Telit Wireless Solutions GE910 - 11 Audio Section Overview; Digital Voice Interface (DVI); DVI Electrical Connections; Analog Front-End

GE910 Hardware User Guide
1vv0300962 Rev.12 2013-10-22
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 54 of 83
Mod. 0805 2011-07 Rev.2
11. Audio Section Overview
The audio paths are:
• Digital Voice Interface (DVI).
• Analog Front-End.
11.1. Digital Voice Interface (DVI)
11.1.1. DVI Electrical Connections
The product is providing the Digital Audio Interface (DVI) on the following Pins:
Digital Voice Interface (DVI)
PAD Signal I/O Function Note Type
B9
DVI_WA0
I/O
Digital Audio Interface (Word
Alignment / LRCLK)
CMOS 1.8V
B6
DVI_RX I Digital Audio Interface (RX) CMOS 1.8V
B7
DVI_TX O Digital Audio Interface (TX) CMOS 1.8V
B8
DVI_CLK
I/O Digital Audio Interface (BCLK) CMOS 1.8V
NOTE:
For more information refer to Telit document: "80000NT10004a Digital Voice Interface
Application Note".
11.2. Analog Front-End
11.2.1. MIC connection
The bias for the microphone has to be as clean as possible; the first connection (single ended) is
preferable since the Vmic noise and ground noise are fed into the input as common mode and
then rejected. This sounds strange; usually the connection to use in order to reject the common
mode is the balanced one. In this situation we have to recall that the microphone is a sound to
current transducer, so the resistor is the current to tension transducer, so finally the resistor feeds
the input in balanced way even if the configuration, from a microphone point of view, seems to
be un-balanced.