LM3909 Datasheet, PDF (1/8 Pages) National Semiconductor (TI) – 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 bat-
tery and capacitor to function as an LED flasher
Packaged in an 8-lead plastic mini-DIP the LM3909 will op-
erate over the extended consumer temperature range of
b25 C to a70 C It has been optimized for low power drain
and operation from weak batteries so that continuous oper-
ation 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 resis-
tors 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 b20% to
a100%
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
Connection Diagram
Dual-In-Line Package
C1995 National Semiconductor Corporation TL H 7969
Top View
TL H 7969 – 2
Order Number LM3909N
See NS Package Number N08E
TL H 7969 – 1
RRD-B30M115 Printed in U S A