ELM415 Datasheet, PDF (1/5 Pages) ELM Electronics – Up/Down Interface

ELM415
Up/Down Interface
Description
Many modern control circuits use the value from
a digital counter to directly determine a setting or
position. Manipulating this value under computer
control is not difficult, but when one has to interface
with a human operator, several other factors must be
considered. Human interfaces often require that the
circuit respond to changes in a setting – up or down,
left or right, clockwise or counterclockwise. These
controls need a simple interface, which the ELM415
provides.
This 8 pin integrated circuit contains all the
timing and logic that is necessary to interface two
pushbuttons to most counter type interfaces. It reads
the position of the switches and translates that into
an appropriate signal for a counter to either
increment or decrement, which in turn controls the
output variable. Logic to filter out contact bounce, to
sense when both keys are pressed simultaneously,
to invert the count output, and to provide continuous
pulses if an input pushbutton stays pressed are all
included.
Applications
• Digital audio potentiometer controls
• Variable voltage or temperature circuits
• Motor positioning controls
• Single-stepping control circuits
• Reset circuits
Features
• Low power CMOS design – typically 1mA at 5V
• Wide supply range – 3.0 to 5.5 volt operation
• Fully debounced switch inputs
• Internal pullup resistors provided
• Protection from simultaneous key presses
• High current drive outputs – up to 25 mA
• User selectable automatic repeat function
• Selectable Count output polarity
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
Up/Down 2
Count 3
Invert 4
8 VSS
7 DownSw
6 UpSw
5 Repeat
Block Diagram
VDD
7
DownSw
VDD
6
UpSw
Debounce
Circuit
Debounce
Circuit
Logic
reset
Latch
set
2 Up/Down
Pulse
Generator
Output
Control
3 Count
Repeat 5
4 Invert
ELM415DSA
Elm Electronics – Circuits for the Hobbyist
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