User's Manual

XT55/56 Hardware Interface Description
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XT55/56_hd_v02.06a Page 105 of 125 17.12.2004
3)
Audio mode 5 and 6 are identical. With AT^SAIC, you can easily switch mode 5 to the
second interface. Therefore, audio mode 6 is only kept for compatibility to earlier
Siemens GSM products.
Note: With regard to acoustic shock, the cellular application must be designed to avoid
sending false AT commands that might increase amplification, e.g. for a high
sensitive earpiece. A protection circuit should be implemented in the cellular
application.
6.5.4 Voiceband receive path
Test conditions:
• The values specified below were tested to 1kHz and 0dB gain stage, unless otherwise
stated.
• Parameter setup: gs = 0dB means audio mode = 5 for GSM_EPP1 to GSM_EPN1 and 6
for GSM_EPP2 to GSM_EPN2, inBbcGain= 0, inCalibrate = 32767, outBbcGain = 0,
OutCalibrate = 16384, sideTone = 0.
Table 32: Voiceband receive path
Parameter Min Typ Max Unit Test condition / remark
Differential output
voltage (peak to peak)
3.33 3.7 4.07 V from GSM_EPPx to GSM_EPNx
gs = 0dB @ 3.14 dBm0
no load
Differential output gain
settings (gs) at 6dB
stages (outBbcGain)
-18 0 dB Set with AT^SNFO
Fine scaling by DSP
(outCalibrate)
- 0 dB Set with AT^SNFO
Output differential
DC offset
100 mV gs = 0dB, outBbcGain = 0 and -6dB
Differential output
resistance
2  from GSM_EPPx to GSM_EPNx
Differential load
capacitance
1000 pF from GSM_EPPx to GSM_EPNx
Absolute gain accuracy 0.8 dB Variation due to change in
temperature and life time
Attenuation distortion 1 dB for 300...3900Hz,
@ GSM_EPPx/ GSM_EPNx
(333Hz) /
@ GSM_EPPx/ GSM_EPNx
(3.66kHz)
Out-of-band
discrimination
60 dB for f > 4kHz with in-band test
signal@ 1kHz and 1kHz RBW
gs = gain setting