General Description
The DS3994 is a 4-channel controller for cold-cathode
fluorescent lamps (CCFLs) that backlight liquid crystal
displays (LCDs) in TV and PC monitor applications. The
DS3994's features make it suitable for use in even the
largest LCDs, while its low BOM cost makes it ideal for
the entire range of LCD TVs and monitors.
The DS3994 can stagger the lamp bursts from each of
the four channels. This feature allows scanning back-
light schemes for video quality improvement to be
implemented using a single CCFL controller IC, making
it very simple and inexpensive to provide this enhance-
ment. In addition, staggering the bursts from each
channel can be used to minimize current ripple on the
display power supply, which is especially important for
larger LCDs. The relative stagger between each of the
channels is programmable, so this feature can be tai-
lored to the specific application.
The DS3994 uses a push-pull drive architecture but it
can also support full and half bridge drive schemes.
Contact the factory for more details.
Applications
LCD Televisions
LCD PC Monitors
Features
o High-Density CCFL Controller for LCD TV and
PC Monitor Backlights
o Programmable Staggered Start for Burst Dimming
on Each Channel
o Strike Frequency Boost Option
o Programmable Strike Time
o Can Be Easily Cascaded
o Minimal External Components
o Analog Brightness Control
o Gate Driver Phasing Minimizes DC Supply Current
Surges
o Per-Channel Lamp Fault Monitoring for Lamp
Open, Lamp Overcurrent, Failure to Strike, and
Overvoltage Conditions
o Accurate (2%) On-Board Oscillator Lamp
Frequency (20kHz to 80kHz)
o Wide Range On-Board DPWM Burst-Dimming
Oscillator (22.5Hz to 440Hz)
o Can Be Synchronized to External Sources for the
Lamp and DPWM Frequencies
o < 10% to 100% Dimming Range
o Soft-Start Minimizes Audible Transformer Noise
o I
2
C-Compatible Serial Port and On-Board
Nonvolatile (NV) Memory Allow Device
Customization
o 3-Byte NV User Memory for Storage of Serial
Numbers and Date Codes
o 4.5V to 5.5V Single-Supply Operation
o -40C to +85C Temperature Range
o 28-Pin SO (300 mils) Package
DS3994
4-Channel Cold-Cathode
Fluorescent Lamp Controller
______________________________________________ Maxim Integrated Products
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSYNC
FAULT
SCL
SDA
OVD4
LCM4
GND
GB4
GA4
OVD3
LCM3
GB3
GA3
V
CC
OVD2
LCM2
GB2
GA2
OVD1
LCM1
GB1
GA1
SVM
BRIGHT
POSC
PSYNC
A0
LOSC
SO-300
TOP VIEW
DS3994
Pin Configurations
Rev 0; 10/06
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.
Ordering Information
Typical Operating Circuits appear at end of data sheet.
PART
TEMP RANGE
PIN-PACKAGE
DS3994Z+
-40C to +85C
28 SO-300
+Denotes lead-free package.
DS3994
4-Channel Cold-Cathode
Fluorescent Lamp Controller
2
_____________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS
(T
A
= -40C to +85C.)
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.
