Datasheet

Maxim Integrated │ 98
MAX98090 Ultra-Low Power Stereo Audio Codec
www.maximintegrated.com
Figure 13. Record Path ADC Section
Analog-to-Digital Converter (ADC)
The stereo ADC architecture includes two independent
audio paths and provides a flexible, fully configurable
input mixer, two performance and power based con-
figuration options, oversampling rate selection, and an
input dither option (Figure 13). Both ADC channels can
be enabled independently allowing the device to support
both stereo and left or right mono configurations (Table 7).
ADC Functional Conguration
The ADC can be configured into one of two operating
modes. One operating mode is optimized for maximum
dynamic performance while the other is optimized for
lower power consumption (Table 5). Input dither can also
be added to the ADC record path. This feature consumes
almost no appreciable power, but raises the RMS level of
the noise floor slightly at the high end of the audio band.
The ADC supports both an over sampling rate (OSR) of
64 and 128 times the configured sampling frequency (f
S
).
An OSR of 128 x f
S
optimizes ADC performance at the
cost of slightly more power consumption than an OSR of
64 x f
S
.
The DSP timing, however, places some limitations on
which OSR can be used. For voice applications using
standard (f
S
= 8kHz) and wideband (f
S
= 16kHz) sampling
rates, the DSP is typically configured to utilize the voice
filters (IIR). If the voice filters are enabled, the OSR is
automatically configured to 128 x f
S
and cannot be manu-
ally reprogrammed in order to meet timing requirements.
In most standard music/full audio range applications
(where f
S
= 32kHz, 44.1kHz, 48kHz, etc.) the music filters
(FIR) are used. If the music filters are enabled, the OSR
can be configured manually, however, the prescaled mas-
ter clock (PCLK) must always be at least twice the fre-
quency of the ADC sampling clock. To ensure this condi-
tion is met, if f
PCLK
< 256 x f
S
, then the OSR must be set
to 64 x f
S
. In addition, if the sampling rate exceeds 48kHz
(DHF = 1, such as f
S
= 96kHz), then the OSR must be
configured to 64 x f
S
regardless of the ratio. In any other
music filter configuration, OSR = 128 can be selected as
desired for optimal ADC performance.
DIGITAL
MIC
LEFT
MUX
DIGMICL
ADC
LEFT
ADC
RIGHT
LEFT
FILTERS
MODE
AHPF
DHF
LEFT
BIQUAD
FILTER
RECBQEN
AVBQ[3:0]
REC_B0[23:0]
REC_B1[23:0]
REC_B2[23:0]
REC_A1[23:0]
REC_A2[23:0]
LEFT
SIDETONE
DSTS[1:0]
DVST[3:0]
FLEXSOUND
TECHNOLOGY DSP
DMDL
DMDR
ADCR
ADCL
ADCHP
OSR128
ADCDITHER
AVLG[2:0]
AVL[3:0]
AVRG[2:0]
AVR[3:0]
DIGITAL
MIC
RIGHT
MUX
RIGHT
FILTERS
DIGMICR
RIGHT RECORD PATH
SIDETONE TO
PLAYBACK PATH
LEFT RECORD PATH
RIGHT
BIQUAD
FILTER
RIGHT
SIDETONE
LEFT
LEVEL
L/R ST
LEVEL
RIGHT
LEVEL
MIXADL[6:0]
MIXADR[6:0]
IN1-IN2
DIGITAL MIC DATA
IN3-IN4
IN5-IN6
LINE A
LINE B
MIC 1
MIC 2
ADC
LEFT
MIXER
IN1-IN2
IN3-IN4
IN5-IN6
LINE A
LINE B
MIC 1
MIC 2
ADC
RIGHT
MIXER
ADLEN
ADREN
DAI