User's Manual

Telit GE863-QUAD / GE863-PY

Hardware User guide

1vv0300715, Rev. ISSUE#0, - 21/02/06

• THD+N 1% @ 330mW

high power external ear

• line coupling: DC

• line type: bridged not referred to GND

• speaker impedance (operating conditions): ≥ 4 Ω

• minimum load impedance: 4 Ω

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

• maximum power output: 6 W

• THD+N 10% @ 6 W

7.2 General Design rules

There are several configurations for the audio output path, but the various design requirements

can be grouped into three different categories:

• handset earphone (low power, typically a handset)

• hands free earphone (low power, typically a headset)

• car kit speakerphone (high power, typically a speaker)

The three groups have different power requirements, usually the first two applications need only

few mW of power, which can be directly drained from the GE863-QUAD/PY pads, provided a

suited speaker is used. This direct connect design is the cheaper and simpler solution and will be

suited for the most of the earphone design requirements. There's no need to decouple the output

ear lines if a suited earpiece is connected. For the last group, the speakerphone, a power

amplifier is required to raise the output power up to 5-10W required in a car cabin application.

All the designs shall comply with the following guidelines:

• Where possible use a bridged earphone circuitry, to achieve the maximum power output from

the device.

• Keep the earphone traces on the PCB and wires as short as possible.

• If your application requires a single ended earpiece and you want a direct connection, then

leave one of the two output lines open and use only the other referred to ground. Remember

that in this case the power output is 4 times lower than the bridged circuit and may not be

enough to ensure a good voice volume.