AMC7150_1 Datasheet, PDF (4/7 Pages) ADDtek Corp – 1.5A POWER LED DRIVER

AMC7150
APPLICATION INFORMATION
Low Voltage DC/DC Application
The AMC7150 was designed for power LED driving application. Only 5 external components were required for
low voltage application. Fig.1 shows the typical application circuit for input voltage range from 4V to 40V. Buck power
conversion topology was used and total forward voltage (at expecting current) of the LED string should lower than
supply voltage by 1.6V at least.
4V~40V
Rsense
VCC
CS OUT
L
CIN
OSC AMC7150
DF
GND
CT
Input Bypass Capacitor
The input by-pass capacitor C_IN holds the input voltage and filters out the switching noise of AMC7150.
Flywheel Diode
The fast recovery diode was recommended for flywheel diode D_F. This is because the high reverse recovery
current will cause the voltage drop across Rsense being higher than 330mV, and consequently the switch will be turned
off which has just been turned on.
LED Driving Current
The peak current I_PK flow though LEDs was decided by:
I _PK
=
330mV
Rsense
The average current on LEDs was determined by the peak-to-peak ripple current that was decided by inductor L.
Assume the target average current 550mA on LEDs and ripple current 100mA then the Rsense should be:
Rsense =
330mV
= 0.55Ω
550mA + 0.5 ⋅100mA
The Rsense value should higher than 200mΩ so that driving current won’t over the recommended maximum driving
current 1.5A.
Copyright © 2006 ADDtek Corp.
4
DD034_A -- JUNE 2006