OVERVIEW
The SSM3582A is a stereo, Class-D audio amplifier with a filterless
modulation scheme that greatly reduces external component
count, conserving board space and reducing system cost. The
SSM3582A does not require an output filter. The device relies
on the inherent inductance of the speaker coil and the natural
filtering of the speaker and human ear to recover the audio
component of the square wave output. Most Class-D amplifiers
use some variation of pulse-width modulation (PWM) to
generate the output switching pattern, whereas the SSM3582A
uses Σ-Δ modulation, resulting in important benefits. Σ-Δ
modulators do not produce a sharp peak with many harmonics
in the AM broadcast band, as pulse-width modulators often do.
Σ-Δ modulation reduces the amplitude of spectral components at
high frequencies, reducing EMI emission that may otherwise
radiate from speakers and long cable traces.
EMI NOISE
The SSM3582A uses a proprietary modulation and spread
spectrum technology to minimize EMI emissions from the
device. The SSM3582A passes FCC Class-B emissions testing
with an unshielded 20 inch cable using ferrite bead-based
filtering. For applications that have difficulty passing FCC
Class-B emission tests, the SSM3582A includes an ultralow EMI
emissions mode that significantly reduces the radiated emissions at
the Class-D outputs, particularly above 100 MHz. Note that
reducing the supply voltage greatly reduces radiated emissions.
POWER SUPPLY DECOUPLING
To ensure high efficiency, low THD, and high PSRR, proper
power supply decoupling is necessary. Noise transients on the
power supply lines are short duration voltage spikes. These spikes
can contain frequency components that extend into the hundreds
of megahertz. The power supply input must be decoupled with
a good quality, low ESL, low ESR bulk capacitor larger than 220 µF.
This capacitor bypasses low frequency noise to the ground
plane. For high frequency decoupling, place 1 µF capacitors as
close as possible to the PVDD pins of the device.
OUTPUT EMI FILTERING
Additional EMI filtering may be required when the speaker
traces and cables are long and present a significant capacitive
load that can create additional draw from the amplifier. Typical
power ferrites present a significant magnetic hysteresis cycle
that affects THD performance and are not recommended for
high performance designs. The NFZ filter series from Murata,
designed in close collaboration with Analog Devices, Inc.,
provides a closed hysteresis loop similar to an air coil with
minimum impact on performance. Products are available at
upwards of 4 A rms, well suited to this application. A small
capacitor can be added between the output of the filter and
ground to further attenuate very high frequencies. Take care
to ensure the capacitor is properly sized to avoid affecting idle
power consumption or efficiency.
[свернуть]
Докатился - "Прикомпьютерный усилитель".
Ответить с цитированием
Сообщение от UnDrew
Работает примерно до 2/3 амплидуды на выходе, потом трындец. Даже без нагрузки, с динамиком полная хрень, чуть погрмче делаешь. 
Социальные закладки