RangeMAX™ LX1688
PRODUCTION DATA SHEET
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 13
Copyright © 2001
Rev. 1.2, 2006-03-09
WWW.Microsemi .COM
Multiple Lamp CCFL Controller
TM
®
THEORY OF OPERATION
Digital Dimming
The following oscilloscope waveforms are showing
gate signals of Master and slaves during digital dimming at
50% and 5% duty cycle.
Figure 6- Gate signals during digital dimming with
50% duty cycle CH2= A
OUT
(Master),
CH3=A
OUT
(Slave1), CH4=A
OUT
(Slave2)
Figure 7- Gate signals during digital dimming with
5% duty cycle CH2= A
OUT
(Master),
CH3=A
OUT
(Slave1), CH4=A
OUT
(Slave2)
Output currents
Figure 8 shows the output current of master and slaves during digital dimming with 5% duty cycle. The lamp currents are
operating in phase and frequency synchronization. This prevents random interface between controllers and reduces EMI.
A
A
P
P
P
P
L
L
I
I
C
C
A
A
T
T
I
I
O
O
N
N
S
S
Figure 8- Output current during
digital dimming with 5%
duty cycle R1= out(Master)
R2=Iout(Slave1)
R3=Iout(Slave2)
Lamp Current at 10mA/Div
