White LED Charge Pump with Mono Class D Audio Amp and Dual LDO

The MAX8821 integrates a charge pump for white LEDs, an audio loudspeaker amplifier, and two low-noise 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 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 reduces the current above +40°C to protect the LEDs.

The high-efficiency mono Class D audio amplifier delivers up to 2W into a 4Ω 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 offers two modulation schemes: a fixed-frequency mode (FFM) and a spread-spectrum mode (SSM) that reduce EMI-radiated emissions due to the modulation frequency. The amplifier also has robust output protection and high power-supply rejection ratio (PSRR). Click-and-pop suppression is active during power-up/down, enable/disable, and for all mode changes. The amplifier's gain is adjustable through an I²C interface, from -3dB to +24dB in 10 3dB steps. Differential inputs improve common-mode noise rejection.

The LDOs in the MAX8821 are designed for low-noise operation. Each LDO output voltage can be individually programmed by the I²C interface. Both LDO1 and LDO2 have a high 70dB PSRR rating.

The MAX8821 includes soft-start, thermal shutdown, open-circuit, and short-circuit protections, and is available in a compact 28-pin, Thin QFN, 4mm x 4mm package (0.8mm max height).

Applications

* Cell Phones and Smartphones * MP3 Players, GPS Devices * PDAs, Digital Cameras, Camcorders

* White LED Inverting Charge Pump

* Independent Adaptive Current Regulators for Each LED

* 6 Low-Dropout Current Regulators

* Flexible I²C Dimming Control for Each LED

* Ramp-Up/Down, Current Control for Each LED

* Low 70µA (typ) Quiescent Current

* TA Derating Function Protects LEDs

* Mono 2W Class D Loudspeaker Amplifier

* 85% Efficiency (RL = 8Ω, POUT = 600mW)

* Low 0.05% THD+N at 1kHz

* High 65dB PSRR at 1kHz

* Fully Differential Inputs

* -3dB to +24dB Gain Settings in 3dB Steps

* Integrated Click-and-Pop Suppression

* Low Quiescent Current

* Dual Low-Noise LDO

* 45µVRMS Output Noise, 70dB PSRR

* Flexible I²C-Controlled Output Voltages

* 200mA and 300mA Output Current Drive