PCM2901

PCM2903

SLES034B − MARCH 2002 − REVISED JUNE 2004

www.ti.com

25

Clock and Reset

The PCM2901/2903 requires a 12-MHz (

±500 ppm) clock for the USB and audio function, which can be

generated by a built-in crystal oscillator with a 12-MHz crystal resonator or supplied by an external clock. The

12-MHz crystal resonator must be connected to XTI (pin 21) and XTO (pin 20) with one high (1-M

Ω) resistor

and two small capacitors, the capacitance of which depends on the load capacitance of the crystal resonator.

If the external clock is used, the clock must be supplied to XTI, and XTO must be open.

exceeds 2.5 V typical (2.7 V to 2.2 V) and about 700

µs is required until internal reset release.

Digital Audio Interface (PCM2903)

The PCM2903 employs both S/PDIF input and output. Isochronous-out data from the host is encoded to the

S/PDIF output and the DAC analog output. Input data is selected as either S/PDIF or ADC analog input. When

the device detects an S/PDIF input and successfully locks on 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.

Supported Input Data (PCM2903)

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

use S/PDIF.

Mismatch between input data format and host command may cause unexpected results except in the following

conditions.

A combination between the above conditions is not accepted.

For the playback, all possible data rate source is converted to 16-bit stereo format at the same source data rate.

Channel Status Information (PCM2903)

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.

Copyright Management (PCM2903)

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

data that is indicated as original data in the control bit, input digital audio data transfers to the host. If the data

is indicated as first generation or higher, transferred data is selected to analog input.

Digital audio data output is always encoded as original with SCMS control.

The implementation of this feature is an option for the customer. Note that it is the user’s responsibility whether

they implement this feature in their product or not.

INTERFACE SEQUENCE

Power On, Attach, and Playback Sequence

The PCM2901/2903 is ready for setup when the reset sequence has finished and the USB bus is attached. In

must rise up with 10 ms / 3.3 V. After connection has been established by setup, the PCM2901/2903 is ready

to accept USB audio data. While waiting, the audio data (idle state) and analog output are set to bipolar zero

(BPZ).