|
LM3421 Datasheet, PDF (1/24 Pages) National Semiconductor (TI) – N-Channel Controllers for Constant Current LED Drivers | |||
|
January 26, 2009
LM3421, LM3423
N-Channel Controllers for Constant Current LED Drivers
General Description
The LM3421/LM3423 devices are versatile high voltage LED
driver controllers. With the capability to be configured in a
Buck, Boost, Buck-Boost (Flyback), or SEPIC topology, and
an input operating voltage rating of 75V, these controllers are
ideal for illuminating LEDs in a very diverse, large family of
applications.
Adjustable high-side current sense with a typical sense volt-
age of 100mV allows for tight regulation of the LED current
with the highest efficiency possible. Output LED current reg-
ulation is based on peak current-mode control with predictive
Off-Time Control. This method of control eases the design of
loop compensation while providing inherent input voltage
feed-forward compensation.
The LM3421/LM3423 include 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
frequencies of up to 2.0MHz, thus enabling compact solu-
tions. Additional features include: âzeroâ current shutdown,
precision reference, logic compatible DIM input suitable for
fast PWM dimming, cycle-by-cycle current limit, and thermal
shutdown.
The LM3423 also includes an LED output status flag, a fault
flag, a programmable fault timer, and a logic input to select
the polarity of the dimming output driver.
Features
â VIN range from 4.5V to 75V
â 2% Internal reference voltage (1.235V)
â Current sense voltage adjustable from 20mV
â High-side current sensing
â 2⦠MOSFET gate driver
â Dimming MOSFET gate driver
â Input under-voltage protection
â Over-voltage protection
â Low shutdown current, IQ < 1µA
â Fast (50kHz) PWM dimming
â Cycle-by-cycle current limit
â Programmable switching frequency
â LED output status flag (LM3423 only)
â Fault timer pin (LM3423 only)
â TSSOP EP 16-lead package (LM3421)
â TSSOP EP 20-lead package (LM3423)
Applications
â LED Drivers
â Constant-Current Buck-Boost Regulator
â Constant-Current Boost Regulator
â Constant-Current Flyback Regulator
â Constant-Current SEPIC Regulator
â Thermo-Electric Cooler (Peltier) Driver
Typical Application Circuit
Boost LED Driver
© 2009 National Semiconductor Corporation 300673
30067331
www.national.com
|
▷ |