What happened to XR-2206 Funct. Gen. IC and XR-2212 Precision PLL ???

[Fraser]

That is interesting to hear that newer XR2206 chips misbehave. My 'new' 2206 chips are are at least 15 year old stock, so maybe there is a market for NOS devices after all

I built two ICL8038 based function generators in the 1980's. They were built on a PCB that Radio Spares used to sell and I added a F to V converter to drive a 7106 meter chip for frequency read-out. They both worked very well and I still have them lurking in my equipment store. They are certainly well passed their sell-by date for new builds now.

I have a couple of commercial 20MHz function Generators that use the MAX038. They work very well and I managed to buy a spare pair of new MAX038 chips for only $5 each a couple of years ago, so I can maintain the units if that chip fails in the future. They seem to demand high prics on e*ay these days.

[gtrc]

I found this old topic about the XR2206 function generator and wanted to share my experience on a project.  I made a device that continuously recorded 'environmental data.' The XR2206 was the audio interface to a PC sound card demodulator.  The system plotted a continuous time vs signal level graph. The computer produced and saved data for 30 minute recordings of information.  Really cool system. Put a few hundred hours into the project, including the programming for the computer and the inst amplifier and conditioning circuit for the system.  Long and the short of it was that after 6 weeks of continuous recording, in the middle of one 30 minute plot, the frequency produced by the XR2206 started increacing by itself.  In increased about 20 hz in each half hour, or possibly more.  This continued until the program could no longer plot any trace on the screen.  I changed to another XR2206 and 6 weeks later the same failure occured.  Bought more from a different supplier trying to get a different lot, and same thing happened again. Very disheartening to say the least.  Called XR factory and they said they would look into it.  Never heard anything back.  My circuit was an exact duplicate of the datasheet. I went from being thrilled at having created a living thing, to complete desolation at having wasted so much time.  And the chip was tunable to get very low harmonic distortion of the sine wave. I'm sure it was just a weak trace inside or some little part that slowly eroded away.  Anyway, I would not recomend the chip for continuous duty.  6 weeks gives you a lot of hours of operating time, and maybe intermittent use preserves the chip. I think the chip should be redesigned to fix that problem.  Then it would be a nice device for experimenters. 

[Kleinstein]

There seem to be new supposedly Chinese copies of the XR2206 around, that don't perform that well.

The original XR2206 was a nice chip for a simple F-Gen in the 1980s, but got replaced with DDS Chips. All 3 such chips XR2206, ICL8038 and max038 are obsolete now for quite some time and with the 8038 and especially the max038 it is hard to get one now. So the Chinese copy is better than nothing - though it would be better with it's own name and data-sheet.

[duak]

I always wanted to build my own instruments and one of the first was a function generator.  I remember a function generator project using the XR2206 in the fall of '72 in Radio-Electronics magazine.  I whipped up the emitter coupled oscillator and diff amp portions using discretes for a cheap and dirty function generator made from all used parts.  I don't recall the chip's schematic having any resistor values but it didn't seem that critical as it worked.

A couple of years later I built a generator based on Dr Michael Lampton's sweep generator: https://www.ssl.berkeley.edu/~mlampton/oscillator.pdf   Here's an analog function generator/VCO that won't likely be obsolete any time soon.  This is an interesting design where an integrator and comparator are connected in a self oscillating loop.  I replaced the sweep/voltage controlled frequency part with a log pot.  I used 741 opamps for the integrator & comparator and got a 1 Hz to about 20 KHz frequency range with one control and no range selection.  With newer parts, especially a decompensated opamp for the comparator, the upper frequency limit could be easily bettered.   BTW, I ran across this circuit years later when looking for information on reverse beta and using reversed bipolar transistors for low Vce sat.  Although the article mentioned using the reversed configuration, I didn't understand it until much later.

As an aside, Dr Lampton is an astronaut and his website shows a bunch of nifty electronic, audio & scientific projects and generally neat stuff :  https://www.ssl.berkeley.edu/~mlampton/

Cheers,

[Jidis]

All 3 such chips XR2206, ICL8038 and max038 are obsolete now for quite some time

With the abundance of modern DIY circuits still using that Exar chip (despite its age), I'm guessing nobody ever picked up the ball on that and came out with anything comparable function and price-wise? I seem to remember running across things when I was looking which had *some* of the features or range, but not the full package. Seems odd as I didn't read many good things about the signal quality of the lower end DDS options.

