ELM410
Triple Debounce Circuit
Description
The ELM410 provides all of the necessary
circuitry to connect as many as three independent
mechanical contacts to an electronic circuit.
All mechanical contacts, whether from switches,
relays, etc. will have inherent ‘bounce’ when they
make or break a connection. Depending on the type
of switch, this fluctuation can be quite pronounced,
often being interpreted as multiple inputs by high
speed digital circuits.
This circuit provides all of the logic required to
remove the bounce from most mechanical sources,
without the use of additional components. As well,
internal pull-up resistors have been provided so that
the switch inputs can be directly connected to the 8
pin package.
The ELM410 provides three separate inverters
which follow the input directly. No latching or
‘memory action’ is provided, as it is in the case of
the ELM411.
Features
• Low power CMOS design - typically 1mA at 5V
• Wide supply range - 3.0 to 5.5 volt operation
• Simultaneous monitoring of three circuits
• Full 25msec debounce period on contact closure
and opening, without external components
• Internal pullup resistors for contact monitoring
• High current drive outputs - up to 25 mA
• Can be cascaded to provide sequential outputs
Connection Diagram
PDIP and SOIC
(top view)
V
DD
Out1
1
2
3
4
8
7
6
5
V
SS
In1
In2
Out3
Applications
• Pushbutton interface for logic circuits
• Limit switch monitoring
• Time delay generation
Out2
In3
Block Diagram
V
DD
Out1
2
Debounce
Timers
V
DD
7
In1
Out2
3
Debounce
Timers
V
DD
6
In2
In3
4
Debounce
Timers
5
Out3
ELM410DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
1 of 4
ELM410
Pin Descriptions
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.
Out1 (pin 2)
This is the output pin for the first debounce
circuit. A logic low applied to pin 7 will cause this
pin to go to a logic high level, once the input is
stable for the debounce period. Similarily, a logic
high (or open circuit) at pin 7 will result in this pin
being driven to a logic low level after the
debounce period.
Out2 (pin 3)
This is the output pin for the second debounce
circuit. Refer to the description for pin 2.
In3 (pin 4)
This is the input for circuit 3. Levels are standard
CMOS, not schmitt trigger, so the use of external
delay capacitors, etc. is not recommended. An
internal pullup resistor is provided to allow direct
interface to mechanical contacts (refer to the
specs for further information).
Out3 (pin 5)
This is the output pin for the third debounce
circuit. Refer to the description for pin 2.
In2 (pin 6)
This is the input pin for the second debounce
circuit. Refer to the description for pin 4.
In1 (pin 7)
This is the input pin for the first debounce circuit.
Refer to the description for pin 4.
V
SS
(pin 8)
Circuit common is connected to this pin. This is
the most negative point in the circuit.
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............................... ELM410P
200 mil SOIC..................................... ELM410SM
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.
ELM410DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
2 of 4
ELM410
Absolute Maximum Ratings
Storage Temperature....................... -65°C to +150°C
Ambient Temperature with
Power Applied....................................-40°C to +85°C
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.
Electrical Characteristics
All values are for operation at 25°C and a 5V supply, unless otherwise noted. For further information, refer to note 1 below.
Characteristic
Supply Voltage, V
DD
V
DD
rate of rise
Average Supply Current, I
DD
Internal pullup resistances
(see note 4)
Debounce Period
Input low voltage
Input high voltage
Output low voltage
Output high voltage
Minimum
3.0
0.05
Typical
5.0
Maximum Units
5.5
V
V/ms
Conditions
see note 2
V
DD
= 5V, see note 3
Pin 4 - Input 3
Pins 6 & 7 - Inputs 1 & 2
see note 5
1.0
300
20
500
30
25
V
SS
0.85 V
DD
2.4
600
50
mA
KΩ
KΩ
msec
0.15 V
DD
V
DD
0.6
V
V
V
V
Current (sink) = 8.7mA
Current (source) = 5.4mA
V
DD
- 0.7
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. Pullup resistor currents are not included in this figure.
4. The value of the internal pullup resistance is both supply and temperature dependent.
5. Time is approximate. The input must remain stable for this period before the output is allowed to change.
ELM410DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
3 of 4
ELM410
Example Application
Figure 1 shows the ELM410 used to interface two
momentary action normally open pushbutton switches to
an ELM310 in a manually controlled stepping motor
circuit. For simplicity, the stepper motor and its drive
transistors are not shown on this diagram.
Using the ELM310 to control a stepper motor has
many advantages - low cost, low power, ease of use,
etc. There is one disavantage however, in that the
integrated circuit is capable of responding quite quickly
to inputs. This would result in multiple steps of the
motor, and perceived erratic operation, if the input were
connected directly to a switch, and not debounced by a
circuit such as the ELM410.
The circuit below shows how easily two control
switches can be debounced and used to control the
ELM310. The two switches are simply connected
between V
SS
and their respective inputs, allowing the
internal pullup resistors to detect the state of the switch.
Power is obtained from the circuit being connected to,
providing the correct logic drive levels. Finally, the
unused debounce circuit is simply left with no
connection to it. This is acceptable in this case, as the
internal pullup resistor will prevent the input to circuit 3
from floating.
Another variation on this circuit would have been to
invert the direction control input by connecting pin 3 to
pin 4 on the ELM410, then use pin 5 to drive pin 3 of the
ELM310. This would have resulted in the direction
pushbutton causing a counter-clockwise rotation when
pressed due to the double inversion from the two
debounce circuits connected in series.
For more permanent installations, consideration
should be given to protecting the ELM410 from
electrostatic discharges, etc. by providing series current
limiting resistors, and additional pullup resistors. For
typical useage in prototyping and experimenter circuits,
however, nothing more than is shown below would
normally be required.
A
+5V
1
8
7
6
5
0.1µF
2
3
4
B
C
D
To winding
drive circuits
Clockwise
5
6
7
8
4
3
2
1
+5V
Step
Figure 1. Manual Control of a Stepper Motor
ELM410DSB
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
4 of 4
京公网安备 11010802033920号
EEWORLD
