AN-7701 Datasheet, PDF (1/3 Pages) Fairchild Semiconductor – FL7701 Design Tool Flow

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AN-7701
FL7701 Design Tool Flow
Overview
This document is intended to provide in-depth guidance to
using the Fairchild Design Tool for FL7701. Use the Design
Tool with the product datasheet.
Step-by-Step
1. Enter the input voltage.
2. Enter the LED characteristics (forward voltage).
3. Enter the LED counts.
4. Enter the LED peak current.
5. Enter the LED rms current.
6. Enter the target system efficiency.
7. Enter the desired switching frequency.
Example:
 220V Input Voltage
 3.5V Forward Voltage
 10 LEDs in series
 500mApk
 300mArms
 85% efficiency
 45kHz
Table 1. Design Values to Enter
Item
Maximum Input Voltage
LED Forward Voltage
Number of LEDs
LED Peak Current
LED rms Current
Efficiency
Switching Frequency
Value Units
V_IN.MAX.AC=
V_f=
N_{umber_LED}=
I_LED.peak=
I_{VAE_rms}=
E_ff=
f_SW=
220
3.5
10
500
300
85
45
V
V
EA
mA
mA
%
kHz
Figure 2. Output Capacitor Selection Guide Plot
© 2011 Fairchild Semiconductor Corporation
Rev. 1.0.1 • 3/21/12
www.fairchildsemi.com