Rainbow Electronics MAX98088 - Manual (Page 96)

Stereo Audio Codec
with FLEXSOUND Technology
MAX98088
96
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% effi-
ciency 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.
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