ELM712
Elm Electronics Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
Connection Diagram
PDIP and SOIC
(top view)
V
DD
V
SS
1
2
3
4
8
7
6
5
LED Runner
The ELM712 is a handy circuit for controlling up
to five LEDs in novelty devices. One pushbutton
press is all it takes to initiate about 15 seconds of
LED activity, before the circuit reverts back to its
very low current standby mode.
All of the logic required for circuit operation is
contained wholly within this 8 pin integrated circuit.
Normally only a pushbutton, the LEDs, and a battery
are all that are needed for a complete circuit. At
higher voltages, a single current limiting resistor may
be required to limit LED current.
The ELM712 drives each LED output in a
sequential fashion, at approximately 10 Hz. By only
driving one output at a time, peak current and thus
battery requirements are reduced.
Description
Campaign buttons
Battery operated toys
Dress ties
Signs
Holiday Ornaments
Applications
Block Diagram
1 of 3
Low power CMOS design
Wide supply range - 3.0 to 5.5 volt operation
Auto-off mode conserves batteries
Single push-button to activate
Direct drive high current outputs
No external timing components required
Features
ELM712DSB
LED2
start
LED1
LED3
LED5
LED4
2
3
5
LED1
7
6
4
V
DD
start
LED2
LED3
LED4
LED5
Output Drivers
Power
Control
Master Oscillator
ELM712
Elm Electronics Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
Pin Descriptions
Ordering Information
These integrated circuits are available in either the 300 mil plastic DIP format, or in the 200 mil SOIC surface
mount type of package. To order, add the appropriate suffix to the part number:
300 mil Plastic DIP............................... ELM712P
200 mil SOIC..................................... ELM712SM
2 of 3
Absolute Maximum Ratings
Storage Temperature....................... -65C to +150C
Ambient Temperature with
Power Applied....................................-40C to +85C
Voltage on V
DD
with respect to V
SS
............ 0 to +7.5V
Voltage on any other pin with
respect to V
SS
........................... -0.6V to (V
DD
+ 0.6V)
Note:
Stresses beyond those listed here will likely damage
the device. These values are given as a design
guideline only. The ability to operate to these levels
is neither inferred nor recommended.
All rights reserved. Copyright 1999 Elm Electronics.
Every effort is made to verify the accuracy of information provided in this document, but no representation or warranty can be
given and no liability assumed by Elm Electronics with respect to the accuracy and/or use of any products or information
described in this document. Elm Electronics will not be responsible for any patent infringements arising from the use of these
products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or
systems. Elm Electronics reserves the right to make changes to the device(s) described in this document in order to improve
reliability, function, or design.
V
DD
(pin 1)
This pin is the positive supply pin, and should
always be the most positive point in the circuit.
Internal circuitry connected to this pin is used to
provide power on reset of the microprocessor, so
an external reset signal is not required. Refer to
the Electrical Characteristics section for further
information.
LED1, LED2, LED3, LED4 and LED5
(pins 5, 6, 7, 2 and 3 respectively)
These are the five active high LED drive outputs.
They are energized in the order listed for
approximately 20msec each, at a rate of 10Hz.
Each output is capable of sourcing a maximum
of 25mA of current, when the ELM712 is
operated at the maximum supply level.
start (pin 4)
Momentarily connecting this pin to V
SS
will
initiate an LED sequence that typically lasts for
about 15 seconds. After this time, the circuit will
revert back to the low power mode, waiting for
another start signal. The circuit automatically
senses a `stuck button' condition as well and
powers down the internal circuits, but not the
internal pull-up resistor.
V
SS
(pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
ELM712DSB
Elm Electronics Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
Example Application
ELM712
Electrical Characteristics
3 of 3
All values are for operation at 25C and a 3V supply, unless otherwise noted. For further information, refer to note 1 below.
Characteristic
Minimum
Typical
Maximum
Conditions
Units
Supply Voltage, V
DD
3.0
3.0
5.5
V
V
DD
rate of rise
0.05
V/ms
Average Supply Current, I
DD
0.60
2.0
mA
Notes:
1. This integrated circuit is produced with a Microchip Technology Inc.'s PIC12C5XX as the core embedded
microcontroller. For further device specifications, and possibly clarification of those given, please refer to the
appropriate Microchip documentation.
2. This spec must be met in order to ensure that a correct power on reset occurs. It is quite easily achieved
using most common types of supplies, but may be violated if one uses a slowly varying supply voltage, as
may be obtained through direct connection to solar cells, or some charge pump circuits.
3. The value of the pullup resistance is both supply and temperature dependent.
LED Drive Current
mA
see note 2
ELM712DSB
Output Pulse Duration
msec
20
any output
Using the ELM712 is straightforward,
requiring little explanation. Typically it is connected
in a circuit as shown at the right. Pressing the start
pushbutton once initiates a sequence of LED
flashes that last approximately 15 seconds.
The value of the resistor shown depends
on the voltage level that the circuit operates at. For
the circuit shown, no resistor is normally used, and
these points are jumpered out. For 5V operation, a
value of about 150 to 300 ohms is generally
inserted.
0.1
5
A
see note 3
Start pin internal pullup resistance
During operation
In low power (standby) mode
K
750
470
1500
No series limiting resistor
9
13
mA
200
series limiting resistor
V
DD
=3V
V
DD
=5V
1
2
3
4
8
7
6
5
3V
+
*see
text
start
712
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