9.2.14 Digital Microphone Inputs
The CSR8640 BGA interfaces to 2 digital microphone inputs (MEMS). Figure 9.2 shows that 1 of the inputs has a
dedicated codec channel and 1 is multiplexed with a high-quality ADC channel.
Figure 9.2 shows that the digital microphone interface on the CSR8640 BGA has:
■
Clock lines linked to any even-numbered PIO as determined by the firmware.
■
Data lines linked to any odd-numbered PIO as determined by the firmware.
Note:
For the digital microphone interface to work in this configuration ensure the microphone uses a tristate
between edges.
■
The left and right selection for the digital microphones are appropriately pulled up or down for selection on
9.2.15 Line Input
Section 9.2.4 states that if the pre-amplifier audio input gain is set at a low gain level it acts as an audio line level
amplifier. In this line input mode the input impedance varies from 6kΩ to 30kΩ, depending on the volume setting.
Figure 9.5 and Figure 9.6 show 2 circuits for line input operation and show connections for either differential or single-
ended inputs.
G-TW
-000847
4.1.2
C3
C4
MIC_BN
MIC_BP
C1
C2
MIC_AN
MIC_AP
Figure 9.5: Differential Input
Advance Information
This material is subject to CSR's non-disclosure agreement
© Cambridge Silicon Radio Limited 2011
Page 43 of 110
CS-209182-DSP1
CSR8640 BGA
Data Sheet
