Chapter 3 — Theory of Operation
CV30 Fixed Mount Computer Service Manual 63
• Multiple audio paths with variable gain and mixers.
• Multiple audio inputs and outputs.
• Integrated headphone amplifier.
• PCM interface for digital audio I/O.
The CODEC is used to route all audio signals to the proper destinations
under software control. The software also controls the gain and mute as
required by the user or application.
Headset Jack
The unit has a headset jack that allows the headphone, microphone, and
speaker to connect to the CODEC. The CODEC directly drives the
headphone speaker.
Bluetooth Digital Audio Interface
In situations where a Bluetooth headset is used, the internal Bluetooth
module on the MLB will communicate over the PCM audio interface to
the CODEC. This communication allows the wireless interface of an
audio headset to the CODEC and then ultimately to the WAN radio or
802.11 radio to be utilized. The PCM audio interface is a serial, digital, bi-
directional bus that routes digitized audio into a special port on the
CODEC.
Audio Power Supplies
The audio CODEC has two power supplies:
• V3P3_CODEC_DIG powers the digital portion of the CODEC.
• V3P3_CODEC_ANLG powers the analog portion of the CODEC.
Both portions of the CODEC must be powered on at the same time or the
CODEC may power up and remain in a confused state with erratic
operation.
The analog section of the audio system has a ferrite bead to isolate the
V3P3_CODEC_ANLG power from the rest of the device. This isolation
ensures that the power is clean and does not inject audible noise that the
user can hear.
The CODEC has a touch panel controller built in. In order to use the
controller to operate the touch panel, power to the TPVDD needs to be
supplied. However this part of controller was not used in the CV30.
A separate LDO is provided to power the loud speaker amplifier TPA2005
from the V5P0_MAIN. The output of the LDO is ferrite filtered prior to
supplying power to the loud speaker amplifier.
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