Digital BTSC Encoder

with Integrated ADC and DAC

AD1970

Rev. 0

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FEATURES

Complete BTSC encoder

Pilot tone generator

Includes subcarrier modulation

Channel separation: 30 dB

Bandwidth up to 14 kHz

Stereo analog or digital input

Phat-Stereo™ algorithm for stereo image enhancement

Dialog enhancement function for playing wide dynamic

range video sources over built-in TV speakers

Includes L − R dual-band compressor

Analog input performance

74 dB dynamic range

−72 dB THD + N

Digital input performance

87 dB dynamic range

−83 dB THD + N

Integrated op amps for analog inputs and outputs

Single-ended output reduces external part count

Integrated PLL generates all clocks from composite video,

48 kHz sample clock, or high speed master clock

Sync stripper to recover video clock from composite

video signal

Output level control for setting aural carrier deviation

Macrovision

Dolby

48-pin LQFP plastic package

APPLICATIONS

Digital set top box

DVD player

DVD recorder

GENERAL DESCRIPTION

The AD1970 is a complete analog or digital-in, analog-out

BTSC encoder which includes pilot-tone generation and sub-

carrier mixing functions. The stereo ADC provides the means

for digitization of the analog baseband audio signal. A built-in

high performance DAC is provided to output the BTSC base-

band composite signal. The output of the AD1970 can be

connected with minimal external circuitry to the input of a

4.5 MHz aural FM modulator.

In addition to the digital BTSC encoder, the AD1970 includes a

stereo image enhancement function, Phat Stereo, to increase the

sense of spaciousness available from closely spaced TV

loudspeakers. A dialog enhancement algorithm solves the

problem of playing wide dynamic range sources over limited-

control of the AD1970’s registers and parameters.

The AD1970 utilizes ADI’s patented multibit Σ-Δ architecture to

provide BTSC performance of up to 87 dB dynamic range and a

THD+N of −83 dB.

The AD1970 includes patented BTSC stereo TV technology

licensed from THAT Corporation.

FUNCTIONAL BLOCK DIAGRAM

ANALOG L/R

INPUTS

GROUP

CONTROL

REGISTERS

ADC

VOLUME

CONTROL

BTSC

ENCODER

CORE

BTSC

ENCODED

OUTPUT

ANALOG

BIAS

3

DAC

DECIMATION

FILTER

PLL

SYNC

STRIPPER

ADC

ADC

4

DIGITAL AUDIO

INTERFACE

COMPOSITE

VIDEO

AD1970

Figure 1.