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DA6180B.002

5 May, 2011

TYPICAL APPLICATION (Continued)

Note 1: Crystals

The crystal as well as ferrite antenna frequencies are chosen according to the time-signal system (Table 1). More

detailed crystal nominal frequency is normally specified for certain load capacitance but in MAS6180 filter circuit

the load capacitance is not used. Effectively this means that most accurate filter frequency is achieved by using

about 3 Hz higher frequency crystal than the received time signal frequency. For example in DCF77 application a

77.503 kHz crystal resonates at the desired DCF77 77.500 kHz frequency when the load capacitor is missing.

Table 1. 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

external compensation capacitor should be matched similarly as well as possible with crystal’s shunt

capacitance. See Compensation Capacitance Options on table 2.

Table 2 . Compensation Capacitance Options

Device

Crystal Description

MAS6180B1

0.75 pF

MAS6180B5

For any crystals, external compensation capacitor

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 1 pF floating package shunt capacitance can have

0.85 pF 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.

In dual band receiver configuration the crystals are best to connect as shown in figure 3. In this configuration the

crystals’ shunt capacitances compensate each other and external compensation capacitor is not needed at all.

Table 3 below presents some crystal suppliers having suitable crystals for time signal receiver application.

Table 3. Crystal Suppliers and Crystal Types in Alphabetical Order for Time Signal Receiver Application

Supplier

Crystal Type

Dimensions

Web Link

Citizen

CFV-206

ø 2.0 x 6.0

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

Epson Toyocom

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

MS3V-T1R

1.45 x 1.45 x 6.7

http://www.microcrystal.com/

Seiko

Instruments

VTC-120

ø 1.2 x 4.7

http://www.sii-crystal.com