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发布时间：2008-03-22 浏览：4323次
- 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.
SUNNYVALE, CA—March 10, 2008—Maxim Integrated Products (Pink Sheets: MXIM) introduces 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 IІC dimming control with 32 pseudo-logarithmic dimming levels. Additionally, this WLED driver achieves low, 70µA quiescent current, and features an on-chip, TA derating function that reduces the current above +40°C to prevent the LEDs from burning out. The integrated, dual LDO regulators deliver over 200mA of current output with low, 45µV 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. 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. In addition, at 1kHz, this device achieves a high, 65dB PSRR gain, which the flexible -3dB to +24dB gain settings realize in 3dB steps. Integrated click-and-pop suppression circuitry ensures rich, clean sound quality.
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. Prices start at $2.55 (1000-up, FOB USA).
Maxim Integrated Products, a two billion dollar company, designs and manufactures ICs for analog and mixed-signal applications. The company's broad portfolio of 27 product categories is among the industry's deepest, with over 5400 products.
