entire chip was crowbarring itself.
We were able to use a few of those samples (no time to wait for the fab to re-package) but it required the hairiest pit-of-snakes interposer socket arrangement I've ever seen.
That's similar to another debugging horror yesterday (yesterday was not a good day) -- the circuit is switched on with a Hall effect switch and a magnet. For board-bringup, I've just had a magnet glued to the Hall sensor. That managed to get knocked off at the same time that I downloaded software, making me think that my software was somehow mysteriously making the thing not power up.
Oh, and my Tek DM-501 was reading 300mA power consumption instead of 100, until I jiggled it in the frame. Grr.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.