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PDF LX1692 Data sheet ( Hoja de datos )
| Número de pieza | LX1692 | |
| Descripción | Full Bridge Resonant CCFL Controller | |
| Fabricantes | Microsemi Corporation | |
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TM
LX1692
® Full Bridge Resonant CCFL Controller
PRODUCTION DATA SHEET
DESCRIPTION
Microsemi’s LX1692 is a cost The LX1692 regulates the CCFL
reduced, third generation Direct Drive brightness in three ways: analog
CCFL (Cold Cathode Fluorescent dimming, digital dimming, or combined
Lamp) controller. The integrated analog and digital dimming methods
controller is optimized to drive simultaneously to achieve the widest
CCFL’s using resonant full bridge dimming range (> 60 to 1).
inverter topology.
The LX1692 can accept a brightness
Resonant full bridge topology control signal that is either an analog
provides near sinusoidal waveforms voltage or a direct low frequency PWM.
over a wide supply voltage range in The LX1692 also features integrated
order to maximize the life of CCFL gate drivers for the four external power
lamps, control EMI emissions, and MOSFETs.
maximize efficiency. This new archi- An integrated 4V LDO powers all
tecture also provides a wide dimming internal control circuitry which greatly
range.
simplifies supply voltage requirements.
The LX1692 includes safety The LX1692 is available in a 20-Pin
features that limit the transformer TSSOP and SOIC.
secondary voltage and protect against
fault conditions which include open
lamp, broken lamp and short-circuit
faults.
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
PRODUCT HIGHLIGHT
LX1692
C_R
A
I_R B
C_BST
C
Part
C_TO
D
BRITE_IN
EA_OUT ISNS
VSUPPLY
DUAL
FET
DUAL
FET
KEY FEATURES
For Wide Voltage Range Inverter
Application (7V to 22V)
Patent Resonant Strike for
Unsurpassed Striking Power
Combined with Best Efficiency
Low Stress to Transformers
Excellent Open Circuit Voltage
Regulation Reduces Transformer
Breakdown Voltage
Requirements While Striking
Higher Voltage Lamps
One Inverter for Multiple Panel
Types
Wide Dimming Range
Analog Dimming: >3 to 1
Digital Dimming : >20 to 1
Combined: >60 to 1
Fool-Proof Striking
Programmable Burst Dimming
Frequency
Programmable Time Out
Protection
Fixed Operating Frequency
Open Lamp Voltage Protection,
Short Lamp Protection, Arc
Protection1
BENEFITS
Even Display Light Distribution
Longer Lamp Life with Optimized
Lamp Current Amplitude
Reduced Operating Voltage
Lowers Corona Discharge and
Prolongs Module Life
High “Nits / Watt” Efficiency
Makes Less Heat and Brighter
Displays
APPLICATIONS
LCD TV
LCD Monitor
TA (°C)
-20 to +85
PACKAGE ORDER INFO
Plastic TSSOP
PW 20-Pin
Plastic SOIC
DW 20-Pin
RoHS Compliant / Pb-free
RoHS Compliant / Pb-free
LX1692IPW
LX1692IDW
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1692IPW-TR)
1 Arc protection is provided if the arcing level is enough to be trigged.
Copyright © 2004
Rev. 1.0, 11/10/2005
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
1 page  
www.DataSheet4U.com
LX1692
TM ® Full Bridge Resonant CCFL Controller
PRODUCTION DATA SHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -20°C ≤ TA ≤ 70°C except where
otherwise noted and the following test conditions:.
Parameter
Symbol
Test Conditions
` POWER
Power Supply Input Voltage
VDDP
Power Supply Output Voltage
VDD_A VDDP = 4.5V to 5.5V, I Load = 5mADC
VDDP Operating Current
` ENABLE INPUT
IBB
CAOUT = CBOUT = CCOUT = CDOUT =2000pF,
fLAMP = 62.5kHz
ENABLE Logic Threshold
ENABLE threshold Hysteresis
ENABLE High
ENABLE Low
Sleep Mode Current
Input Resistance
` UNDER VOLTAGE LOCKOUT
VTH_EN
VH_EN
VEN_HIGH
VEN_LOW
IDD_SLEEP
RENR
VENABLE = 0V
UVLO Threshold VDDP
UVLO Hysteresis
` BRIGHTNESS CONTROL
VTH_UVLO_P Rising edge
VH_UVLO
BRITE_A Voltage Range
VR_BR_A
Full Brightness BRITE_A Input
VBR_FULL _A VR_BR_D = VDDA, TA=25°C
Full Darkness BRITE_A Input
VDARK_FULL_A VR_BR_D = VDDA
Full Darkness BRITE_A input Offset VDARKFULL_OS VR_BR_D = VDDA, BRITE_A = 0V
BRITE_D Voltage Range
VR_BR_D VR_BR_A = VDDA, TA = 25°C
Full Brightness BRITE_D Input
VBR_FULL _D VR_BR_A = VDDA
Full Darkness BRITE_D Input
` BURST RAMP GENERATOR
VDARK_FULL_D VR_BR_A = VDDA
Ramp Valley Voltage
Ramp Peak Voltage
Ramp Frequency
Burst Duty Cycle Range
VRVV
VRPV
FRamp
C_BST = 10nF, I_R = 40K
BRITE_D to DIMPWM Jitter
Burst PWM min Duty Resolution
` LAMP FREQUENCY GENERATOR
JBDD
DRBST
C_BST = 10nF, BRITE_D = 2.4V
Lamp Frequency Range
Max Lamp Strike Frequency
Lamp Run Ramp Frequency
FLAMP
FLAMP_STK
FLAMP_RUN
Lamp is not ignited
Lamp Ignited, Run Mode, TA = 25°C, I_R = 40K,
C_R = 100pF
Lamp Run Ramp Frequency
Regulation
FLAMP_REG
4.5 > VDDP < 5.5V, TA = 25°C
VDDP = 5.5V
Ramp Valley Voltage
Ramp Peak Voltage
Ramp PWM Jitter
` VIN_SNS RAMP
VLRVV
VLRPV
LFJ
Ramp Peak Clamp Voltage
VRPCV
VIN = 8V, C_P = C_R = 100pF, R_P = TBD,
VDDP = 5V
VIN_SNS Discharge Current
IVRVV
LX1692
Units
Min Typ Max
4.5 5.5
