DA9180.004
15 September, 2005
TYPICAL APPLICATION (Continued)
Note 1: Crystals
The crystal as well as ferrite antenna frequencies are chosen according to the time-signal system (Table 1). The
crystal shunt capacitance C0 should be matched as well as possible with the internal shunt capacitance
compensation capacitor CC of MAS9180. MAS9180A5 and MAS9180AF are options for external crystal
compensation capacitor. The external compensation capacitor should be matched similarly as well as possible
with crystals shunt capacitance. See Compensation Capacitance Options on table 2.
Table 1Time-Signal System Frequencies
Time-Signal System
Location
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
Table 2Compensation Capacitance Options
Device
CC
Crystal Description
Input
MAS9180A1
MAS9180A5
MAS9180AB
MAS9180AC
MAS9180AD
MAS9180AE
MAS9180AF
0.75 pF
CC_EXT
0.75 pF
1.25 pF
1.5 pF
2.5 pF
CC_EXT
For low C0 crystal
For any crystals, external compensation capacitor
For low C0 crystal
For low C0 crystal
For low C0 crystal
Differential
Differential
Asymmetric
Asymmetric
Asymmetric
Asymmetric
Asymmetric
For low C0 crystal
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 can be connected in parallel thus external compensation
capacitor value CC_EXT must be sum of two crystals’ shunt capacitances. Instead of parallel crystal connection it is
also possible to connect other crystal from QOP pin and the other crystal from QOM pin to common QI pin (figure
3). In this circuit configuration no external compensation capacitor is required since the crystals compensate
each other. The sensitivity of dual band receiver configuration will be lower than that of single band receiver
configuration since the noise band width of crystal filter with two parallel crystals is double.
Table 3 below presents some crystal manufacturers having suitable crystals for timesignal receiver application.
Table 3. Crystal Manufacturers and Crystal Types in Alphaphetical Order for Timesignal Receiver Application
Manufacturer
Crystal Type
Dimensions
Web Link
Citizen
Epson
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.epsondevice.com/e/
KDS Daishinku
Microcrystal
http://www.kdsj.co.jp/english.html
http://www.microcrystal.com/
Seiko
http://speed.sii.co.jp/pub/compo/quartz/topE.jsp
Instruments
7 (15)
MAS [ MICRO ANALOG SYSTEMS ]
