U4224B TEMIC Semiconductors, U4224B Datasheet - Page 3

• Manufacturer Part Number: U4224B
• Description: Time Code Receiver
• Manufacturer: TEMIC Semiconductors

TELEFUNKEN Semiconductors
Rev. A3, 02-Apr-96
Q1A, Q1B
In order to achieve a high selectivity, a crystal is con-
nected between the pins Q1A and Q1B. It is used with the
serial resonance frequency of the time code transmitter
(e.g. 60 kHz WWVB, 77.5 kHz DCF or 40kHz JG2AS).
The equivalent parallel capacitor of the filter crystal is
internally compensated. The compensated value is about
0.7 pF. If the full sensitivity and selectivity is not needed,
the crystal filter can be substituted by a capacitor of 10 pF
for DCF and WWVB and 22 pF for JG2AS.
REC
Rectifier output and integrator input: The capacitor C1
between REC and INT is the lowpass filter of the rectifier
and at the same time a damping element of the gain
control.
DEC
Decoder input: Senses the current through the integration
capacitor C2. The dynamic input resistance has a value of
about 420k
C2.
94 8382
94 8376
W
Q1A
and is low compared to the impedance of
DEC
GND
REC
GND
Q1B
GND
94 8374
SL
AGC hold mode: SL high (V
tion, SL low (V
the voltage V
amplifier gain.
INT
Integrator output: The voltage V
for the AGC. The capacitor C2 between INT and DEC
defines the time constant of the integrator. The current
through the capacitor is the input signal of the decoder.
FLA, FLB
Lowpass filter: A capacitor C3 connected between FLA
and FLB supresses higher frequencies at the trigger
circuit of the decoder.
94 8378
FLB
INT
SL
at the integrator output and also the AGC
V
= 0) disconnects the rectifier and holds
CC
SL
SL
= V
INT
GND
INT
U4224B
CC
is the control voltage
) sets normal func-
FLB
94 8377
94 8375
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