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FAN7311 LCD Backlight Inverter Drive IC
May 2005
FAN7311 LCD Backlight Inverter Drive IC
Features
* High-Efficiency Single-Stage Power Conversion * Wide Input Voltage Range : 5V to 25.5V * Back Light Lamp Ballast and Soft Dimming * Reduces Number of Required External Components * Precision Voltage Reference Trimmed to 2% * ZVS Full-Bridge Topology * Soft Start * PWM Control at Fixed Frequency * Analog and Burst Dimming Function * Programmable Striking Frequency * Open Lamp Protection * Open Lamp Regulation * 20-Pin SSOP
Description
The FAN7311 provides all the control functions for a series parallel resonant converter as well as a pulse width modulation (PWM) controller to develop a supply voltage. Typical operating frequency range is between 30kHz and 250kHz, depending on the CCFL and the transformer's characteristics. The FAN7311 uses a new patent-pending phase-shift control.
20-SSOP
1
(c)2005 Fairchild Semiconductor Corporation
1
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FAN7311 Rev. 1.0.0
FAN7311 LCD Backlight Inverter Drive IC
Internal Block Diagram
RT max. 2V min. 0.5V 6uA S_S MRT1
OSCILLATOR Output Driver
OUTA
OUTB CT + + Output Control Logic Output Driver OUTD Striking Logic OLP S_S 1.4uA EA_OUT ADIM EA_IN Solr + 2.5V 105uA Solr Voltage Reference & Internal Bias 2.5VREF 2V REF Error Amp. UVLO
Q
SET
PGND OUTC
RT1
+
S
VOLP+ VOLP 2.5V 1.5V
OLP
Q
CLR
R
UVLO +
OLR
max. 2V min. 0.5V
Sburst 85uA Va+
BCT BDIM AGND
Sburst + UVLO
ENA 1.4V VIN VIN UVLO 5V
2 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Pin Assignments
RT1
OUTB
OUTA
VIN
PGND
OUTC
OUTD
CT
RT
BCT
20
19
18
17
16
15
14
13
12
11
FAN7311
1
OLP
2
OLR
3
ENA
4
S_S
5
GND
6
REF
7
ADIM
8
BDIM
9
10
EA_IN EA_OUT
Pin Definitions
No
1 2 3 4 5 6 7 8 9 10
Name
OLP OLR ENA S_S GND REF ADIM BDIM EA_IN EA_OUT
Function/Description
Open Lamp Protection Open Lamp Regulation Enable Input Soft Start Analog Ground 2.5V Reference Voltage Analog Dimming Input Burst Dimming Input Error Amplifier Input Error Amplifier Output
No
11 12 13 14 15 16 17 18 19 20
Name
BCT RT CT OUTD OUTC PGND VIN OUTA OUTB RT1
Function/Description
Burst Dimming Timing Capacitor Timing Resistor Timing Capacitor NMOSFET Drive Output D PMOSFET Drive Output C Power Ground Supply Voltage PMOSFET Drive Output A NMOSFET Drive Output B Striking Frequency Resistor
3 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Absolute Maximum Ratings
For typical values Ta=25C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with -25C Ta 85C and 5V Vcc 25.5V, unless otherwise specified.
Characteristics
Supply Voltage Operating Temperature Range Storage Temperature Range Thermal Resistance Junction-Air (Note1,2) Power Dissipation
Symbol
VCC Topr Tstg RJA Pd
Value
5 ~ 25.5 -25 ~ 85 -65 ~ 150 112 1.1
Unit
V C C C/W W
Note:
1. Thermal resistance test board Size: 76.2mm * 114.3mm * 1.6mm(1S0P) JEDEC standard: JESD51-3, JESD51-7 2. Assume no ambient airflow
4 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Electrical Characteristics
For typical values Ta=25C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with -25C Ta 85C and 5V Vcc 25.5V, unless otherwise specified.
Characteristics
Line Regulation 2.5V Regulation Voltage
Symbol
Vref V25
Test Condition
5 VCC 25.5V -
Min.
2.45
Typ.
2 2.5
Max.
