User's Guide

UC864-E-AUTO / AWS-AUTO Hardware User Guide
1vv0300795 Rev.11 – 2010/11/18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights Reserved. Page 50 of 78
11.2. Electrical Characteristics
Electrical CharacteristicsElectrical Characteristics
Electrical Characteristics
11.2.1. Input Lines (
((
( MIC1 and MIC2
MIC1 and MIC2MIC1 and MIC2
MIC1 and MIC2 )
))
) Characteristics
Line coupling AC (*)
Line type Balanced / Unbalanced
Coupling capacitor >= 100nF
Differential input impedance 20Kohm
Differential input voltage
908mV
rms
(
≤
1290mV
rms
)
@ MicG=0dB
“Mic_MT” and “Mic_HF”
“Mic_MT” and “Mic_HF”“Mic_MT” and “Mic_HF”
“Mic_MT” and “Mic_HF” microphone paths
(*) WARNING :
(*) WARNING : (*) WARNING :
(*) 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:
WARNING: WARNING:
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 thus the useful input signal will be halved.
TIP:
TIP: TIP:
TIP: Being the microphone circuitry the more noise sensitive, its design and layout
must be realized 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.
.