MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
General Description
The MAX8759 integrated cold-cathode fluorescent lamp
(CCFL) inverter controller is designed to drive CCFLs
using a full-bridge resonant inverter. The resonant opera-
tion ensures reliable striking and provides near-sinusoidal
waveforms over the entire input range. The controller
operates over a wide input-voltage range of 4.5V to
28V with high power to light efficiency. The device also
includes safety features that effectively protect against
single-point fault conditions such as lamp-out, secondary
overvoltage, and secondary short-circuit faults.
The MAX8759 provides accurate lamp-current regulation
(±2.5%) for superior CCFL inverter performance. The lamp
current is adjustable with an external resistor; 10:1 dim-
ming range can be achieved by turning the CCFL on and
off using a digital pulse-width modulation (DPWM) method,
while maintaining the lamp-current constant. The MAX8759
provides three mechanisms for controlling brightness:
2-wire SMBus™-compatible interface, external ambient-
light sensor (ALS), or system PWM control. The MAX8759
supports Intel display power-saving technology (DPST) to
maximize battery life. The device includes two lamp-current
feedback input pins that support dual-lamp applications with
a minimum number of external components.
The MAX8759 controls a full-bridge inverter for maximum
efficiency and directly drives four external n-channel
power MOSFETs. An internal 5.35V linear regulator pow-
ers the MOSFET drivers and most of the internal circuitry.
The MAX8759 is available in a space-saving, 28-pin, thin
QFN package and operates over a -40°C to +85°C tem-
perature range.
Features
●
Accurate Dimming Control Using SMBus, PWM
Interface, or Ambient Light Sensor
●
10:1 Dimming Range with 256-Step Resolution
●
Resonant-Mode Operation
• Longer Lamp Life with Near Sinusoidal Lamp
Current Waveform
• Guaranteed Striking Capability
• High-Power-to-Light Efficiency
●
Wide Input-Voltage Range (4.5V to 28V)
●
Input Feed-Forward for Excellent Line Rejection
●
±2.5% Lamp-Current Regulation
●
Adjustable 1.5% Accurate DPWM Frequency
●
Dual Lamp-Current Feedback Inputs
●
Comprehensive Fault Protection
• Secondary Voltage Limiting
• Primary Current Limit with Lossless Sensing
• Lamp-Out Protection with Adjustable Timeout
• Secondary Short-Circuit Protection
●
Small 28-Pin, 5mm x 5mm, Thin QFN Package
Minimal Operating Circuit
INPUT VOLTAGE
7.5V TO 24V
V
CC
1
27
BATT
GND
BST2
BST1
GH1
24
18
17
V
DD
21
11
DEL
V
CC
28
V
CC
MAX8759
SMB_DATA
2
SDA
LX1
LX2
SCL
GL1
PWMI
PGND1
8
PWMO
9
FREQ
PGND2
GL2
GH2
IFB1
ALS SUPPLY
5
IFB2
VALS
VFB
ISEC
6
ALS
COMP
TFLT
16
26
20
Applications
●
Notebooks
●
LCD Monitors
SMB_CLOCK
3
PWM INPUT
7
19
23
22
25
12
13
14
15
10
4
V
CC
CCFL
Ordering Information
PIN-
PKG
PART
TEMP RANGE
PACKAGE
CODE
28 Thin QFN-EP*
MAX8759ETI+ -40°C to +85°C
T2855-6
5mm x 5mm
+Denotes a lead-free package.
*EP = Exposed paddle.
Pin Configuration appears at end of data sheet.
SMBus is a trademark of Intel Corp.
ALS OUTPUT
19-3874; Rev 3; 4/14
MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
Absolute Maximum Ratings
BATT to GND ........................................................-0.3V to +30V
BST1, BST2 to GND .............................................-0.3V to +36V
BST1 to LX1, BST2 to LX2 .....................................-0.3V to +6V
FREQ, V
CC
, V
DD
to GND .......................................-0.3V to +6V
SDA, SCL to GND ...................................................-0.3V to +6V
ALS, COMP, PWMI, PWMO,
TFLT, DEL, VALS to GND .................... -0.3V to (V
CC
+ 0.3V)
GH1 to LX1............................................-0.3V to (V
BST1
+ 0.3V)
GH2 to LX2............................................-0.3V to (V
BST2
+ 0.3V)
GL1, GL2 to GND..................................... -0.3V to (V
DD
+ 0.3V)
IFB1, IFB2, ISEC, VFB to GND .................................-3V to +6V
PGND1, PGND2 to GND .....................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
28-Pin Thin QFN 5mm x 5mm
(derate 21.3mW/°C above +70°C) ............................1702mW
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................. +300°C
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.
