User's Manual

GE865 Hardware User Guide
1vv0300799 Rev.11 – 13-07-2010
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 52 of 82
10.1 Electrical Characteristics
TIP: Being the microphone circuitry the more noise sensitive, its design and layout
must be done with particular care. Both microphone paths are balanced and the
OEM circuitry must be balanced designed to reduce the common mode noise
typically generated on the ground plane. However the customer can use the
unbalanced circuitry for particular application.
10.1.1 Input Lines
differential microphone path
Line Coupling
AC*
Line Type
Balanced
Coupling capacitor
≥ 100nF
Differential input resistance
50kΩ
Differential input voltage
≤ 1,03V
pp
@ MicG=0dB
(*) WARNING : AC means that the signals from the microphone have to be connected
to input lines of the module through capacitors which value has to be ≥ 100nF.
Not respecting this constraint, the input stages will be damaged.
WARNING: when particular OEM application needs a Single Ended Input configuration,
it is forbidden connecting the unused input directly to Ground, but only through a
capacitor which value has to be ≥ 100nF..