relevant pins of super single-chip TMPA8899-XXXX. Pin 57 and Pin 58 of the micro-
processor (CPU) input I
2
C bus tuning data to SCL and SDA pin of the high frequency
head.
The high frequency head of this device is frequency synthesis high frequency head, which
performs automatic frequency synthesis tuning based in the SCL and SDA bus data
output by Pin 57 and Pin 58 of the micro-processor. The 33V voltage of the high
frequency head is provided by +110V (21”)+130V (29”) via R518 voltage reduction and
N505 voltage regulation.
This frequency synthesis method is also known as phase-locked-loop (PLL) frequency
synthesis. The CPU gives band switching signal under the control of the program
selection data provided by program reservation program, band switch and remote
control receiver, sets the frequency dividing ratio of the variable division frequency
divider in the PLL according to the local frequency of the channel received; the variable
division frequency divider divides the local frequency from the high frequency head,
outputs the frequency and compares the frequency with the benchmark frequency; then
it adjusts the local frequency according to the difference to meet the local frequency
needed for various channels.
2. Image intermediate frequency circuit:
The intermediate frequency signal from the high frequency head is amplified by pre-
amplifier made up of V103 and others, enters the surface acoustic wave filter Z101
(F45C) and is filtered according to intermediate frequency characteristics and sent to
Pin 41 and Pin 42 of N101. The purpose of setting up the pre-amplifier is to compensate
the insertion loss of the surface acoustic wave filter and improve the signal to noise
ratio.
The intermediate frequency signal entering TMPA8899-XXXX is amplified by the internal
pre-amplifier and video filtered, then PIF detection signal (full TV signal) is output from
Pin 30, passes the emitter follower made up of the external R155, R156, V104 and
R158. Then it is coupled via C147 and returns to the selector switch in the TMPA8873-
XXXX via Pin 26.
3. Audio processing circuit:
