Rev 0; 9/06
Two-Channel, Push-Pull CCFL Controller
General Description
The DS3992 is a low-cost, two-channel controller for
cold-cathode fluorescent lamps (CCFLs) that are used
to backlight liquid crystal displays (LCDs). The DS3992
can drive multiple CCFLs per channel, making it ideal
for 4- and 6-lamp LCD PC monitor and TV applications.
The DS3992 uses a push-pull drive scheme to convert 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 drive scheme uses a minimal
number of external components, which reduces compo-
nent and assembly cost and makes the printed circuit
board (PC board) design easy to implement. The push-
pull drive scheme also provides an efficient DC-to-AC
conversion and produces near-sinusoidal waveforms.
Features
o
Two-Channel CCFL Controller for Backlighting
LCD Panels for PC Monitors and LCD-TVs
o
Minimal BOM Provides Low-Cost Inverter Solution
o
Per-Channel Lamp Fault Monitoring for Lamp-
Open, Lamp Overcurrent, Failure to Strike, and
Overvoltage Conditions
o
Accurate (±10%) On-Board Oscillator for Lamp
Frequency (40kHz to 80kHz)
o
Accurate (±10%) On-Board Oscillator for DPWM
Burst-Dimming Frequency (90Hz to 220Hz or
180Hz to 440Hz)
o
Device Supply Undervoltage Lockout
o
Inverter Supply Undervoltage Lockout
o
Burst-Dimming Soft-Start Minimizes Audible
Transformer Noise
o
Strike Frequency Boost
o
100% to < 10% Dimming Range
o
4.5V to 5.5V Single-Supply Operation
o
-40°C to +85°C Temperature Range
o
16-Pin SO Package (150 mils)
DS3992
Applications
LCD PC Monitors
LCD-TVs
Ordering Information
PART
DS3992Z-09P+
DS3992Z-09N+
DS3992Z-18P+
DS3992Z-18N+
DS3992Z-09P+T&R
DS3992Z-09N+T&R
DS3992Z-18P+T&R
DS3992Z-18N+T&R
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
DIMMING
FREQUENCY RANGE
90Hz to 220Hz
90Hz to 220Hz
180Hz to 440Hz
180Hz to 440Hz
90Hz to 220Hz
90Hz to 220Hz
180Hz to 440Hz
180Hz to 440Hz
BRIGHT POLARITY
Positive
Negative
Positive
Negative
Positive
Negative
Positive
Negative
PIN-PACKAGE
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
16 SO-16 (150 mils)
+Denotes
lead-free package.
T&R denotes tape-and-reel package.
TOP VIEW
LOSC
1
POSC
2
BRIGHT
3
Pin Configuration
16
V
CC
15
V
CC
14
OVD2
13
LCM2
Typical Operating Circuits appear at end of data sheet.
