Not Recommended For New Design
LX1686
I N T E G R A T E D
P R O D U C T S
Digital Dimming CCFL Controller IC
P
RODUCTION
D
ATA
SHEET
DESCRIPTION
KEY FEATURES
WWW .
Microsemi
.C
OM
The LX1686 Backlight Controller
IC provides all the control functions
needed to implement Microsemi’s
direct drive inverters used to operate
cold cathode fluorescent lamps
(CCFL’s). This IC can be used to
control single or multiple-lamp
configurations. CCFL’s are used for
back or edge lighting of liquid crystal
flat panel displays (LCD’s) and
typically find application in notebook
computers, web browsers, automotive
and industrial instrumentation, and
entertainment systems.
The LX1686 includes a PWM
controlled lamp current burst circuit
that can provide a > 100:1 dimming
range from a simple zero to 2.5V
potentiometer input.
The PWM
dimming burst rate is easily
synchronized to the LCD panel’s frame
rate to prevent interference from
optical beat frequencies.
Safety and reliability features include
a new 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 at the same time conservatively
limit maximum open circuit voltage.
An innovative new strike voltage
generation technique enables the nodule
designer to optimize high voltage
transformer design for maximum
operating efficiency with no power
dissipating overhead to guarantee strike
capability
Direct drive topology is a non-
resonant, oscillator-controlled PWM
regulation method. The LX1686 allows
a wide choice of fixed operating
frequencies to match lamp current
frequency to the lamp’s most efficient
operating point, and to minimize high
frequency interference.
RangeMAX™ Wide Range
Dimming (>100:1)
Synchronizable to Display Video
Frequency
High Voltage Feedback Loop
Directly Controls Maximum Open
Lamp
Micro-Amp Sleep Mode
User Programmable Fixed
Frequency Operation
Under-Voltage Lockout Feature
With Power-Up Reset
Built-In Soft-Start Feature
Operates With 3.3V or 5V power
Supplies
100mA Output Drive Capability
APPLICATIONS
Notebooks
Instrumentation Display
Desktop Computer Monitors
Low Ambient Light Displays
(used in Aircraft, Automobiles,
and Hand-Held Equipment)
BENEFITS
Extremely High Efficiency From
3.3V to 5V Power Supplies
Lower Cost Than Conventional
Buck / Royer Inverter Topologies
Improved Lamp Strike Capability
Improved Over-Voltage Control
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
Protected by U.S. Patents 5,615,093; 5,923,129; 5,930,121; 6,198,234; Patents Pending
PRODUCT HIGHLIGHT
5
4
Standard Analog
Dimming Inverter
Power Used (Watts)
3
2
Microsemi's
RangeMAX
1
0
0
30
45
60
75
90
105
Light emitted by a CCFL is proportional to the current flowing through it.
There are two ways to control the current: by adjusting the amplitude of a
continuous AC current; or, as with RangeMAX technology, by varying the
amount of time a burst of full current is present. RangeMAX technology
frees the backlight inverter module designer to operate in a lower
brightness and lower power consumption mode than is possible with
conventional amplitude control methods.
LX1686
LX1686
Light Output (Nits)
PACKAGE ORDER INFO
T
A
(°C)
0 to 85
-40 to 85
Copyright
©
2000
Rev. 1.2a, 2005-01-27
PW
Plastic TSSOP
24-PIN
LX1686CPW
LX1686IPW
RoHS Complaint / Pb-free Transition D/C: 0442
Note: Available in Tape & Reel.
Append the letters “TR” to the part number. (i.e. LX1686CPW-TR)
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
Not Recommended For New Design
LX1686
I N T E G R A T E D
P R O D U C T S
Digital Dimming CCFL Controller IC
P
RODUCTION
D
ATA
SHEET
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VDD
,
VDD_P) .................................................................................. 6.5V
Digital Inputs ........................................................................................ -0.3 to VDD +0.5V
Analog Inputs........................................................................................ -0.3 to VDD +0.5V
Digital Outputs...................................................................................... -0.3 to VDD +0.5V
Analog Outputs ..................................................................................... -0.3 to VDD +0.5V
Operating Junction Temperature ...............................................................................150°C
Storage Temperature ................................................................................... -65°C to 150°C
RoHS / Pb-free Peak Package Solder Reflow Temperature
(40 second maximum exposure).....................................................................260°C (+0,-5)
Note:
Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal
PACKAGE PIN OUT
WWW .
