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PRINCIPLES OF OPERATION

Single-End

/Differential

Converter

BCK

Reference

Single-End

/Differential

Converter

Delta-Sigma

Modulator

Delta-Sigma

Modulator

×1/64 (×1/128)

Decimation

Filter

with

High-Pass Filter

Power Supply

AGND

DGND

Clock and Timing Control

Serial

Interface

Mode/

Format

Control

LRCK

FSYNC

DOUT

FMT0

FMT1

MODE0

MODE1

BYPAS

OSR

PDWN

SCKI

B0004-07

PCM1802

SLES023C – DECEMBER 2001 – REVISED JANUARY 2005

The PCM1802 consists of a reference circuit, two channels of single-ended-to-differential converter, a fifth-order

delta-sigma modulator with full differential architecture, a decimation filter with high-pass filter, and a serial

interface circuit. Figure 19 illustrates the total architecture of the PCM1802, Figure 20 illustrates the architecture

of single-ended-to-differential converter and antialiasing filter, and Figure 21 is the block diagram of the fifth-order

delta-sigma modulator and transfer function. An on-chip high-precision reference with one external capacitor

provides all reference voltages that are needed in the PCM1802 and defines the full-scale voltage range for both

channels. On-chip single-ended-to-differential signal converters save the design, space, and extra parts cost for

external signal converters. Full-differential architecture provides a wide dynamic range and excellent

power-supply rejection performance. The input signal is sampled at a

×64 or ×128 oversampling rate, thus

eliminating an external sample-hold amplifier. A fifth-order delta-sigma noise shaper, which consists of five

integrators using the switched capacitor technique and a comparator, shapes the quantization noise generated

by the comparator and 1-bit DAC outside of the audio signal band. The high-order delta-sigma modulation

components with a decimation filter. The dc component of the signal is removed by the HPF, and the HPF output

is converted to a time-multiplexed serial signal through the serial interface, which provides flexible serial formats.

Figure 19. Block Diagram

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