Rainbow-electronics MAX8759 Manual de usuario

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller10 ______________________________________________________________________________________Pin Descript

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller12 ______________________________________________________________________________________N2A19242121C

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

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

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

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

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

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

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller2 _______________________________________________________________________________________ABSOLUTE MAX

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

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

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

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

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

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

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

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

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller______________________________________________________________________________________ 29N2A1924211C7

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

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

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller4 _______________________________________________________________________________________ELECTRICAL C

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller6 _______________________________________________________________________________________ELECTRICAL C

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

MAX8759Low-Cost, SMBus, CCFL Backlight Controller8 _______________________________________________________________________________________Typical Oper

MAX8759Low-Cost, SMBus, CCFL Backlight Controller_______________________________________________________________________________________ 9020604080100