max9706etxt Maxim Integrated Products, Inc., max9706etxt Datasheet - Page 15

• Manufacturer Part Number: max9706etxt
• Description: 3-channel, 2.3w, Filterless Class D Amplifiers With Active Crossover
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9706/MAX9707 feature a unique, patented
spread-spectrum mode that flattens the wideband
spectral components, improving EMI emissions that
can be radiated by the speaker and cables. Enable
SSM mode by setting SYNC_IN = V
SSM mode, the switching frequency varies randomly by
±50kHz around the center frequency (1.15MHz). The
modulation scheme remains the same, but the period
of the sawtooth waveform changes from cycle to cycle
(Figure 3). 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. A
proprietary amplifier topology ensures this does not
corrupt the noise floor in the audio bandwidth.
Figure 3. Output with an Input Signal Applied (SSM Mode)
3-Channel, 2.3W, Filterless Class D Amplifiers
V
OUT_+
V
V
IN_+
IN_-
- V
OUT_-
OUT_+
OUT_-
______________________________________________________________________________________
Spread-Spectrum (SSM) Mode
t
ON(MIN)
DD
t
SW
(Table 1). In
t
SW
Table 1. Operating Modes
GND
FLOAT
V
Clocked
with Active Crossover
DD
SYNC_IN
t
SW
FFM with f
FFM with f
SSM with f
FFM with f
t
SW
OSC
OSC
OSC
OSC
= 1100kHz
= 1340kHz
= external clock frequency
= 1150kHz ±50kHz
MODE
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