Rev 1; 2/08
Low-Cost CCFL Controller
General Description
The DS3991 is a controller for cold-cathode fluorescent
lamps (CCFLs) that are used to backlight liquid-crystal
displays (LCDs). The DS3991 is available for both
push-pull and half-bridge drive topologies.
The DS3991 converts a DC voltage (5V to 24V) to the
high-voltage (300V
RMS
to 1400V
RMS
) AC waveform that
is required to power the CCFLs. The push-pull and half-
bridge drive schemes use a minimal number of external
components, which reduces component and assembly
cost and makes the printed circuit board (PCB) design
easy to implement. Both drive schemes provide an effi-
cient DC to AC conversion and produce near-sinu-
soidal waveforms.
Features
♦
CCFL Controller for Backlighting LCD Panels
♦
Minimal External Components Required
♦
Lamp Fault Monitoring for Lamp-Open, Lamp-
Overcurrent, Failure-to-Strike, and Overvoltage
Conditions
♦
Accurate (±5%) On-Board Oscillator for Lamp
Frequency (40kHz to 80kHz)
♦
Accurate (±5%) On-Board Oscillator for DPWM
Burst-Dimming Frequency (80Hz to 300Hz)
♦
Device Supply Undervoltage Lockout
♦
Inverter Supply Undervoltage and Overvoltage
Lockouts
♦
Soft-Start on Burst-Dimming Minimizes Audible
Transformer Noise
♦
Strike Frequency Boost
♦
100% to < 10% Dimming Range
♦
Low Cost
♦
Single-Supply Operation Range: 4.5V to 5.5V
♦
Temperature Range: -40°C to +85°C
♦
16-Pin SO Package (150 mils)
DS3991
Applications
LCD PC Monitors
LCD TVs
Ordering Information
PART
DS3991Z+PP
DS3991Z+T&R/PP
DS3991Z+HB
DS3991Z+T&R/HB
CONFIGURATION
Push-Pull
Push-Pull
Half-Bridge
Half-Bridge
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
DIMMING FREQUENCY RANGE (Hz)
80 to 300
80 to 300
80 to 300
80 to 300
PIN-PACKAGE
16 SO (150 mils)
16 SO (150 mils)
16 SO (150 mils)
16 SO (150 mils)
+Denotes
a lead-free package.
T&R = Tape and reel.
TOP VIEW
SLOPE 1
VCC 2
Pin Configuration
16 SVML
15 SVMH
14 VCC
13 GND
Typical Operating Circuits appear at end of data sheet.
VCC 3
VCC 4
LOSC 5
POSC/PWM 6
BRIGHT 7
PWM_EN 8
DS3991
12 OVD
11 LCM
10 GB
9 GA
SO
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Low-Cost CCFL Controller
DS3991
ABSOLUTE MAXIMUM RATINGS
Voltage Range on VCC Relative to Ground ..........-0.5V to +6.0V
Voltage Range on Any Lead
Other than VCC
..............................................
-0.5V to (V
CC
+ 0.5V),
not to exceed +6.0V
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Soldering Temperature ............................Refer to the J-STD-020
Specification.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
(T
A
= -40°C to +85°C.)
PARAMETER
Supply Voltage
Input Logic 1
Input Logic 0
BRIGHT, SVML, SVMH Voltage
Range
LCM and OVD Voltage Range
Gate-Driver Output Charge
Loading
LOSC and POSC Loading
SYMBOL
V
CC
V
IH
V
IL
V
RA
V
RC
Q
G
C
OSC
(Note 2)
(Note 1)
CONDITIONS
MIN
4.5
2.2
-0.3
-0.3
-0.3
TYP
MAX
5.5
V
CC
+
0.3
+0.8
V
CC
+
0.3
V
CC
+
0.3
20
20
UNITS
V
V
V
V
V
nC
pF
ELECTRICAL CHARACTERISTICS
(V
CC
= +4.5V to 5.5V, T
A
= -40°C to +85°C.)
PARAMETER
Supply Current
Low-Level Output Voltage
(GA, GB)
High-Level Output Voltage
(GA, GB)
UVLO Threshold: V
CC
Rising
UVLO Threshold: V
CC
Falling
UVLO Hysteresis
SVML Falling Threshold
SVMH Rising Threshold
SVML and SVMH Hysteresis
LCM and OVD DC Bias Voltage
LCM and OVD Input Resistance
Lamp-Off Threshold
Lamp Overcurrent Threshold
SYMBOL
I
CC
V
OL
V
OH
V
UVLOR
V
UVLOF
V
UVLOH
V
SVMLT
V
SVMHT
V
SVMH
V
DCB
R
DCB
V
LOT
V
LOCT
(Note 3)
(Note 3)
1.65
3.25
1.94
1.94
3.7
100
2.00
2.00
150
1.35
50
1.75
3.35
1.85
3.45
2.06
2.06
CONDITIONS
GA, GB loaded with 300pF
I
OL
= 4mA
I
OH
= -1mA
2.4
4.3
MIN
TYP
5
MAX
10
0.4
UNITS
mA
V
V
V
V
mV
V
V
mV
V
k
V
V
2
_______________________________________________________________________________________
Low-Cost CCFL Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.5V to 5.5V, T
A
= -40°C to +85°C.)
