LM3409EVAL National Semiconductor, LM3409EVAL Datasheet - Page 6
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LM3409EVAL
Manufacturer Part Number
LM3409EVAL
Description
BOARD EVALUATION FOR LM3409
Manufacturer
National Semiconductor
Series
PowerWise®r
Specifications of LM3409EVAL
Current - Output / Channel
1A
Outputs And Type
1, Non-Isolated
Voltage - Output
15V
Features
Dimmable
Voltage - Input
6 ~ 42 V
Utilized Ic / Part
LM3409
Kit Contents
Board, Datasheet
Svhc
No SVHC (15-Dec-2010)
Kit Features
Drives 4 LEDs At Maximum Average LED Current 1A From DC Input Voltage 24V
Mcu Supported Families
LM3409
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
www.national.com
10. PWM DIMMING / SHUTDOWN METHOD
The LM3409 demonstration board allows for PWM dimming
and low power shutdown to be evaluated. The desired
method is chosen as follows:
Method #1: If no PWM dimming is desired, a jumper should
be placed in position 1 (shorts pins 1 and 2) on header J1.
This shorts VIN and EN which ensures the controller is always
enabled if an input voltage greater than 1.74V is applied.
Typical Waveforms
T
A
Analog dimming minimum (R5 fully counterclockwise)
= +25°C, V
IN
20kHz 50% EN pin PWM dimming
= 24V and V
O
= 15V.
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Method #2: Low power shutdown (typically 110µA) can be
evaluated by placing the jumper in position 2 (shorts pins 2
and 3) on header J1. This shorts EN and GND which ensures
the controller is shutdown.
Method #3: Internal PWM dimming using the EN pin can be
evaluated by removing the jumper from header J1. An exter-
nal PWM signal can then be applied to the EN terminal to
provide PWM dimming. The R5 potentiometer should be ro-
tated fully clockwise to use PWM dimming across the entire
LED current range of the demonstration board. The Typical
Waveforms section shows a typical LED current waveform
during PWM dimming.
11. BYPASS CAPACITOR
The internal regulator requires at least 1µF of ceramic capac-
itance with a voltage rating of 16V.
The chosen component from step 11 is:
Analog dimming with maximum (R5 fully clockwise)
20kHz 50% EN pin PWM dimming (rising edge)
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