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PDF ( 数据手册 , 数据表 ) LX1688IPW

零件编号 LX1688IPW
描述 MULTIPLE LAMP CCFL CONTROLLER
制造商 Microsemi Corporation
LOGO Microsemi Corporation LOGO 


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LX1688IPW 数据手册, 描述, 功能
RangeMAX™
LX1688
INTEGRATED PRODUCTS
MULTIPLE LAMP CCFL CONTROLLER
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 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.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
DIM M ING (BRITE)
ENABLE
LAMPS
IN PUT
CONNECTOR
LX1688
MASTER
KEY FEATURES
ƒ Provision to synchronize lamp
current & frequency with other
controllers
ƒ Dimming with analog or digital
(PWM) methods (>20:1)
ƒ Programmable Fixed frequency
ƒ Adjustable Power-up reset
ƒ ENABLE/BRITE Polarity Selection
ƒ Voltage limiting on step-up
transformer secondary winding
ƒ Open lamp timeout circuitry
ƒ Switched VDD output (10mA)
ƒ Micro-Amp Sleep Mode
ƒ Operates with 3.3V to 5V Supply
ƒ 100mA output drive capability
APPLICATIONS/BENEFITS
ƒ Desktop LCD Monitors
ƒ Multiple lamp panels
ƒ Low Ambient Light Displays
ƒ High Efficiency
ƒ Lower Cost than Conventional
Buck/Royer Inverter Topologies
ƒ Improved Lamp Strike Capability
ƒ Improved Over-Voltage Control
FAULT 1
FAULT 2
Copyright 2001
Rev. 1.1a, 2003-03-21
FAULT 1
ENABLE
BRITE
STRIKE
STATUS
125 Hz 5% Duty cycle Burst
65KHz run frequency
LX1688
SLAVE
VDD
FAULT 2
S T R IK E
STATUS
Ch3 10.0mV
Ch2 10.0mV M 100µs
Simplified quad lamp inverter showing synchronized output waveforms
TJ (°C)
0 to 70
-40 to 85
PACKAGE ORDER INFO
MIN VDD
PWMAX VDD
Plastic TSSOP
24-Pin
3.0V
5.5V
LX1688CPW
3.0V
5.5V
LX1688IPW
Microsemi
Integrated Products, Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1







LX1688IPW pdf, 数据表
RangeMAX™
LX1688
INTEGRATED PRODUCTS
MULTIPLE LAMP CCFL CONTROLLER
DETAILED DESCRIPTION (CONTINUED)
and may or may not be externally synchronized to the
LCD video frame rate. It will directly gate the signal
BRT. CPWM should not be used in this case.
Fault Pin
The fault pin is a digital output that indicates that the
maximum numbers of strike attempts has occurred
without lamp ignition. In this condition the FAULT pin
will go active high with typically 20mA drive capability.
Holding the OLSNS pin low (<200mV) will also force
timeout and activate the FAULT pin. When used as a
master, fault condition true does not inhibit master clock
outputs PHA_SYNC and RMP_RST.
I_R Pin
The run mode frequency of the output is one half the
internal ramp frequency, which is proportional to a bias
current set by resistor RI of 80.6K. The output frequency
can thus be adjusted by varying the value of RI-R, the typical
range from about 50K to 100K. Since there is some
variation in the frequency due to change in the input supply
(VDD) it is recommended that the value of RI-R be selected
at the nominal input voltage.
Sleep Mode (ENABLE Signal) and Switched VDD
(VDDSW)
Since the LX1688 can be used in portable battery
operated systems, a very low power sleep mode is included.
The IC will consume less than 10µA quiescent current from
both the VDD and VDD_P pins combined, when the
ENABLE pin is deactivated. The polarity of the ENABLE
pin is programmable by the BEPOL input (see table 1). In
addition the controller provides a switched supply pin
VDDSW this output supplies at least 10mA at VDD .2V
for external circuitry. This output can be used to power
additional circuitry that can be enabled with the controller.
BIAS & TIMING EQUATIONS
Formula 1:
Triangular Wave Generator Frequency, FTRI
FTRI
=
(25 ×
1
RI × CTRI )
[Hz]
Formula 2:
Lamp Frequency (AOUT’s switching frequency), FLAMP
FLAMP =
1 [Hz]
200e-12× RI
Formula 3:
Minimum Current Error Amp Bandwidth, BWIEA_MIN
BWIEA_MIN = 0.000048 [Hz]
CICOMP
Formula 4:
Minimum Voltage Error Amp Bandwidth, BWVEA_MIN
BWVEA_MIN = 0.000048 [Hz]
CVCOMP
Formula 5:
Softstart time, TSS
TSS = 4,500,000 × CVCOMP [sec]
Formula 6:
Minimum Power-on Reset Pulse Width, TMIN_POR
TMIN_POR = 2.3e6 × CPOR [sec]
Copyright 2001
Rev. 1.1a, 2003-03-21
Microsemi
Integrated Products, Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8














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