PARAMETER
Lamp Regulation Threshold
OVD Threshold
Lamp Frequency
Lamp Frequency Tolerance
Burst-Dimming PWM Frequency
Burst-Dimming PWM Frequency
Tolerance
BRIGHT Voltage: Minimum
Brightness
BRIGHT Voltage: Maximum
Brightness
Gate-Driver Output Rise/Fall
SYMBOL
V
LRT
V
OVDT
LF
OSCI
LF
TOL
PF
OSCI
PF
TOL
V
BMIN
V
BMAX
t
R
/t
F
POSC resistor ±0.1% over temperature
SLOPE = 0
SLOPE = 1
SLOPE = 0
SLOPE = 1
C
L
= 600pF
3.3
3.3
0
100
LOSC resistor ±0.1% over temperature;
measured from 0°C to +85°C
(Note 3)
(Note 3)
CONDITIONS
MIN
2.29
2.25
40
-5
80
-5
TYP
2.35
2.35
MAX
2.41
2.45
80
+5
300
+5
0
UNITS
V
V
kHz
%
Hz
%
V
V
V
V
ns
DS3991
Note 1:
All voltages are referenced to ground unless otherwise noted. Currents into the IC are positive; currents out of the IC are
negative.
Note 2:
During fault conditions, if AC-coupled, LCM and OVD can go below ground by up to 1V for up to 1s.
Note 3:
Threshold voltage includes the DC bias-voltage offset.
Typical Operating Characteristics
(V
CC
= 5.0V, T
A
= +25°C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3991 toc01
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
DS3991 toc02
INTERNAL FREQUENCY CHANGE
vs. TEMPERATURE
0.8
FREQUENCY CHANGE (%)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
-40.0
22.5
TEMPERATURE (°C)
85.0
LAMP FREQUENCY
DPWM FREQUENCY
DS3991 toc03
6.0
5.5
SUPPLY CURRENT (mA)
5.0
4.5
4.0
DPWM = 10%
3.5
SVM TRIPPED
3.0
4.5
4.7
4.9
GATE Q
C
= 4.5nC
f
LOSC
= 49.6kHz
5.1
5.3
DPWM = 100%
DPWM = 50%
6.0
1.0
SUPPLY CURRENT (mA)
5.5
V
CC
= 5.5V
5.0
V
CC
= 5.0V
4.5
V
CC
= 4.5V
GATE Q
C
= 4.5nC
f
LOSC
= 49.6kHz
DPWM = 100%
22.5
TEMPERATURE (°C)
85.0
4.0
5.5
-40.0
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
3
Low-Cost CCFL Controller
DS3991
Typical Operating Characteristics (continued)
(V
CC
= 5.0V, T
A
= +25°C, multilamp configuration, unless otherwise noted.)
PUSH-PULL TYPICAL OPERATION
AT V
INV
= 12.5V
20μs
5.0V
20μs
5.0V
20μs
2.0V
20μs
2.0V
PUSH-PULL TYPICAL STARTUP
WITH SVM
DS3991 toc05
DS3991 toc04
GA
50ms
2.0V
50ms
5.0V
50ms
2.0V
50ms
2.0V
SVM
GB
GB
LCM
LCM
OVD
OVD
PUSH-PULL SOFT-START
AT V
INV
= 12.5V
0.1ms
5.0V
0.1ms
5.0V
0.1ms
2.0V
0.1ms
2.0V
PUSH-PULL LAMP STRIKE,
EXPANDED VIEW
DS3991 toc06
DS3991 toc07
GA
50ms
5.0V
50ms
5.0V
50ms
2.0V
50ms
2.0V
GA
GB
GB
LCM
LCM
OVD
OVD
PUSH-PULL BURST DIMMING
AT 133Hz, 10%
DS3991 toc08
PUSH-PULL BURST DIMMING
AT 133Hz, 50%
DS3991 toc09
1ms
5.0V
1ms
5.0V
1ms
2.0V
1ms
2.0V
GA
1ms
5.0V
1ms
5.0V
1ms
2.0V
1ms
2.0V
GA
GB
GB
LCM
LCM
OVD
OVD
4
_______________________________________________________________________________________
Low-Cost CCFL Controller
Typical Operating Characteristics (continued)
(V
CC
= 5.0V, T
A
= +25°C, single-lamp configuration, unless otherwise noted.)
DS3991
HALF-BRIDGE NORMAL OPERATION,
20μs
DS3991 toc10
HALF-BRIDGE SOFT-START
AT V
INV
= 12.5V
50μs
5.0V
50μs
5.0V
50μs
2.0V
50μs
2.0V
DS3991 toc11
20μs
5.0V
20μs
5.0V
20μs
2.0V
20μs
2.0V
GA
GA
GB
GB
LCM
LCM
OVD
OVD
HALF-BRIDGE LAMP STRIKE,
EXPANDED VIEW
DS3991 toc12
HALF-BRIDGE BURST DIMMING
AT 166Hz, 10%
DS3991 toc13
0.5ms
5.0V
0.5ms
5.0V
0.5ms
2.0V
0.5ms
2.0V
GA
1ms
5.0V
1ms
5.0V
1ms
2.0V
1ms
2.0V
GA
GB
GB
LCM
LCM
OVD
OVD
HALF-BRIDGE BURST DIMMING
AT 166Hz, 50%
DS3991 toc14
1ms
5.0V
1ms
5.0V
1ms
2.0V
1ms
2.0V
GA
GB
LCM
OVD
_______________________________________________________________________________________
5
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