28LF-94H - Sharp TV Service Manual (repair manual). Page 8

MPIF IC consists of following OVERALL blocks;
(1)- Video / Audio switching
(2)- IF processing
(3)- A/D conversion for digital TV (DTV) processor (ADOC-PNX300X)

Main building blocks:

_ Vision PLL-IF, auto-calibrated, selectable IF frequency, 4 selectable AGC time constants, built-in sound trap and
selectable group delay. The demodulated CVBS signal is fed outside for use with SCART.
_ Synthesizer mode, meant for down mixing of DTV signals to a suitable 2nd IF which can be handled by a digital DTV
decoder. Using a suitable SAW filter at the input the synthesizer mode can also be used to downmix FM radio frequencies
from the Tuner to a suitable 2nd IF frequency for the FM demodulator.
_ Two Video IF inputs, selectable by internal switch to enable use of optimized SAW filters
_ Sound QSS IF, demodulated 2nd SIF can be either from SIF input (QSS) or Video IF (intercarrier). The Sound IF also
contains an AM demodulator for SECAM L/L’
_ CVBS and Y/C crossbar switch, with 2 video outputs for further processing in the Digital TV Signal Processor after A/
D conversion and 2 selectable video outputs which are available on output pins for external connections
_ Two YUV / RGB inputs, which can handle also YPrPb and sync on Y for DVD players Also 2Fh YUV / RGB signals can
be handled by the A/D converters.
_ An audio stereo crossbar switch with two outputs (one stereo, one stereo or mono) for further processing in the
processor after A/D conversion and three stereo outputs for external connections. Extra inputs are provided to enable
also the selection of demodulated RF sound (mono, NICAM, 2CS) from the Digital TV Signal Processor for use on
external connections.
_ Low pass filtering and A/D conversion. The audio and video sampling clocks use the same reference so it is possible
to interleave video and audio data into one serial data stream.
_ For control, I 2 C control is built-in with a selectable address.
_ Auxiliary building blocks which perform some functions which have typical better performance in analogue design
environment than in digital and are used by the Digital TV Signal Processor:
- Reference voltage for vertical deflection and audio ADC’s
- Voltage to current conversion of the E/W
The set-up with an analogue and a digital part has the following advantages:

_ High frequent parts (IF) can be included in the concept

_ Less A/D and D/A converters needed for source switching
_ Better performance for AD converters (realized in analogue design environment, more accurate, less tolerance)
_ Critical items like reference voltages can be realized in the analogue environment