IS31LT3918 Datasheet, PDF (1/11 Pages) Integrated Silicon Solution, Inc – HIGH VOLTAGE LED LIGHTING DRIVER WITH SWITCH DIMMING

IS31LT3918
HIGH VOLTAGE LED LIGHTING DRIVER WITH SWITCH DIMMING
OCTOBER 2011
GENERAL DESCRIPTION
IS31LT3918 LED driver IC is a peak current detection
buck converter which operates in constant off time
mode. It operates over a very wide input voltage supply
range of 6VDC to 450VDC or 110VAC/220VAC.
IS31LT3918 incorporates the special feature of switch
dimming by detecting OFF-ON cycles of the main
power switch. When the switch is cycled within a 2
second period (typical) the device automatically
switches the dimming level to the next step. As a result,
dimming can be achieved without replacing any wiring
in the original system. There are multiple modes of
switch dimming that the user may configure 2 steps or
3 steps, as well as different levels of dimming via the
external pins DIM1 and DIM2.
IS31LT3918 can also realize LED dimming using an
external PWM signal. It can accept a PWM signal from
0% to 100% duty cycle. The LED current may also be
adjusted linearly by applying an analog input voltage in
the range of 0.5V to 2.5V.
IS31LT3918 adopts a peak current mode control
architecture, which eliminates the need for any
additional loop compensation while maintaining a good
degree of constant output current regulation.
FEATURES
 User configurable switch dimming levels
 3% output current accuracy
 Over current, voltage and temperature protection
 High efficiency (typical up to 95%)
 Wide input voltage range: 6VDC~450VDC or
85Vac~ 265Vac
 Linear and PWM dimming
 Very few external components
APPLICATIONS
 DC/DC or AC/DC constant current LED driver
 Signal and decorative lighting
 Backlight LED driver
TYPICAL APPLICATION CIRCUIT
Switch K
D1
85Vac- 265Vac
D3
Fuse
D2
C1
D4
R2
C6
C4
D5
C3
R1
R5
C2
DZ
L1
Q2
D6
R6
VIN
Gate
Q1
DIM1
CS
IS3^I1^SL³T⁹3¹9⁸18
DIM2
ADJ
GND
TOFF
R4
R3
LED+
LED-
Copyright © 2011 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time
without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised
to obtain the latest version of this device specification before relying on any published information and before placing orders for products.
Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the
product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized
for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that:
a.) the risk of injury or damage has been minimized;
b.) the user assume all such risks; and
c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances
Integrated Silicon Solution, Inc. – www.issi.com
1
Rev. A, 09/01/2011