SVM
4
GA1
5
GB1
6
LCM1
7
OVD1
8
DS3992
12
GB2
11
GA2
10
V
CC
9
GND
SO-150
______________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Two-Channel, Push-Pull CCFL Controller
DS3992
ABSOLUTE MAXIMUM RATINGS
Voltage on V
CC
Relative to Ground.......................-0.5V to +6.0V
Voltage on Any Leads Other
Than V
CC
..............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...................See 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
SVM Voltage Range
BRIGHT Voltage Range
LCM Voltage Range
OVD Voltage Range
Gate-Driver Output Charge Loading
SYMBOL
V
CC
V
SVM
V
BRIGHT
V
LCM
V
OVD
Q
G
(Note 2)
(Note 2)
(Note 1)
CONDITIONS
MIN
4.5
-0.3
-0.3
-0.3
-0.3
TYP
MAX
5.5
V
CC
+
0.3
V
CC
+
0.3
V
CC
+
0.3
V
CC
+
0.3
20
UNITS
V
V
V
V
V
nC
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
SVM Falling-Edge Threshold
SVM Hysteresis
LCM and OVD DC Bias Voltage
LCM and OVD Input Resistance
Lamp-Off Threshold
Lamp Over Current
Lamp Regulation Threshold
OVD Threshold
Lamp Frequency Range
SYMBOL
I
CC
V
OL
V
OH1
V
UVLOR
V
UVLOF
V
UVLOH
V
SVM
V
SVMH
V
DCB
R
DCB
V
LOT
V
LOC
V
LRT
V
OVDT
f
LFS:OSC
(Note 3)
(Note 3)
(Note 3)
(Note 3)
1.65
3.15
2.25
2.25
40
1.9
3.7
100
2.0
150
1.35
50
1.75
3.35
2.35
2.35
1.85
3.55
2.45
2.45
80
2.1
CONDITIONS
G
A
, G
B
loaded with 600pF, 2 channels
active
I
OL
= 4mA
I
OH1
= -1mA
V
CC
-
0.4
4.3
MIN
TYP
8
MAX
16
0.4
UNITS
mA
V
V
V
V
mV
V
mV
V
kΩ
V
V
V
V
kHz
2
_____________________________________________________________________
Two-Channel, Push-Pull CCFL Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.5V to +5.5V, T
A
= -40°C to +85°C.)
PARAMETER
Lamp Frequency Tolerance
DPWM Frequency Range
DPWM Frequency Tolerance
BRIGHT Voltage:
Minimum Brightness
BRIGHT Voltage:
Maximum Brightness
Gate-Driver Output Rise/Fall Time
GAn and GBn Duty Cycle
Strike Time
t
STRIKE
500
SYMBOL
f
LFS:TOL
f
DSR:OSC
f
DSR:TOL
V
BMIN
V
BMAX
t
R
/ t
F
CONDITIONS
LOSC resistor ±2% over temperature
DS3992Z-09P/N
DS3992Z-18P/N
POSC resistor ±2% over temperature
DS3992Z-09P / DS3992Z-18P
DS3992Z-09N / DS3992Z-18N
DS3992Z-09P / DS3992Z-18P
DS3992Z-09N / DS3992Z-18N
C
L
= 600pF
50
2.0
2.0
0.5
100
44
MIN
-10
90
180
-10
TYP
MAX
+10
220
440
+10
0.5
UNITS
%
Hz
%
V
V
ns
%
ms
DS3992
Note 1:
All voltages are referenced to ground unless otherwise noted. Currents into the I.C. are positive, out of the I.C. negative.
Note 2:
During fault conditions, the AC-coupled feedback values are allowed to be below the Absolute Maximum Rating of the LCM or
OVD pin for up to 1s.
Note 3:
Voltage with respect to V
DCB.
Typical Operating Characteristics
(V
CC
= 5.0V, T
A
= +25°C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3992 toc01
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
9.5
SUPPLY CURRENT (mA)
9.0
8.5
8.0
7.5
7.0
6.5
6.0
GATE Q
C
= 3.5nC
f
LFOSC
= 64kHz
DPWM = 100%
-40.0
22.5
TEMPERATURE (°C)
85.0
V
CC
= 4.5V
V
CC
= 5.5V
V
CC
= 5.0V
DS3992 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
DS3992 toc03
9.0
8.5
8.0
SUPPLY CURRENT (mA)
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
GATE Q
C
= 3.5nC
f
LFOSC
= 64kHz
SVM
≤
2V
DPWM = 10%
DPWM = 100%
DPWM = 50%
10.0
1.0
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5
SUPPLY VOLTAGE (V)
_____________________________________________________________________
3
Two-Channel, Push-Pull CCFL Controller
DS3992
Typical Operating Characteristics (continued)
(V
CC
= 5.0V, T
A
= +25°C, unless otherwise noted.)
