PCM2906C_15 Datasheet, PDF (21/28 Pages) Texas Instruments – Stereo Audio Codec with USB Interface, Single-Ended Analog Input/Output, and S/PDIF

PCM2906C
www.ti.com
SBFS037 – NOVEMBER 2011
Clock and Reset
The PCM2906C requires a 12-MHz (±500 ppm) clock for the USB and audio functions. The clock can be
generated by a built-in oscillator with a 12-MHz crystal resonator. The 12-MHz crystal resonator must be
connected to XTI (pin 21) and XTO (pin 20) with one high-value (1-MΩ) resistor and two small capacitors, the
capacitance of which depends on the load capacitance of the crystal resonator. An external clock can be
supplied to XTI (pin 21). If an external clock is used, XTO (pin 20) must be left open. Because there is no clock
disabling signal, use of the external clock supply is not recommended. SSPND (pin 28) is unable to use clock
disabling.
The PCM2906C has an internal power-on reset circuit, which triggers automatically when V_BUS (pin 3) exceeds
2.5 V typical (2.7 V to 2.2 V). Approximately 700 μs is required until internal reset release.
Digital Audio Interface
The PCM2906 employs S/PDIF for both input and output. Isochronous-out data from the host are encoded to the
S/PDIF output and the DAC analog output. Input data are selected from either the S/PDIF or ADC analog input.
When the device detects S/PDIF input and successfully locks the received data, the isochronous-in transfer data
source automatically selected is S/PDIF; otherwise, the data source selected is the ADC analog input.
This feature is a customer option. It is the responsibility of the user to implement this feature.
Supported Input/Output Data
The following data formats are accepted by S/PDIF for input and output. All other data formats are unusable as
S/PDIF.
• 48-kHz 16-bit stereo
• 44.1-kHz 16-bit stereo
• 32-kHz 16-bit stereo
Any mismatch of the sampling rate between the input S/PDIF signal and the host command is not acceptable.
Any mismatch of the data format between the input S/PDIF signal and the host command may cause unexpected
results, with the following exceptions:
• Recording in monaural format from stereo data input at the same data rate
• Recording in 8-bit format from 16-bit data input at the same data rate
A combination of these two conditions is not acceptable.
For playback, all possible data-rate sources are converted to the 16-bit stereo format at the same source data
rate.
Channel Status Information
The channel status information is fixed as consumer application, PCM mode, copyright, and digital/digital
converter. All other bits are fixed as 0's except for the sample frequency, which is set automatically according to
the data received through the USB.
Copyright Management
Isochronous-in data are affected by the serial copy management system (SCMS). When the control bit indicates
that the received digital audio data are original, the input digital audio data are transferred to the host. If the data
are indicated as first generation or higher, the transferred data are routed to the analog input.
Digital audio data output is always encoded as original with SCMS control.
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): PCM2906C
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