RangeMAX™
TM
®
LX1688
Multiple Lamp CCFL Controller
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
The LX1688 is a fixed frequency, dual
current/voltage mode, switching regulator
that provides the control function for Cold
Cathode Fluorescent Lighting (CCFL).
This controller can be used to drive a
single lamp, but is specifically designed
for multiple lamp LCD panels. The IC can
be configured as a master or slave and
synchronize up to 12 controllers.
The LX1688 includes highly integrated
universal ‘PWM or DC’ dim input that
allows either a PWM or DC input to adjust
brightness without requiring external
conditioning, since a single external
capacitor CPWM can be used to integrate
a PWM input. Burst mode dimming is
possible if the user supplies a low
frequency PWM signal on the BRITE
input and no CPWM capacitor is used. The
controller utilizes Microsemi’s patented
direct drive fixed frequency topology and
patented resonant lamp strike generation
technique.
Safety and reliability features include a
dual feedback control loop that permits
regulation of maximum lamp strike voltage
as well as lamp current.
Regulating
maximum lamp voltage permits the designer
to provide for ample worst-case lamp strike
voltage while conservatively limiting
maximum open circuit voltage. In addition
the controller features include auto
shutdown for an open or broken lamp, and a
lamp fault detection with a status reporting
output.
To improve design flexibility the IC
includes the ability to select the polarity of
both the chip enable and dim (BRITE)
inputs. Also included is a switched VDD
output of up to 10mA that will allow the
user to power other circuitry that can be
switched on and off with the inverters
enable input. This preserves the micro
power sleep mode with no additional
components.
KEY FEATURES
Provision to Synchronize Lamp
Current & Frequency With Other
Controllers
Dimming With Analog or Digital
(PWM) Methods (>20:1)
Programmable Fixed Frequency
Adjustable Power-up Reset
ENABLE/BRITE Polarity Selection
Voltage Limiting on Step-up
Transformer Secondary Winding
Open Lamp Timeout Circuitry
Switched VDD Output (10mA)
Micro-Amp Sleep Mode
Operates With 3.3V to 5V Supply
100mA Output Drive Capability
APPLICATIONS / BENEFITS
WWW .
Microsemi
.C
OM
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
Protected by U.S. Patents 5,615,093; 5,923,129; 5,930,121; 6,198,234; Patents Pending
Desktop LCD Monitors
Multiple Lamp Panels
Low Ambient Light Displays
High Efficiency
Lower Cost than Conventional
Buck/Royer Inverter Topologies
Improved Lamp Strike Capability
Improved Over-Voltage Control
PRODUCT HIGHLIGHT
DIMMING (BRITE)
ENABLE
LAMPS
FETS
PHASE SYNC
RAMP RESET
INPUT
CONNECTOR
12
13
LX1688
MASTER
24
STRIKE
STATUS
FAULT 1
FAULT 1
FAULT 2
ENABLE
BRITE
125 Hz 5% Duty cycle Burst
65KHz run frequency
FETS
12
13
LX1688
SLAVE
24
VDD
FAULT 2
STRIKE
STATUS
Ch3
10.0mV
Ω
Ch2
10.0mV
Ω
M
100µs
Simplified Quad Lamp Inverter Showing Synchronized Output Waveforms
PACKAGE ORDER INFO
T
J
(°C)
M
IN
V
DD
M
AX
V
DD
LX1688
LX1688
PW
Plastic TSSOP
24-Pin
RoHS compliant / Pb-free Transition DC: 0442
0 to 70
-40 to 85
3.0V
3.0V
5.5V
5.5V
LX1688CPW
LX1688IPW
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1688CPW-TR)
Copyright
©
2001
Rev. 1.2, 2006-03-09
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
MICROSEMI [ MICROSEMI CORPORATION ]