3.8 4.0 4.2
V
V
10 15 mA
1.6 1.85 2.0
V
500 mV
2.4 VDDP V
0 0.8 V
20 50 µA
100 KΩ
3.8 4.2 V
200 mV
0 VDDP V
1.9 2 2.1 V
0V
0.35 0.45 0.55
V
0.4 VDDP V
2.37 2.5 2.63
V
0.43 0.55 0.67
V
0.43 0.55 0.67
2.37 2.5 2.63
230 250 270
0 100
13
1
V
V
Hz
%
µs
%
30 150 KHz
150 KHz
59.3 62.5 65.7 KHz
±0.5 % / V
±0.1 %/°C
0.2 V
2.0 V
1 µs
5
VDDP+0
.9
V
7
12.5 18
mA
Copyright © 2004
Rev. 1.0, 11/10/2005
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
5 Page 
www.DataSheet4U.com
LX1692
TM ® Full Bridge Resonant CCFL Controller
PRODUCTION DATA SHEET
FUNCTIONAL DESCRIPTION
OPERATING MODES
Two operating modes, Strike and Run, are employed by
the LX1692. Upon power up or ENABLE going true, strike
mode is entered. After a successful strike, e.g., lamp is
ignited, run mode is entered. If ignition is unsuccessful, or
if the lamp extinguishes while running, a fault is declared
and the controller automatically shuts down.
OSCILLATOR CHARACTERISTICS
The main oscillator in the LX1692 has two frequency
control loops; a resonant tracking loop and a fixed
frequency loop. The fixed frequency loop is user set via the
I_R resistor and the C_R capacitor value. The resonant
tracking loop follows the natural resonant frequency of the
load.
STRIKING THE LAMP
Lamp ignition is determined by monitoring the lamp
current feedback voltage at the ISNS pin. If less than 1.0V
during the strike period, the lamp is considered not ignited
and Strike mode continues until ignition is detected or
strike time out (approximately 1 - 2 seconds) is reached. If
greater than 1.0V, strike is declared and a latch is set. The
IC is now in “run” mode. And threshold voltage for strike
detect is reduced to 0.3V to permit a minimum 3:1 analog
dimming ratio to be achieved.
During strike, lamp operating frequency is always
controlled by the resonant frequency tracking loop. At
power up the lamp is not ignited and the loads’ natural
resonant frequency will be typically1.3 to 1.5 times higher
than after the lamp has ignited.
The tracking oscillator frequency will slew to near the
natural resonant frequency of the load. At open circuit
resonance load Q is high and produces a large rise of
voltage across the lamp, eliminating the need to use a high
transformer turns ratio.
Additionally, since frequency is high, the volt-seconds
applied to the transformer primary is minimized. This
permits the use of smaller transformers that have reduced
core cross sectional area. During striking operation, ICOMP
is limited to 2.5V until ignition latch is set.
When it starts the striking operation, it starts the striking
frequency as user programmed operating frequency.
And when OVSNS is detected zero cross point , then
tracking oscillator will start to sweep the frequency up to
near to the circuit resonant frequency and it will track the
frequency to reach user programmed open lamp voltage.
At the moment of lamp ignition, operating frequency
immediately switches to the programmed value of the fixed
frequency oscillator. Lamp current flow is sensed by the
strike detection comparator, which decides to return PWM
timing control to the fixed frequency oscillator
FAULT PROTECTION
The LX1692 has shut down protection for all common
lamp fault conditions. These include the following:
a. Open or broken lamp
b. High Voltage Arcing on transformer secondary side
c. Short across lamp terminals
d. Short from high side of lamp to ground
e. Short from low side of lamp to ground ( current
sense resistor shorted)
Three inputs from the lamp are monitored to detect these
conditions, ISNS, OV_SNS, and OC_SNS. Fault
protection is designed to prevent fire or smoke from being
generated by terminating inverter operation in the event of
failures in the high voltage components and the power
FET’s. All fault shut down events can only be reset by
ENABLE or VDDP cycling.
OPEN LAMP
When the IC is first powered on or enabled, the inverter
output voltage must be made higher than the normal
operating voltage of the lamp to cause ignition. The
LX1692 generates this higher “strike” voltage by operating
at the open circuit resonant frequency of the load
inductance and capacitance. Because of its high unloaded
Q, a large resonant rise of voltage occurs across the lamp,
and produces ignition. Both resonant frequency and Q of
the lamp circuit are higher when the lamp is off than when
on. The lamp may not ignite immediately when specified
strike voltage is applied. It is customary to apply strike
voltage for from 0.3 to 3 seconds to insure ignition of cold,
dark, or aged lamps. The LX1692 has a programmable
time out for this purpose. During strike time out, open
lamp voltage is regulated to a value programmed by a
voltage divider across the lamp and sensed at the OV_SNS
pin.
Copyright © 2004
Rev. 1.0, 11/10/2005
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet LX1692.PDF ] | |
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