TDA1305T Integrated Circuit Chip Stereo 1fs data input up-sampling filter with bitstream continuous dual DAC BCC-DAC2

Stereo 1fs data input up-sampling filter with bitstream continuous dual DAC (BCC-DAC2)

Noise shaper

In the normal speed mode the 2nd order digital noise shaper operates at 96fs (fsys = 384fs) or 128fs (fsys = 256fs). The digital noise shaper operates at 48fs (fsys = 384fs) or 64fs (fsys = 256fs) in double-speed mode. It shifts in-band quantization noise to frequencies well above the audio band. This noise shaping technique used in combination with a special data coding enables extremely high signal-to-noise ratios to be achieved. The noise shaper outputs a 5-bit pulse duration modulation (PDM) bitstream signal to the DAC.

Continuous calibration

DAC The dual 5-bit DAC uses the continuous calibration technique. This method, based on charge storage, involves exact duplication of a single reference current source. In the TDA1305T, 32 such current sources plus 1 spare source are continuously calibrated. The spare source is included to allow continuous converter operation.

The DAC receives a 5-bit data bitstream from the noise shaper. This data is then converted so that only small currents are switched to the output during digital silence (input 00000H). Using this technique extremely high signal-to-noise performance is achieved.

Operational amplifiers

High precision, low-noise amplifiers together with the internal conversion resistors RCONV1 and RCONV2 convert the converter output current to a voltage capable of driving a line output. This voltage is available at VOL and VOR (1.5 V RMS typical).

Connecting external capacitors CEXT1 and CEXT2 between FILTCL and VOL and between FILTCR and VOR respectively provides the required 1st order post filtering for the left and right channels (see Fig.1). The combinations of RCONV1 with CEXT1 and RCONV2 with CEXT2 determine the 1st order fall-off frequencies.

Internal reference circuitry

Internal reference circuitry ensures that the output voltage signal is proportional to the supply voltage, thereby maintaining maximum dynamic range for supply voltages from 3.4 to 5.5 V and making the circuit also suitable for battery-powered applications.

LIMITING VALUES

In accordance with the Absolute Maximum Rating System (IEC 134)