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3. TECHNICAL BRIEF
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LGE Internal Use Only
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Only for training and service purposes
3.12.3 Analog Part
The analog part of the X-GOLD™213 audio front-end in audio-out direction consists of a stereo digital to
analog converter (multi-bit oversampling converter) which transforms the output of the digital interpolation
filter into analog signals. It is followed by the gain control/amplifier section. The DAC outputs can be switched
to several output buffers. In audio-in section there is an input multiplexer which selects either one of two
differential microphone inputs to be connected to the low-noise amplifier and analog pre-filter. The signals
from the analog pre-filter are input to a second-order sigma-delta analog-to-digital converter. In addition
there is a connection for FM-radio playing.
̲
Audio-out Part
The analog audio-out part consists of two multi-bit digital-to-analogue converters (DAC) and an output stage.
The signal sources are switched to the output drivers in the output stage. The output drivers consist of: a) one
mono, differential class-D Loudspeaker driver, b) one mono, differential Earpiece driver and c) one stereo,
single-ended (with uni- or bipolar signals), Headset driver.
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Digital-to-analog converters
The multi-bit oversampling DACs of the X-GOLD™215 audio front-end convert the 16-bit data words coming
from the digital interpolation filters to analogue signals.
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Output Amplifier
The different output buffers in X-GOLD™215 are driven by the outputs of the selection block. The differential
earpiece driver can be used to drive a 16
ȳ
earpiece and works in differential. The two single ended headset
drivers can be used to drive a 16
ȳ
headset. They can work unipolar mode, where an AC coupling of the
headset might be needed, or can work also in bipolor mode. The differential loudspeaker driver can be used to
drive a 8
ȳ
loudspeaker. As it is a class-D amplifier the needed suppression of the higher harmonics of the
switching signals has to be achieved by the external circuitry. The buffers are designed to be short circuit
protected.