MAS9079 查看數據表（PDF） - Micro Analog systems
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MAS9079 Datasheet PDF : 9 Pages
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DA9079.003
19 May, 2005
TYPICAL APPLICATION (Continued)
Note 1: Crystals
The crystals as well as ferrite antenna frequencies are chosen according to the time-signal system (Table 3).
The crystal shunt capacitance C0 should be matched as well as possible with the internal shunt capacitance
compensation capacitor CC of MAS9079. See Compensation Capacitance Options on table 2.
Table 2 Compensation Capacitance Options
Device
CC
Crystal Description
MAS9079A1
MAS9079A2
MAS9079A3
MAS9079A4
0.75 pF
0.875 pF
1.25 pF
1.5 pF
For low C0 crystal
For low C0 crystal
For high 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 3 Time-Signal System Frequencies
Time-Signal System Location
DCF77
HGB
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
Table 4 below presents some crystal manufacturers having suitable crystals for timesignal receiver application.
Table 4. Crystal Manufacturers and Crystal Types in Alphaphetical Order for Timesignal 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.epsondevice.com/e/
http://www.kdsj.co.jp/english.html
http://www.microcrystal.com/
http://speed.sii.co.jp/pub/compo/quartz/topE.jsp
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. DEC capacitor can be low
leakage chip capacitor.
7 (9)
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