Rev 0; 4/05
8-Channel Cold-Cathode
Fluorescent Lamp Controller
General Description
The DS3988 is an 8-channel controller for cold-cathode
fluorescent lamps (CCFLs) used to backlight liquid
crystal displays (LCDs) in TV and PC monitor applica-
tions. The DS3988 supports configurations of 1 to 8
lamps, and multiple DS3988 controllers can be cascad-
ed to support applications requiring more than 8 lamps.
Features
♦
High-Density CCFL Controller for LCD TV and PC
Monitor Backlights
♦
Can Be Easily Cascaded to Support More Than
8 Lamps
♦
Minimal External Components
♦
Analog Brightness Control
♦
Per-Channel Lamp Control Ensures Equal
Brightness Among Lamps and Maximizes Lamp
Life
♦
Gate Driver Phasing Minimizes DC Supply Current
Surges
♦
Per-Channel Lamp Fault Monitoring for Lamp
Open, Lamp Overcurrent, Failure to Strike, and
Overvoltage Conditions
♦
Accurate (±5%) Independent On-Board Oscillators
for Lamp Frequency (40kHz to 80kHz) and DPWM
Burst Dimming Frequency (22.5Hz to 440Hz)
♦
Can Be Synchronized to External Sources for the
Lamp and DPWM Frequencies
♦
<10% to 100% Dimming Range
♦
Programmable Soft-Start Minimizes Audible
Transformer Noise
DS3988
Applications
LCD Televisions
LCD PC Monitors
Ordering Information
PART
DS3988T
DS3988T+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
48 TQFP
48 TQFP
+Denotes
lead-free package.
Pin Configuration
SVM
BRIGHT
PSYNC
A0
LOSC
LSYNC
GND
POSC
48
V
CC
47
46
45
44
43
42
41
40
39
38
37
SDA
TOP VIEW
FAULT
SCL
GA1
GB1
LCM1
OVD1
GA2
GB2
LCM2
OVD2
GA3
GB3
LCM3
OVD3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
36
35
34
33
32
31
30
29
28
27
26
25
OVD8
LCM8
GB8
GA8
OVD7
LCM7
GB7
GA7
OVD6
LCM6
GB6
GA6
♦
I
2
C-Compatible Serial Port and On-Board
Nonvolatile (NV) Memory Allow Device
Customization
♦
8-Byte NV User Memory for Storage of Serial
Numbers and Date Codes
♦
4.5V to 5.5V Single-Supply Operation
♦
-40°C to +85°C Temperature Range
♦
48-Lead TQFP (7mm x 7mm) Package
DS3988
48-LEAD TQFP
7 x 7 x 1.0mm
Typical Operating Circuit appears at end of data sheet.
GB5
LCM5
OVD5
V
CC
GND
GA4
GB4
LCM4
OVD4
GND
GA5
GND
______________________________________________
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.
