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<strong>UAC</strong> <strong>357xB</strong><br />
ADVANCE INFORMATION<br />
2.10.4.2. Line Out Mode<br />
In line out mode 1) it is possible to reduce external<br />
ground noise by AC-coupling of the external ground to<br />
the pin SREFO. This method is re<strong>com</strong>mended in home<br />
stereo equipment with USB connection to a PC. If the<br />
home stereo system uses an antenna, the use of an<br />
additional antenna insulator is re<strong>com</strong>mended to avoid<br />
hum.<br />
Alternatively, external ground can be connected to<br />
AVSS while SREFO is left open. However, care must<br />
be taken to avoid ground loop noise.<br />
OUTL<br />
2.10.4.3. Mono Speaker Mode<br />
In mono speaker mode, the DC coupling capacitors<br />
are not required. In this mode, the output pins OUTL/R<br />
operate in bridge mode with <strong>com</strong>plementary signals.<br />
Therefore, the maximum output power increases,<br />
allowing small speakers to be driven directly.<br />
OUTR<br />
OUTL<br />
Fig. 2–13: Loudspeaker connection for mono mode 2)<br />
2.11. Special I/O<br />
OUTR<br />
SREFO<br />
Pins: SOF, SEN, SUSPEND, RESET<br />
The following sections describe some pins with special<br />
functions.<br />
Fig. 2–12: Lineout mode with ground noise<br />
<strong>com</strong>pensation<br />
2.11.1. SOF (Start of Frame)<br />
The SOF pin provides a 1 ms periodic signal which is<br />
derived from the USB frame rate. It can be used for<br />
test purpose or as an USB-synchronous reference for<br />
vendor-specific external circuitry.<br />
1) this is not a standard line out, because all audio processing<br />
is active on the analog output.<br />
2) load capacitance must not exceed 400pF at OUTL,<br />
OUTR and OUTC. Otherwise series resistors are<br />
required.<br />
16 Aug. 20, 2004; 6251-650-1AI Micronas
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