interest?
For a test your method would be faster. For production, not so much, because you'd have to have a servo'ed dual MOSFET in that path. Rohm makes them, cheap, if that's the plan at the end.
They should be rather hungry in this economy. Might just take one phone call ;-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Eek! Heavens, no! John is cute as a button! It's just that he's about
5'6" or so, a bit wiry, and Irish. :-) (I met him face-to-face at a trade show in Long Beach a couple of years ago, and picked up some of his refrigerator magnets.) :-)Cheers! Rich
interest?
I don't follow that. If I make a simple triangle wave, maybe 0.5 volts p-p, a few KHz maybe, and run it through a big resistor into the regulator pin that the timing resistor connects to, it should FM the switcher's frequency. I'll check all the regs to make sure, but the Fset pins are usually at DC, and the Fset resistor usually sets a DC current that the chip uses to make frequency.
If I have, say, a 1 MHz switcher and push it +-1%, that's 20 KHz p-p, so I should reduce the amplitude of a 1 MHz birdie by about 20,000:1 in a 1 Hz BW situation. Not that much in real life, but even 100:1 is a good number.
John
Was that an earthquake or was the Joerg?
To calarify, this is rev 30 of the working layout. We haven't fabbed any boards yet.
The PCB file will be formally released as 26D150A.PCB, to make rev A of the product. During layout, we number every iteration. If we change a net or add a resistor or whatever, we start with schematic
26S150A29.SCH, change it to 26S150A30.SCH and save that, make the differences file ECO30, apply that onto pcb 26D150A29.PCB, and save as 26D150A30.PCB. So we have all the iterations and all the ECO files, all organized. When we release the schematic and pcb as rev A, we delete all that working junk. Since we're iterating on the BGA pinout, we're spinning a lot of ECOs.If we go A to B, we start the sequence all over, 26S150B1.SCH etc.
John
That's what we give out these days, instead of pots of gold.
John
No, it worked, must have been an earthquake then ;-)
I do it similarly, except adding X1, X2 and so on. And I usually cannot erase the intermediates upon ECO-release because federal agencies often require that a complete design history be kept. So if you do medical, maybe better not to toss it.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
interest?
On most newer ones it does (simulating one right now). But there are some that do it "NE555-style". Even then you can sometimes get away with current injection but it needs to be vetted for each chip type you are using.
Why not go all out and do +/-10% or more?
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Just got assembled boards back from AA-PCB yesterday. They threw in a bag of trail mix. Sweet. Needless to say, it was all gone before I had the first scope shots on the server and I wasn't too hungry at dinner time.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Funny what extraneous stuff can end up in a shipment. Recently found a chocolate chip 2-pack in my Amazon order ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
They seem to do that with all shipments. The one last week also had trail mix in it but arrived at a client so their engineers got to enjoy it.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
corner
interest?
The issue would be whether FMing the switch frequency would result in ripple on the output rail. First-order, it shouldn't. I'll have to try it. I've been doing too much business crud and need some hardware time anyhow.
Maybe I'll include an FM deviation trimpot on the board. Or make the amplitude and frequency programmable from the FPGA. Or go with Rob's idea and synthesize the switch frequencies and sync all the regulators.
John
corner
interest?
at
some
I don't think 10% will cause much in additional ripple. Certainly not if it's current-controlled siwtchers.
Trimpot? Euww ...
With a new "Larkin Switcher Agility" taskbar on the GUI :-)
Seems nowadays every li'l program wants its own taskbar until the browser screen arrives at the size of a stamp.
I'd scatter them and not let them run in unison. Makes for a finer mush, or in chef-speak "puree'd".
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
corner
interest?
at
some
some
The point being that, when the actual instrument is up and being driven by chemists, I'd like a quick and easy way to play with the spread-spectrum parameters to see the effects. I can always nail down the values once I know what works best. I often use fixed resistors but also put down pads for a pot so we can tweak the first articles without soldering.
Exactly. The trimpot sounds easier.
Certainly, if we do the digital sync thing, each reg would have its own synthesizer. If analog, I can just set their cf's here and there and scale the FMs with resistors.
John
I just had my potmeter comeuppance yesterday. I am very much against those things and it proved the point. Built a tester jig for a client, just for engineering, they didn't want SCADA controls on that (tried to convince them and now wish they had agreed ...). Sure enough the Murata "10-turn" potmeter exhibits a huge dead spot around the point where they said they wanted it. Like a half turn of slack and you can't get the pot inside that area. Hurumph!
I believe nowadays they just put cheap regular pots in there and roach a worm gear onto them so they can be called 10-turn.
[...]-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Did it loook like it was packed intentionally, or more like it fell out of an inattentive packer's pocket? ;-)
Cheers! Rich
Once, while on recycling duty, I was breaking down boxes, and found two
12-packs of brand new pencils. ;-)Cheers! Rich
I usually get Bible verse flyers.
John
Yes. Single-turn trimpots are as good as, or better than, most multi-turns. And the singles are less likely to jump in value if shocked later.
We did find a trimpot that makes a good DC-to-1 GHz gain trimmer, which is really hard to do any other way. Digital pots have rotten bandwidths. Ditto MDACs. VGAs aren't accurate at DC. Fets and such, if you can make them fast enough, have distortion and temperature problems. PINs don't work at low frequencies. Wot's a boy to do?
John
I wouldn't mind those at all. But wasn't it you guys who have a custom transformer vendor sending home-baked cookies along?
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Nope, same thing with another delivery to a client last week.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
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.