MAS6179 데이터 시트보기 (PDF) - Micro Analog systems

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MAS6179

AM Receiver IC

Micro Analog systems 

DA6179.000

22 January, 2007

TYPICAL APPLICATION (Continued)

Note 1: Crystals

The crystals as well as ferrite antenna frequencies are chosen according to the time signal system (Table 2).

The reason why the crystal frequency is about 3 Hz higher than the signal frequency is that the crystal is

operated without the loading capacitor. Without loading capacitor the actual resonance frequency is about 3 Hz

lower thus 77.503 kHz crystal resonates at 77.500 kHz when no loading capacitor is used.

Table 2. Time Signal System Frequencies

Time Signal System Location

DCF77

HBG

MSF

WWVB

JJY

BPC

Germany

Switzerland

United Kingdom

USA

Japan

China

Antenna Frequency

77.5 kHz

75 kHz

60 kHz

60 kHz

40 kHz and 60 kHz

68.5 kHz

Recommended Crystal Frequency

77.503 kHz

75.003 kHz

60.003 kHz

60.003 kHz

40.003 kHz and 60.003 kHz

68.505 kHz

The crystal shunt capacitance C0 should be matched as well as possible with the internal shunt capacitance

compensation capacitor CC of MAS6179. See Compensation Capacitance Options in table 3.

Table 3. Compensation Capacitance Options

Device

CC

Crystal Description

MAS6179A1

MAS6179A2

0.75 pF

1.3 pF

For low C0 crystal

For high C0 crystal

It should be noted that grounded crystal package has reduced shunt capacitance. This value is about 85% of

floating crystal shunt capacitance. For example crystal with 1pF floating package shunt capacitance can have

0.85pF grounded package shunt capacitance. PCB traces of crystal and external compensation capacitance

should be kept at minimum to minimize additional parasitic capacitance which can cause capacitance

mismatching.

Highest frequency crystal is connected to crystal output pin 1 (QO1). Medium frequency crystal is connected to

crystal output pin 2 (QO2). Lowest frequency crystal is connected to crystal output pin 3 (QO3). The other pin of

each crystal is connected to common crystal input pin QI.

Table 4 below presents some crystal manufacturers having suitable crystals for time signal receiver application.

Table 4. Crystal Manufacturers and Crystal Types in Alphabetical Order for Time Signal Receiver Application

Manufacturer Crystal Type Dimensions

Web Link

Citizen

Epson

KDS Daishinku

Microcrystal

Seiko

Instruments

CFV-206

C-2-Type

C-4-Type

DT-261

MX1V-L2N

MX1V-T1K

VTC-120

ø 2.0 x 6.0

ø 1.5 x 5.0

ø 2.0 x 6.0

ø 2.0 x 6.0

ø 2.0 x 6.0

ø 2.0 x 8.1

ø 1.2 x 4.7

http://www.citizen.co.jp/tokuhan/quartz/

http://www.epsontoyocom.co.jp/english/

http://www.kds.info/index_en.htm

http://www.microcrystal.com/

http://www.sii-crystal.com

Note 2: AGC Capacitor

The AGC and DEC capacitors must have low leakage currents due to very small signal currents through the

capacitors. The insulation resistance of these capacitors should be at minimum 100 MΩ. Also probes with at

least 100 MΩ impedance should be used for voltage probing of AGC and DEC pins. Electrolytic AGC capacitor

should have voltage rating at least 25 V for low enough leakage. DEC capacitor can be low leakage chip

capacitor.

7 (10)

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