Telit Wireless Solutions GL865 V3, Руководство пользователя

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HW User Guide
1vv0301018 Rev. 15 Page 46 of 72 2019-01-07
Electrical Characteristics
10.4.1. Input Lines
Microphone/Line-in path
Line Type Differential
Coupling capacitor ≥ 100nF
Differential input resistance 50kΩ
Levels
To have 0 dBfs @1KHz
(*) Differential input voltage
MIC Gain = 0dB 290mVrms
MIC Gain = +6dB 145mVrms
MIC Gain = +12dB 72mVrms
MIC Gain = +18dB 36mVrms
MIC Gain = +24dB 18mVrms
MIC Gain = +30dB 9mVrms
MIC Gain = +36dB 4.5mVrms
MIC Gain = +42dB 2.25mVrms
(*) 0 dBfs in the network are +3.14 dBm0
TIP: The Electret microphone is internally amplified by a J-Fet transistor,
thus the sound is carried out as saturation drain current; this means that the
Norton equivalence has to be considered. The signal is converted to voltage
on the 2.2KΩ resistance, from there on circuitry has to be routed in order to
not pick up common mode noise; beware of the return path (ground).
10.4.2. Output Lines
EAR/Line-out Output
Differential line coupling
Direct connection (V
DC
=1.7÷2.1V)
output load resistance ≥ 8 Ω
signal bandwidth 250÷3400Hz
(@ -3dB with default filter)
max. differential output voltage 1120 mV
pp
@3.14dBm0 (*)
differential output voltage 550mV
rms
@ 0dBm0 (*)
volume increment 2dB per step
volume steps 0..10
(*)
in default condition: Output Volume = +20dB, Output Attenuation = 0dB
TIP: We suggest driving the load differentially; this kills all the common mode
noises (click and pop, for example), the output swing will double (+6dB) and
the big output coupling capacitor will be avoided.
In order to get the maximum power output from the device, the resistance of
the tracks has to be negligible in comparison to the load.