MAX8678

The MAX8678 integrates a charge pump for white lightemitting 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 of MAX8678 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 of MAX8678 are maintained throughout the adjustment range. Individual adaptive mode switching for each LED provides high efficiency with a wide range of LED forward voltages.

Features of the MAX8678 are:(1)individual adaptive supply for each LED; (2)4 low-dropout LED current regulators; (3)24mA to 0.1mA dimming range; (4)single-wire, serial-pulse dimming interface; (5)1% (typ) accuracy; (6)low 0.004% THD+N at 1kHz; (7)high 90dB PSRR at 1kHz; (8)fully differential inputs; (9)-9dB to +18dB gain settings in 3dB steps; (10)integrated click/pop suppression; (11)low quiescent current; (12)soft-start limits inrush current; (13)thermal shutdown, open- and short-circuit protection; (14)16-pin, 3mm x 3mm thin QFN package.The mono class AB audio amplifier directly drives an 8 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 singlewire serial-pulse interface. Clicks and pops are suppressed during on/off and all gain adjustments.Differential inputs of MAX8678 improve common-mode noise rejection.

The absolute maximum ratings of the MAX8678 can be summarized as:(1)IN to GND:-0.3V to +6.0V;(2)storage temperature range:-65 to +150;(3)IN to NEG:-0.3V to +6.0V;(4)junction temperature:+150;(5)GND to NEG:-0.3V to +6.0V;(6)continuous power dissipation:1398mW.Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied.Exposure to absolute maximum rating conditions for extended periods may affect device reliability.The MAX8678 integrates a charge pump for white LEDs with an audio loudspeaker amplifier. The high-efficiency,adaptive charge pump drives up to four LEDs with constant current for uniform brightness for display backlighting or camera flash. 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. Figure 1 is the MAX8678 functional diagram.