Microsemi
.C
OM
A
OUT
VSS_P
VSS
AFD_C
RAMP_C
RAMP_R
FVERT
PD_CR
VCO_C
BRT_POS
BRITE
DIG_DIM
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
B
OUT
VDD_P
VDD
TRI_C
OLSNS
ISNS
ICOMP
VSNS
VCOMP
BRT
I_R
ENABLE
PW P
ACKAGE
(Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
THERMAL DATA
PW
P
ACKAGE
100°C/W
THERMAL RESISTANCE
-
JUNCTION TO AMBIENT
,
θ
JA
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the device/pc-board
system. All of the above assume no ambient airflow.
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
Copyright
©
2000
Rev. 1.2a, 2005-01-27
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
Not Recommended For New Design
LX1686
I N T E G R A T E D
P R O D U C T S
Digital Dimming CCFL Controller IC
P
RODUCTION
D
ATA
SHEET
FUNCTIONAL PIN DESCRIPTION
WWW .
Microsemi
.C
OM
P
IN
N
AME
AOUT
VSS_P
VSS
AFD_C
RAMP_C
RAMP_R
FVERT
PD_CR
VCO_C
BRT_POS
BRITE
DIG_DIM
ENABLE
I_R
BRT
VCOMP
VSNS
ICOMP
ISNS
OLSNS
TRI_C
VDD
VDD_P
BOUT
Output driver A.
Power ground for output drivers only.
Signal ground.
D
ESCRIPTION
Connects to an external capacitor, C
AFD
. Forcing to ground or VDD will make the VCO oscillate at approximately
50% of the maximum VCO frequency. Forcing to VDD/2 will make the VCO oscillate at 2x the FVERT frequency.
Connects to external capacitor C
RAMP
for setting Direct Drive PWM operating frequency.
Connects to external resistor R
RAMP
for setting Direct Drive PWM operating frequency.
Vertical frequency reference digital input. Has internal pull down.
Phase Detector Filter. Part of phase lock loop. Connects to external capacitor and resistor network.
Connects to external capacitor C
VCO
Brightness control polarity. Has internal pull up. Leave open or pull up to VDD for dimming brightness
proportional to BRITE voltage, connect to ground for brightness inversely proportional to BRITE voltage.
Analog voltage input for brightness control.
Digital Dimming Enable internal pull up. Leave open or pull up to VDD for operating in digital dimming mode.
Connect to ground for analog dimming mode.
Chip Enable internal pull up. High enables the chip. Low disables.
Current Reference Resistor. External resistor to ground (Ri) determines internal capacitor C
ICOMP
.
Current Error Amplifier non-inverting input
Voltage Error Amplifier output. Connects to external frequency compensation capacitor C
VCOMP
. Controls soft-
start timing.
Voltage Error Amplifier inverting input.
Current Error Amplifier output. Connects to external frequency compensation capacitor C
ICOMP
.
Current Error Amplifier inverting Input.
Open Lamp Sense Input.
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
Connects to external capacitor C
TRI
for setting strike Frequency ramp slope.
VDD
Dedicated VDD for output buffers only.
Output Driver B.
Copyright
©
2000
Rev. 1.2a, 2005-01-27
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
Not Recommended For New Design
LX1686
I N T E G R A T E D
P R O D U C T S
Digital Dimming CCFL Controller IC
P
RODUCTION
D
ATA
SHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -0°C
≤
T
A
≤
85°C for the
LX1686CPW and -40°C
≤
T
A
≤
85°C for the LX1686IPW except where otherwise noted. Test conditions: VDD = VDD_P = 3.0 to
5.5V, Ri = 40kΩ, C
VCO
= 0.01µF, C
AFD
= 0.22µF, C
TRI
= 0.83µF, C
RAMP
= 208pF, R
RAMP
= 15kΩ, C
PD
= 0.22µF, C
PDB
= 0.047µF, R
PD
=
110kΩ
Parameter
Power Supply Voltage
Operating Current
Power Supply Voltage
Output Buffer Operating Current
UVLO Threshold
UVLO Hysteresis
WWW .
