FAN7318B [FAIRCHILD]
LCD Backlight Inverter Drive IC; LCD背光逆变器驱动IC型号: | FAN7318B |
厂家: | FAIRCHILD SEMICONDUCTOR |
描述: | LCD Backlight Inverter Drive IC |
文件: | 总24页 (文件大小:1386K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
August 2009
FAN7318B
LCD Backlight Inverter Drive IC
Features
Description
The FAN7318B is a LCD backlight inverter drive IC that
controls P-N half-bridge topology.
High-Efficiency Single-Stage Power Conversion
Wide Input Voltage Range: 6V to 30V
Backlight Lamp Ballast and Soft Dimming
Minimal External Components Required
Precision Voltage Reference Trimmed to 2%
Half-Bridge Topology
The FAN7318B provides a low-cost solution and reduces
external components by integrating proprietary wave
rectifiers for open-lamp protection and regulation. The
operating voltage range of the FAN7318B is wide, so an
external regulator isn’t necessary to supply the voltage to
the IC.
Soft-Start
PWM Control at Fixed Frequency
Analog Dimming Function
Burst Dimming Function
The FAN7318B provides various protections, such as
open-lamp regulation, over-voltage protection, open-
lamp protection, short-Lamp protection, CMP-high
protection, to increase the system reliability. The
FAN7318B provides burst dimming and analog dimming.
Programmable Striking Frequency
Open-Lamp Protection
The FAN7318B is available in a 20-SOIC package.
Open-Lamp Regulation
Over-Voltage Protection
Short-Lamp Protection
CMP-High Protection
Thermal Shutdown
20-Pin SOIC
Applications
LCD TV
LCD Monitor
Ordering Information
Part
Number
Operating
Temperature
Packing
Method
Eco
Status
Package
FAN7318BM
Rail
-25 to +85°C
20-Lead, Small Outline Integrated Circuit (SOIC)
RoHS
FAN7318BMX
Tape & Reel
For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
Protected under U.S. patent no. 5,652,479.
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
Block Diagram
Short-Lamp Protection
OLR1
OLR2
Min.
-
50µA @ OVP,SLP
2µA @ OLP.CMP high
3V/1V @ striking/normal
TIMER
0.3V
+
Over-Voltage Protection
Protection
Min. &
Max.
Detector
/Full Wave
Recifier
Max.
+
TSD 150oC
1.34V
2V
-
OLR3
OLR4
+
-
OUTA
OUTB
0μA
Output Driver
+
3.2μA
1.34V
2.2V
-
Error. Amp. source
current change
Gm Amp.
-
+
Open-Lamp Regulation
Oscillator
max. 2V
Control
Logic
On @ striking
min. 0.5V
CT
-
GND
+
CMP
Error. Amp. source
current change
-
UVLO 5.5V
Error Amp.
Negative
Analog
Dimming
Vref
+
ADIM
+
VIN
+
-
Hys. 0.45V
High_CMP
-
3.5V
-
1.35V
High CMP Protection
disable @ striking
+
52μA burst
sink current on
ENA
200k
OLP max.
Striking off
Voltage Reference
& Internal Bias
5V, max. 3mA
OLP1
OLP2
OLP3
OLP4
REF
17 Pulses Counter
And OLR<1.4V
Min. & Max.
Detector
/Full or Half
Wave
max. 2V
OLP
Rectifier
min. 0.5V
-
BCT
OLP min.
-
150μs
Delay
52μA burst
disable @ striking
sink current on
0.7V/0.5V
Striking/normal
+
+
BDIM
If ENA>2.5V, OLP & SLP disable.
If ENA<2.1V, OLP & SLP enable.
Figure 1. Internal Block Diagram
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
2
Pin Configuration
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
Figure 2. Package Diagram
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
3
Pin Definitions
Pin #
Name
Description
This pin is for protection delay time setting.
1
TIMER
Error amplifier output. Typically, a compensation capacitor is connected to this pin from the
ground.
2
3
4
CMP
ADIM
CT
This pin is the input for negative analog dimming.
This pin is for programming the switching frequency. Typically, a capacitor is connected to
this pin from ground and a resistor is connected to this pin from the REF pin.
This pin is 5V reference output. Typically, resistors are connected to this pin from the CT pin
and the BCT pin.
5
6
7
REF
BCT
This pin is for programming the frequency of the burst dimming. Typically, a capacitor is
connected to this pin from ground and a resistor is connected to this pin from the REF pin.
This pin is the input for negative burst dimming. The voltage range of 0.5 to 2V at this pin
controls the burst-mode duty cycle from 0% to 100%.
BDIM
8
ENA
GND
OUTB
OUTA
VIN
This pin turns the IC on / off.
9
This pin is the ground.
10
11
12
13
This pin is NMOS gate-drive output.
This pin is PMOS gate-drive output.
This pin is the supply voltage of the IC.
This pin is for open-lamp regulation. Its functions are the same as the OLR1 pin.
OLR4
This pin is for open-lamp protection and feedback control of lamp currents. Its functions are
the same as the OLP1 pin.
14
15
16
17
18
OLP4
OLR3
OLP3
OLR2
OLP2
This pin is for open-lamp regulation. Its functions are the same as the OLR1 pin.
This pin is for open-lamp protection and feedback control of lamp currents. Its functions are
the same as the OLP1 pin.
This pin is for open-lamp regulation. Its functions are the same as the OLR1 pin.
This pin is for open-lamp protection and feedback control of lamp currents. Its functions are
the same as the OLP1 pin.
This pin is for open-lamp regulation and short-lamp protection. It has the same functions as
other OLR pins and is connected to the full-wave rectifier internally. When the maximum of
rectified OLR inputs is between 1.34V and 2V, the error amplifier output current is limited to
3.0µA. When the maximum of rectified OLR inputs reaches 2V, the error amplifier output
current is 0A and its output voltage maintains constant. The maximum of rectified OLR
inputs is inputted to the negative of another error amplifier for feedback control of lamp
voltage. When the maximum of rectified OLR inputs is more than 2.2V, another error
amplifier for OLR is operating and lamp voltage is regulated. In normal mode, if the
maximum of rectified OLR inputs is higher than 1.34V or if the minimum of rectified OLR
inputs is lower than 0.3V for a predetermined time by the TIMER pin capacitor and an
internal current source 50µA; the IC shuts down to protect the system in over-voltage
condition or short-lamp condition, respectively.
19
OLR1
This pin is for open-lamp protection and feedback control of lamp currents. It has the same
functions as other OLP pins and is connected to the half-wave rectifier and the full-wave
rectifier internally. In striking mode, if the minimum of rectified OLP inputs is less than 0.7V
for a time predetermined by the TIMER pin capacitor and an internal current source or; in
normal mode, if the minimum of rectified OLP inputs is less than 0.5V for another
predetermined time by the TIMER pin capacitor and another internal current source; the IC
shuts down to protect the system in open-lamp condition. The maximum of rectified OLP
inputs is inputted to the negative of the error amplifier for feedback control of lamp current.
20
OLP1
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
4
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In
addition, extended exposure to stresses above the recommended operating conditions may affect device reliability.
The absolute maximum ratings are stress ratings only.
Symbol
VIN
Parameter
Min.
6
Max.
30
Unit
V
IC Supply Voltage
TA
Operating Temperature Range
Operating Junction Temperature
Storage Temperature Range
Thermal Resistance Junction-Air(1,2)
Power Dissipation
-25
+85
+150
+150
90
°C
TJ
°C
TSTG
θJA
-65
°C
°C/W
W
PD
1.4
Notes:
1. Thermal resistance test board; size: 76.2mm x 114.3mm x 1.6mm (1S0P); JEDEC standard: JESD51-2, JESD51-3.
2. Assume no ambient airflow.
Pin Breakdown Voltage
Pin #
1
Name
TIMER
CMP
ADIM
CT
Value
Unit
7
7
7
7
7
7
7
7
2
3
4
5
REF
6
BCT
7
BDIM
ENA
8
9
GND
OUTB
OUTA
VIN
10
11
12
13
14
15
16
17
18
19
20
30
30
30
±7
±7
±7
±7
±7
±7
±7
±7
V
OLR4
OLP4
OLR3
OLP3
OLR2
OLP2
OLR1
OLP1
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
5
Electrical Characteristics
For typical values, TA=25°C, VIN=15V, and -25°C ≤ TA ≤ 85°C, unless otherwise specified. Specifications to -25°C ~
85°C are guaranteed by design based on final characterization results.
Symbol
Parameter
Test Conditions
Min.
Typ. Max.
Unit
Under-Voltage Lockout Section (UVLO)
Vth
Vthhys
Ist
Start Threshold Voltage
Start Threshold Voltage Hysteresis
Startup Current
Increase VIN
4.9
0.20
10
5.2
0.45
70
5.5
0.60
100
3.5
V
V
Decrease VIN
VIN=4.5V
µA
mA
Iop
Operating Supply Current
VIN=15V, Not Switching
0.5
2.0
ON/OFF Section
Von
Voff
On-State Input Voltage
1.4
5.0
0.7
V
V
Off-State Input Voltage
Standby Current
Isb
ENA=0V
ENA=2V
50
120
200
190
280
µA
kΩ
RENA
Pull-Down Resistor
120
Reference Section (Recommend 1µF X7R Capacitor)
V5
5V Regulation Voltage
5V Line Regulation
5V Load Regulation
4.9
5.0
4
5.1
50
50
V
V5line
V5load
mV
mV
6 ≤ VIN ≤ 30V
4
10µA ≤ I5 ≤ 3mA
Oscillator Section (Main)
TA=25°C, CT=220pF,
RT=100kΩ
101.3
101
105.0
105
108.3
109
fosc
Oscillation Frequency
kHz
kHz
CT=220pF, RT=100kΩ
TA=25°C, CT=220pF,
RT=100kΩ
126.5
131.0
135.5
fstr
Oscillator Frequency in Striking Mode
CT Discharge Current
CT=20pF, RT=100kΩ
Striking
126
1.03
770
-15
131
1.18
870
-12
2
136
1.33
970
-9
Ictdcs
Ictdc
Ictcs
Vcth
Vctl
mA
μA
μA
V
Normal
CT Charge Current
CT High Voltage
CT Low Voltage
Striking
0.45
V
Oscillator Section (Burst)
TA=25°C, BCT=4.7nF,
BRT=1.4MΩ
321
330
330
342
foscb
Burst Oscillation Frequency
Hz
BCT=4.7nF,
BRT=1.4MΩ
317
20
343
32
Ibctdc
Vbcth
Vbctl
BCT Discharge current
BCT High Voltage
BCT Low Voltage
26
2
μA
V
0.5
V
Continued on the following page…
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
6
Electrical Characteristics (Continued)
For typical values, TA=25°C, VIN=15V, and -25°C ≤ TA ≤ 85°C, unless otherwise specified. Specifications to -25°C ~
85°C are guaranteed by design based on final characterization results.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
Analog Dimming Section
ADIM=0V, TA=25°C
ADIM=0V
1.225
1.212
1.310
1.310
1.16
1.402
1.408
AVrexx
Reference Voltage
V
ADIM=0.5V
ADIM=1.0V
0.99
Error Amplifier Section
lsin
Output Sink Current
OLP=2.5V, ADIM=2.5V
OLP=0V, ADIM=0V
CMP=3V
63
-65
-1.4
41
76
-50
-1.0
52
94
-35
-0.6
63
µA
µA
µA
µA
µA
µA
V
lsur1
lsur2
Ibsin
Iolpi
Iolpo
Output Source Current 1
Output Source Current 2
Burst CMP Sink Current
OLP Input Current
BDIM=5V, BCT=0V
OLP=2V
0
OLP Output Current
OLP=-2V
-30
-20
0.34
1.55
-10
OLP=0.3V
Vlpfx
Rectifiers Output of OLP
OLP=1.5V
V
Volpr
OLP Input Voltage Range(3)
-4
4
V
Open-Lamp Regulation Section
Iolr1
Iolr2
Striking, OLR=1.6V
OLR Sweep
-3.4
-2.8
0
-2.3
µA
µA
V
Error Amplifier Source Current for
Open-Lamp Regulation
Volr1
Volr2
Volr3
Open-Lamp Regulation Voltage 1
Open-Lamp Regulation Voltage 2
Open-Lamp Regulation Voltage 3
OLR Sweep
1.24
1.88
2.1
1.34
1.98
2.2
1.44
2.08
2.3
Striking, OLR Sweep
V
V
OLR Error Amplifier
Trans-conductance
GmOLR
180
40
310
440
80
µmho
Iors
Iolri
OLR Error Amplifier Sink Current
OLR Input Current
Normal, OLR=2.5V
OLR=2.5V
60
0
µA
µA
µA
V
Iolro
Volrr
OLR Output Current
OLR Input Voltage Range(3)
OLR=-2.5V
-35
-4
-25
-15
4
Continued on the following page…
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
7
Electrical Characteristics (Continued)
For typical values, TA=25°C, VIN=15V, and -25°C ≤ TA ≤ 85°C, unless otherwise specified. Specifications to -25°C ~
85°C are guaranteed by design based on final characterization results.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
Protection Section
Volp0
Volp1
Vcmpr
Vhfbp
Vslp
Open-Lamp Protection Voltage 0(3)
Open-Lamp Protection Voltage 1
CMP-High Protection Voltage
High-FB Protection Voltage(3)
Short-Lamp Protection Voltage
Timer Threshold Voltage 1
Timer Threshold Voltage 2
Timer Current 1
Striking
0.65
0.42
3.4
0.70
0.49
3.5
0.75
0.56
3.6
V
V
Sweep OLP
Sweep CMP
V
3.4
3.5
3.6
V
Sweep TIMER
Striking, Sweep TIMER
Sweep TIMER
OLP=0V
0.22
2.87
1.0
0.30
3.02
1.1
0.38
3.17
1.2
V
Vtmr1
Vtmr2
Itmr1
V
V
1.7
2.1
2.5
µA
µA
°C
V
Itmr2
Timer Current 2
Thermal Shutdown(3)
OLR=1.8V
40
50
60
TSD
Vovp
150
1.34
Over-Voltage Protection Voltage
Sweep OLR
1.24
2.1
1.44
2.5
ENA2.3V OLP Disable/Enable Change
Voltage
dcr
2.3
V
Output Section
Vpdhv
Vpdlv
Vndhv
Vndlv
PMOS Gate High Voltage(3)
VIN=15V
VIN=15V
VIN=15V
VIN=15V
VIN
V
V
V
V
PMOS Gate Low Voltage
NMOS Gate High Voltage
NMOS Gate Low Voltage(3)
VIN-9.0 VIN-7.5 VIN-6.5
7.5
8.5
0
10.0
PMOS Gate Voltage with UVLO
Activated
NMOS Gate Voltage with UVLO
Activated
Vpuv
Vnuv
VIN=4.5V
VIN=4.5V
VIN-0.3
V
V
0.3
Ipdsur
Ipdsin
Indsur
Indsin
PMOS Gate Drive Source Current(3)
PMOS Gate Drive Sink Current(3)
NMOS Gate Drive Source Current(3)
NMOS Gate Drive Sink Current(3)
VIN=15V
VIN=15V
VIN=15V
VIN=15V
-300
400
mA
mA
mA
mA
300
-400
Maximum / Minimum Duty Cycle
DCMIN
DCMAX
Minimum Duty Cycle(3)
Maximum Duty Cycle(3)
fosc=100kHz
fosc=100kHz
0
%
%
45
49
Note:
3. These parameters, although guaranteed, are not 100% tested in production.
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
8
Typical Performance Characteristics
Figure 3. Start Threshold Voltage vs. Temperature
Figure 4. Start Threshold Voltage Hysteresis
vs. Temperature
Figure 5. Startup Current vs. Temperature
Figure 6. Operating Current vs. Temperature
Figure 7. Standby Current vs. Temperature
Figure 8. 5V Regulation Voltage vs. Temperature
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
9
Typical Performance Characteristics (Continued)
Figure 9. Oscillation Frequency vs. Temperature
Figure 10. Oscillation Frequency in Striking
vs. Temperature
Figure 11. CT High Voltage vs. Temperature
Figure 12. CT Low Voltage vs. Temperature
Figure 13. Burst Dimming Frequency vs. Temperature
Figure 14. BCT Discharge Current vs. Temperature
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
10
Typical Performance Characteristics (Continued)
Figure 15. BCT High Voltage vs. Temperature
Figure 16. BCT Low Voltage vs. Temperature
Figure 17. Analog Dimming Reference Voltage 0
vs. Temperature
Figure 18. Analog Dimming Reference Voltage 05
vs. Temperature
Figure 19. Error Amplifier Source Current 1
vs. Temperature
Figure 20. Error Amplifier Source Current 2
vs. Temperature
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
11
Typical Performance Characteristics (Continued)
Figure 21. Error Amplifier Source Current for OLR
vs. Temperature
Figure 22. Error Amplifier Sink Current
vs. Temperature
Figure 23. Burst CMP Sink Current vs. Temperature
Figure 24. OLR Error Amplifier Sink Current
vs. Temperature
Figure 25. Open-Lamp Protection Voltage 1
vs. Temperature
Figure 26. High-CMP Protection Voltage
vs. Temperature
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
12
Typical Performance Characteristics (Continued)
Figure 27. Short-Lamp Protection Voltage
vs. Temperature
Figure 28. Open Lamp Regulation Voltage 1
vs. Temperature
Figure 29. Open Lamp Regulation Voltage 2
vs. Temperature
Figure 30. Open Lamp Regulation Voltage 3
vs. Temperature
Figure 31. TIMER Threshold Voltage 1
vs. Temperature
Figure 32. TIMER Threshold Voltage 2
vs. Temperature
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
13
Typical Performance Characteristics (Continued)
Figure 33. TIMER Current 1 vs. Temperature
Figure 34. TIMER Current 2 vs. Temperature
© 2009 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FAN7318B • 1.0.0
14
Functional Description
UVLO
The under-voltage lockout (UVLO) circuit guarantees
stable operation of the IC 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
5.2V. When VIN is lower than 4.75V, the IC startup
current is less than 100µA.
1
fstr
=
Hz
[
]
⎛
⎜
⎜
⎜
⎜
⎞
⎟
⎟
⎟
⎟
13.65 + 3I − 4.55I RT
−I ⋅I ⋅RT2
13.65 + 4.55I − 3I RT
(
)
1
2
1
2
(2)
RT ⋅CT ⋅ln
(
)
1
2
2
⎜
⎟
⎠
−I1 ⋅I2 ⋅RT
QI1 = 12×10-6A, I2 = 1.128×10-3A
⎝
Burst Dimming Oscillator
ENA
The burst dimming timing capacitor (BCT) is charged by
the current flowing from the reference voltage source,
which is formed by the burst dimming timing resistor
(BRT) and the burst dimming timing capacitor (BCT).
The sawtooth waveform charges up to 2V. Once the
BCT voltage reaches 2V, the capacitor begins
discharging down to 0.5V. Next, the BCT starts charging
again and a new burst dimming cycle begins, as shown
in Figure 36. The burst dimming frequency is
programmed by adjusting the BCT and BRT values. The
burst dimming frequency is calculated as:
Applying voltage higher than 1.4V to the ENA pin
enables the IC. Applying voltage lower than 0.7V to the
ENA pin disables the IC. In terms of the protections,
applying voltage higher than 2.5V to the ENA pin
disables OLP and SLP. Applying voltage lower than
2.1V to the ENA pin enables the OLP and the SLP.
Main Oscillator
In normal mode, the external timing capacitor (CT) is
charged by the current flowing from the reference
voltage source, which is formed by the timing resistor
(RT) and the timing capacitor (CT). The sawtooth
waveform charges up to 2V. Once CT voltage reaches
2V, the CT begins discharging down to 0.4V. Next, the
CT starts charging again and a new switching cycle
begins, as shown in Figure 35. The main frequency is
programmed by adjusting the RT and CT value. The
main frequency is calculated as:
1
fOSCB
=
[
Hz
]
(3)
0.039 ⋅BRT − 4500
0.026 ⋅BRT − 4500
⎛
⎞
⎟
BRT ⋅BCT ⋅ln
⎜
⎝
⎠
To avoid visible flicker, the burst dimming frequency
should be greater than 120Hz.
1
fOSC
=
Hz
[
]
3.9585⋅RT −13650
2.61⋅RT −13650
⎛
⎞
(1)
RT ⋅CT ⋅ln
⎜
⎝
⎟
⎠
Figure 36. Burst Dimming Oscillator Circuit
Analog Dimming
For analog dimming, the lamp intensity is controlled with
the external dimming signal (VADIM) and resistors. Figure
37 shows how to implement an analog dimming circuit.
Figure 35. Main Oscillator Circuit
CMP
In striking mode, the external timing capacitor (CT) is
charged by the current flowing from the reference
voltage source and 12μA current source, which
increases the frequency. If the product of RT and CT
value is constant, the striking frequency depends on CT
and is calculated as:
Error Amp.
Negative
Analog
Dimming
V
REF
ADIM
+
-
VADIM
OLP max.
Figure 37. Analog Implementation Circuit
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
15
In full brightness, the maximum rms value of the lamp
current is calculated as:
π
max
i
= Vref _max
A
(4)
[
]
rms
2 2RS1
The lamp intensity is inversely proportional to VADIM. As
VADIM increases, the lamp intensity decreases and the
rms value of the lamp current is calculated as:
π
max
i
= Vref
A
[
]
rms
2 2Rs
(5)
Vref = Vref _max − 0.30VADIM
A
[
]
Figure 38 shows the lamp current waveform vs. VADIM in
an analog dimming mode.
Figure 39. Negative Burst Dimming Waveform Using
DC Voltage
VREF
2.0
Burst dimming can be implemented, not only with DC
voltage, but also using PWM pulse as the BDIM signal.
Figure 40 shows how to implement burst dimming using
PWM pulse as BDIM signal.
1.5
1.0
0.5
0
0.5
0.5
1.0
1.0
1.5
1.5
2.0
2.0
2.5
2.5
ADIM
15mA
10mA
5mA
0
-5mA
-10mA
-15mA
Lamp Current
Figure 38. Analog Dimming Waveforms
Figure 40. Negative Burst Dimming Implementation
Circuit Using an External Pulse
Burst Dimming
Figure 41 shows the lamp current waveform vs. an
external pulse in negative burst dimming mode.
Lamp intensity is controlled with the BDIM signal over a
wide range. FAN7318B provides polarity selection.
When BDIM is inputted, DC voltage or PWM pulse
signal and BCT sets the sawtooth waveform or DC
voltage, respectively. This structure can be implemented
as negative dimming polarity. When BDIM voltage is
lower than BCT voltage, the lamp current is turned on;
0V on BDIM commands full brightness. The duty cycle of
the PWM pulse determines the lamp brightness. The
lamp intensity is inversely proportional to BDIM voltage.
As BDIM voltage increases, the lamp intensity
decreases. Figure 39 shows the lamp current waveform
vs. DIM in negative burst dimming mode.
Figure 41. Negative Burst Dimming Waveform Using
an External Pulse
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
16
During striking mode, burst dimming operation is
disabled to guarantee continuous striking time. Figure
42 shows burst dimming disabled during striking mode.
Soft-Start
A soft-start circuit ensures a gradual increase in the
input and output power. FAN7318B has no soft-start pin,
but provides soft-start function using the first BCT
waveform. The first BCT waveform limits CMP voltage at
initial operation, so lamp current increases gradually, as
shown in Figure 45 and Figure 46
2.5
2
1.5
1
0.5
0
2
2
2
3
3
3
4
4
4
5
5
5
6
6
6
7
7
7
8
8
8
9
9
9
10
10
10
11
11
11
12
x 10-3
2
1.5
1
0.5
0
12
x 10-3
0.01
0.005
0
-0.005
-0.01
-0.015
Figure 45. Soft-Start in Normal Mode
12
x 10-3
Figure 42. Burst Dimming During Striking Mode
When BDIM is setting over 2.2VDC and BCT is inputted
PWM pulse signal, positive dimming polarity can be
implemented. Figure 43 shows how to implement burst
dimming using PWM pulse as the BDIM signal.
Figure 46. Soft-Start in Burst Dimming Mode
Output Drives
FAN7318B is designed to drive P-N half-bridge
MOSFETs with symmetric duty cycle. FAN7318B can
drive P-MOSFET directly without a level-shift capacitor
and a Zener diode. A fixed dead time of 500ns is
introduced between two outputs at maximum duty cycle,
as shown in Figure 47.
Figure 43. Positive Burst Dimming Implementation
Circuit Using an External Pulse
Dead time
500ns at max. duty
Figure 44 shows the lamp current waveform vs. an
external pulse in positive burst dimming mode.
CT
CMP
SYNC
T
OUTA
OUTB
Figure 47. MOSFETs Gate Drive Signal
Figure 44. Positive Burst Dimming Waveform Using
an External Pulse
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
17
Open-Lamp Regulation
Lamp Current Feedback Circuit
When the maximum of the rectified OLR input voltages
max
OLR
FAN7318B has four OLP pins for lamp current feedback
and protections. The inputs of four OLP pins are
connected to the internal half-wave and full-wave
rectifier circuits. The half-wave rectified signals of four
OLP inputs are connected to the maximum detector
circuit. The full-wave rectified signals of four OLP inputs
are connected to the minimum detector circuit.
( V ) is more than 2V, the IC enters regulation mode
and controls CMP voltage. The IC limits the lamp
max
OLR
voltage by decreasing CMP source current. If V
is
between 1.34V and 2V, CMP source current decreases
max
OLR
to 3.0µA. Then, if V
reaches 2V, CMP source current
decreases to 0µA, so the CMP voltage remains constant
and the lamp voltage also remains constant, as shown
in Figure 49.
Two inputs of the four OLP pins should be inverse
phase with the other two inputs.
Lamp Voltage Feedback Circuit
FAN7318B has four OLR pins for lamp voltage feedback
and protections. The inputs of four OLR pins are
connected to the internal full-wave rectifier circuit. The
full-wave rectified signals of the four OLR inputs are
connected to the maximum detector circuit.
Furthermore, they are connected to the minimum
detector circuit for protections.
Protections
The FAN7318B provides the following latch-mode
protections: Open-Lamp Regulation (OLR), Open-Lamp
Protection (OLP), Short-Lamp Protection (SLP), CMP-
High Protection and Thermal Shutdown (TSD). The latch
is reset when VIN falls to the UVLO voltage or ENA is
pulled down to GND.
Figure 49. Open-Lamp Regulation in Striking Mode
max
Finally, if V
is more than 2.2V, the error amplifier for
OLR
The protection delay time can be adjusted by a capacitor
between the TIMER pin and GND.
OLR is operating and CMP sink current increases, so
CMP voltage decreases and the lamp voltage maintains
the determined value, as shown in Figure 50.
CMP
OLR
2V OLR
2.2V OLR
0
2.2V
2V
0
-2V
-2.2V
Figure 48. Protection Timing Delay
Assume that the TIMER pin capacitor is 1µF.
The striking time is calculated as:
0
iCMP
CΔVstr
Isur1
1μF •3V
2μA
(6)
(7)
tstrike
=
=
= 1.5s
Figure 50. 2.2V Open-Lamp Regulation
The OVP and SLP delay time are calculated as:
Over-Voltage Protection
max
OLR
V
CΔVnor
Isur 2
1μF •1V
50μA
In normal mode, while
is higher than 1.34V, the
tOVP _SLP
=
=
= 20ms
TIMER pin capacitor is charged by an internal current
source of 50µA. Once the TIMER reaches 1V, the IC
enters shutdown, as shown in Figure 51. This protection
is disabled in striking mode to ignite lamps reliably.
The CMP high protection and OLP delay time are
calculated as:
CΔVnor
Isur1
1μF •1V
2μA
(8)
tOLP _CMPH
=
=
= 500ms
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
18
The IC starts operating in striking mode and remains in
min
OLP
striking mode until 17 pulses of V
higher than 0.7V
and OLR < 1.34V occur. If more than 17 pulses and
OLR < 1.34V, the IC changes from striking mode into
normal mode, as shown in Figure 54.
Figure 51. Over-Voltage Protection in Normal Mode
max
OLR
In burst dimming mode, while V
is higher than 1.34V,
burst dimming is disabled, so that the TIMER pin
capacitor is charged continuously by an internal current
source of 50µA. Once the TIMER reaches 1V, the IC
enters shutdown, as shown in Figure 52.
Figure 54. Mode Change from Striking to Normal
min
OLP
After ignition, if V
is less than 0.5V for a time
predetermined by the TIMER pin capacitor and an
internal current source, 2µA in normal mode, the IC is
shut down, as shown in Figure 55 and Figure 56.
Figure 52. Over-Voltage Protection in Burst
Dimming Mode
OLP1
OLP
Open-Lamp Protection
OLP2
Min. & Max.
OLP min.
min
OLP
If the minimum of the rectified OLP voltages ( V ) is
Detector
-
150μs
/Full or Half
Delay
less than 0.7V during initial operation, the IC operates in
striking mode for a time predetermined by the TIMER pin
capacitor and an internal current source, 2µA, as shown
in Figure 53.
0.5V
Wave
Rectifier
+
OLP3
OLP4
Figure 55. OLP in Normal Mode (Configuration)
Figure 53. Open-Lamp Protection in Striking Mode
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
19
Figure 56. OLP in Normal Mode
Figure 58. OLP Disable in DCR Mode
Short-Lamp Protection
min
In burst dimming mode, if V
is less than 0.5V for
OLP
min
OLR
another time predetermined by the TIMER pin capacitor
and an internal current source, 2µA; the IC is shut down,
as shown in Figure 57. The open-lamp protection delay
in burst dimming mode is shorter than in full brightness
because a short-lamp condition is detected at rising
interval of lamp voltage in burst dimming, then another
internal current source is turned on during the interval.
If the minimum of the rectified OLR voltages ( V ) is
less than 0.3V for a time predetermined by the TIMER
pin capacitor and a internal current source of 50µA in
normal mode, the IC is shut down, as shown in Figure
59. This protection is disabled in striking mode to ignite
lamps reliably.
Figure 59. Short-Lamp Protection in Normal Mode
Figure 57. OLP in Burst Dimming Mode
min
OLR
In burst dimming mode, if V
is less than 0.3V for a
Applying voltage lower than 2.1V to the ENA pin enables
OLP. Applying voltage higher than 2.5V to the ENA pin
disables OLP and is called as DCR mode. Regardless of
DCR mode, OLP is enabled in striking mode.
time predetermined by the TIMER pin capacitor and a
internal current source of 50µA turned on only burst
dimming on time, the IC is shut down, as shown in
Figure 60. SLP protection delay changes, depending on
burst dimming on duty ratio.
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
20
This protection is disabled by a pull-down resistor (a few
MΩ) between CMP and GND. If CMP voltage reaches
2.5V, CMP source current decreases to 2µA. Determine
a pull-down resistor value such that the whole of this
current can flow through the resistor. If so, CMP-high
protection can be disabled, as shown Figure 63. This
protection is disabled in striking mode to ignite the
lamps reliably.
Figure 60. SLP in Burst Dimming Mode
Applying voltage higher than 2.5V to the ENA pin
disables SLP. Applying voltage lower than 2.1V to the
ENA pin enables SLP.
Figure 63. CMP-High Protection Disable by a Pull-
Down Resistor
Thermal Shutdown
The IC provides the function to detect abnormal over-
temperature. If the IC temperature exceeds
approximately 150°C, the thermal shutdown triggers.
Figure 61. Short-Lamp Protection Disable in DCR
Mode
CMP-High Protection
If CMP is more than 3.5V for a time predetermined by
the TIMER pin capacitor and a internal current source of
50µA in normal mode, the IC is shut down, as shown in
Figure 62.
Figure 62. CMP-High Protection
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
21
Typical Application Circuit (LCD Backlight Inverter)
Application
Device
Input Voltage Range
Number of Lamps
22-Inch LCD Monitor
FAN7318B
15V±10%
4
1. Features
High-Efficiency, Single-Stage Power Conversion
P-N Half-Bridge Topology
Reduces Required External Components
Enhanced System Reliability through Protection Functions
Figure 64. Typical Application Circuit
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
22
Physical Dimensions
13.00
12.60
A
11.43
20
11
B
9.50
10.65 7.60
10.00 7.40
2.25
1
PIN ONE
INDICATOR
10
0.65
0.51
0.35
1.27
1.27
M
0.25
C B A
LAND PATTERN RECOMMENDATION
SEE DETAIL A
2.65 MAX
0.33
0.20
C
0.10
C
0.30
0.10
SEATING PLANE
0.75
0.25
X 45°
NOTES: UNLESS OTHERWISE SPECIFIED
(R0.10)
(R0.10)
A) THIS PACKAGE CONFORMS TO JEDEC
MS-013, VARIATION AC, ISSUE E
GAGE PLANE
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS DO NOT INCLUDE MOLD
FLASH OR BURRS.
0.25
8°
0°
D) CONFORMS TO ASME Y14.5M-1994
1.27
0.40
SEATING PLANE
E) LANDPATTERN STANDARD: SOIC127P1030X265-20L
F) DRAWING FILENAME: MKT-M20BREV3
(1.40)
DETAIL A
SCALE: 2:1
Figure 65. 20-Lead, Small Outline Integrated Circuit (SOIC) Package
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
23
© 2009 Fairchild Semiconductor Corporation
FAN7318B • 1.0.0
www.fairchildsemi.com
24
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