Electrical Characteristics
(Circuit of Figure 1, V
BATT
= 12V, V
CC
= V
DD
,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
BATT Input Voltage Range
BATT Quiescent Current
BATT Quiescent Current, Shutdown
VCC Output Voltage, Normal Operation
VCC Output Voltage, Shutdown
VCC Undervoltage Lockout Threshold
VCC Undervoltage Lockout Hysteresis
VCC POR Threshold
VCC POR Hysteresis
GH1, GH2, GL1, GL2 On-Resistance,
Low State
GH1, GH2, GL1, GL2 On-Resistance,
High State
BST1, BST2 Leakage Current
Resonant Frequency Range
Minimum On-Time
Maximum Off-Time
Current-Limit Threshold
Zero-Current-Crossing Threshold
Current-Limit Leading-Edge Blanking
IFB1, IFB2 Input-Voltage Range
IFB1 Regulation Point
IFB2 Regulation Point
-3
765
780
785
800
LX1 - PGND1, LX2 - PGND2
LX1 - PGND1, LX2 - PGND2
ITEST = 100mA, VCC = VDD = 5V
ITEST = 100mA, VCC = VDD = 5V
VBST_ = 12V, VLX_ = 7V
Guaranteed by design
30
350
40
415
3
500
60
430
8
350
+3
805
820
Rising edge
CONDITIONS
VCC = VDD = VBATT
VCC = VDD = open
MAX8759 is enabled
MAX8759 is disabled
MAX8759 is enabled, 6V < VBATT < 28V,
0 < ILOAD < 10mA
MAX8759 is disabled, no load
VCC rising (leaving lockout)
VCC falling (entering lockout)
3.7
230
1.75
50
3
10
4
6
18
10
80
700
80
445
13
5.2
3.5
VBATT = 28V
VBATT = VCC = 5V
MIN
4.5
5.5
2.5
100
5.35
4.3
TYP
MAX
5.5
28.0
5
5
200
5.5
5.5
4.3
UNITS
V
mA
µA
V
V
V
mV
V
mV
Ω
Ω
µA
kHz
ns
µs
mV
mV
ns
V
mV
mV
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MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
Electrical Characteristics (continued)
(Circuit of Figure 1, V
BATT
= 12V, V
CC
= V
DD
,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
IFB1, IFB2 Input Bias Current
IFB1, IFB2 Lamp-Out Threshold
IFB1, IFB2 to COMP Transconductance
COMP Output Impedance
COMP Discharge Current During
Overvoltage or Overcurrent Fault
COMP Discharge Current During
DPWM Off-Time
DPWM Rising-to-Falling Ratio
ISEC Input Voltage Range
ISEC Overcurrent Threshold
ISEC Input Bias Current
VFB Input Voltage Range
VFB Input Impedance
VFB Overvoltage Threshold
VFB Undervoltage Threshold
VFB Undervoltage Delay
RFREQ
= 169kΩ
RFREQ
= 169kΩ, T
A = +25°C to +85°C
DPWM Oscillator Frequency
RFREQ
= 169kΩ
RFREQ
= 340kΩ
RFREQ
= 100kΩ
PWMO Output Impedance
PWMI Input Low Voltage
PWMI Input High Voltage
PWMI Input Hysteresis
PWMI Input Bias Current
PWMI Input Frequency Range
PWMI Full-Range Accuracy
PWMI duty cycle = 100%
PWMI Brightness Setting
ALS Full-Adjustment Range
ALS Full-Range Accuracy
ALS Input Bias Current
VALS Output Voltage
VALS Leakage Current
VALS On-Resistance
MAX8759 is enabled, 6V < VBATT < 28V,
ILOAD = 1mA
MAX8759 is disabled, VALS = GND
MAX8759 is enabled
-0.1
5.10
-3
30
5.30
PWMI duty cycle = 50%
PWMI duty cycle = 0%
98
48
9.7
0
100
50
10.0
52
10.3
1.8
5
+0.1
5.50
+3
60
V
LSB
µA
V
µA
Ω
%
-0.3
5
2.1
300
+0.3
50
5
20
207
205
VISEC = 1.25V
VVFB = 2.6V or VISEC = 1.5V
VCOMP = 1.5V
VIFB1,2 = 0
-3
1.18
-0.3
-4
150
2.2
210
300
2.3
240
250
210
210
106
343
40
60
0.7
kΩ
V
V
mV
µA
kHz
LSB
213
215
Hz
1.21
0.5V < VCOMP < 4V
0 < VIFB1,2 < 3V
-3V < VIFB1,2 < 0
CONDITIONS
MIN
-3
-230
575
60
6
500
90
600
100
12
1000
110
2.5
+3
1.26
+0.3
+4
450
2.4
280
V
V
µA
V
MΩ
V
mV
µs
625
160
24
2000
130
TYP
MAX
+3
UNITS
µA
mV
µS
MΩ
µA
µA
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MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
Electrical Characteristics (continued)
(Circuit of Figure 1, V
BATT
= 12V, V
CC
= V
DD
,
T
A
= 0°C to +85°C.
