Audio Interface (J28); Table 3-21. Ethernet Port 2 Pin/Signal Descriptions (J32) - Ampro Little Board 700 Reference Manual

Chapter 3

Table 3-21. Ethernet Port 2 Pin/Signal Descriptions (J32)

Pin # GND Digital Ground
1 TX+ Analog Twisted Pair Ethernet Transmit Differential Pair. These pins transmit the serial bit
stream for transmission on the Unshielded Twisted Pair Cable (UTP). These signals interface
2 TX-
directly with an isolation transformer.
3 RX
Analog Twisted Pair Ethernet Receive Differential Pair. These pins receive the
serial bit stream from the isolation transformer.
6 RX-
4 Term Termination
5
Term Termination
7 Term Termination
8
Term Termination
Note: Termination involves connecting a 75 ohm resistor between the connector and a capacitance
plane created on an inner layer power plane.

Audio Interface (J28)

The audio solution on the LB 700 is provided by the VT82C686B and the LM4549 audio CODEC.
These two chips use a digital interface to communicate between the two, which is defined by AC97 and
is revision 2.1 compliant. The LB 700 supports its own audio amplifier (LM4863), which drives the
audio signals into an external audio load. Output signals for the audio interface are through the 26-pin
2mm connector (J28) to an external board, which has the respective audio connections on it.
Audio CODEC (LM4549) features
• Analog Mixer Dynamic Range 97dB (typ)
• D/A Dynamic Range 89dB (typ)
• A/D Dynamic Range 90dB (typ)
• AC'97 Rev 2.1 compliant
• 3D Sound circuitry
• High quality Sample Rate Conversion (SRC) from 4kHz to 48kHz
• PC-Beep passthrough to Line Out while reset is held active low
• True Line Level Output with volume control independent of Line Out
Audio Amplifier (LM4863) features
• Dual bridge-connected audio power amplifier
• 2.2W to a 4? load or 1.1W to an 8? load.
• Dual Bridge speaker amplifiers
• Stereo headphone amplifier
• External Audio Interface
50 Reference Manual
Hardware
LittleBoard 700