MAX1579

Complete Bias and White LED Power Supplies for Small TFT Displays

First Complete LCD Bias and WLED Backlight Supplies for Small TFT Displays


Please check latest availability status for a specific part variant.

Description

The MAX1578/MAX1579 provide four regulated outputs to meet all the voltage requirements for small activematrix TFT-LCD displays in handheld devices where minimum external components and high efficiency are required. Each device consists of three advanced charge pumps for LCD bias power and a step-up converter for driving up to 8 series white LEDs for backlighting. The input voltage range is from 2.7V to 5.5V.

The charge pumps provide fixed +5V, +15V, and -10V for the LCD bias circuits. No external diodes are needed. A high-efficiency, fractional (1.5x/2x) charge pump followed by a low-dropout linear regulator provides +5V to power the source driver. Automatic mode changing achieves the highest conversion efficiency. Two multistage, high-voltage charge pumps generate +15V and -10V to provide VON and VOFF, respectively. Utilizing a unique clocking scheme and internal drivers, these charge pumps eliminate parasitic charge-current glitches and reduce maximum input current, resulting in low electromagnetic emissions. The outputs are sequenced during startup and shutdown. In shutdown, the outputs are discharged to zero.

The high-efficiency inductor step-up converter drives up to 8 white LEDs in series with a constant current to provide backlighting. The series connection allows the LED currents to be identical for uniform brightness and minimizes the number of traces to the LEDs. The MAX1578 regulates constant LED current over the entire temperature range. The MAX1579 features a temperature derating function to avoid overdriving the white LEDs during high ambient temperatures, enabling higher drive current below +42°C.

The MAX1578/MAX1579 are available in space-saving 24-lead 4mm x 4mm thin QFN packages.

MAX1578, MAX1579: Typical Application Circuit MAX1578, MAX1579: Typical Application Circuit Enlarge+

Key Features

  • Four Regulators in One Package
  • Bias Power Using Charge Pumps
    +5V at 25mA for Source Driver`
    +15V at 100µA for VON
    -10V at 100µA for VOFF
    No External Diodes Required
    Output Sequencing
    POS, NEG, and MAIN Are Autodischarged During Shutdown
  • LED Backlight Power Using Boost Converter
    Series LED Connection for Uniform Illumination
    Supports Up to 8 LEDs at 25mA (max)
    900mW (max) Power
    PWM or Analog Dimming Control
    Overvoltage Protection
    Low Input/Output Ripple
    Soft-Start with Zero Inrush Current
    Fast 1MHz PWM Operation for Small Component Size
    Temperature Derating Function (MAX1579)
  • High Efficiency
    Bias: 83% (5.0V at 25mA, 15V/-10V at 100µA)
    LED: 84% (6 LEDs at 20mA)
  • Uses Only Ceramic Capacitors and Only One Inductor
  • Independent Enable Inputs for LED and Bias Power
  • Thermal-Shutdown Protection
  • 1µA Shutdown Current
  • Tiny 4mm x 4mm Thin QFN Package
  • Applications/Uses

    • Internet Appliances
    • LCD Displays with White LED Backlight
    • PDAs, Palmtops
    • Smartphones
    Part NumberBattery InputRegulation TopologyMax. No. of LEDsLED ChannelsLED ConfigurationILED per Channel
    (A)
    PWM Dimming Freq.
    (kHz)
    Dimming ControlVCURR_SENSE
    (mV)
    POUT
    (W)
    VIN
    (V)
    VIN
    (V)
    ICC
    (mA)
    LED String Volt.
    (V)
    Oper. Freq.
    (kHz)
    Package/PinsBudgetary
    Price
    maxmaxminmaxmaxmaxSee Notes
    MAX1579 1-Cell Li+Inductor Based81Series0.025200
    Analog
    PWM
    3000.92.75.55321000
    TQFN/24
    $3.95 @1k
    See All LED Drivers (79)
    Pricing Notes:
    This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

    Quality and Environmental Data

    Product Reliability Reports: MAX1579.pdf 
    Lead-Free Package Tin (Sn) Whisker Reports
    Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C  

    Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

    Quality Management System >
    Environmental Management System >

     
    Status:
    Package:
    Temperature:

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