Datasheet

PDMfromdigital
microphoneinterface
Error
cancellation
A/Doutput
Audio
interface
SINCfilter
differentiator
4thorder
SINCfilter
integrator
4thorder
1storderhigh-
passfilter
Low-pass
filter
032-042
TPS65950
SWCS032E–OCTOBER 2008–REVISED JANUARY 2011 www.ti.com
Table 6-22. MCPC and USB-CEA Carkit Audio Uplink Electrical Characteristics
Parameter Test Conditions Min Typ Max Unit
Gain range
(1)
–1 60 dB
USB-CEA default gain setting –1.5 1.5
Absolute gain, 0 dBFs at 1.02 kHz
(1) (2) (3)
dB
MCPC default gain setting –1.5 1.5
Speech delay Voice path 0.5 ms
Input common mode voltage
(4)
USB-CEA 1.3 1.9 V
USB-CEA 8 120
Phone microphone amplifier input impedance at 1 kHz kΩ
MCPC 5 100
Peak-to-peak single-ended input voltage (0 dBFs) Default setting 1.414 V
PP
Total harmonic distortion (sine wave at 1 kHz), default gain setting At –1 dBFs –74 –60 dB
At –6 dBFs
At –10 dBFs
At –20 dBFs
At –60 dBFs
THD + N (20 Hz to 20 kHz, A-weighted) At 0 dBFs 60 dB
Signal noise ratio (20 Hz to 20 kHz, A-weighted) At 0 dBFs 60 dB
USB-CEA –77
Idle channel noise (20 Hz to 20 kHz, A-weighted), default gain
dBFs
setting
MCPC –80 –77
USB-CEA 50
Output PSRR (20 Hz to 20 kHz, A-weighted) dB
MCPC 35
(1) Gain range is defined by: MCPC/CEA amplifier = 0.56 dB/–1.02 dB; Preamplifier = 0 to 30 dB; Filter = 0 to 31 dB (1-dB steps).
(2) The CEA default gain setting assumes 0 dB on the preamplifier, 1 dB on the digital filter, and the MCPC/CEA amplifier at –1.02 dB.
(3) The MCPC default gain setting assumes 0 dB on the preamplifier, 0 dB on the digital filter, and the MCPC/CEA amplifier at 0.56 dB.
(4) Full-scale input voltage is 1 V minimum.
6.2.9 Digital Audio Filter Module
Figure 6-29 shows the digital audio filter uplink full path characteristics for the audio interface.
Figure 6-29. Digital Audio Filter Uplink Path Characteristics
The HPF can be bypassed. It is controlled by the MISC_SET_2 ATX_HPF_BYP bit, address 0x49.
Table 6-23 lists the audio filter frequency responses relative to reference gain at 1 kHz.
Table 6-23. Digital Audio Filter TX Electrical Characteristics
Parameter Test Conditions Min Typ Max Unit
Passband 0.0005 0.42 F
S
Passband gain In region 0.0005*F
S
to 0.42*F
S
(1)
–0.25 0.25 dB
Stopband 0.6 F
S
Stopband attenuation In region 0.6*F
S
to 1*F
S
(1)
60 dB
Group delay 15.8/F
S
μs
(1) F
S
is the sampling frequency (8, 11.025, 12, 16, 22.05, 24, 32, 44.1, or 48 kHz).
94 Audio/Voice Module Copyright © 2008–2011, Texas Instruments Incorporated
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