RangeMAX™
I N T E G R A T E D
P R O D U C T S
LX1688
M
ULTIPLE
L
AMP
CCFL C
ONTROLLER
DESCRIPTION
KEY FEATURES
WWW .
Microsemi
.C
OM
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 Linfinity’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.
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
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
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
PRODUCT HIGHLIGHT
D IM M IN G (B R IT E )
ENABLE
LAM PS
FETS
PHASE SYNC
RAMP RESET
IN P U T
CO NNECTO R
12
13
LX1688
MASTER
24
S T R IK E
STATUS
FAULT 1
FAULT 1
FAULT 2
ENABLE
B R IT E
125 Hz 5% Duty cycle Burst
65KHz run frequency
FETS
12
13
LX1688
SLAVE
24
LX1688
LX1688
VDD
FAULT 2
S T R IK E
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
PW
Plastic TSSOP
24-Pin
0 to 70
-40 to 85
Copyright
2001
Rev. 1.1a, 2003-03-21
3.0V
3.0V
5.5V
5.5V
LX1688CPW
LX1688IPW
Page 1
Microsemi
Integrated Products, Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
MICROSEMI [ MICROSEMI CORPORATION ]