Typical values are at T
A
= +25°C, unless otherwise noted.)
PARAMETER
Zero-Crossing Delay
Maximum Zero-Crossing Delay
DEL Disable Threshold
CONDITIONS
VBATT = 9V, RTHR = 120kW
VBATT = 12V, RTHR = 120kW
VBATT = 18V, RTHR = 120kW
DEL rising
DEL falling
VISEC < 1.25V and VIFB < 540mV; VFLT = 2V
TFLT Charge Current
TFLT Trip Threshold
SDA, SCL, Input Low Voltage
SDA, SCL, Input High Voltage
SDA, SCL, Input Hysteresis
SDA, SCL, Input Bias Current
SDA Output Low Sink Current
SMBus Frequency
SMBus Free Time
SCL Serial Clock High Period
SCL Serial Clock Low Period
START Condition Setup Time
START Condition Hold Time
STOP Condition Setup Time from SCL
SDA Valid to SCL Rising-Edge Setup
Time, Slave Clocking in Data
SCL Falling Edge to SDA Transition
SCL Falling Edge to SDA Valid, Reading
Out Data
tBUF
tHIGH
tLOW
tSU:STA
tHD:STA
tSU:STO
tSU:DAT
tHD:DAT
tDV
VSDA = 0.4V
-1
4
10
4.7
4
4.7
4.7
4
4
250
0
200
1
100
2.1
100
+1
VISEC < 1.25V and VIFB > 660mV; VFLT = 2V
VISEC > 1.25V and VIFB > 660mV; VFLT = 2V
Rising edge
3.8
0.9
-1.5
115
3.7
1.0
-1.2
135
4
1.1
-0.8
155
4.3
0.7
V
V
V
mV
µA
mA
kHz
µs
µs
µs
µs
µs
µs
ns
ns
ns
µA
MIN
0
1.50
3.2
TYP
0.15
1.80
3.8
MAX
0.30
2.10
4.4
4.5
UNITS
µs
µs
V
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MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
Electrical Characteristics
(Circuit of Figure 1, V
BATT
= 12V, V
CC
= V
DD
,
T
A
= -40°C to +85°C).(Note
1)
PARAMETER
BATT Input Voltage Range
BATT Quiescent Current
V
CC
Output Voltage, Normal Operation
V
CC
Output Voltage, Shutdown
V
CC
Undervoltage Lockout Threshold
GH1, GH2, GL1, GL2 On-Resistance,
Low State
GH1, GH2, GL1, GL2 On-Resistance,
High State
Resonant Frequency Range
Minimum On-Time
Maximum Off-Time
Current-Limit Threshold
Zero-Current Crossing Threshold
IFB1, IFB2 Input Voltage Range
IFB1 Regulation Point
IFB2 Regulation Point
IFB1, IFB2 Input Bias Current
IFB1, IFB2 Lamp-Out Threshold
IFB1, IFB2 to COMP Transconductance
COMP Output Impedance
COMP Discharge Current During
Overvoltage or Overcurrent Fault
COMP Discharge Current During
DPWM Off-Time
ISEC Input Voltage Range
ISEC Overcurrent Threshold
VFB Input Voltage Range
VFB Input Impedance
VFB Overvoltage Threshold
VFB Undervoltage Threshold
DPWM Oscillator Frequency
PWMO Output Impedance
R
FREQ
= 169kΩ
V
VFB
= 2.6V or V
ISEC
= 1.5V
V
COMP
= 1.5V
0.5V < V
COMP
< 4V
-3V < V
IFB1,2
< 0
LX1 - PGND1, LX2 - PGND2
LX1 - PGND1, LX2 - PGND2
CONDITIONS
V
CC
= V
DD
= V
BATT
V
CC
= V
DD
= open
MAX8759 is enabled
V
BATT
= 28V
V
BATT
= V
CC
= 5V
5.2
3.5
3.7
6
18
30
350
40
410
3
-3
760
775
-230
565
60
6
500
90
-3
1.18
-4
150
2.2
210
203
20
635
160
25
2000
130
+3
1.26
+4
450
2.4
280
217
60
80
700
80
450
13
+3
810
825
MIN
4.5
5.5
TYP
MAX
5.5
28.0
5
5
5.5
5.5
4.3
UNITS
V
mA
V
V
V
Ω
Ω
kHz
ns
µs
mV
mV
V
mV
mV
µA
mV
µS
MΩ
µA
µA
V
V
V
MΩ
V
mV
Hz
kΩ
MAX8759 is enabled, 6V < V
BATT
< 28V,
0 < I
LOAD
< 10mA
MAX8759 is disabled, no load
V
CC
rising (leaving lockout)
V
CC
falling (entering lockout)
I
TEST
= 100mA, V
CC
= V
DD
= 5V
I
TEST
= 100mA, V
CC
= V
DD
= 5V
Guaranteed by design
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