User's Manual

Telit GM862-QUAD/-QUAD-PY

Hardware User Guide

1vv0300692, Rev. ISSUE#0, - 04/10/2005

6 Speaker

6.1 Speaker lines characteristics and requirements

The Telit GM862-QUAD provides two audio paths for both the microphone and the earpiece: the

internal and the external audio paths. Only one of the two paths can be active at a time and it is

selectable by hardware line AXE or by AT command. The audio characteristics of the two paths are

slightly different and this should be kept in mind when designing your application. The internal

audio path should be used for handset function, while the external audio path is suited for hands free

function (car kit).

Both speaker outputs from the Telit GM862-QUAD are bridged type 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 for particular OEM application needs

also a single ended circuitry can be designed.

The GM862-QUAD speaker output lines characteristics are:

internal speaker path ( EAR_MT+ , EAR_MT- )

• line coupling: DC

• line type: bridged

• speaker impedance (operating conditions): ≥ 16 Ω ± 5% @ 1kHz

• minimum load impedance: 15 Ω

• signal bandwidth: 150 - 8000 Hz @ -3 dB

• maximum differential output: 850 mV

rms

• rated output power: 10 mW

• maximum power output: 30 mW

• volume level steps (SW): - 2 dB

• number of volume steps(SW): 10

external speaker path ( EAR_HF+ , EAR_HF- )

• line coupling: DC

• line type: bridged

• speaker impedance (operating conditions): ≥ 16 Ω ± 15% @ 1kHz

• minimum load impedance: 15 Ω

• signal bandwidth: 150 - 8000 Hz @ -3 dB

• maximum differential output: 425 mV

rms

• rated output power: 2.5 mW