LM3407 Datasheet, PDF (2/22 Pages) National Semiconductor (TI) – 350 mA, Constant Current Output Floating Buck Switching Converter for High Power LEDs

LM3407
SNVS553B – JANUARY 2008 – REVISED MAY 2013
CONNECTION DIAGRAM
1
ISNS
2
DIM
3
EN
4
FS
Top View
EP
8
LX
7
GND
6
VCC
5
VIN
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Figure 1. 8-Lead Plastic MSOP-8 PowerPAD Package
See Package Number DGN0008A
PIN DESCRIPTIONS
Pin
Name
Description
Application Information
1
ISNS
LED Current Sense pin Connect resistor R_ISNS from this pin to ground for LED current sensing. The current
sensing resistor should be placed close to this pin.
2
DIM PWM Dimming Input pin Applying logic level PWM signal to this pin controls the average brightness of the LED
string.
3
EN
Device Enable pin
Applying logic high to this pin or leaving this pin open enables the switcher. When this pin
is pulled low, the switcher is disabled and will enter low power shutdown mode.
4
FS
Switching Frequency Connect resistor R_FS from this pin to ground to set the switching frequency.
Setting pin
5
VIN
Input Voltage pin
The input voltage should be in the range of 4.5V to 30V.
6
VCC Internal Regulator Output This output pin should be bypassed by a ceramic capacitor with a minimum value of 1µF.
pin
High quality X5R or X7R ceramic capacitor is recommended.
7
GND
Device Ground pin This pin should be connected to the system ground.
8
LX
Drain of N-MOSFET Connect this pin to the output inductor and anode of the Schottky diode.
Switch
EP
GND
Thermal Pad
The bottom pad should be connected to ground. For good thermal performance, place 4
to 6 thermal vias from EP to bottom layer PCB ground plane.
2
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