ELM380
Battery Charger Timer
Description
Features
The ELM380 is an 8 pin integrated circuit that is
• Low power CMOS design - typically 1mA at 5V
• Wide supply range - 3.0 to 5.5 volt operation
• Quick settings of 8 or 14 hours
used to provide very long time interval outputs. It is
typically used for enabling the charge circuit in
Nickel Cadmium battery chargers, but can be easily
adapted for many other applications.
• Complementary outputs simplify designs
• External reset input for system use
An express ‘one button’ mode is provided on
chip specifically for rechargeable battery circuits. In
this mode, pressing the start button once initiates a
user selectable 8 or 14 hour timing interval, after
which the circuit shuts off. If one prefers, pressing
that same button multiple times will allow for user
programmable intervals of from 2 to 77 hours.
• Internal pullup resistors for switch inputs
• High current drive outputs - up to 25 mA
• Line frequency input for accurate timing
The circuit requires a 60Hz full-wave rectified
signal for its operation. This 120Hz time base is
used for all of the timekeeping functions, providing
good long term stability and low cost.
Connection Diagram
PDIP and SOIC
(top view)
Interfacing to the ELM380 is simplified by the
provision of internal pull-up resistors so that the
mechanical switches can be directly connected
without additional components, or simply not used,
depending on the application.
1
2
3
4
8
7
6
5
VDD
Out
VSS
start
Out
8/14 hrs
Clock
reset
Applications
• Ni-Cd battery chargers
• Yard lighting or watering controls
• Houseplant grow lamp controllers
Block Diagram
VDD
Debounce
Timers
7
2
3
Out
Out
start
Control
and
Counters
VDD
6
8/14 hrs
VDD
5
Clock
4
reset
ELM380DSB
Elm Electronics – Circuits for the Hobbyist
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