AIWA LM3909 Service Manual

LM3909 LED Flasher/Oscillator

LM3909 LED Flasher/Oscillator

February 1995

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

a

100%.

b

20% to

Schematic Diagram

Typical 1.5V Flasher

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

Connection Diagram

Dual-In-Line Package

Top View

TL/H/7969– 2

Order Number LM3909N

See NS Package Number N08E

TL/H/7969– 1

C

1995 National Semiconductor Corporation RRD-B30M115/Printed in U. S. A.

TL/H/7969

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

a

V

Voltage 6.4V

Operating Temperature Range

Lead Temperature (Soldering, 10 sec.) 260§C

b

25§Ctoa70§C

Electrical Characteristics

Parameter

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

Conditions

(Applications Note 3)

Min Typ Max Units

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

a

V

6V 2 400 mF 1k 1.5k 5V – 25V

15V 2 180 mF 3.9k 1k 13V–50V

100V 1.7 180 mF

TL/H/7969– 4

1.5V Flasher

Typical Operating Conditions

Nominal
Flash Hz

C

T

RSRFBV

43k
1W

a

RANGE

1k 85V– 200V

Estimated Battery Life

TL/H/7969– 6

(Continuous 1.5V Flasher Operation)

Note: Nominal flash rate: 1 Hz.

TL/H/7969– 5

Size Cell

Standard Alkaline

Type

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

Note 3: Unless noted, measurements above are made with a 1.4V supply, a 25

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.

g

5% capacitor tolerance. Electrolytics may varyb20% toa100% of their stated value.

C ambient temperature, and an LED with a forward drop of 1.5V to 1.7V at 1 mA

§

3

Typical Applications (Continued) (See applications notes on previous page)

3V Flasher

Minimum Power at 1.5V

Note: Nominal flash rate: 1 Hz. Average I

Fast Blinker

Note: Nominal flash rate: 2.6 Hz. Average I

DRAIN

DRAIN

e

0.77 mA.

e

1.2 mA.

TL/H/7969– 7

TL/H/7969– 9

Note: Nominal flash rate: 1.1 Hz. Average I

Note: Winking LED inside, locates light in total darkness.

DRAIN

e

0.32 mA.

TL/H/7969– 8

TL/H/7969– 11

4

Typical Applications (Continued) (See applications notes above)

Flashlight Finder

Note: LM3909, capacitor, and LED are installed in a white translucent cap on the flashlight’s back end. Only one

contact strip (in addition to the case connection) is needed for flasher power. Drawing current through the bulb
simplifies wiring and causes negligible loss since bulb resistance cold is typically less than 2X.

4 Parallel LEDs

High Efficiency Parallel Circuit

TL/H/7969– 10

Note: Nominal flash rate: 1.3 Hz. Average I

DRAIN

TL/H/7969– 12

e

2 mA.

Note: Nominal flash rate: 1.5 Hz. Average I

DRAIN

e

TL/H/7969– 13

1.5 mA.

5

Typical Applications (Continued) (See applications notes above)

1 kHz Square Wave

TL/H/7969– 14

‘‘Buzz Box’’ Continuity and Coil Checker

Note: Differences between shorts, coils, and a few ohms of resistance can be

heard.

TL/H/7969– 16

Note: Output voltage through a 10k load to ground.

TL/H/7969– 15

Variable Flasher

TL/H/7969– 17

Note: Flash rate: 0 Hz– 20 Hz.

6

Typical Applications (Continued) (See applications notes above)

LED Booster

Incandescent Bulb Flasher

Note: High efficiency, 4 mA drain. Continuous appearing light obtained by supplying

short, high current, pulses (2 kHz) to LEDs with higher than battery voltage available.

TL/H/7969– 18

Emergency Lantern/Flasher

Note: Nominal flash rate: 1.5 Hz.

Note: Flash rate: 1.5 Hz.

TL/H/7969– 19

TL/H/7969– 20

7

Physical Dimensions inches (millimeters)

LM3909 LED Flasher/Oscillator

Molded Dual-In-Line Package (N)

Order Number LM3909N

NS Package Number N08E

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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL
SEMICONDUCTOR CORPORATION. As used herein:

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systems which, (a) are intended for surgical implant support device or system whose failure to perform can
into the body, or (b) support or sustain life, and whose be reasonably expected to cause the failure of the life
failure to perform, when properly used in accordance support device or system, or to affect its safety or
with instructions for use provided in the labeling, can effectiveness.
be reasonably expected to result in a significant injury
to the user.

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