8-Channel Cold-Cathode
Fluorescent Lamp Controller
DS3988
ABSOLUTE MAXIMUM RATINGS
Voltage on V
CC
, SDA, and SCL
Relative to Ground.............................................-0.5V to +6.0V
Voltage on Leads Other than V
CC
,
SDA, and SCL…………………………..-0.5V to (V
CC
+ 0.5V),
not to exceed +6.0V
Operating Temperature Range ...........................-40°C to +85°C
EEPROM Programming Temperature Range .........0°C to +70°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
Input Logic 1
Input Logic 0
SVM Voltage Range
BRIGHT Voltage Range
LCM Voltage Range
OVD Voltage Range
Gate-Driver Output Charge
Loading
SYMBOL
V
CC
V
IH
V
IL
V
SVM
V
BRIGHT
V
LCM
V
OVD
Q
G
(Note 2)
(Note 2)
(Note 1)
CONDITIONS
MIN
4.5
0.7 x
V
CC
-0.3
-0.3
-0.3
-0.3
-0.3
TYP
MAX
5.5
V
CC
+
0.3
0.3 x
V
CC
V
CC
+
0.3
V
CC
+
0.3
V
CC
+
0.3
V
CC
+
0.3
20
UNITS
V
V
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
Input Leakage (Digital Pins)
Output Leakage (SDA,
FAULT)
Low-Level Output Voltage
(SDA, Fault)
Low-Level Output Voltage
(PSYNC, LSYNC)
Low-Level Output Voltage
(GA, GB)
High-Level Output Voltage
(PSYNC, LSYNC)
SYMBOL
I
CC
I
L
I
LO
V
OL1
V
OL2
V
OL3
V
OL4
V
OH1
High impedance
I
OL1
= 3mA
I
OL2
= 6mA
I
OL3
= 4mA
I
OL4
= 4mA
I
OH1
= -1mA
V
CC
- 0.4
CONDITIONS
G
A
, G
B
loaded with 600pF,
8 channels active
-1.0
-1.0
MIN
TYP
15
MAX
20
+1.0
+1.0
0.4
0.6
0.4
0.4
UNITS
mA
µA
µA
V
V
V
V
2
_____________________________________________________________________
8-Channel Cold-Cathode
Fluorescent Lamp Controller
DS3988
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.5V to +5.5V, T
A
= -40°C to +85°C.)
PARAMETER
High-Level Output Voltage
(GA, GB)
UVLO Threshold—V
CC
Rising
UVLO Threshold—V
CC
Falling
UVLO Hysteresis
SVM Threshold
SVM Hysteresis
LCM and OVD Source Current
LCM and OVD Sink Current
LCM and OVD DC Bias Voltage
LCM and OVD Input Resistance
Lamp Off Threshold
Lamp Overcurrent Threshold
Lamp Regulation Threshold
OVD Threshold
Lamp Frequency Range
Lamp Frequency Source
Frequency Tolerance
Lamp Frequency Receiver
Duty Cycle
DPWM Frequency Range
DPWM Source Frequency
Tolerance
DPWM Receiver Duty Cycle
DPWM Receiver
Frequency Range
DPWM Receiver
Minimum Pulse Width
BRIGHT Voltage—Minimum
Brightness
BRIGHT Voltage—Maximum
Brightness
Gate-Driver Output Rise/Fall Time
GAn and GBn Duty Cycle
V
DCB
R
DCB
V
LOT
V
LOC
V
LRT
V
OVDT
f
LF:OSC
f
LFS:TOL
f
LFR:DUTY
f
D:OSC
f
DSR:TOL
f
DFE:DUTY
f
DR:OSC
t
DR:MIN
V
BMIN
V
BMAX
t
R
/t
F
C
L
= 600pF
(Note 5)
2.0
100
44
(Note 4)
POSC resistor ±2% over temperature
LOSC resistor ±2% over temperature
(Note 3)
(Note 3)
(Note 3)
(Note 3)
0.3
1.8
0.9
0.9
40
-5
40
22.5
-5
40
22.5
25
0.5
SYMBOL
V
OH2
V
UVLOR
V
UVLOF
V
UVLOH
V
SVMT
V
SVMH
1.8
3.7
100
2.0
50
4
4
1.35
50
0.4
2.0
1.0
1.0
0.5
2.2
1.1
1.1
80
+5
60
440.0
+5
60
440.0
2.2
I
OH2
= -1mA
CONDITIONS
MIN
V
CC
- 0.4
4.3
TYP
MAX
UNITS
V
V
V
mV
V
mV
µA
µA
V
kΩ
V
V
V
V
kHz
%
%
Hz
%
%
Hz
µs
V
V
ns
%
_____________________________________________________________________
3
8-Channel Cold-Cathode
Fluorescent Lamp Controller
DS3988
I
2
C AC ELECTRICAL CHARACTERISTICS (See Figure 9)
(V
CC
= +4.5V to +5.5V, timing referenced to V
IL(MAX)
and V
IH(MIN)
, T
A
= -40°C to +85°C.)