Voltage Range on V
CC
, SDA, and SCL
Relative to Ground.............................................-0.5V to +6.0V
Voltage Range on Leads Other than V
CC
,
SDA, and SCL................................-0.5V to (V
CC
+ 0.5V),
not to exceed +6.0V
Operating Temperature Range ...........................-40C to +85C
EEPROM Programming Temperature Range .........0C to +70C
Storage Temperature Range .............................-55C to +125C
Soldering Temperature...................See J-STD-020 Specification
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
V
CC
(Note 1)
4.5
5.5
V
Input Logic 1
V
IH
2.2
V
CC
+
0.3
V
Input Logic 0
V
IL
-0.3
0.8
V
SVM Voltage Range
V
SVM
-0.3
V
CC
+
0.3
V
BRIGHT Voltage Range
V
BRIGHT
-0.3
V
CC
+
0.3
V
LCM Voltage Range
V
LCM
(Note 2)
-0.3
V
CC
+
0.3
V
OVD Voltage Range
V
OVD
(Note 2)
-0.3
V
CC
+
0.3
V
Gate-Driver Output Charge
Loading
Q
G
20
nC
ELECTRICAL CHARACTERISTICS
(V
CC
= +4.5V to +5.5V, T
A
= -40C to +85C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Current
I
CC
G
A
, G
B
loaded with 600pF,
4 channels active
9
16
mA
Input Leakage (Digital Pins)
I
L
-1.0
+1.0
A
Output Leakage (SDA,
FAULT)
I
LO
High impedance
-1.0
+1.0
A
V
OL1
I
OL1
= 3mA
0.4
Low-Level Output Voltage
(SDA,
FAULT)
V
OL2
I
OL2
= 6mA
0.6
V
Low-Level Output Voltage
(PSYNC, LSYNC)
V
OL3
I
OL3
= 4mA
0.4
V
Low-Level Output Voltage
(GA, GB)
V
OL4
I
OL4
= 4mA
0.4
V
High-Level Output Voltage
(PSYNC, LSYNC)
V
OH1
I
OH1
= -1mA
V
CC
- 0.4
V
DS3994
4-Channel Cold-Cathode
Fluorescent Lamp Controller
_____________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.5V to +5.5V, T
A
= -40C to +85C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
High-Level Output Voltage
(GA, GB)
V
OH2
I
OH2
= -1mA
V
CC
- 0.4
V
UVLO Threshold--V
CC
Rising
V
UVLOR
4.3
V
UVLO Threshold--V
CC
Falling
V
UVLOF
3.7
V
UVLO Hysteresis
V
UVLOH
100
mV
SVM Falling Edge Threshold
V
SVMT
1.95
2.0
2.05
V
SVM Hysteresis
V
SVMH
150
mV
LCM and OVD Source Current
4
A
LCM and OVD Sink Current
4
A
LCM and OVD DC Bias Voltage
V
DCB
1.35
V
LCM and OVD Input Resistance
R
DCB
50
k
Lamp Off Threshold
V
LOT
(Note 3)
1.65
1.75
1.85
V
Lamp Overcurrent Threshold
V
LOC
(Note 3)
3.15
3.35
3.55
V
Lamp Regulation Threshold
V
LRT
(Note 3)
2.29
2.35
2.41
V
OVD Threshold
V
OVDT
(Note 3)
2.25
2.35
2.45
V
Lamp Frequency Range
f
LF:OSC
20
80
kHz
Lamp Frequency Source
Frequency Tolerance
f
LFS:TOL
LOSC resistor 0.1% over temperature
-2
+2
%
Lamp Frequency Receiver
Duty Cycle
f
LFR:DUTY
40
60
%
DPWM Frequency Range
f
D:OSC
22.5
440.0
Hz
DPWM Source Frequency
Tolerance
f
DSR:TOL
POSC resistor 0.1% over temperature
-2
+2
%
DPWM Receiver Duty Cycle
f
DFE:DUTY
40
60
%
DPWM Receiver
Frequency Range
f
DR:OSC
22.5
440.0
Hz
DPWM Receiver
Minimum Pulse Width
t
DR:MIN
(Note 4)
25
s
BRIGHT Voltage--Minimum
Brightness
V
BMIN
Positive slope (CR2.7 = 0)
0.5
V
BRIGHT Voltage--Maximum
Brightness
V
BMAX
Positive slope (CR2.7 = 0)
2.0
V
BRIGHT Voltage--Minimum
Brightness
V
BMIN
Positive slope (CR2.7 = 1)
0
V
BRIGHT Voltage--Maximum
Brightness
V
BMAX
Positive slope (CR2.7 = 1)
3.3
V
Gate-Driver Output Rise/Fall Time
t
R
/t
F
C
L
= 600pF
50
100
ns
GAn and GBn Duty Cycle
(Note 5)
44
%
DS3994
4-Channel Cold-Cathode
Fluorescent Lamp Controller
4
_____________________________________________________________________
I
2
C AC ELECTRICAL CHARACTERISTICS (See Figure 10)
(V
CC
= +4.5V to +5.5V, timing referenced to V
IL(MAX)
and V
IH(MIN)
, T
A
= -40C to +85C.)
Note 1:
All voltages are referenced to ground, unless otherwise noted. Currents into the IC are positive, out of the IC negative.
Note 2:
During fault conditions, the AC-coupled feedback values are allowed to be outside the Absolute Maximum Rating of the
LCM or OVD pin for up to 1 second.
Note 3:
Voltage including the DC offset, VDCB.
