SC9257 データシートの表示（PDF） - Silan Microelectronics

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SC9257

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

Silan Microelectronics 

Silan

Semiconductors

SC9257

2. Prescaler and programmable counter circuit configuration

(1) Pulse swallow mode circuit configuration

PSC

P0-P3

FMIN

AMIN

1/2 FMH

FML

HF

FM,MODE

2 modulus

prescaler

Prescaler section

Fig.3

4bit swallow counter

Preset

12bit programmable counter

P4-P15

To phase

comparator

This circuit consists of a 2 modulus prescaler, a 4 bit swallow counter and a 12bit programmable counter.

During FMIN(FMIN mode),a 1/2 prescaler is added to the preceding step.

(2) Direct dividing method circuit configuration

AMIN

Amp

Preset

12bit program counter

To phase comparator

P4-P15

Fig.4

With the direct dividing mode, the prescaler section is bypassed and the 12bit programmable counter is used.

(3) Both FMIN and AMIN have built-in amps. Data are input by capacitor coupling. FMIN and AMIN operate at

low amplitude.

General-purpose counter

The general-purpose counter is a 20bit counter. It has such uses as counting AM/FM band intermediate

frequencies (IF) and detecting auto-stop signals during auto-search tuning. It also features a cycle measurement

function for such uses as measuring low-frequency pilot signal cycles.

1. General-purpose counter control bits

(1) Bits G0 and G1 … Used for selecting the general-purpose counter gate time.

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

REV: 1.0

13

2001.10.18

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