AN-6016 Datasheet, PDF (1/18 Pages) Fairchild Semiconductor – LCD Backlight Inverter Drive IC

www.fairchildsemi.com
Application Note AN6016
tm
LCD Backlight Inverter Drive IC (FAN7311)
1. Description
Design goals for a Cold Cathode Fluorescent Lamp (CCFL)
inverter for use in a notebook computer or other portable
applications include small size, high efficiency, and low cost.
The FAN7311 provides the necessary circuit blocks to
implement a highly efficient CCFL backlight power supply
in 20-SSOP and 20-SOIC packages. The FAN7311 typically
consumes less than 4mA of operating current, improving
overall system efficiency. External parts count is minimized
and system cost is reduced by the integration of features
including; feedback-controlled Pulse Width Modulation
(PWM) driver stage, soft start, open lamp regulation, and
Under Voltage Lockout protection (UVLO). The FAN7311
includes an internal shunt regulator that allows operation
with an input voltage from 5V to 25.5V. It supports analog
and burst dimming modes of operation. The FAN7311 pro-
vides open lamp regulation and protection. Open lamp regu-
lation protects the transformer from over-voltage during start
up or when an open lamp occurs. The transformer voltage is
regulated by reducing duty cycle when an over-voltage is
detected. Open lamp protection can be used to shut down an
IC when an open lamp condition continues longer than a
specified time.
F1
FUSE
CN5
1
2
12V
3
4
5
6
7
8
9
ON/OFF ^R24
10
10k
12505WR-10
0
C22
220μ
25V
0
C28
10n
0
DIM (0~3.3V)
REF
R2
56k
R4
22 k
C21 R3
10n 18k
00
IC1 FAN7311
OLP RT1
OLR OUTB
C26
0.1μ
R6
82k
OUTB
0
RT
C1
0
0.22μ
0
C2
0
1μ
R70
ENA OUTA
S_S
VIN
GND PGND
REF OUTC
ADIM OUTD
BDIM CT
EA_IN RT
C3
EA_OUT BCT
4.7n
R8
OU TA
C6
0
1μ
0
J1
0
C5 220p
0
R527k
0
C4 4.7n
0
RT
100k
R9
9.1k
0
R25
10k
0
R27
10k
M1
SN
DN
GN
DN
SP
DP
GP
DP
FDS8958A
M2
SN
DN
GN
DN
SP
DP
GP
DP
FDS8958A
R15
FB
10 k
OLR
OLP
REF
Q1
R14
100k
0
R1
330k _D11
C9
1μ
KST2222
BAW56
OLP3
D1
R20
R21
BAW56
D10 ^10k
10k
0
BAW56 C18
C17
2.2n
2.2n
0
0
0
OLP1
OLP2
R22
R28
10k
10k
OLP4
C19
2.2n
0
C20
2.2n
0
C25
1μ
0
C27
1μ
0
C7 10μ
TX1
C8 10μ
OLR
D4
BAV70
TX2
OLR
D3
BAV70
Figure 1. Application Circuit
LTM190EX
C10
15p
C11
15p
1 _HOT
CN2
2 _COLD ^CCFL
1 _HOT
CN1
2 _COLD ^CCFL
OLP1
OLP2
R26 C14
1k 10n
00
C12
15p
R13 C30
1k 10n
00
FB
D6
R16
1k
BAV99
0
0
D7
R17
1k
BAV99
0
0
C13
15p
OLP3
1 _HOT
CN4
2 _COLD ^CCFL
OLP4
1 _HOT
CN3
2 _COLD ^CCFL
R12 C29
1k 10n
00
R11 C15
1k 10n
00
FB
D8
R18
1k
BAV99
00
D9
R19
1k
BAV99
0
0
REV. 1.0.1 4/20/06