ELM382
50 Hz Long Interval Counter
Description
The ELM382 is a digitally configurable, multi-
stage counter circuit in a single 8 pin package. When
connected to a 50Hz source, four time periods from
one hour to one week are possible, as shown in
Table 1 below.
Although the circuit has been optimized for a
50Hz input frequency, it is capable of being operated
over a very wide range of frequencies. Of particular
interest is the ability to interface directly to very low
frequencies with varying waveforms due to the use
of a Schmitt trigger input circuit.
The ELM382 provides two outputs – a standard
50% duty cycle divider output, and a momentarily
pulsed output. The pulse output is useful for audibly
or visually signalling the beginning of a time period,
or as a trigger for other circuitry. Refer to the
Example Applications section for two typical circuits.
Features
• Low power CMOS design - typically 1mA at 5V
• Wide supply range – 3.0 to 5.5 volt operation
• Digitally selectable delays
• Schmitt trigger circuitry on the clock input
• Completely static operation
• Long term accuracy with line frequency clock
• High current drive outputs – up to 25 mA
• Reset input provided with a pullup resistor
Connection Diagram
PDIP and SOIC
(top view)
Applications
• Long term (daily or weekly) event timers
• Missing event detectors
• Automatic shutoff circuits
V
DD
D1
D0
reset
1
2
3
4
8
7
6
5
V
SS
Out
Pulse
Clock
Block Diagram
V
DD
Clock
5
7
Out
V
SS
D1
D0
2
Digital
Counters
Pulse
Generator
6
Pulse
3
Setting
D1
D0
V
DD
Divisor
x 1000
180
2160
4320
30,240
Table 1
Period
(50Hz)
1 hour
12 hrs
24 hrs
7 days
L
L
L
H
L
H
reset
4
H
H
ELM382DSA
Elm Electronics – Circuits for the Hobbyist
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