1.2W Low-EMI, Filterless, Mono Class D Amplifier

with Stereo DirectDrive Headphone Amplifiers

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11

OUT+

OUT-

Figure 1. MAX9770 Outputs with an Input Signal Applied

parator (Figure 1). As the input voltage increases or

decreases, the duration of the pulse at one output

increases (the first comparator trip point) while the

Operating Modes

The switching frequency of the charge pump is 1/2 the

switching frequency of the Class D amplifier, regard-

less of the operating mode. When SYNC is driven exter-

spectrum pattern.

Fixed-Frequency Modulation (FFM) Mode

The MAX9770 features two FFM modes. The FFM

modes are selected by setting SYNC = GND for a

1.1MHz switching frequency, and SYNC = FLOAT for a

1.45MHz switching frequency. In FFM mode, the fre-

quency spectrum of the Class D output consists of the

SYNC INPUT

MODE

GND

FLOAT

±120kHz

Clocked

Table 1. Operating Modes