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參數(shù)資料
| 型號： | U4224B-CFL |
| 英文描述： | Time Code Receiver |
| 中文描述： | 時間碼接收機 |
| 文件頁數(shù)： | 4/17頁 |
| 文件大小： | 225K |
| 代理商： | U4224B-CFL |
U4224B
TELEFUNKEN Semiconductors
Rev. A3, 02-Apr-96
4 (17)
Q2A, Q2B
According to Q1A, Q1B a crystal is connected between
the pins Q2A and Q2B. It is used with the serial resonance
frequency of the time code transmitter (e.g. 60 kHz
WWVB, 77.5 kHz DCF or 40 kHz JG2AS). The equi-
valent parallel capacitor of the filter crystal is internally
compensated. The value of the compensation is about
0.7 pF.
Q2A
Q2B
94 8383
GND
PON
If PON is connected to GND
,
the U 4224 B receiver IC
will be activated. The set-up time is typical 0.5s after
applying GND at this pin. If PON is connected to V
CC
, the
receiver will go into power down mode.
V
CC
PON
94 8373
TCO
The digitized serial signal of the time code transmitter can
be directly decoded by a microcomputer. Details about
the time code format of several transmitters are described
separately.
The output consists of a PNP
should be taken into account that in the power down mode
(PON = high) TCO will be high.
NPN push-pull-stage. It
V
CC
TCO
GND
PON
94 8380
An additional improvement of the driving capability may
be achieved by using a CMOS driver circuit or a NPN
transistor with pull-up resistor connected to the collector
(see figure KEIN MERKER). Using a CMOS driver this
circuit must be connected to V
CC
.
10 k
V
CC
pin16
TCO
TCO
94 8395 e
100 k
Figure 1.
Please note:
The signals and voltages at the pins REC, INT, FLA, FLB,
Q1A, Q1B, Q2A and Q2B cannot be measured by stan-
dard measurement equipment due to very high internal
impedances. For the same reason the PCB should be pro-
tected against surface humidity.
Design Hints for the Ferrite Antenna
The bar antenna is a very critical device of the complete
clock receiver. But by observing some basic RF design
knowledge, no problem should arise with this part. The IC
requires a resonance resistance of 50 k to 200 k . This
can be achieved by a variation of the L/C-relation in the
antenna circuit. But it is not easy to measure such high
resistances in the RF region. It is much more convenient
to distinguish the bandwidth of the antenna circuit and
afterwards to calculate the resonance resistance.
Thus the first step in designing the antenna circuit is to
measure the bandwidth. Figure 4 shows an example for
the test circuit. The RF signal is coupled into the bar
antenna by inductive means, e.g. a wire loop. It can be
measured by a simple oscilloscope using the 10:1 probe.
The input capacitance of the probe, typically about 10 pF,
should be taken into consideration. By varying the
frequency of the signal generator, the resonance
frequency can be determined.
Scope
RF - Signal
generator
77.5 kHz
C
res
Probe
10 : 1
10 M
wire loop
94 7907 e
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