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ELM440 데이터시트 PDF




ELM에서 제조한 전자 부품 ELM440은 전자 산업 및 응용 분야에서
광범위하게 사용되는 반도체 소자입니다.


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부품번호 ELM440 기능
기능 60Hz Generator
제조업체 ELM
로고 ELM 로고


ELM440 데이터시트 를 다운로드하여 반도체의 전기적 특성과 매개변수에 대해 알아보세요.




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ELM440 데이터시트, 핀배열, 회로
ELM440
60Hz Generator
Description
The ELM440 is an 8 pin digital divider integrated
circuit, that provides both 60Hz and 1Hz outputs
from a common 3.58MHz NTSC colourburst crystal.
Externally, the designer need only provide the
crystal and two appropriate loading capacitors, as
well as a suitably bypassed power supply. Internal
oscillator circuits then use this reference frequency
to precisely derive a stable 60Hz signal. This signal
is then further divided to provide a 1Hz output.
The ELM440 can also be locked in synchronism
to an external 60 or 120 Hz line frequency signal. If
derived from the electrical grid voltage, this results in
excellent long-term stability, as the power generation
frequency is traceable to national standards. The
transition to or from sync-lock with this external
signal occurs automatically.
A reset input is also provided to restart the
internal counters, if desired. An active low signal on
this pin will force both outputs to an open or tristate
condition.
Applications
• Stable 60Hz and 1Hz reference sources
• Master oscillator for clock / timekeeping functions
• DC powered backup 60Hz reference signal
Features
• Low power CMOS design
• Wide supply range - 3.0 to 5.5 volt operation
• Generates both 60Hz and 1Hz references
• Automatically synchronizes to the line frequency
for long term stability, when it’s available
• Uses a standard 3.58MHz crystal for the time
reference if there is no sync input
• High current drive outputs - up to 25 mA
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
XT1 2
XT2 3
reset 4
8 VSS
7 60Hz
6 1Hz
5 sync
Block Diagram
sync 5
XT1 2
XT2 3
Master
Oscillator
Divider
÷ 60
VDD
7 60Hz
6 1Hz
4 reset
ELM440DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
1 of 4
Free Datasheet http://www.datasheet4u.com/




ELM440 pdf, 반도체, 판매, 대치품
ELM440
Example Application
The ELM440 can be easily configured to
provide a 60Hz output as shown in Figure 1 below.
A 3.579545MHz crystal is connected to the
integrated circuit, along with suitable loading
capacitors, and the 60Hz output is then taken from
pin 7. Pin 5 is grounded, as no reference signal is
supplied. As usual, it is also good practise to place
a bypass capacitor across the power supply as
well.
Figure 2 shows how easily this circuit can be
modified to operate in synchronism with the AC
power line. A reference signal is taken from one
half of a 16Vrms CT transformer winding through a
47Kresistor. Both circuits share a common VSS.
The resistor was chosen to limit peak currents in
this circuit to about 0.24 mA, which is well within
the IC’s capabilities. The ELM440 will continue to
use this signal as it’s reference, as long as it is
available. Upon loss of the AC, the circuit will
automatically switch over to using the crystal as a
reference.
Using a rectifier circuit for the reference signal
can pose some problems if one is not careful. Full-
wave circuits can be particularly troublesome as
all of the diodes may cease to conduct after the
peak of the waveform, and the input voltage level
is then essentially floating. In this case, at
minimum, a large value (470K) resistor should
also be connected between the sync input and
VSS, to provide a ground reference during these
times.
Both circuits shown are simple, leaving little
room for change. One modification that might be
considered for either is to replace one of the fixed
value capacitors with a variable one, in order to be
able to trim the oscillator frequency for greater
accuracy.
+5V 0.1µF
27pF
3.58MHz
1
2
3
4
8
7
6
5
60Hz Out
+5V 0.1µF
27pF
Figure 1. Typical Connections
27pF
3.58MHz
1
2
3
4
27pF
8
7 60Hz Out
6
5
47K
8V
Figure 2. Using the Sync Input
8V
+
ELM440DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
4 of 4
Free Datasheet http://www.datasheet4u.com/

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