Network Hardware User Manual

UC864-E Hardware User Guide
1vv0300766a Rev.1 - 31/01/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 39 of 51
10.4 Electrical Characteristics
10.4.1 Input lines (microphone)
The two transmit blocks are fully equivalent, connected in Differential mode
Line coupling AC (*)
Line type Balanced
Coupling capacitor ≥ 100nF
Differential input resistance 20kΩ
Differential input voltage ≤ 1,03V
pp
@ HSMicG=0dB
Table 1. “Mic_MT” 1st differential microphone path
Line coupling AC (*)
Line type Balanced
Coupling capacitor ≥ 100nF
Differential input resistance 20kΩ
Differential input voltage ≤ 1,03V
pp
@ HFMicG=0dB
Table 2. “Mic_HF” 2nd differential microphone path
Due to the fact that particular OEM applications need a single line connection, a Single Ended
configuration could be
implemented, but halving the useful microphone signal.
In both cases the OEM circuitries shall be carefully designed to reduce the common mode noise
typically generated on the ground plane.
WARNING
In the previous tables, the line coupling definition AC (*) means that:
the signals from microphone must be connected to the input lines
of the UC864-E through CAPACITORS, not less than 100nF
Not respecting this constraint, the input stage will be damaged!