Product category:
Power Supply ICs and Controllers
News Release from: Maxim Integrated Products | Subject: MAX8821
Edited by the Electronicstalk Editorial
Team on 11 March 2008
White LED driver integrates audio
circuitry
Device combines a negative charge pump with a fully differential bridged audio amplifier and two low-noise low-dropout current regulators.
According to Maxim Integrated Products, the MAX8821 is 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 maximise efficiency, this LED driver features a negative architecture that completely eliminates high-side inline switch resistance loss in 1x mode, delaying 1x to 1.5x mode transitions during battery discharge
This article was originally published on Electronicstalk on 27 Aug 2002 at 8.00am (UK)
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The MAX8821 uses 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 cellphones, 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 maximise flexibility, the MAX8821 supports I2C dimming control with 32 pseudo-logarithmic dimming levels.
Additionally, this WLED driver achieves low, 70uA quiescent current, and features an on-chip TA derating function that reduces the current above +40C to prevent the LEDs from burning out.
The integrated, dual LDO regulators deliver over 200mA of current output with low, 45uV 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 -3 to +24dB gain settings realise in 3dB steps.
Integrated click-and-pop suppression circuitry ensures rich, clean sound quality.
The MAX8821 is available in a tiny 4 x 4 x 0.8mm, 28-pin TQFN package and is fully specified over the -40 to +85C extended temperature range.
Prices start at US $2.55 (1000-up).
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