MAS9178 View Datasheet(PDF) - Micro Analog systems
Part Name
Description
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MAS9178 Datasheet PDF : 8 Pages
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DA9178.001
10 Dec, 2003
TYPICAL APPLICATION (Continued)
Note 1
Ferrite
Antenna
RFP
RFM
QOP
QI
AGC Amplifier
Note 4
Optional
Control
for AGC on/hold
QOM
AON
Demodulator
&
OUT
Comparator
Receiver
Output
Figure 3
Antenna
Frequency
Selection
Power Supply/Biasing
VDD VSS PDN
AGC DEC
1.4 V
CAGC +
10 µF
CDEC
47 nF
Note 3
Note 2
Power Down /
Fast Startup
Control
Dual band application circuit of external compensation capacitance version MAS9178A5.
Note 1: Crystal
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=0.875 pF of MAS9178A1. External compensation pad QOM is unconnected in
MAS9178A1. MAS9178A5 does not have internal compensation capacitance CC and it requires use of external
compensation capacitor CC_EXT. It must be connected between pins QOM and QI (see figure 2). CC_EXT should
have equal value with crystal’s effective shunt capacitance C0. External compensation version MAS9178A5
should be used when fixed 0.875 pF compensation capacitance of MAS9178A1 does not match well with used
crystal’s shunt capacitance.
It should be noted that grounded crystal package has reduced shunt capacitance. This value is about 85% of
floating crystal 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.
Time-Signal System Location
Antenna Frequency
DCF77
MSF
WWVB
JJY
Table 1
Germany
77.5 kHz
United Kingdom
60 kHz
USA
60 kHz
Japan
40 kHz and 60 kHz
Time-Signal System Frequencies
Recommended Crystal Frequency
77.503 kHz
60.003 kHz
60.003 kHz
40.003 kHz and 60.003 kHz
5 (8)
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