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參數資料
| 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： | 5/17頁 |
| 文件大小： | 225K |
| 代理商： | U4224B-CFL |
U4224B
TELEFUNKEN Semiconductors
Rev. A3, 02-Apr-96
5 (17)
Afterwards, the two frequencies where the voltage of the
rf signal at the probe drops 3 dB down can be measured.
The difference between these two frequencies is called
the bandwidth BW
A
of the antenna circuit. As the value
of the capacitor C
res
in the antenna circuit is well known,
it is easy to compute the resonance resistance according
to the following formula:
R
res
1
BW
A
2
C
res
whereas
R
res
is the resonance resistance,
BW
A
is the measured bandwidth (in Hz)
C
res
is the value of the capacitor in the antenna circuit
(in Farad)
If high inductance values and low capacitor values are
used, the additional parasitic capacitances of the coil
must be considered. It may reach up to about 20 pF. The
Q-value of the capacitor should be no problem if a high
Q-type is used. The Q-value of the coil is more or less
distinguished by the simple DC-resistance of the wire.
Skin effects can be observed but do not dominate.
Therefore it shouldn’t be a problem to achieve the recom-
mended values of resonance resistance. The use of thicker
wire increases Q and accordingly reduces bandwidth.
This is advantageous in order to improve reception in
noisy areas. On the other hand, temperature compen-
sation of the resonance frequency might become a
problem if the bandwidth of the antenna circuit is low
compared to the temperature variation of the resonance
frequency. Of course, Q can also be reduced by a parallel
resistor.
Temperature compensation of the resonance frequency is
a must if the clock is used at different temperatures.
Please ask your dealer of bar antenna material and of ca-
pacitors for specified values of temperature coefficient.
Furthermore some critical parasitics have to be consid-
ered. These are shortened loops (e.g. in the ground line of
the PCB board) close to the antenna and undesired loops
in the antenna circuit. Shortened loops decrease Q of the
circuit. They have the same effect like conducting plates
close to the antenna. To avoid undesired loops in the
antenna circuit it is recommended to mount the capacitor
C
res
as close as possible to the antenna coil or to use a
twisted wire for the antenna coil connection. This twisted
line is also necessary to reduce feedback of noise from the
microprocessor to the IC input. Long connection lines
must be shielded.
A final adjustment of the time code receiver can be done
by pushing the coil along the bar antenna. The maximum
of the integrator output voltage V
INT
at pin INT indicates
the resonant point. But attention: The load current should
not exceed 1 nA, that means an input resistance
of the measuring device is required. Therefore a special
DVM or an isolation amplifier is necessary.
1 G
Absolute Maximum Ratings
Parameters
Symbol
V
CC
T
amb
R
stg
T
j
±
V
ESD
Value
5.25
–25 to +75
–40 to +85
125
2000
Unit
V
C
C
C
V
Supply voltage
Ambient temperature range
Storage temperature range
Junction temperature
Electrostatic handling
(MIL Standard 883 D), excepted pins 5, 6, 13 and 14
Thermal Resistance
Parameters
Symbol
R
thJA
Value
70
Unit
K/W
Thermal resistance
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