MAX9759(2005_10) データシートの表示（PDF） - Maxim Integrated

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MAX9759
(Rev.:2005_10)

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 spread-spectrum mode

that reduces peak component energy in the wideband

spectrum, improving EMI emissions that may be radiat-

ed by the speaker and cables by 5dB. Proprietary tech-

niques 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 wave-

form changes from cycle to cycle (Figure 2). Instead of a

large amount of spectral energy present at multiples of

the switching frequency, the energy is now spread over

a bandwidth that increases with frequency. Above a few

megahertz, the wideband spectrum looks like white

noise for EMI purposes (Figure 3).

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