LM3409MY National Semiconductor, LM3409MY Datasheet - Page 18

• Manufacturer Part Number: LM3409MY
• Description: LM3409 LM3409HV PFET Buck Controller for High Power LED Drives; Package: MINI SOIC EXP PAD; No of Pins: 10; Qty per Container: 1000/Reel
• Manufacturer: National Semiconductor

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Design Example #1
EN PIN PWM DIMMING APPLICATION FOR 10 LEDS
SPECIFICATIONS
f
V
V
I
Δi
Δv
V
η = 0.95
1. NOMINAL SWITCHING FREQUENCY
Assume C
The closest 1% tolerance resistor is 24.9 kΩ therefore the
actual t
SW
LED
IN
O
TURN-ON
LED-PP
IN-PP
= 35V
= 48V; V
= 525kHz
= 2A
OFF
= 1.44V
= Δi
= 10V; V
OFF
and target f
IN-MAX
L-PP
= 470pF and η = 0.95. Solve for R
= 1A
HYS
= 75V
= 1.1V
SW
are:
OFF
:
18
The chosen components from step 1 are:
2. INDUCTOR RIPPLE CURRENT
Solve for L1:
The closest standard inductor value is 15 µH therefore the
actual Δi
The chosen component from step 2 is:
L-PP
is:
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