MC145170-1 Просмотр технического описания (PDF) - Motorola => Freescale

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MC145170-1

PLL Frequency Synthesizer with Serial Interface

Motorola => Freescale 

PHASE–LOCKED LOOP — LOW PASS FILTER DESIGN

(A)

PDout

VCO

R1

C

ωn =

ζ=

F(s) =

Kφ KVCO

NR1C

Nωn

2KφKVCO

1

R1sC + 1

(B)

PDout

VCO

R1

R2

C

ωn =

Kφ KVCO

NC(R1 + R2)

ζ=

0.5 ωn

ǒ R2C

+

NǓ

KφKVCO

F(s) =

R2sC + 1

(R1 + R2)sC + 1

R2

(C)

φR

R1

C

–

φV

A

VCO

+

R1

ωn =

Kφ KVCO

NCR1

ωnR2C

ζ=

2

R2

ASSUMING GAIN A IS VERY LARGE, THEN:

C

F(s) = R2sC + 1

R1sC

NOTE:

For (C), R1 is frequently split into two series resistors; each resistor is equal to R1 divided by 2. A capacitor CC is then placed from the

midpoint to ground to further filter the error pulses. The value of CC should be such that the corner frequency of this network does not

significantly affect ωn.

DEFINITIONS:

N = Total Division Ratio in Feedback Loop

Kφ (Phase Detector Gain) = VDD / 4π V/radian for PDout

Kφ (Phase Detector Gain) = VDD / 2π V/radian for φV and φR

KVCO (VCO Gain) =

2π∆fVCO

∆VVCO

For a nominal design starting point, the user might consider a damping factor ζ ≈ 0.7 and a natural loop frequency ωn ≈ (2πfR/50) where

fR is the frequency at the phase detector input. Larger ωn values result in faster loop lock times and, for similar sideband filtering, higher

fR–related VCO sidebands.

RECOMMENDED READING:

Gardner, Floyd M., Phaselock Techniques (second edition). New York, Wiley–Interscience, 1979.

Manassewitsch, Vadim, Frequency Synthesizers: Theory and Design (second edition). New York, Wiley–Interscience, 1980.

Blanchard, Alain, Phase–Locked Loops: Application to Coherent Receiver Design. New York, Wiley–Interscience, 1976.

Egan, William F., Frequency Synthesis by Phase Lock. New York, Wiley–Interscience, 1981.

Rohde, Ulrich L., Digital PLL Frequency Synthesizers Theory and Design. Englewood Cliffs, NJ, Prentice–Hall, 1983.

Berlin, Howard M., Design of Phase–Locked Loop Circuits, with Experiments. Indianapolis, Howard W. Sams and Co., 1978.

Kinley, Harold, The PLL Synthesizer Cookbook. Blue Ridge Summit, PA, Tab Books, 1980.

Seidman, Arthur H., Integrated Circuits Applications Handbook, Chapter 17, pp. 538–586. New York, John Wiley & Sons.

Fadrhons, Jan, “Design and Analyze PLLs on a Programmable Calculator,” EDN. March 5, 1980.

AN535, Phase–Locked Loop Design Fundamentals, Motorola Semiconductor Products, Inc., 1970.

AR254, Phase–Locked Loop Design Articles, Motorola Semiconductor Products, Inc., Reprinted with permission from Electronic Design,

1987.

AN1207, The MC145170 in Basic HF and VHF Oscillators, Motorola Semiconductor Products, Inc., 1992.

MC145170–1

16

MOTOROLA

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