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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

Antenna Frequency

Recommended Crystal Frequency

DCF77

Germany

77.5 kHz

77.503 kHz

HBG

Switzerland

75 kHz

75.003 kHz

MSF

United Kingdom

60 kHz

60.003 kHz

WWVB

USA

60 kHz

60.003 kHz

JJY

Japan

40 kHz and 60 kHz

40.003 kHz and 60.003 kHz

BPC

China

68.5 kHz

68.505 kHz

Table 3. Compensation Capacitance Options

Device

Crystal Description

MAS6179A1

0.75 pF

MAS6179A2

1.3 pF

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

CFV-206

ø 2.0 x 6.0

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

Epson

C-2-Type

C-4-Type

ø 1.5 x 5.0

ø 2.0 x 6.0

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

KDS Daishinku

DT-261

ø 2.0 x 6.0

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

Microcrystal

MX1V-L2N

MX1V-T1K

ø 2.0 x 6.0

ø 2.0 x 8.1

http://www.microcrystal.com/

Seiko

Instruments

VTC-120

ø 1.2 x 4.7

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.