User Manual

G610 GPRS Module Hardware User Manual Page 29 of 47
command. It has an impedance of 2 kΩ.
The bias voltage would be supplied after G610 powered on.
Parameter Conditions Min Typ Max Unit
Bias Voltage
No load
2.5 V
Gain Programmable
in 3 dB steps
0 45 dB
AC Input
Impedance
2 kΩ
3.9.4 2
nd
Audio Channel: Speaker
This channel is switched on by AT Command. It is designed as a differential output and can be
droved a 8Ω speaker directly.
Parameter Conditions Min Typ Max Unit
Output Voltage
No load Single
ended
500 mVPP
AC Output
Impedance
8 Ω
DC Voltage 1.38 V
3.9.5 Audio Design
The audio quality delivered by G610 is highly affected by the application audio design,
particularly when using the analog audio interface. Therefore, special care must be taken when
designing the G610 audio interface. Improper design and implementation of the audio interface will
result in poor audio quality.
Poor audio quality is a result of electrical interferences, or noises, from circuits surrounding the
audio interface. There are several possible sources for the audio noise:
 Transients and losses on the power supply
 EMI from antenna radiations
 Digital logic switching noise
Most of the audio noise originates from the GSM transmit burst current surges (217 Hz TDMA
buzz), which appear on the main power supply lines and antenna, but also indirectly penetrate the
internal application's supplies and signals. The noises are transferred into the G610's audio circuits