Texas Instruments LM3407 Evaluation Board LM3407EVAL/NOPB LM3407EVAL/NOPB Datenbogen
Produktcode
LM3407EVAL/NOPB
VIN
LX
+
-
198mV
+
-
Clock
Generator
PWM
Comparator
DIM
GND
ISNS
+
-
3.6V
UVLO
FS
SWITCH
CONTROL
+
-
EA
gm
gm
Reset
6
Set
Slope Compensation
Waveform shaping and
Average
Current Sense
VCC
regulator
VCC
EN
3.6V
VIN
3.6V
DIM
VCC
SD
400 k
:
SD
DIM
5
P
A
Q1
SNVS553B – JANUARY 2008 – REVISED MAY 2013
SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM
FUNCTIONAL DESCRIPTION
OVERVIEW
The LM3407 is a constant current output floating buck switching converter with wide input voltage range and low
feedback current sense reference voltage. These characteristics make the LM3407 an efficient solution to
provide constant current to high power LEDs. The device is ideal for automotive, industrial and general lighting
applications where high power LEDs are used as the lighting source. The LM3407 has an integrated power N-
MOSFET that makes the application solution compact and simple to implement. An external 1% thick-film
resistor allows the converter output voltage to adjust as needed to deliver constant current within 10% accuracy
to a serially connected LED string of varying number and type. Converter switching frequency is adjustable from
300 kHz to 1 MHz. The LM3407 features a dimming input to enable LED brightness control by Pulse Width
Modulation (PWM). Additionally, a separate enable pin allows for low power shutdown. An exposed pad MSOP-8
PowerPAD package provides excellent heat dissipation and thermal performance. Input UVLO and output open-
circuit protection ensure a robust LED driver solution.
feedback current sense reference voltage. These characteristics make the LM3407 an efficient solution to
provide constant current to high power LEDs. The device is ideal for automotive, industrial and general lighting
applications where high power LEDs are used as the lighting source. The LM3407 has an integrated power N-
MOSFET that makes the application solution compact and simple to implement. An external 1% thick-film
resistor allows the converter output voltage to adjust as needed to deliver constant current within 10% accuracy
to a serially connected LED string of varying number and type. Converter switching frequency is adjustable from
300 kHz to 1 MHz. The LM3407 features a dimming input to enable LED brightness control by Pulse Width
Modulation (PWM). Additionally, a separate enable pin allows for low power shutdown. An exposed pad MSOP-8
PowerPAD package provides excellent heat dissipation and thermal performance. Input UVLO and output open-
circuit protection ensure a robust LED driver solution.
FLOATING BUCK SWITCHING CONVERTER
The LM3407 is designed for floating buck configuration. Different from conventional buck converters, a low side
power N-MOSFET is used. The floating buck configuration simplifies the driver stage design and reduces the die
size of the power MOSFET. Additionally, the connections of the power diode, inductor and output capacitor are
switched to ground with a ground referenced power switch, Q1. The extraction of inductor current information can
be easily realized by a simple current sensing resistor. These benefits combine to provide a high efficiency, low
cost, and reliable solution for LED lighting applications.
power N-MOSFET is used. The floating buck configuration simplifies the driver stage design and reduces the die
size of the power MOSFET. Additionally, the connections of the power diode, inductor and output capacitor are
switched to ground with a ground referenced power switch, Q1. The extraction of inductor current information can
be easily realized by a simple current sensing resistor. These benefits combine to provide a high efficiency, low
cost, and reliable solution for LED lighting applications.
8
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