So the Chinese copy is better than nothing - though it would be better with it's own name and data-sheet.

Aside from the all-out malfunctions and supply range weirdness, did anybody ever run any more thorough performance tests to see how close some of the other specs are?

Thanks!

[David Hess]

Study some of the old function generator designs from before the availability of the XR2206 and XR2212 to see how it was done.  Except for frequency stability, they provided higher performance anyway and the frequency stability problem is solvable if necessary.

Having each student implement them from scratch would probably be a waste of time except for the analog students if they even exist however they could be built in module form to replace the XR2206 and XR2212 for everybody else.

[danadak]

Consider as PSOC (it has a wavedac component), sine, tri, square, arbitrary, ARM core,
lots of analog, easy to design a pulsed fgen, like pulse N sine cycles, or for that matter
a sinx/x pulse train of N pulses. Can be swept.

http://www.cypress.com/documentation/application-notes/an69133-psoc-3-psoc-5lp-easy-waveform-generation-wavedac8-component

Besides that you get the following in the PSOC -


For me what stands out is -

1) Routability
2) Fast 12 bit SAR A/D and slow 20 bit DelSig
3) DFB (Digital Filter Block) that is dual channel, handle FIR or IIR filters, or DFB
can be used as a GP fast processor block, similar to RISC block
4) MSI logic elements GUI based and/or the UDB Verilog capability. Eg. the FPGA
like capability
5) Onboard Vref
6) IDAC, VDAC, OpAmps (up to 4), comparator, mixer, switch cap, analog mux....
7) LCD,  COM, UART, I2C, I2S, One Wire, SPI, Parallel, LIN, CAN, BLE, USB
9) Custom components capability, create with schematic capture or Verilog
10) DMA to offload processes like filters, COM, Display
11) ARM M0 (PSOC 4) or M3 (PSOC  5LP) or 8051 core(PSOC 3)
12) Extensive clock generation capabilities
13) All components supported by extensive prewritten APIs

https://www.element14.com/community/thread/23736/l/100-projects-in-100-days?displayFullThread=true

http://www.cypress.com/documentation/code-examples/psoc-345-code-examples

Great video library

Attached component list.  A component is an on chip HW resource.

Free GUI design tool with schematic capture, "Creator". Components have rich API library attached
to each component. Compilers free as well.

PSOC 4 is low end of family, consider 5LP parts as well. PSOC 4 also has arduino footprint boards (pioneer) as well, PSOC 6 dual ARM core.....

https://www.elektormagazine.com/labs/robot-build-with-cypress-psoc

http://www.cypress.com/products/32-bit-arm-cortex-m-psoc


Contact the local sales office, "RSM", regional sales manager, and FAE as well, maybe they can give you some stuff as well.
Never be afraid to ask. Even contact the Manufacturers Rep, sometimes they can have some boards laying around not being
used.

https://brightcove.hs.llnwd.net/e1/uds/pd/1362235890001/1362235890001_5241352463001_2606504288001.mp4?pubId=1362235890001&videoId=2606504288001

http://www.embedded.com/design/prototyping-and-development/4421857/Configuring-a-PSoC-for-a-DIY-oscilliscope-logic-analyzer---Part-1


Regards, Dana.

[eugenenine]

So what is a good simple replacement for either/or of the two?

[danadak]

If you have ever done any embedded stuff, take a look at this
short video.





Regards, Dana.

[Kleinstein]

For some applications one can replace the analog generator with a DDS based one. Something as small as an AD9833 could replace it. DDS offers usually better frequency stability and better quality sine wave, but triangle might be limited in frequency / accuracy. The very simple square of the AD9833 is poor, a good square would be from sine with an extra comparator. There are also rather cheap DDS modules with an AD9850 that might be an option (through no triangle). Thus new frequency generator usually use some kind of DDS.

One can still build a similar circuit, like in older frequency generators. The sine shaper can be a little tricky to get temperature stable - but here the XR2206 and 8038 were not that good either. Depending on the effort it can be better (e.g. higher speed, better temperature stability) than the XR2206 in many respects. Duak posted a link for such a generator circuit - though more an very old, slow one. Usually there is no need to replicate all the function. Features like FSK modulation are not that often needed.