AD1970

Rev. 0 | Page 9 of 20

THEORY OF OPERATION

The AD1970 is comprised of a BTSC encoder with stereo

analog inputs and a sync separator to derive the pilot signal

from the composite video stream. Figure 1 shows the block

diagram of the device.

Signal processing parameters are stored in a parameter RAM,

which is initialized on power-up by an internal boot ROM. The

values stored in the parameter RAM control all the filter coef-

ficients, mixing, and dynamics-processing code used in the

BTSC algorithm.

capability of the parameter RAM, as well as a control port and

several other registers that allow the various signal processing

parameters to be controlled. The AD1970 can run as a stand-

alone processor without external control.

The AD1970 has a very flexible serial data input port that allows

for glueless interconnection to a variety of digital signal sources.

justified, or DSP serial port-compatible modes. It can support

16, 20, and 24 bits in all modes. The AD1970 accepts serial

audio data in MSB first, twos complement format.

The AD1970 operates from a single 3.3 V power supply. It is

fabricated on a single monolithic integrated circuit and is

housed in a 48-pin LQFP package for operation over the

temperature range of 0°C to 70°C.