User's Manual

GE/GC864-QUAD V2 and GE864-GPS Hardware User Guide
1vv0300915 Rev.2 – 2011-06-15
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights
Reserved. Page 68 of 97
10.2. 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 its particular application.
10.2.1. Input Lines Characteristics
“MIC_MT” and “MIC_HF” differential microphone paths
Line Coupling AC*
Line Type Balanced
Differential input voltage ≤ 1,03V
pp
@ Mic G=0dB
Gain steps 7
Gain increment 6dB per step
Coupling capacitor ≥ 100nF
Differential input resistance 50KΩ
Input capacitance ≤ 10pF
(*) 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 100nF capacitor.
Don’t forget that the useful input signal will be halved in
Single Ended Input configuration.