Rainbow Electronics MAX98089 - Manual (Page 100)

��������������������������������������������������������������� Maxim Integrated Products 100
MAX98089
Low-Power, Stereo Audio Codec
with FlexSound Technology
Speaker Amplifiers
The IC integrates a stereo filterless Class D amplifier that
offers much higher efficiency than Class AB without the
typical disadvantages.
The high efficiency of a Class D amplifier is due to the
switching operation of the output stage transistors. In a
Class D amplifier, the output transistors act as current
steering switches and consume negligible additional
power. Any power loss associated with the Class D out-
put stage is mostly due to the I
2 R loss of the MOSFET
on-resistance, and quiescent current overhead.
The theoretical best efficiency of a linear amplifier is 78%,
however, that efficiency is only exhibited at peak output
power. Under normal operating levels (typical music
reproduction levels), efficiency falls below 30%, whereas
the IC’s Class D amplifier still exhibits 80% efficiency
under the same conditions.
Traditional Class D amplifiers require the use of exter-
nal LC filters or shielding to meet EN55022B and FCC
electromagnetic-interference (EMI) regulation standards.
Maxim’s patented active emissions limiting edge-rate
control circuitry reduces EMI emissions, allowing opera-
tion without any output filtering in typical applications.
Figure 26. Speaker Amplifier Path Block Diagram
DALEN
DACL
DAREN
DACR
MIXSPR
MIX
MIXSPL
MIX
SPKLP
SPKLN
SPVOLL:
+8dB TO -62dB SPKLVDD
SPKLGND
SPKRVDD
SPKRP
SPKRN
SPLEN
SPREN
POWER/
DISTORTION LIMITER
SPVOLR:
+8dB TO -62dB
SPKRGND
+6dB
+6dB