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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 regula-
tion (±2.5%) for superior CCFL inverter performance.
The lamp current is adjustable with an external resistor;
10:1 dimming 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 sys-
tem 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 maxi-
mum efficiency and directly drives four external n-chan-
nel power MOSFETs. An internal 5.35V linear regulator
powers 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 temperature range.
Applications
Notebooks
LCD Monitors
Automotive Infotainment
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
MAX8759
Low-Cost, SMBus, CCFL Backlight Controller
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
MAX8759
Minimal Operating Circuit
19-3874; Rev 0; 10/05
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.
PART
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
MAX8759ETI+
-40°C to +85°C
28 Thin QFN-EP*
5mm × 5mm
T2855-6
+ Denotes lead-free package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
SMBus is a trademark of Intel Corp.
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Inhaltsverzeichnis

Seite 1 - Minimal Operating Circuit

General DescriptionThe MAX8759 integrated cold-cathode fluorescent lamp(CCFL) inverter controller is designed to drive CCFLsusing a full-bridge resona

Seite 2 - ELECTRICAL CHARACTERISTICS

MAX8759Low-Cost, SMBus, CCFL Backlight Controller10 ______________________________________________________________________________________Pin Descript

Seite 3

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 11PIN NAME FUN

Seite 4

MAX8759Low-Cost, SMBus, CCFL Backlight Controller12 ______________________________________________________________________________________N2A19242121C

Seite 5

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 13Typical Oper

Seite 6

MAX8759Low-Cost, SMBus, CCFL Backlight Controller14 ______________________________________________________________________________________Figure 2. MA

Seite 7

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 15Figure 3. MA

Seite 8

MAX8759The second peak fPis the parallel resonant peak deter-mined by the secondary leakage inductance (L), theparallel capacitor (CP), and the series

Seite 9

AC lamp current is sensed with a resistor connected inseries with the low-voltage terminal of the lamp. TheMAX8759 has two lamp-current feedback input

Seite 10 - Pin Description

MAX8759Dimming ControlThe MAX8759 controls the brightness of the CCFL by“chopping” the lamp current on and off using a low-fre-quency (between 100Hz a

Seite 11 - Pin Description (continued)

Fault ProtectionsLamp-Out ProtectionFor safety, the MAX8759 monitors the lamp-currentfeedback inputs (IFB1 and IFB2) to detect faulty oropen CCFL tube

Seite 12

MAX8759Low-Cost, SMBus, CCFL Backlight Controller2 _______________________________________________________________________________________ABSOLUTE MAX

Seite 13 - Detailed Description

MAX8759values. POR occurs when VCCrises above 1.75V (typ).The UVLO occurs when VCCis below 4.2V (typ). TheMAX8759 disables both high-side and low-side

Seite 14

and an ALS high-limit register (0x06). The MAX8759only acknowledges these seven registers.Communication starts with the master signaling thebeginning

Seite 15

MAX8759Low-Cost, SMBus, CCFL Backlight Controller22 ______________________________________________________________________________________Table 3. Com

Seite 16 - Lamp-Current Regulation

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 23BIT 7 BIT 6B

Seite 17 - Lamp Startup

MAX8759The relationships among these 3 control bits can bethought of as specifying an operating mode for the invert-er. The defined modes are shown in

Seite 18 - SMBus with DPST Mode

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 25BIT 7 (R) BI

Seite 19 - POR and UVLO

MAX8759Applications InformationMOSFETsThe MAX8759 requires four external n-channel powerMOSFETs: NL1, NL2, NH1, and NH2 to form a full-bridge inverter

Seite 20 - SMBus Interface (SDA, SCL)

using the following equation to set the desired maxi-mum RMS secondary voltage VLAMP(RMS)_MAX:where the 2.3V is the typical value of the VFB peak volt

Seite 21 - SMBus Register Definitions

MAX8759The transformer core saturation should also be consid-ered when selecting the operating frequency. The pri-mary winding should have enough turn

Seite 22 - Table 3. Commands Description

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 29N2A1924211C7

Seite 23

MAX8759Low-Cost, SMBus, CCFL Backlight Controller_______________________________________________________________________________________ 3ELECTRICAL C

Seite 24 - Control Register Bits 5, 4

MAX87596) Ensure the feedback connections are short anddirect. To the extent possible, IFB1, IFB2, VFB, andISEC connections should be far away from th

Seite 25

MAX8759Low-Cost, SMBus, CCFL Backlight ControllerMaxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in

Seite 26 - Applications Information

MAX8759Low-Cost, SMBus, CCFL Backlight Controller4 _______________________________________________________________________________________ELECTRICAL C

Seite 27 - Component Selection

MAX8759Low-Cost, SMBus, CCFL Backlight Controller_______________________________________________________________________________________ 5ELECTRICAL C

Seite 28 - Layout Guidelines

MAX8759Low-Cost, SMBus, CCFL Backlight Controller6 _______________________________________________________________________________________ELECTRICAL C

Seite 29

MAX8759Low-Cost, SMBus, CCFL Backlight Controller_______________________________________________________________________________________ 7CDBAA: VFB,

Seite 30 - Pin Configuration

MAX8759Low-Cost, SMBus, CCFL Backlight Controller8 _______________________________________________________________________________________Typical Oper

Seite 31 - Package Information

MAX8759Low-Cost, SMBus, CCFL Backlight Controller_______________________________________________________________________________________ 9020604080100

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