SC9257 查看數據表（PDF） - Silan Microelectronics

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生产厂家

SC9257

0.3-6.0V PLL for digital tuning systems (DTS)

Silan Microelectronics 

Silan

Semiconductors

SC9257

Phase comparator

The phase comparator outputs the phase error after comparing the phase difference of the reference frequency

signal supplied by the reference counter and the divided output from the programmable counter. The frequencies

and phase differences of these two signals are then equalized by passing them through low-pass filters. These

signals then control the VCO.

The filter constants can be customized for FM and AM bands since the signals are output in parallel from the

phase comparator then pass through the two tristate buffer pins, DO1 and DO2.

Reference frequency signal

Programmable

counter output

R

phase

S comparator

VDD

DO1

L.P.F

VDD

DO2

L.P.F

FM

VCO

AM

VCO

Fig.7

VCC

R

S

DO

Low level

floating

High level

DO Output Timing Chart

R1

DO

R2 C RL

Tr1

Tr2

R3

Standard

Tr1:2SC1815

Tr2:2SK246

To VCO varactor diode

Typical low-pass filter constants

(FM band reference values)

C=0.33­F

R1=10K¡

R2=8.2K¡

R3=330¡

RL=10K¡

Typical Active Low-Pass Filter Circuit

Fig.8

Fig.9

The figures above show the DO output timing chart and a typical active low-pass filter circuit featuring a

Darlington connection between the FET and transistor.

The filter circuit shown above is just one example. Actual circuits should be designed based on the band

composition and the properties desired from the system.

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.0

20

2001.10.18

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