MAX8821

The MAX8821 integrates a charge pump for white LEDs, an audio loudspeaker amplifier, and two lownoise LDOs controlled by an I2C control interface. The high-efficiency, adaptive-mode inverting charge pump drives up to six LEDs with constant current for uniform brightness. The LED current of MAX8821 is controlled by an I2C interface and adjusts from 0.1mA to 25.6mA per LED into 32 pseudo-logarithmic steps. Independent voltages for each LED maximize efficiency even with large LED forward voltage (VF) mismatch. An internal temperature derating function of MAX8821 reduces the current above +40 to protect the LEDs.

Features of the MAX8821 are:(1)independent adaptive current regulators for each LED; (2)6 low-dropout current regulators; (3)ramp-up/down, current control for each LED; (4)low 0.05% THD+N at 1kHz; (5)high 65dB PSRR at 1kHz; (6)fully differential inputs; (7)-3dB to +24dB gain settings in 3dB steps; (8)integrated click-and-pop suppression; (9)low quiescent current.The high-efficiency mono Class D audio amplifier delivers up to 2W into a 4 speaker from a 5V input supply.The amplifier features proprietary filterless Active Emissions Limiting (AEL) technology. AEL prevents high-frequency emissions resulting from conventional Class D free-wheeling behavior in the presence of an inductive load. The amplifier MAX8821 offers two modulation schemes: a fixed-frequency mode (FFM) and a spreadspectrum mode (SSM) that reduce EMI-radiated emissions due to the modulation frequency.

The absolute maximum ratings of the MAX8821 can be summarized as:(1)IN1, IN2, IN3, VDD to AGND:-0.3V to +6.0V;(2)storage temperature range:-65 to +150;(3)AGND to C2N:-0.3V to +6.0V;(4)junction temperature:+150;(5)IN1, IN2 to IN3:-0.3V to +0.3V;(6)continuous power dissipation:2286mW.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 MAX8821 reliability.When VIN is higher than the forward voltage of the white LED plus the 0.15V headroom of the current regulator,the LED current returns through ground. If this condition of MAX8821 is satisfied for all six white LEDs the charge pump remains inactive. When the input voltage drops so that the current regulator head room cannot be maintained for any of the individual white LEDs, the inverting charge pump activates and generates a voltage on NEG that is no greater than 5V below VIN. Each current regulator MAX8821 contains circuitry that detects when it is in dropout and switches that current regulator return path from GND to NEG.