25 2.55
Unit
mV V
REFERENCE SECTION ( Recommend X7R Capacitor )
OSCILLATOR SECTION(MAIN)
Oscillation Frequency CT High Voltage CT Low Voltage fosc Vcth Vctl Ta = 25C, Ct = 270pF Rt = 18k Ct = 270pF, Rt = 18k 108 106 115 115 2.0 0.5 122 kHz 124 V V
OSCILLATOR SECTION(BURST)
Oscillation Frequency BCT High Voltage BCT Low Voltage foscb Vbcth Vbctl Ctb = 10nF, Rt=18k 195 225 2 0.5 255 Hz V V
ERROR AMP SECTION
Open Loop Gain Unit Gain Bandwidth Feedback Output High Voltage Output Sink Current Output Source Current EA_IN Driving Current On OLR EA_IN Driving Current On Burst Dimming Feedback High Voltage On Burst Dimming Veh lsin lsur Iolr Iburst Vfbh EA_IN = 0V EA_OUT = 1.5V EA_OUT = 1.5V R(EA_IN) = 60k 2.0 1 75 61 Va+0.1 80 1.5 2.27 105 85 Va+0.4 2.54 -1 135 109 Va+0.7 dB MHz V mA mA uA uA V
SOFT START SECTION
Soft Start Current Soft Start Clamping Voltage ISS Vssh S_S=2V 4 6 5 8 uA V
PROTECTION SECTION
Open Lamp Protection Voltage 0 Open Lamp Protection Voltage 1 Open Lamp Regulation Voltage Open Lamp Protection Charging Current Volp0 Volp1 Volr Iolp Start at open lamp Normal -> open lamp 2.2 1.3 1.75 0.7 2.5 1.5 2 1.4 2.8 1.7 2.25 2.1 V V V uA
UNDER VOLTAGE LOCK OUT SECTION
Start Threshold Voltage Start Up Current Operating Supply Current Stand-by Current Vth Ist Iop Isb VCC = Vth-0.2 VCC = 12V VCC = 12V 130 1.5 200 5 180 4 370 V uA mA uA
ON/OFF SECTION
On State Input Voltage Off Stage Input Voltage Von Voff 2 5 0.7 V V
5 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Electrical Characteristics (Continued)
For typical values Ta=25C, Vcc=12V and for min/max values Ta is the operating ambient temperature range with -25C Ta 85C and 5V Vcc 25.5V, unless otherwise specified.
Characteristics OUTPUT SECTION
PMOS Gate High Voltage PMOS Gate Low Voltage NMOS Gate Drive Volgate NMOS Gate Drive Volgate PMOS Gate Voltage With UVLO Activated NMOS Gate Voltage With UVLO Activated Rising Time Falling Time
Symbol
Vpdhv Vphlv Vndhv Vndhv Vpuv Vnuv Tr Tf
Test Condition
VCC = 12V VCC = 12V VCC = 12V VCC = 12V VCC = Vth-0.2 VCC = Vth-0.2 VCC = 12V, Cload=2nF VCC = 12V, Cload=2nF
Min.
Vcc-10.5 6.5 Vcc-0.3 -
Typ.
Vcc Vcc-8.5 8.5 0 200 200
Max.
Vcc-6.5 10.5 0.3 500 500
Unit
V V V V V V ns ns
MAX./MIN OVERLAP
Min. Overlap between diagonal switches Max. Overlap betwwen diagonal switches fosc=100KHz fosc=100KHz 0 100 % %
DELAY TIME
PDR_A/NDR_B PDR_C/NDR_D Rt=18k Rt=18k 450 450 ns ns
6 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Function Description
UVLO: The under voltage lockout circuit guarantees stable operation of the IC's control circuit by stopping and starting it as a function of the Vin value. The UVLO circuit turns on the control circuit when Vin exceeds 5V. When Vin is lower than 5V, the IC's standby current is less than 200uA. ENA: Applying voltage higher than 2V to the ENA pin enables the operation of the IC. Applying voltage lower than 0.7V to the ENA pin will disable the operation of the inverter. Soft start: The soft start function requires that the S_S pin is connected through a capacitor to GND. A soft start circuit ensures a gradual increase in the input and output power. The capacitor connected to the S_S pin determines the rate at which the duty ratio rises. It is charged by a 6uA current source.
