Re: PLL as modulator og demodulator

Ben Jackson 20 years ago

I would like to use one PLL for both FSK modulator and demodulator

> because of price. I probably gonna switch between a tvxco and FSK input
> to "sig in" on a 4046. I gonna modulate the FSK on after the Loop
> filter. My consern is about the loop filter.

Variable bandwidth loop filters are also used to get faster lock time (and better frequency agility) while still having good stability once lock is achived. If you google around you'll find some appnotes with techniques for accomplishing that.

You might want to consider other PLLs like the MC145170. It has serial programming of the divider/counter values which saves on external parts, but it does lack an integrated VCO.

Ben Jackson http://www.ben.com/

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rasmusms 20 years ago

My center carrier is about 1-3Mhz

Do you know who makes the MC145170? I can't find it on fairchild/motorola homepage anymore. It might be a alternativ.

Do you have a example on an appnote?

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Winfield Hill 20 years ago

The modern pin-compatible version is the mc145170-2, which had a new 32-page rev-5 Freescale datasheet issued last year

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The official p/n was the mc145170P2, D2, DT2, etc.

Freescale (the Motorola RF semi spinoff) has dropped the part (along with many other "legacy" ICs), perhaps to avoid making RoHS versions, but some are available from surplus distributors.

Lansdale Semiconductor is offering a version, the ML145170. Get a 13MB (!) datasheet on their webpage,

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Two classic appnotes were the an1207 and the an1671.

Thanks, - Win

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