U4224B Datasheet, PDF (4/17 Pages) TEMIC Semiconductors – Time Code Receiver

U4224B
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
94 8383
Q2B
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 NPN push-pull-stage. It
should be taken into account that in the power down mode
(PON = high) TCO will be high.
V_CC
PON
TCO
94 8380
GND
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.
V_CC
100 kW
10 kW
TCO
pin16
TCO
94 8395 e
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
W W ^{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.
RF - Signal
generator
77.5 kHz
wire loop
C_res
Scope
Probe
w10
10
M: ¹W
94 7907 e
4 (17)
TELEFUNKEN Semiconductors
Rev. A3, 02-Apr-96