U4223B ATMEL Corporation, U4223B Datasheet - Page 3

• Manufacturer Part Number: U4223B
• Description: Time-code Receiver With A/d Converter
• Manufacturer: ATMEL Corporation

Rev. A7, 06-Mar-01
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 resonant frequency of the time-code transmitter
(e.g., 60 kHz WWVB, 77.5 kHz DCF or 40 kHz JG2AS).
The equivalent parallel capacitor of the filter crystal is
internally compensated. The compensated value is about
0.7 pF. If full sensitivity and selectivity are not needed,
the crystal filter can be substituted by a capacitor of 82 pF.
REC
Rectifier output and integrator input: The capacitor C
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 C
about 420 kW and is low compared to the impedance of
C
2
.
2
. The dynamic input resistance has a value of
Q1A
DEC
Figure 5.
Figure 6.
Figure 7.
GND
REC
GND
Q1B
GND
1
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 C
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 C
and FLB suppresses higher frequencies at the trigger
circuit of the decoder.
FLB
INT
SL
at the integrator output and also the AGC
VCC
= 0) disconnects the rectifier and holds
SL
Figure 10.
Figure 8.
Figure 9.
SL
3
2
= V
connected between FLA
INT
between INT and DEC
GND
INT
U4223B
CC
is the control voltage
) sets normal func-
FLB
94 8377
3 (18)