Microsemi
.C
OM
Symbol
VDD
I
DD
VDD_P
I
DD_P
V
TH_UVLO
V
H_UVLO
Test Conditions
VDD = VDD_P
VDD = VDD_P = 5V
VDD = VDD_P
Volsns = VDD = VDD_P = 5V, CA = CB = 1000pF
Min
3
LX1686
Typ
5
Max
5.5
7
5.5
10
2.9
Units
V
mA
V
mA
V
mV
3
2
2.7
160
DIRECT DRIVE RAMP BLOCK
Triangular Wave Generator Analog
V
P_TRI
Output Peak Voltage
Triangular Wave Generator Analog
V
V_TRI
Output Valley Voltage
Triangular Wave Generator Oscillation
F
_TRI
Frequency
Triangular Wave Generator Oscillation
I
CHG_TRI
Charge Current
Triangular Wave Generator Oscillation
I
DISCHG_TRI
Discharge Current
Ramp Generator Analog Output Peak
V
P_RAMP
Voltage
Ramp Generator Analog Output Valley
V
V_RAMP
Voltage
Ramp Frequency Change Threshold
Ramp Generator Oscillation
Frequency – Nominal
Ramp Generator Oscillation
Frequency – Maximum
OLSNS Threshold Voltage
OLSNS Hysteresis
OLSNS-to-ICOMP Propagation Delay
DIGITAL DIMMER BLOCK
FVERT Input Frequency Capture
Range
FVERT Logic Threshold
FVERT Input Resistance
VCO Analog Output Peak Voltage
VCO Analog Output Valley Voltage
VCO Forced Source Current
Forced VCO Oscillation Frequency
Auto-Frequency Detection Response
BRITE Voltage Range
Full-Brightness Brite Input Voltage
Full-Darkness Brite Input Voltage
V
TH_RAMP_R
F
RAMP
F
RAMP_HI
V
TH_OLSNS
V
H_OLSNS
T
D_OLSNS
2.25
0.75
10
Tri_c = 0V
Tri_c = 3V
-2.3
2.3
-2.55
2.65
2.25
0.75
VDD = 3V
VDD = 5.5V
V
TRI_C
= 1.4V
V
TRI_C
= 2.25V
VDD = 3V
VDD = 3V
GBD
1.35
1.55
84
170
200
1.5
1.65
100
200
300
45
1
1.65
1.85
116
256
400
-2.9
2.9
V
V
Hz
µA
µA
V
V
V
V
KHz
KHz
mV
mV
µS
F
R_FVERT
V
TH_FVERT
R
FVERT
V
P_VCO
V
V_VCO
F
R_VCO_I_SRC
F
X_VCO
T
D_AFD
Design Reference Only
Design Reference Only
45
VDD/2
50
2.5
0.65
-5.8
250
1000
0
2.35
2.35
0.35
0.35
2.5
2.5
0.5
0.5
200
Hz
V
kΩ
V
V
µA
Hz
ms
V
V
V
V
V
E
LECTRICALS
E
LECTRICALS
VPD_CR = 3V, VDD = 3V
AFC_C = 0V, CVCO = 0.01µF
FVERT Frequency is 200Hz, VDD = 3V
-6.4
-5.2
V
R_BRITE
V
BRITE_FULL
V
BRT_POS
= VDD or float; BRITE = 2.5V
VBRT_POS = 0V, BRITE = 0.5V
V
BRITE_DARK
VBRT_POS = VDD or float, BRITE = 0.5V
VBRT_POS = 0V, BRITE = 2.5V
VDD
2.65
2.65
0.65
0.65
Copyright
©
2000
Rev. 1.2a, 2005-01-27
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
Not Recommended For New Design
LX1686
I N T E G R A T E D
P R O D U C T S
Digital Dimming CCFL Controller IC
P
RODUCTION
D
ATA
SHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature -0°C