Note 4:
This is the minimum pulse width guaranteed to generate an output burst, which will generate the DS3994's minimum burst
duty cycle. This duty cycle may be greater than the duty cycle of the PSYNC input. Once the duty cycle of the PSYNC input
is greater than the DS3994's minimum duty cycle, the output's duty cycle will track the PSYNC's duty cycle. Leaving
PSYNC low (0% duty cycle) disables the GAn and GBn outputs in DPWM Slave mode.
Note 5:
This is the maximum lamp frequency duty cycle that will be generated at any of the GAn or GBn outputs.
Note 6:
I
2
C interface timing shown is for fast-mode (400kHz) operation. This device is also backward compatible with I
2
C stan-
dard-mode timing.
Note 7:
After this period, the first clock pulse can be generated.
Note 8:
CB--total capacitance allowed on one bus line in picofarads.
Note 9:
EEPROM write begins after a stop condition occurs.
Note 10: Guaranteed by design.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCL Clock Frequency
f
SCL
(Note 6)
0
400
kHz
Bus Free Time Between Stop and
Start Conditions
t
BUF
1.3
s
Hold Time (Repeated) Start
Condition
t
HD:STA
(Note 7)
0.6
s
Low Period of SCL
t
LOW
1.3
s
High Period of SCL
t
HIGH
0.6
s
Data Hold Time
t
HD:DAT
0
0.9
s
Data Setup Time
t
SU:DAT
100
ns
Start Setup Time
t
SU:STA
0.6
s
SDA and SCL Rise Time
t
R
(Note 8)
20 +
0.1C
B
300
ns
SDA and SCL Fall Time
t
F
(Note 8)
20 +
0.1C
B
300
ns
Stop Setup Time
t
SU:STO
0.6
s
SDA and SCL Capacitive
Loading
C
B
(Note 8)
400
pF
EEPROM Write Time
t
W
(Note 9)
20
30
ms
NONVOLATILE MEMORY CHARACTERISTICS
(V
CC
= +4.5V to +5.5V)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
EEPROM Write Cycles
+70C (Note 10)
50,000
Cycles
DS3994
4-Channel Cold-Cathode
Fluorescent Lamp Controller
_____________________________________________________________________
5
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3994 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
5.3
5.1
4.9
4.7
6
7
8
9
10
5
4.5
5.5
4
DPWM = 10%
DPWM = 50%
DPWM = 100%
GATE Q
C
= 3.5nC
SVM < 2V
f
LF:OSC
= 64kHz
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
DS3994 toc02
TEMPERATURE (
C)
SUPPLY CURRENT (mA)
22.5
6.5
7.0
7.5
8.0
9.0
8.5
9.5
10.0
10.5
11.0
6.0
-40.0
85.0
V
CC
= 5.5V
V
CC
= 5.0V
DPWM = 100%
f
LF:OSC
= 64kHz
GATE Q
C
= 3.5nC
V
CC
= 4.5V
INTERNAL FREQUENCY CHANGE
vs. TEMPERATURE
DS3994 toc03
TEMPERATURE (
C)
FREQUENCY CHANGE (%)
22.5
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
-0.6
-0.8
-1.0
-40.0
85.0
LAMP FREQUENCY
DPWM FREQUENCY
TYPICAL OPERATION AT 12V
DS3994 toc04
10
s
5.0V G
A
10
s
5.0V G
B
10
s
2.0V LCM
10
s
2.0V OVD
BURST DIMMING AT 150Hz AND 10%
DS3994 toc08
1ms
5.0V G
A
1ms
5.0V G
B
1ms
2.0V LCM
1ms
2.0V OVD
TYPICAL OPERATION AT 15V
DS3994 toc05
10
s
5.0V G
A
10
s
5.0V G
B
10
s
2.0V LCM
10
s
2.0V OVD
TYPICAL OPERATION AT 18V
DS3994 toc06
10
s
5.0V G
A
10
s
5.0V G
B
10
s
2.0V LCM
10
s
2.0V OVD
TYPICAL STARTUP WITH SVM
DS3994 toc07
5ms
2.0V SVM
5ms
5.0V G
B
5ms
2.0V LCM
5ms
1.0V OVD
Typical Operating Characteristics
(V
CC
= +5.0V, T
A
= +25C, unless otherwise noted.)
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