Specifications

Audio Interface
Rev 2.0 Apr.10 Proprietary and Confidential 53
Audio signal interface
The differential microphone input offers superior noise rejection performance to
the single-ended approach. The termination of the differential pair rejects
common signals (such as noise). The pair should be routed together for optimal
noise rejection. Since MIC_P and MIC_N are high impedance inputs, it is
important to isolate these from possible noise sources (toggling digital lines with
fast edges).
The speaker interface can be single-ended or differential depending on product.
Single-ended speaker outputs rely on modem ground as an audio reference.
The audio passband for both receive and transmit paths (speaker and
microphone) extends from 300 Hz to 3.4 kHz. A programmable sidetone with a
range from mute to unity gain is available for both headset and main audio paths.
Sidetone should be muted for speakerphone use.
Note that certain carriers now require use of hearing-aid compatible transducers
in a handset design. The Primary audio path can be interfaced directly to such
devices. Refer to ANSI C63.19 for details regarding reduced RF emissions ("U3
rating") and inductive/telecoil coupling ("U3T" rating) devices.
Car kit • Long echo path (<64 ms travel time from speaker to micro-
phone)
• Loud echo
• For use with hands-free car kit or speakerphone applications
with mild distortion
Speakerphone • Long echo path (<64 ms travel time from speaker to micro-
phone)
• Loud echo
• For use with speakerphone applications with high distortion
• Half-duplex algorithm, very aggressive in near-end Tx muting
to eliminate transmitted echo
Off
Table 4-5: Primary audio signal interface
Signal Pin # Type Direction Description
MIC_P 1 Analog Input Non-inverted microphone input (+)
MIC_N 3 Analog Input Inverted microphone input (-)
SPK_P 5 Analog Output Non-inverted speaker output (+)
SPK_N 7 Analog Output Inverted speaker output (-)
Table 4-4: Echo cancellation details (Continued)
Mode Details