≤
T
A
≤
85°C for the
LX1686CPW and -40°C
≤
T
A
≤
85°C for the LX1686IPW except where otherwise noted. Test conditions: VDD = VDD_P = 3.0 to
5.5V, Ri = 40kΩ, C
VCO
= 0.01µF, C
AFD
= 0.22µF, C
TRI
= 0.83µF, C
RAMP
= 208pF, R
RAMP
= 15kΩ, C
PD
= 0.22µF, C
PDB
= 0.047µF, R
PD
=
110kΩ
Parameter
Symbol
Test Conditions
LX1686
Typ
300
VDD/2
VDD/2
DIG_DIM = VDD
VCOMP = 1.25V
VCOMP = 1.5V
VCOMP = 1.5V
VCOMP = VSNS
VCOMP = 0.5V, VDD = 3V
BRITE = 0.5 – 2.6V
ICOMP = 1.5V, VDD = 3V
ICOMP = 1.5V, VDD = 3V
VCOMP = 1.25V, VDD = 3V
VDD = 3V
ICOMP = 0.5 to 2.25V, VDD = 3V
BRITE = 1.25V, RAMP_C = 2V, VDD = 3V
AOUT, BOUT = VDD = 3V
AOUT, BOUT = 1V, VDD = 3V
AOUT, BOUT = 0V, VDD = 3V
AOUT, BOUT = 2V, VDD = 3V
0
10
15
0
1.12
0.8
70
-15
20
0
-10
-10
400
50
70
1.25
1.5
200
-40
60
3
250
3
1100
45
35
-50
-40
2.5
110
120
VDD
1.38
10
700
-80
100
VDD
10
500
10
WWW .
Microsemi
.C
OM
Min
Max
Units
DIGITAL DIMMING BLOCK (CONTINUED)
BRITE-to-ICOMP Propagation Delay
BRITE_POS Logic Threshold
DIG-DIM Logic Threshold
DIRECT DRIVE PWM BLOCK
ISNS Threshold Voltage Range
VAMP Transconductance
VAMP Output Source Current
VAMP Output Sink Current
VAMP Output Voltage Range
VSNS Threshold Voltage
VCOMP Discharge Current
IAMP Transconductance
IAMP Output Source Current
IAMP Output Sink Current
IAMP Output Voltage Range
VCMP Input Offset Voltage
VCOMP-to-Output Propagation Delay
ICMP Input Offset Voltage
ICOMP-to-Output Propagation Delay
OUTPUT BUFFER BLOCK
Output Sink Current
Output Source Current
BIAS CONTROL BLOCK
Voltage at Pin I_R
Pin I_R Maximum Source Current
VBG Output Resistance
ENABLE Logic Threshold – 3V
ENABLE Logic Threshold – 5.5V
ENABLE Threshold Hysteresis – 3V
ENABLE Threshold Hysteresis – 5.5V
V
IR
I
MAX_IR
R
O_VBG
V
EN3V
V
EN5.5
V
H_EN3
V
H_EN5.5
.975
Design Reference Only
Design Reference Only
VDD = 3V
VDD = 5.5V
50
10
1.9
3.2
450
350
1.02
V
µA
kΩ
V
V
mV
mV
I
SK_OUTBUF
I
SOUT_BUF
25
20
-35
-20
85
85
85
85
mA
mA
mA
mA
V
R_ISNS
G
M_VAMP
I
S_VAMP
I
SK_VAMP
V
R_VAMP
V
TH_VSNS
I
D_VCOMP
G
M_IAMP
I
S_IAMP
I
SK_IAMP
V
R_IAMP
V
OS_VCMP
T
D_VCOMP
V
OS_ICMP
T
D_ICOMP
V
µmho
µA
µA
V
V
mA
µmho
µA
µA
V
mV
ns
mV
ns
T
D_BRITE
ns
V
V
1.5
2.7
2.4
3.6
E
LECTRICALS
E
LECTRICALS
Copyright
©
2000
Rev. 1.2a, 2005-01-27
Microsemi
Integrated Products
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
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