PARAMETER
SCL Clock Frequency
Bus Free Time Between Stop and
Start Conditions
Hold Time (Repeated) Start
Condition
Low Period of SCL
High Period of SCL
Data Hold Time
Data Setup Time
Start Setup Time
SDA and SCL Rise Time
SDA and SCL Fall Time
Stop Setup Time
SDA and SCL Capacitive
Loading
EEPROM Write Time
SYMBOL
f
SCL
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
HD:DAT
t
SU:DAT
t
SU:STA
t
R
t
F
t
SU:STO
C
B
t
W
(Note 8)
(Note 9)
20
(Note 8)
(Note 8)
(Note 7)
(Note 6)
CONDITIONS
MIN
0
1.3
0.6
1.3
0.6
0
100
0.6
20 +
0.1C
B
20 +
0.1C
B
0.6
400
30
300
300
0.9
TYP
MAX
400
UNITS
kHz
µs
µs
µs
µs
µs
ns
µs
ns
ns
µs
pF
ms
NONVOLATILE MEMORY CHARACTERISTICS
(V
CC
= +4.5V to +5.5V)
PARAMETER
EEPROM Write Cycles
SYMBOL
CONDITIONS
+70°C (Note 10)
MIN
50,000
TYP
MAX
UNITS
Cycles
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 Max Rating of the LCM or
OVD pin for up to 1 second.
Note 3:
Voltage with respect to VDCB.
Note 4:
This is the minimum pulse width guaranteed to generate an output burst, which will generate the DS3988’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 DS3988’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 time applies to all the EEPROM memory. EEPROM write begins after a stop condition occurs.
Note 10:
Guaranteed by design.
4
_____________________________________________________________________
8-Channel Cold-Cathode
Fluorescent Lamp Controller
Typical Operating Characteristics
(V
CC
= +5.0V, T
A
= +25°C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3988 toc01
DS3988
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
19
18
SUPPLY CURRENT (mA)
17
16
15
14
13
12
f
LF:OSC
= 71kHz
GATE Q
C
= 3.5nC
-40
-15
10
35
V
CC
= 4.5V
V
CC
= 5.0V
V
CC
= 5.5V
DS3988 toc02
INTERNAL FREQUENCY CHANGE
vs. TEMPERATURE
3
FREQUENCY CHANGE (%)
2
1
0
-1
-2
-3
-4
-40
-15
10
35
60
85
DPWM FREQUENCY
LAMP FREQUENCY
DS3988 toc03
20
4
19
SUPPLY CURRENT (mA)
17
15
f
LF:OSC
= 71kHz
GATE Q
C
= 3.5nC
DPWM = 100%
DPWM = 50%
13
11
9
7
5
4.5
4.7
4.9
5.1
5.3
5.5
SUPPLY VOLTAGE (V)
SVM = 0V
DPWM = 10%
11
10
DPWM = 100%
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TYPICAL OPERATION AT 12V
DS3988 toc04
TYPICAL OPERATION AT 15V
DS3988 toc05
TYPICAL OPERATION AT 18V
DS3988 toc06
10µs
5.0V G
A
10µs
5.0V G
B
10µs
2.0V LCM
10µs
2.0V OVD
10µs
5.0V G
A
10µs
5.0V G
B
10µs
2.0V LCM
10µs
2.0V OVD
10µs
5.0V G
A
10µs
5.0V G
B
10µs
2.0V LCM
10µs
2.0V OVD
TYPICAL STARTUP WITH SVM
2ms
2.0V SVM
DS3988 toc07
BURST DIMMING AT 150Hz AND 10%
DS3988 toc08
1ms
5.0V G
A
1ms
5.0V G
B
1ms
2.0V LCM
2ms
5.0V G
B
2ms
2.0V LCM
2ms
2.0V OVD
1ms
2.0V OVD
_____________________________________________________________________
5
Analogue and Mixed Signal
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