Sony Ericsson GM48, GM47 manual Analogue Audio, Afms

GM47/GM48 INTEGRATOR’S MANUAL

2.6 Analogue Audio

Pin	Signal	Dir	Description
57	AFMS	O	Audio from mobile station
59	ATMS	I	Audio to mobile station
60	AGND	-	Ground (return) for analogue audio

ATMS is the audio input, and AFMS is the audio output, of the module.

These signals can be used in Hands-free or Portable Hands-free mode.

Hands-free Mode

This mode is used for audio accessories, such as car kits and hands-free equipment.

Portable Hands-free Mode

This is the default mode. It activates a different amplification factor in the ME, and activates a 2V microphone bias level for ATMS. The bias level is adjustable using AT*E2EAMS.

2.6.1 Audio To Mobile Station - ATMS

ATMS is the analogue audio input to the module. Internally, the signal is sent to the CODEC (COder/DECoder), where it is converted to digital audio in PCM (Pulse Code Modulation) format. The encoded audio is sent to PCMOUT via the internal PCM bus.

ATMS provides a DC bias when it is used as the microphone input in Portable Hands-free applications. All other sources must be a.c.-coupled to avoid attenuation of low frequencies, and to prevent incorrect biasing or damage to the ATMS input. Use a capacitor greater than the value shown in the table below.

The ATMS input is a passive network followed by the transmit part of the CODEC.

Parameter	Limit
Application driving impedance (0.3 - 3.5kHz)	≤300Ω
AC coupling capacitance a	≥1µF
Module input impedance (0.3 - 3.5kHz)	>50kΩ
Low frequency cut-off (-3dB)	300Hz ± 50Hz

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