MAS9178 MAS, MAS9178 Datasheet - Page 5

• Manufacturer Part Number: MAS9178
• Description: Stand-alone am Receiver ic
• Manufacturer: MAS

TYPICAL APPLICATION (Continued)
Antenna
Figure 3
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 C
compensation capacitor C
MAS9178A1. MAS9178A5 does not have internal compensation capacitance C
compensation capacitor C
have equal value with crystal’s effective shunt capacitance C
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 the crystals can be connected in parallel thus external compensation capacitor value
C
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.
Time-Signal System
DCF77
MSF
WWVB
JJY
Table 1
Note 2: AGC Capacitor
The AGC and DEC capacitors must have low leakage currents due to very small 40 nA signal currents through
the capacitors. The insulation resistance of these capacitors should be higher than 70 M . Also probes with at
least 100 M ==impedance should be used for voltage probing of AGC and DEC pins. Electrolyte capacitors
cannot be used due to their large leakage current. Instead low leakage tantalum capacitor can be used as AGC
capacitor. DEC capacitor can be low leakage chip capacitor.
Ferrite
C_EXT
must be sum of two crystals’ shunt capacitances. In dual band receiver it is also possible to connect other
Dual band application circuit of external compensation capacitance version MAS9178A5.
Time-Signal System Frequencies
RFM
RFP
1.4 V
Location
Germany
United Kingdom
USA
Japan
VDD
C_EXT
C
Power Supply/Biasing
=0.875 pF of MAS9178A1. External compensation pad QOM is unconnected in
0
QOP
AGC Amplifier
. It must be connected between pins QOM and QI (see figure 2). C
Note 1
should be matched as well as possible with the internal shunt capacitance
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VSS
Power Down /
Fast Startup
PDN
QI
Control
Note 3
Antenna Frequency
77.5 kHz
60 kHz
60 kHz
40 kHz and 60 kHz
QOM
C
10 F
AGC
AGC
for AGC on/hold
Demodulator
Note 2
Comparator
Optional
+
Control
Note 4
0
. External compensation version MAS9178A5
&
DEC
AON
Recommended Crystal Frequency
77.503 kHz
60.003 kHz
60.003 kHz
40.003 kHz and 60.003 kHz
C
47 nF
OUT
DEC
C
and it requires use of external
Receiver
Output
22 Apr, 2003
DA9178.000
C_EXT
should
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