LM3434 Datasheet, PDF (1/20 Pages) National Semiconductor (TI) – Common Anode Capable High Brightness LED Driver with High Frequency Dimming

LM3434
www.ti.com
SNVS619B – MARCH 2010 – REVISED MAY 2013
Common Anode Capable High Brightness LED Driver with High Frequency Dimming
Check for Samples: LM3434
FEATURES
1
•2 Operating Input Voltage Range of –9V to -30V
w.r.t. LED Anode
• Control Inputs are Referenced to the LED
Anode
• Output Current Greater than 6A
• Greater than 30kHz PWM Frequency Capable
• Negative Output Voltage Capability Allows
LED Anode to be Tied Directly to Chassis for
Maximum Heat Sink Efficiency
• No Output Capacitor Required
• Up to 1MHz Switching Frequency
• Low I_Q, 1mA Typical
• Soft Start
• Adaptive Programmable ON Time Allows for
Constant Ripple Current
• 24-Pin WQFN Package
APPLICATIONS
• Projection Systems
• Solid State Lighting
• Automotive Lighting
DESCRIPTION
The LM3434 is an adaptive constant on-time DC/DC
buck (step-down) constant current controller (a true
current source). The LM3434 provides a constant
current for illuminating high power LEDs. The output
configuration allows the anodes of multiple LEDs to
be tied directly to the ground referenced chassis for
maximum heat sink efficacy. The high frequency
capable architecture allows the use of small external
passive components and no output capacitor while
maintaining low LED ripple current. Two control
inputs are used to modulate LED brightness. An
analog current control input is provided so the
LM3434 can be adjusted to compensate for LED
manufacturing variations and/or color temperature
correction. The other input is a logic level PWM
control of LED current. The PWM functions by
shorting out the LED with a parallel switch allowing
high PWM dimming frequencies. High frequency
PWM dimming allows digital color temperature
control, interference blanking, field sequential
illumination, and brightness control. Additional
features include thermal shutdown, V_CC under-voltage
lockout, and logic level shutdown mode. The LM3434
is available in a low profile 24-pin WQFN package.
TYPICAL APPLICATION CIRCUIT
44.2k
0.1
PF
-12V
ADJ
EN
DIM
+3.3V
GND
270 pF
4.7 PF
-12V
HO
T_ON
HS
ADJ
EN _{LM3434 BST}
DIM
V_CC
V_IN
LO
0.01
PF
Q1
0.47 PF
Q2
2.2 PF
LED ANODE
Q3
LED
6 PH
0.01
22 PF
LED CATHODE
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2010–2013, Texas Instruments Incorporated