GE864-QUAD Automotive V2 Hardware User Guide
1vv0300840 Rev.0.1 24/11/09
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 43 of 65
9.2 OUTPUT LINES (Speaker)
9.2.1 Short description
The Telit GE864-QUAD Automotive V2 provides two audio paths in receive section. Only one of the
two paths can be active at a time, selectable by
AXE
hardware line or by AT command.
You must keep in mind the different audio characteristics of the receive blocks when designing:
Æ
the
“
EAR_MT
”
lines
EPN1
and
EPP1
are the
Differential Line-Out Drivers
; they can drive an
external amplifier or directly a
16
Ω
earpiece
at –12dBFS (*) ;
Æ
the “
EAR_HF
”
lines
EPPA1_2
and
EPPA2
are the
Fully Differential Power Buffers ;
they can
directly drive a
16
Ω
speaker
in differential (
balanced
) or single ended (
unbalanced
) operation mode .
(*)
FS
: acronym of
Full Scale.
It is equal to 0dB, the maximum Hardware Analog Receive Gain of
BaseBand Chip.
The
“
EAR_MT
”
audio path should be used for handset function, while the “
EAR_HF
”
audio path is
suited for hands-free function (car kit).
Both receiver outputs are B.T.L. type (Bridged Tie Load) and the OEM circuitry shall be designed
bridged to reduce the common mode noise typically generated on the ground plane and to get the
maximum power output from the device; however also a single ended circuitry can be designed for
particular OEM application needs.
