LM3424
August 22, 2009
Constant Current N-Channel Controller with Thermal
Foldback for Driving LEDs
General Description
The LM3424 is a versatile high voltage N-channel MosFET
controller for LED drivers . It can be easily configured in buck,
boost, buck-boost and SEPIC topologies. In addition, the
LM3424 includes a thermal foldback feature for temperature
management of the LEDs. This flexibility, along with an input
voltage rating of 75V, makes the LM3424 ideal for illuminating
LEDs in a very diverse, large family of applications.
Adjustable high-side current sense voltage allows for tight
regulation of the LED current with the highest efficiency pos-
sible. The LM3424 uses standard peak current-mode control
providing inherent input voltage feed-forward compensation
for better noise immunity. It is designed to provide accurate
thermal foldback with a programmable foldback breakpoint
and slope. In addition, a 2.45V reference is provided.
The LM3424 includes a high-voltage startup regulator that
operates over a wide input range of 4.5V to 75V. The internal
PWM controller is designed for adjustable switching frequen-
cies of up to 2.0 MHz and external synchronization is possible.
The controller is capable of high speed PWM dimming and
analog dimming. Additional features include slope compen-
sation, softstart, over-voltage and under-voltage lock-out, cy-
cle-by-cycle current limit, and thermal shutdown.
Features
■
V
IN
range from 4.5V to 75V
■
High-side adjustable current sense
■
2Ω
, 1A Peak MosFET gate driver
■
Input under-voltage and output over-voltage protection
■
PWM and analog dimming
■
Cycle-by-cycle current limit
■
Programmable slope compensation
■
Programmable, synchronizable switching frequency
■
Programmable thermal foldback
■
Programmable softstart
■
Precision voltage reference
■
Low power shutdown and thermal shutdown
Applications
■
LED Drivers - Buck, Boost, Buck-Boost, and SEPIC
■
Indoor and Outdoor Area SSL
■
Automotive
■
General Illumination
■
Constant-Current Regulators
Typical Application Circuit
300857k9
300857b6
© 2009 National Semiconductor Corporation
300857
www.national.com
LM3424 Constant Current N-Channel Controller with Thermal Foldback for Driving LEDs
