+
-
OUT A
+
-
JP1 - Open
OUT B
JP2 - Open
2.1.4
USB Interface
2.1.5
Digital Audio Interface SPDIF (RCA/OPTO)
2.1.6
ADC Interface
Installation
www.ti.com
Figure 6. Single-Ended Connection
The TAS5706A registers are accessed through I
2
C™ bus lines SDA and SCL. The USB circuit and USB
connector on the MC57xxPSIA board facilitates the connection between a host computer and the device.
The EVM USB circuit is powered by the 5-V USB line of the host PC and is independent of the power
supplies available on the board. The USB device that is used is a TAS1020B from Texas Instruments.
The Digital Audio Interface accepts digital audio data using the I
2
S protocol. See the TAS5706A data
sheet (
) for more information.
The RCA connector and the OPTO connector are the two SPDIF interfaces on the MC57xxPSIA board.
The switch S3 toggles between the OPTO and RCA connector to accommodate the signal source. When
the RCA cable or optical cable is connected and the signal source is powered up, verify that the SPDIF
lock indicator (blue LED5) illuminates, confirming that a viable signal is available to the device. Install a
jumper on JP4 across the middle pin and the pin marked SPDIF to connect the digital source to
SDIN1.Install jumper on JP5 to connect the digital source to SDIN2.
For detailed information on how the data and clocks are provided to the TAS5706A, see the schematic
appearing at the end of this document and the DIR9001 device data sheet (
In the absence of a digital signal source, the PCM1808 ADC can be used to convert an analog audio
signal to a digital signal to the TAS5706A. The DIR9001 still provides clock signals to the ADC in this
process. The DIR9001 oscillator frequency (Y2) determines the sampling frequency in the absence of a
digital signal. If the OSC frequency is 24 MHz, the sampling frequency is set at 96 kHz; if the OSC is set
at 12 MHz, the sampling frequency defaults to 48 kHz when no signal is on the SPDIF input terminals. A
12-MHz crystal is installed on the MC57xxPSIA board. The ADC is an additional feature of this board to
provide flexibility in sourcing an audio signal to the TAS5706A. Review the PCM1808 data sheet
(
) for a detailed description of the ADC on this EVM. Install the jumper on JP4 across the middle
pin and the pin marked ADC to select ADC as the source for SDIN1.Do the same for JP5 to select the
ADC as the source for SDIN2. The jumpers JP2 and JP3 on MC57xxPSIA board are IN for 1 Vrms analog
input and OUT for 2 Vrms inputs.
TAS5706EVM2
8
SLOU220 – September 2008