Xircom An Intel Company GEM3501 User Manual
Core Engine GSM/GPRS Modem Developer Guide Preliminary Draft: 7/6/2001
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Part Number: 07100026, Revision: 002
Confidential
© 2001 Xircom, Inc., an Intel company All rights reserved.
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
7.3 Speaker Output
The Core Engine speaker (output) interface specification is shown in Table 9:
Differential output voltage typical
3.7V
Output differential maximum DC offset
100mV
Differential output load resistance minimum
15ohm
Output load capacitance maximum
4700pF
Table 8: Core Engine speaker interface specification.
The baseband is powered at 2.5V in the audio circuit design. The minimum load is 15
ohms.
ohms.
The 3.7V peak-to-peak specification is a differential measurement with the reference of
SPK_N1 or SPK_N2 (pins 9 and 36 respectively of the Core Engine I/O interface). Each
SPK_xx positive/negative pair can swing approximately 1.85V peak, with respect to
ground. The 3.7V peak-to-peak is obtainable because the SPK_Px positive is 180
degrees out of phase with the negative. Since this occurs simultaneously, the differential
measurement is (2 * 1.85V), or 3.7V peak-to-peak.
SPK_N1 or SPK_N2 (pins 9 and 36 respectively of the Core Engine I/O interface). Each
SPK_xx positive/negative pair can swing approximately 1.85V peak, with respect to
ground. The 3.7V peak-to-peak is obtainable because the SPK_Px positive is 180
degrees out of phase with the negative. Since this occurs simultaneously, the differential
measurement is (2 * 1.85V), or 3.7V peak-to-peak.
There is no audio power amp component in our design. The signals are driven directly by
the baseband processor.
the baseband processor.