Burst oscillator & burst dimming: The timing capacitors (BCTs) are charged by the reference current source, which is formed by the timing resistor (RT). The timing resistor's voltage is regulated at 1.25V. The sawtooth waveform charges up to 2V. Once this voltage is reached, the capacitors begin discharging down to 0.5V. Next the timing capacitors start charging again and a new switching cycle begins. The burst dimming frequency can be programmed by adjusting the Rt and BCT values. The burst dimming frequency can be calculated as shown below.
f
burst
3.75 ---------------------------------64 R T BC T
Main oscillator: The timing capacitors (CTs) are charged by the reference current source, which is formed by the timing resistor (RT). The timing resistor's voltage is regulated at 1.25V. The sawtooth waveform charges up to 2V. Once this voltage is reached, the capacitors begin discharging down to 0.5V. Next, the timing capacitors start charging again and a new switching cycle begins. The main frequency can be programmed by adjusting the Rt and CT values. The main frequency can be calculated as shown below.
To avoid visible flicker, the burst dimming frequency should be greater than 120Hz. What does the following sentence mean? Please rewrite.To compare the input of BDIM pin with the 0.5~2V triangular wave of burst oscillator makes the PWM pulse for burst dimming. The PWM pulse controls EA_OUT's voltage by summing 85uA into the EA_IN pin.
f op
19 -----------------------------32 R T C T
7 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
VIN
8.5V
8.5V
VIN 8.5V
8.5V
Open lamp regulation & open lamp protection: It is necessary to suspend power stage operation if an open lamp occurs, because the power stage has high gain. When a voltage higher than 2V is applied to the OLR pin, the part enters regulation mode and controls the EA_OUT voltage. This limits the lamp voltage by summing 105uA into the feedback node. At the same time, the OLP capacitor, connected to the OLP pin, is charged by the 1.4uA internal current source. Once it reaches 2.5V, the IC enters shut down where all the output is high.
Output Drives: The four output drives are designed so that switches A and B, C and D never turn on simultaneously. The OUTA-OUTB pair is intended to drive one half-bridge in the external power stage. The OUTC-OUTD pair will drive the other half-bridge.
8 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Timing Diagram
The FAN7311 uses the improved phase-shift control full-bridge to drive CCFL. As a result, the temperature difference between the left and the right leg is almost zero. The detail timing is shown below.
EA_OUT CT
SYNC
T
T1
POUT A
NOUT B
POUT C
NOUT D
9 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Typical Application Circuits
VCC
C25 100u
IC1 FAN7311
R6 120k OLP RT1 C8
RT
0
0.1u R25 10k
C27 1u R26
C22 1u
0
OLR R24 ENA 10k C28 10n OUTB OUTA VIN C6 1u GND C2 REF R2 56k PGND OUTC OUTD CT R5 27k C21 10n R3 20k C3 EA_OUT BCT EA_IN RT C4 4.7n
0
10k
0
OUTB OUTA
0 0
M1 FDS8958A C7 10u M2 FDS8958A TX1
ENA
0
C1 1u
S_S
0
0 0
REF
REF ADIM BDIM
OUTC OUTD
C5 220p
1u R4 22k
DIM(0~3.3V)
0 0 0 0 0
0
C10 15p
CCFL
OLP1 OLR FB
D4 BAV99 C14 20n D6 BAV99 R16 1.5k
0
0
4.7n R8
RT
R9 8.2k
R15
FB
100k 2k
0
0
0
0
0
OLR
R14 100k C16 2.2n
OLP1 OLP
R1 330k R22 10k
0
0
C9 1u
Q1 KST2222 D1 D1N4148
D11 D1N4148
C19 2.2n
0
0
10 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Mechanical Dimensions
Package Dimensions in millimeters
20-SSOP
11 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
Ordering Information
Product number
FAN7311G FAN7311GX
Package
20-SSOP
Operating Temperature
-25C ~ 85C
12 FAN7311 Rev. 1.0.0
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FAN7311 LCD Backlight Inverter Drive IC
13 FAN7311 Rev. 1.0.0
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