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Numéro de sérieMAX8722C
CategoriePower Management => Lighting Controllers
DescriptionLow-Cost CCFL Backlight Controller
The MAX8722C integrated backlight controller is optimized to drive cold-cathode fluorescent lamps (CCFLs) using a full-bridge resonant inverter architecture. Resonant operation maximizes striking capability and provides near-sinusoidal waveforms over the entire input range to improve CCFL lifetime. The controller operates over a wide input voltage range (4.6V to 28V) with high power to light efficiency. The device also includes safety features that effectively protect against many single-point fault conditions including lamp-out and short-circuit faults.
SociétéMaxim Integrated Products
DatasheetTélécharger MAX8722C datasheet
 
 
  • Description courte

  • o Synchronized to Resonant Frequency Longer Lamp Life Guaranteed Striking Capability High Power to Light Efficiency o Wide Input Voltage Range 28V) o Input-Voltage Feed-Forward for Excellent Line Rejection o Accurate Dimming Control with Analog Interface o 10:1 Dimming Range o Adjustable Accurate DPWM Frequency with Sync Function o Adjustable Lamp Current Rise and Fall Time o Secondary Voltage Limit Reduces Transformer Stress o Lamp-Out Protection with Adjustable Timeout o Secondary Overcurrent Protection with Adjustable Timeout o Low-Cost, 24-Pin QSOP Package

    The MAX8722C integrated backlight controller is optimized to drive cold-cathode fluorescent lamps (CCFLs) using a full-bridge resonant inverter architecture. Resonant operation maximizes striking capability and provides near-sinusoidal waveforms over the entire input range to improve CCFL lifetime. The controller operates over a wide input voltage range to 28V) with high power to light efficiency. The device also includes safety features that effectively protect against many single-point fault conditions including lamp-out and short-circuit faults. The MAX8722C achieves 10:1 dimming range by "chopping" the lamp current on and off using a digital pulsewidth modulation (DPWM) method. The DPWM frequency can be accurately adjusted with a resistor or synchronized to an external signal. The brightness is controlled by an analog voltage on the CNTL pin. The device directly drives the four external n-channel power MOSFETs of the full-bridge inverter. An internal 5.4V linear regulator powers the MOSFET drivers, the DPWM oscillator, and most of the internal circuitry. The MAX8722C is available in a low-cost, 24-pin QSOP package and operates over to +85°C temperature range.

    Applications

    BATT 1 SHDN 2 ILIM 3 TFLT 4 CNTL 5 DPWM 6 SYNC 7 FREQ 8 COMP 9 IFB 10 VFB 11 ISEC 12 24 GND 23 VCC 22 VDD 21 PGND

    PGND SHDN CNTL SYNC DPWM COMP TFLT GL2 GH2 VFB ISEC IFB

    For pricing, delivery, and ordering information, please contact Maxim Direct 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.

    BATT to +6V CNTL, FREQ, SYNC, VCC, VDD to +6V COMP, DPWM, ILIM, TFLT GND.............-0.3V to (VCC GND.......................................-0.3V to (VDD + 0.3V) IFB, ISEC, VFB to +6V SHDN to +6V PGND to +0.3V Continuous Power Dissipation (TA +70°C) 24-Pin QSOP (derate 9.5mW/°C above +70°C)........761.9mW Operating Temperature to +85°C Junction Temperature......................................................+150°C Storage Temperature 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.

    (Circuit of Figure 1. VBATT = 12V, VCC = VDD, V SHDN to +85°C. Typical values are = +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 (VUVLO) VCC Undervoltage-Lockout Hysteresis GL1, GL2 OnResistance, High GL1, GL2 OnResistance, Low GL1, GL2 Maximum Output Current BST1, BST2 Leakage Current Resonant Frequency Range Minimum Off-Time Maximum Off-Time Power-On First Pulse Current-Limit Threshold LX1 to PGND, LX2 to PGND (Fixed) First pulse GH2 ILIM = VCC VBST = 12V, VLX_ = 7V Guaranteed by design ITEST = 10mA, VCC = VDD = 5.3V ITEST = 10mA, VCC = VDD = 5.3V VCC = VDD = VBATT VCC = VDD = open VSHDN = VCC, VIFB = 1V SHDN = GND VSHDN 6V < VBATT 0 < ILOAD < 10mA SHDN = GND, no load VCC rising (leaving lockout) VCC falling (entering lockout) VBATT = 28V VBATT = VCC 5.40 4.6 CONDITIONS MIN 5.5 1 TYP MAX UNITS mV A kHz s mV

    (Circuit of Figure 1. VBATT = 12V, VCC = VDD, V SHDN to +85°C. Typical values are = +25°C, unless otherwise noted.)

    PARAMETER Current-Limit Threshold LX1 to PGND, LX2 to PGND (Adjustable) Zero-Current Crossing Threshold LX1 to GND, LX2 to GND Current-Limit Leading Edge Blanking IFB Input Voltage Range IFB Regulation Point IFB Input Bias Current IFB Lamp-Out Threshold IFB to COMP Transconductance IFB Soft-Start Disable COMP Output Impedance COMP Discharge Current During Overvoltage or Overcurrent Fault COMP Soft-Start Charge Current ISEC Overcurrent Threshold ISEC Input Bias Current VFB Input Bias Current VFB Undervoltage Threshold VFB Overvoltage Threshold VFB Undervoltage Protection Timeout RFREQ = 169k RFREQ = 100k RFREQ = 340k RFREQ = 100k DPWM Chopping Frequency DPWM Input Low Voltage DPWM Input High Voltage DPWM Input Hysteresis DPWM Input Bias Current DPWM Output Low Resistance DPWM Output High Resistance SYNC Input Low Voltage SYNC Input High Voltage SYNC Input Hysteresis SYNC Input Bias Current VSYNC = 2V RFREQ = 169k RFREQ = 340k SYNC = VCC, RFREQ = 169k SYNC = VCC, RFREQ = 169k SYNC = VCC, RFREQ = 169k SYNC = VCC, RFREQ = 169k SYNC = GND, FREQ = VCC SYNC = VCC, FREQ = VCC VISEC -4V < VVFB < +4V VIFB = 800mV, VISEC 0.5V < VCOMP 0 < VIFB -2V < VIFB < 0 VILIM = 0.5V VILIM = 2.0V CONDITIONS MIN s TYP MAX mV V UNITS