LM3409EVAL National Semiconductor, LM3409EVAL Datasheet - Page 6

• 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

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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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