MAX9759 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX9759

3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier

Maxim Integrated 

3.2W, High Efficiency, Low-EMI, Filterless,

Class D Audio Amplifier

tSW

VIN-

VIN+

OUT-

OUT+

tON(MIN)

VOUT+ - VOUT-

Figure 1. MAX9759 Outputs with an Input Signal Applied

Table 1. Operating Modes

SYNC INPUT

GND

FLOAT

VDD

Clocked

MODE

FFM with fS = 1100kHz

FFM with fS = 1500kHz

SSM with fS = 1200kHz ±70kHz

FFM with fS = external clock frequency

Spread-Spectrum Modulation (SSM) Mode

The MAX9759 features a unique, patented spread-spec-

trum mode that reduces peak component energy in the

wideband spectrum, improving EMI emissions that may

be radiated by the speaker and cables by 5dB.

Proprietary techniques ensure that the cycle-to-cycle

variation of the switching period does not degrade audio

reproduction or efficiency (see the Typical Operating

Characteristics). Select SSM mode by setting SYNC =

VDD. In SSM mode, the switching frequency varies by

±70kHz around the center frequency (1.2MHz). The

modulation scheme remains the same, but the period of

the sawtooth waveform changes from cycle to cycle

(Figure 2). Instead of a large amount of spectral energy

present at multiples of the switching frequency, the ener-

gy is now spread over a bandwidth that increases with

frequency. Above a few megahertz, the wideband spec-

trum looks like white noise for EMI purposes (Figure 3).

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