DA1017.002
29 May, 2002
TYPICAL APPLICATION
77503 Hz
QO
Ferrite-
An tenna
RFI
AG C Am plifier
QI
Dem odulator
&
Com parator
DCF
Receiver
output
Pow er Supply/Biasing
VDD
VSS
PDN
AG C
470 nF
DEC
47 nF
PUP
+1.1V to +3.6V
Note 1: Ferrite Antenna and Crystal
The crystal as well as ferrite antenna frequencies are chosen according to the time signal system frequency.
DCF-77 transmitter frequency is 77.5 kHz. The ferrite antenna center frequency has to be tuned to 77.5 kHz.
The optimal crystal frequency is 77503 Hz but also 77500 Hz crystal can be used. The shunt capacitance of the
crystal should be as close as possible to internal shunt capacitance compensation capacitor of 0.75 pF for
optimal noise filtering.
Note 2: AGC and DEC Capacitors
The AGC and DEC capacitors should 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 MΩ. Also probes
with at least 100 MΩ impedance should be used for voltage probing of AGC and DEC pins.
4(6)
MAS [ MICRO ANALOG SYSTEMS ]