TYPICAL OPERATION AT 16V
DS3992 toc04
BURST DIMMING AT 150Hz AND 10%
DS3992 toc05
TYPICAL STARTUP WITH SVM
2ms
2.0V SVM
DS3992 toc06
10μs
5.0V G
A
10μs
5.0V G
B
10μs
2.0V LCM
10μs
2.0V OVD
1ms
5.0V G
A
1ms
5.0V G
B
1ms
2.0V LCM
2ms
5.0V G
B
2ms
2.0V LCM
1ms
2.0V OVD
2ms
2.0V OVD
BURST DIMMING AT 150Hz AND 50%
DS3992 toc07
SOFT-START AT V
INV
= 16V
DS3984 toc08
LAMP STRIKE—EXPANDED VIEW
DS3992 toc09
1ms
5.0V G
A
1ms
5.0V G
B
1ms
2.0V LCM
1ms
2.0V OVD
50μs
5.0V G
A
50μs
5.0V G
B
50μs
2.0V LCM
1ms
5.0V G
A
1ms
5.0V G
B
1ms
2.0V LCM
1ms
2.0V OVD
50μs
2.0V OVD
LAMP OUT (LAMP OPENED),
AUTORETRY DISABLED
DS3992 toc10
0.25
5.0V
G
A
0.25
5.0V
G
B
LAMP OPENED
0.25
2.00V LCM
0.25
2.00V OVD
4
_____________________________________________________________________
Two-Channel, Push-Pull CCFL Controller
Pin Description
PIN
NUMBER
1
NAME
LOSC
I/O
⎯
FUNCTION
Lamp Oscillator Resistor Adjust.
A resistor (R
LOSC
) to ground on this pin sets the frequency of
the lamp oscillator (f
LFS:OSC
). [R
LOSC
x f
LFS:OSC
= 1.6E9].
Burst Dimming DPWM Oscillator Resistor Adjust.
A resistor (RPOSC) to ground on this lead
sets the frequency (f
DSR:OSC
) of the burst-dimming DPWM oscillator. [R
POSC
x f
DSR:OSC
= 4.0E6
for DS3992Z-09P and DS3992Z-09N and R
POSC
x f
DSR:OSC
= 8.0E6 for DS3992Z-18P and
DS3992Z-18N].
Lamp Brightness Control.
An analog voltage at this input controls the lamp brightness. See
Table 1 for details.
Supply Voltage Monitor.
The DC inverter supply voltage is monitored by an external resistor
divider. The resistor-divider should be set such that it provides 2V at this pin for the minimum
allowable range of the DC inverter supply. Pulling this input below 2V will turn the lamps off and
reset the controller. Connect to V
CC
if not used.
MOSFET Gate Drive A for Channel 1.
Connect directly to the gate of a logic-level mode
n-channel MOSFET.
MOSFET Gate Drive B for Channel 1.
Connect directly to the gate of a logic-level mode
n-channel MOSFET.
Lamp Current Monitor Input for Channel 1.
Lamp current is monitored by a resistor placed in
series with the low-voltage side of the lamp.
Over Voltage Detection for Channel 1.
Lamp voltage is monitored by a capacitor divider
placed on the high-voltage side of the lamp.
Signal Ground
Supply.
4.5V to 5.5V.
MOSFET Gate Drive A for Channel 2.
Connect directly to the gate of a logic-level mode
n-channel MOSFET.
MOSFET Gate Drive B for Channel 2.
Connect directly to the gate of a logic-level mode
n-channel MOSFET.
Lamp Current Monitor Input for Channel 2.
Lamp current is monitored by a resistor placed in
series with the low-voltage side of the lamp.
Overvoltage Detection for Channel 2.
Lamp voltage is monitored by a capacitor divider
placed on the high-voltage side of the lamp.
Supply.
4.5V to 5.5V.
Supply.
4.5V to 5.5V.
DS3992
2
POSC
⎯
3
BRIGHT
I
4
SVM
I
5
6
7
8
9
10
11
12
13
14
15
16
GA1
GB1
LCM1
OVD1
GND
V
CC
GA2
GB2
LCM2
OVD2
V
CC
V
CC
O
O
I
I
⎯
⎯
O
O
I
I
⎯
⎯
_____________________________________________________________________
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