• The MAX8821 is the first negative-charge-pump, white-LED driver to integrate a Class D audio amplifier and two low-noise, low-dropout (LDO) current regulators.
• This highly integrated device saves PCB space and reduces BOM costs.
• These benefits are enabled by the MAX8821's unique integration of a highly efficient negative charge pump, a Class D audio amplifier, and two low-noise LDO regulators.
• The MAX8821 is ideal for handheld devices in which battery life is precious and PCB space is limited.

Maxim Integrated Products introduced the MAX8821-the only white-LED (WLED) driver to combine a highly efficient, negative charge pump with a fully differential, bridged audio amplifier and two low-noise, low-dropout (LDO) current regulators. To maximize efficiency, this LED driver features a negative architecture that completely eliminates high-side, in-line switch resistance loss in 1x mode, delaying 1x to 1.5x mode transitions during battery discharge. The MAX8821 utilizes independent adaptive-mode switching for each LED to further extend battery life, even with large LED forward-voltage (VF) mismatching. Moreover, the audio amplifier accepts differential input signals, offering excellent noise immunity to improve audio reproduction. This superior performance and integration make the MAX8821 ideal for use in cell phones, smartphones, PDAs, and portable media players in which every milliamp-hour of battery life is precious and PCB space is limited.

This innovative device drives six WLEDs with 1% accurate current matching. To maximize flexibility, the MAX8821 supports I2C dimming control with 32 pseudo-logarithmic dimming levels. Additionally, this WLED driver achieves low, 70 microamp quiescent current, and features an on-chip, TA derating function that reduces the current above +40 degrees Celsius to prevent the LEDs from burning out. The integrated, dual LDO regulators deliver over 200mA of current output with low, 45 microvolt noise and low, 60dB PSRR for sensitive circuitry.

The MAX8821's Class D audio amplifier delivers 2W to the speaker differentially by the use of a bridge-tied load (BTL) output stage and is also representing a space and cost saving filterless solution. This provides up to four times more output power than a conventional, single-ended output stage and eliminates the need for an output-coupling capacitor. 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 spreadspectrum 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 to ensure rich, clean sound quality. 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 and, at 1kHz, this device achieves a high, 65dB PSRR gain.

The MAX8821 is available in a tiny, 4mm x 4mm x 0.8mm, 28-pin TQFN package and is fully specified over the -40 °C to +85 °C extended temperature range.
MAX8821 Data Sheet, Samples and EvKit are available.