National Semiconductor LM3424 Manual

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.
Typical Application Circuit
© 2009 National Semiconductor Corporation
LM3424
Features
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300857k9
300857
V range from 4.5V to 75V
IN
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
LED Drivers - Buck, Boost, Buck-Boost, and SEPIC
Indoor and Outdoor Area SSL
Automotive
General Illumination
Constant-Current Regulators
August 22, 2009
300857b6
www.national.com