NSC LM3909MX, LM3909M Datasheet
TL/H/7969
LM3909 LED Flasher/Oscillator
February 1995
LM3909 LED Flasher/Oscillator
General Description
The LM3909 is a monolithic oscillator specifically designed
to flash Light Emitting Diodes. By using the timing capacitor
for voltage boost, it delivers pulses of 2 or more volts to the
LED while operating on a supply of 1.5V or less. The circuit
is inherently self-starting, and requires addition of only a battery and capacitor to function as an LED flasher.
Packaged in an 8-lead plastic mini-DIP, the LM3909 will operate over the extended consumer temperature range of
b
25§Ctoa70§C. It has been optimized for low power drain
and operation from weak batteries so that continuous operation life exceeds that expected from battery rating.
Application is made simple by inclusion of internal timing
resistors and an internal LED current limit resistor. As
shown in the first two application circuits, the timing resistors supplied are optimized for nominal flashing rates and
minimum power drain at 1.5V and 3V.
Timing capacitors will generally be of the electrolytic type,
and a small 3V rated part will be suitable for any LED flasher
using a supply up to 6V. However, when picking flash rates,
it should be remembered that some electrolytics have very
broad capacitance tolerances, for example
b
20% to
a
100%.
Features
Y
Operation over one year from one C size flashlight cell
Y
Bright, high current LED pulse
Y
Minimum external parts
Y
Low cost
Y
Low voltage operation, from just over 1V to 5V
Y
Low current drain, averages under 0.5 mA during
battery life
Y
Powerful; as an oscillator directly drives an 8X speaker
Y
Wide temperature range
Applications
Y
Finding flashlights in the dark, or locating boat mooring
floats
Y
Sales and advertising gimmicks
Y
Emergency locators, for instance on fire extinguishers
Y
Toys and novelties
Y
Electronic applications such as trigger and sawtooth
generators
Y
Siren for toy fire engine, (combined oscillator, speaker
driver)
Y
Warning indicators powered by 1.4V to 200V
Schematic Diagram
Typical 1.5V Flasher
TL/H/7969– 1
Connection Diagram
Dual-In-Line Package
TL/H/7969– 2
Top View
Order Number LM3909N
See NS Package Number N08E
C
1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Power Dissipation 500 mW
V
a
Voltage 6.4V
Operating Temperature Range
b
25§Ctoa70§C
Lead Temperature (Soldering, 10 sec.) 260§C
Electrical Characteristics
Parameter
Conditions
Min Typ Max Units
(Applications Note 3)
Supply Voltage (In Oscillation) 1.15 6.0 V
Operating Current 0.55 0.75 mA
Flash Frequency 300 mF, 5% Capacitor 0.65 1.0 1.3 Hz
High Flash Frequency 0.30 mF, 5% Capacitor 1.1 kHz
Compatible LED Forward Drop 1 mA Forward Current 1.35 2.1 V
Peak LED Current 350 mF Capacitor 45 mA
Pulse Width 350 mF Capacitors at (/2 Amplitude 6.0 ms
Typical Applications (See applications notes on following page)
Triac Trigger
Provides 40 mA. 10 ms pulses at about 8 kHz.
Triac gate may be pulse transformer isolated if
desired.
TL/H/7969– 3
2
Typical Applications (Continued)(See applications notes below)
Warning Flasher High Voltage Powered
TL/H/7969– 4
Typical Operating Conditions
V
a
Nominal
C
T
RSRFBV
a
RANGE
Flash Hz
6V 2 400 mF 1k 1.5k 5V – 25V
15V 2 180 mF 3.9k 1k 13V–50V
100V 1.7 180 mF
43k
1k 85V– 200V
1W
1.5V Flasher
TL/H/7969– 5
Note: Nominal flash rate: 1 Hz.
TL/H/7969– 6
Estimated Battery Life
(Continuous 1.5V Flasher Operation)
Size Cell
Type
Standard Alkaline
AA 3 months 6 months
C 7 months 15 months
D 1.3 years 2.6 years
Note: Estimates are made from our tests and manufacturers
data. Conditions are fresh batteries and room temperature. Clad
or ‘‘leak-proof’’ batteries are recommended for any application
of five months or more. Nickel Cadmium cells are not recommended.
APPLICATIONS NOTES
Note 1: All capacitors shown are electrolytic unless marked otherwise.
Note 2: Flash rates and frequencies assume a
g
5% capacitor tolerance. Electrolytics may varyb20% toa100% of their stated value.
Note 3: Unless noted, measurements above are made with a 1.4V supply, a 25
§
C ambient temperature, and an LED with a forward drop of 1.5V to 1.7V at 1 mA
forward current.
Note 4: Occasionally a flasher circuit will fail to oscillate due to an LED defect that may be missed because it only reduces light output 10% or so. Such LEDs can
be identified by a large increase in conduction between 0.9V and 1.2V.
3
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