DA6180C.001
17 September, 2014
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
Location
Time-Signal System
Antenna Frequency Recommended Crystal Frequency
DCF77
HGB
MSF
WWVB
JJY
BPC
Germany
Switzerland
United Kingdom
USA
Japan
China
77.5 kHz
75 kHz
60 kHz
60 kHz
40 kHz and 60 kHz
68.5 kHz
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 MAS6180. See Compensation Capacitance Options on table 2.
Table 2. Compensation Capacitance Options
CC
Device
Crystal Description
MAS6180C1
0.75 pF
For low C0 crystals
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 should be kept at minimum to minimize
additional parasitic capacitance which can cause capacitance mismatching.
Table 3 below presents some crystal manufacturers having suitable crystals for time signal receiver application.
Table 3. Crystal Manufacturers and Crystal Types in Alphabetical Order for Time Signal Receiver Application
Dimensions
Manufacturer
Crystal Type
Web Link
Citizen
CFV-206
ø 2.0 x 6.0
ø 1.5 x 5.0
ø 2.0 x 6.0
ø 2.0 x 6.0
1.45 x 1.45 x 6.7
ø 1.2 x 4.7
http://www.citizen.co.jp/tokuhan/quartz/
http://www.epsontoyocom.co.jp/english/
Epson Toyocom C-2-Type
C-4-Type
KDS Daishinku
Microcrystal
Seiko
DT-261
MS3V-T1R
VTC-120
http://www.kds.info/index_en.htm
http://www.microcrystal.com/
http://www.sii-crystal.com
Instruments
5 (12)
MAS [ MICRO ANALOG SYSTEMS ]
