ELM413
LED Driver
Description
The ELM413 is both an LED controller and a
circuit startup timer in an 8 pin package. The high
current capabilities of its outputs allow most LEDs to
be directly driven, usually only requiring a single
current limiting resistor.
The circuit startup, or warmup feature is useful
for allowing a stabilizing time period to pass before
enabling other circuits. This type of function is often
used in audio amplifier circuits where it is desirable
to block the speaker outputs until the amplifier
stages have stabilized. This can eliminate the
annoying ‘pop’ occasionally heard from audio
amplifiers.
The duration of the warmup period is selected
by logic levels on two input pins, providing four
discrete time intervals. All circuit timing is derived
from internal circuitry, and no additional timing
components are required for circuit operation.
Features
• Low power CMOS design - typically 1mA at 5V
• Operates over a supply range of 3.0 to 5.5 volts
• Schmitt trigger controlled operation
• Requires no external timing components
• Warmup periods from 0.1 to 5 seconds
• Auxiliary output active after warmup period
• High current drive outputs - up to 25 mA
Connection Diagram
PDIP and SOIC
(top view)
V
DD
AuxOut
W1
1
2
3
4
8
7
6
5
V
SS
Red
Green
Trigger
Applications
•
•
•
•
•
Pilot ‘lamp’ circuits
Sequentially enabled systems
Delay on operate circuits
Audio amplifier power managers
Monostable (one-shot) circuits
W0
Block Diagram
Trigger
5
7
Red
6
Green
Warmup Period
W1
L
L
H
H
W0
L
H
L
H
Period
0.1 sec
0.5 sec
1 sec
5 sec
W1
W0
3
4
Control
and
Timing
Flasher
2
AuxOut
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ELM413
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 normally not required.
Refer to the Electrical Characteristics section for
further information.
AuxOut (pin 2)
This is an output signal for gating auxiliary circuits
off and on. It is set to its active high level after the
trigger input has been at a high level for the time
determined by W1 and W0. It is forced low if the
trigger input drops below the lower threshold.
W1 (pin 3), and W0 (pin 4)
These are the two digital input pins that are used
to select the warmup period as shown in the chart
on page 1.
Trigger (pin 5)
This is a schmitt trigger input that is used to
initiate the circuit activity. A rising (low to high)
edge at this pin will cause the red LED to go off,
the green LED to become active, and the warmup
timer to begin timing. Once initiated, pin activity is
ignored until the warmup period is complete.
Green (pin 6)
This output pin signifies the power on (trigger
above the threshold) condition. It becomes
active once the threshold is exceeded, and
remains so until the trigger resets and the
warmup period is complete.
During the warmup period, this output will flash if
either the 1 second or the 5 second time is
selected. Flash rates are nominally 2 Hz and 1
Hz respectively. For the 0.1 and 0.5 second
periods, the pin remains at a constant high level.
Red (pin 7)
This is the red LED drive output. It will be at a
high level when the circuit is at idle and the
trigger input is a low level. At all other times, this
pin is at a low output level.
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............................... ELM413P
200 mil SOIC..................................... ELM413SM
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.
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ELM413
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
Maximum allowable input current
Input low voltage
Input high voltage
Trigger pulse width
Trigger input thresholds
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
trigger input only, see note 4
W0 or W1
W0 or W1
during idle periods, see note 5
transition point - rising edge
transition point - falling edge
Current (source) = 8 mA
Current (source) = 13 mA
Current (sink) = 8 mA
Current (sink) = 13 mA
1.0
-0.5
V
SS
4.25
4
2.8
1.3
4.4
4.0
0.4
0.75
2.4
+0.5
0.75
V
DD
mA
mA
V
V
µsec
4.25
0.75
Output high voltage
V
V
V
V
V
V
Output low voltage
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. Device only. Does not include any current supplied to external components.
4. This is the maximum allowable current through the protection diodes when applying large voltages to the
trigger input (pin 5) through a current limiting resistance. With V
DD
> V
in
> V
SS
, the circuit presents a typical
CMOS input load.
5. The trigger input is ignored during the warmup period.
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ELM413
Example Application
Figure 1 below shows the ELM413 used in a
typical speaker control and pilot lamp circuit for an
audio amplifier. In this instance, the majority of the
circuit components required are associated with
the relay that is used to block the speaker outputs
until the power has stabilized.
For this application, W0 and W1 are both tied
to a logic high level, so the warmup period is
selected to be 5 seconds. This is likely a good
choice for most circuits of this type, although some
may be able to use the 1 second setting.
The ELM413 has its trigger pin connected
directly to Vdd, causing the circuit to sequence
whenever the power is turned on. If the trigger
input should be connected to another voltage
source, keep in mind that a series resistor should
always be used. The resistor limits current flow
when either supply is at a different level than the
other. Typical values would be about 100KΩ, so
that the input current shown under the Electrical
Characteristics section is not exceeded.
Only one LED is used for this circuit, as a red
LED would never be lit in this instance. Other
applications may require that both red and green
LEDs be used, and the ELM413 adapts easily to
this as it has separate outputs for both. The
outputs can easily drive back to back two wire
LEDs as well as the common cathode three wire
types, and of course, discrete diodes. As the red
and green outputs are not active at the same time,
a single series current limiting resistor is usually all
that is required.
The circuit shown below causes the green
LED to flash for 5 seconds, followed by a steady
output. If one wanted a solid output without
flashing, the LED could have been connected
directly to V
DD
, or it could have been connected
from V
DD
to pin 7 of the ELM413 (with a series
resistor). The latter case would likely be needed
for circuits that are retriggered using pin 5, without
the power being cycled.
The ELM413 is a simple yet versatile circuit
that is convenient and easy to use. Other uses
would include generating pulses from a trigger
input, or connecting several in series to generate
sequential events…
270Ω
Green
LED
8
7
6
5
+12V
+5V
1
413
2
3
4
12V Relay
1N4001
2.2KΩ
0.1µF
2N3904
L
R
Speaker
Enable
Figure 1. Typical Speaker Control Circuit
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