Where to get a simple datasheet? for LMF90

Have you got the part number right? National's first generation filter like that had some other prefix (I can't remember what, I'd know the minute I saw it). I'm thinking "MFC" but I don't know why. It didn't start with National's traditional prefix, "LM". Maybe later they used some other prefix, but I'd double check.

Michael

Just got a copy from: .

THANK YOU !!!!

At first I couldn't figure out the significance of the giant offer to download a spec for a PIC, but below that was indeed a URL that yielded the .pdf ending so I could download. Got it thanks

...now any AppNotes floating around?

National's classic switched-cap filter was the MF10, metal-gate CMOS. There was a later poly-gate version, can't remember the part number.

Overall, switched-cap filters weren't all that great. OK for some apps, but they were really noisy, and aliased anything available, including power supply crud.

I once designed a double-conversion superhet FSK modem full of MF10s, for Reuters' landline newswire service. Sold a few before PCs and the Internet made the classic newswire thing obsolete.

The LMF100. Nice part if you needed to do anything fancy and low SNR was okay. I used it to make a SSB mixer once, and it worked great.

The clock-tunable thing was pretty convenient for some jobs, especially back when tight-tolerance capacitors were expensive.

Cheers

Phil Hobbs

Yeah, the modem did any channel, and any one of three baud rate/bandwidths, with just dip switches. The older stuff had plug-in LC filters.

The app note mentioning the LMF90 was AN779, but they edited it out of AN 779A. The old version is at

Cheers

Phil Hobbs

And there's a real datasheet at

Since the parasites have taken over the search engine ecosystem, Datasheetarchive's built-in search works better than using Google to search DSA.

Cheers

Phil Hobbs

This one was one of the first in a google search:

Even has listing for brokers still selling it.

Google search terms "LMF90 switched capacitor datasheet" and it went straight to it.

Yes, that's what I was remembering.

It's one of those things that were transitory, like charge coupled delay lines. Fill in a gap, relatively late, that soon could be done by converting to digital and doing the work there.

Michael

The thing with switched capacitor designs is everyone bitched when they could see the output of the filter, i.e. the charge injection glitch. As products were designed at higher levels of integration, i.e. modems, the charge injection was less of an issue because the performance of the system as a whole was better than the discrete solutions, mostly because nobody could throw the kind of iron (complex circuitry) at the system as we could do on silicon.

Until the oversampled converters came along, many systems were implemented in custom switched capacitor chips.

Actually, I only really needed the DataSheet and any AppNotes. but is ok, got the data sheet and an AppNote.