User Manual

GM862-QUAD / PY Hardware User Guide

1vv0300748 Rev. 5 - 20/09/07

9 OUTPUT LINES (Speaker)

9.1 Short Description

The Telit GM862-QUAD / PY 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:

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 16Ω 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.