Datasheet
Onboard Chip
C
AUXL/R
C
AUXL/R.M
AUXL/R
032-038
TPS65950
www.ti.com
SWCS032E–OCTOBER 2008–REVISED JANUARY 2011
6.2.4 FM Radio/Auxiliary Stereo Input
The auxiliary inputs AUXL/FML and AUXR/FMR can be used as the left and right stereo inputs,
respectively, of the FM radio. In that case (because both input amplifiers are busy), the other input
terminals are discarded and set to a high-impedance state. Both microphone amplification stages amplify
the FM radio stereo signal. Both amplification stage outputs are connected to the ADC input. The left and
right channel inputs of the FM radio can also be output through an audio output stage (mono output stage
in case of mono input FM radio, stereo output stage in case of stereo input FM radio).
6.2.4.1 External Components
Figure 6-25 shows the external components of the auxiliary stereo input.
Figure 6-25. Audio Auxiliary Input
NOTE
For other component values, see Table 15-1.
6.2.5 PDM Interface for Digital Microphones
The PDM interface is used as digital microphone inputs; each microphone is directly connected to the TX
filter decimator to extract the audio samples at the desired accuracy and sample rate. Each digital
microphone is stereo (two paths). The digital microphone interface is DIG.MIC.CLK (clock input to the
microphone) and DIG.MIC (PDM data output from the microphone). The appropriate frequency of
DIG.MIC.CLK is generated by the audio PLL, and the ratio between DIG.MIC.CLK and the sample rate is
50 (see Figure 6-26). The PDM interface is available only when F
S
= 48 kHz.
The data signal output is a 3-state output from the microphone. When a falling-edge DIG.MIC.CLK is
detected, DIG.MIC is actively driven. When a rising DIG.MIC.CLK is detected, DIG.MIC is high
impedance. The latter DIG.MIC.CLK half-cycle is reserved for stereo operation (the second microphone
receives DIG.MIC.CLK inverted).
The Σ-Δ converter in the digital microphones produces PDM.
Digital microphone characteristics:
• PDM clock rate 2.4 MHz
• Fourth-order Σ-Δ converter in the microphone component
Figure 6-26 is an example of PDM interface circuitry.
Copyright © 2008–2011, Texas Instruments Incorporated Audio/Voice Module 91
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