Datasheet

PCM2900C

PCM2902C

www.ti.com

SBFS039 –SEPTEMBER 2011

Clock and Reset

The PCM2900C/2902C requires a 12-MHz (±500 ppm) clock for the USB and audio functions, which can be

generated by a built-in crystal 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 (1-MΩ) resistor and two small capacitors, the

capacitance of which depends on the load capacitance of the crystal resonator. The external clock can be

supplied from XTI (pin 21). If the external clock is supplied, XTO (pin 20) must be left open. Because there is no

clock-disabling signal, it is not recommended to use the external clock supply. SSPND (pin 28) is unable to use

clock disabling.

The PCM2900C/2902C 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 (PCM2902C)

The PCM2902C employs both S/PDIF 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 as either S/PDIF or ADC analog input. When

the device detects an S/PDIF input and successfully locks the received data, the isochronous-in transfer data

source is automatically selected from S/PDIF itself; otherwise, the data source is selected to ADC analog input.

This feature is a customer option. It is the responsibility of the user to implement this feature.

Supported Input/Output Data (PCM2902C)

The following data formats are accepted by the S/PDIF input and output. All other data formats are unable to use

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 16-bit stereo format at the same source data rate.

Channel Status Information (PCM2902C)

The channel status information is fixed as consumer application, PCM mode, copyright, and digital/digital

converter. All other bits are fixed as 0s except for the sample frequency, which is set automatically according to

the data received through the USB.

Isochronous-in data are affected by the serial copy management system (SCMS). When receiving digital audio

data that are indicated as original data in the control bit, input digital audio data transfer 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.

Product Folder Link(s): PCM2900C PCM2902C