Rainbow-electronics GM862-QUAD-PY Manual de usuario descargar pdf (Pagina 38)

GM862-QUAD / PY Hardware User Guide

1vv0300748 Rev. 5 - 20/09/07

8.1 Microphone Paths Characteristic and

Requirements

TIP: being the microphone circuitry the more noise sensitive, its design and layout must be

done with particular care. Both microphone paths are balanced and the OEM circuitry should

be balanced designed to reduce the common mode noise typically generated on the ground

plane. However also an unbalanced circuitry can be used for particular OEM application needs.

TIP: due to the difference in the echo canceller type, the “Mic_MT” audio path is suited for

Handset applications, while the “Mic_HF”audio path is suited for hands-free function (car kit).

The Earphone applications should be made using the “Mic_HF” audio path but DISABLING the

echo canceller by software AT command. If the echo canceller is left active with the Earphone,

then some echo might be introduced by the echo cancel algorithm.

“Mic_MT” 1

differential microphone path

• line coupling AC (*)

• line type balanced

• coupling capacitor ≥ 100nF

• differential input resistance 50kΩ

• max differential input voltage 1,03V

(365mV

rms

)/@MicG=0

• microphone nominal sensitivity -45 dBV

rms

/Pa

• analog g

ain suggested + 20dB

• echo canceller type handset

“Mic_HF” 2

differential microphone path

• line coupling AC (*)

• line type balanced

• coupling capacitor ≥ 100nF

• differential input resistance 50kΩ

• max differential input voltage 1,03V

(365mV

rms

)

MicG=0

• microphone nominal sensitivity -45 dBV

rms

/Pa

• analog

gain suggested +10dB

• echo canceller type car kit hands-free

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Rainbow-electronics GM862-QUAD-PY Manual de usuario Pagina 38

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