Circuit Operation

The LC78857V consists of three main blocks: the digital filter block, the sigma-delta D/A converter block, and the

analog filter block.

[Digital Filter Block]

The LC78857V performs the following calculations.

• Normal speed mode:

• Double speed mode:

This mode is used, for example, when dubbing a CD to cassette tape at double speed. Although the XIN has the same

frequency as normal speed mode, BCLK, LRCK, and DATA are input at twice the rate used in normal speed.

[Sigma-Delta D/A Converter Block]

This circuit accepts 8fs data input and outputs a 384fs 1-bit data sequence.

[Analog Low-Pass Filter Block]

This block consists of an analog low-pass filter that consists of on-chip resistors, capacitors, and operational amplifiers.

This block converts the 384fs 1-bit data streams A and B directly to an analog voltage output.

No. 5537-5/11

LC78857V

Input

Attenuator

Deemphas

is first-

order IIR

filter

31st-order

FIR filter

11th-order

FIR filter

3rd-order

FIR filter

To the sigma-delta

D/A converter

Input

Attenuator

Deemphas

is first-

order IIR

filter

31st-order

FIR filter

3rd-order

FIR filter

To the sigma-delta

D/A converter

fs* = double speed input = 2

× fs.

From the

digital filters

Front-end

interpolation

3rd-order

noise

shaper

PWM D/A

converter

1-bit output A

1-bit output B

1-bit output A

1-bit output B