White LED Charge Pump with 1.1W Audio Amplifier

Industry’s First LED Charge Pump with Integrated Audio Amplifier Saves 50% PCB Area While Providing Highest Efficiency

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The MAX8678 integrates a charge pump for white light-emitting diodes (LEDs) with an audio loudspeaker amplifier. The high-efficiency, adaptive charge pump drives up to four LEDs with constant current for uniform brightness. The LED current is adjustable from 0.1mA/LED to 24mA/LED in 31 pseudo-logarithmic steps through a single-wire serial-pulse interface. High accuracy and LED-to-LED current matching are maintained throughout the adjustment range. Individual adaptive mode switching for each LED provides high efficiency with a wide range of LED forward voltages.

The mono class AB audio amplifier directly drives an 8Ω loudspeaker with 1.1W RMS continuous power from a 5V supply with less than 1% THD+N. The gain is adjustable from -9dB to +18dB in ten 3dB steps through a single-wire serial-pulse interface. Clicks and pops are suppressed during on/off and all gain adjustments. Differential inputs improve common-mode noise rejection.

The MAX8678 includes soft-start, thermal shutdown, open-circuit and short-circuit protection, and is available in the 16-pin, 3mm x 3mm Thin QFN package (0.8mm max height).

MAX8678: Typical Operating Circuit MAX8678: Typical Operating Circuit Enlarge+

Key Features

  • High-Efficiency White LED Charge Pump
    • Individual Adaptive Supply for Each LED
    • 4 Low-Dropout LED Current Regulators
    • 24mA to 0.1mA Dimming Range
    • Single-Wire, Serial-Pulse Dimming Interface
    • 1% (typ) Accuracy
    • Low 140µA Quiescent Current
  • Mono Class AB Audio Amplifier
    • 1.1W RMS Mono BTL Output (8Ω, VIN = 5V)
    • Low 0.004% THD+N at 1kHz
    • High 90dB PSRR at 1kHz
    • Fully Differential Inputs
    • -9dB to +18dB Gain Settings in 3dB Steps
    • Integrated Click/Pop Suppression
    • Low Quiescent Current
  • Soft-Start Limits Inrush Current
  • Thermal Shutdown, Open- and Short-Circuit Protection
  • 16-Pin, 3mm x 3mm Thin QFN Package


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  • PDAs, Digital Cameras, Camcorders

Technical Documents

App Note 4427 Demonstrating Green Technology with Apples, Oranges, Lemons, and Limes

Quality and Environmental Data

Request Reliability Report for: MAX8678 
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.

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