TDA9809 Philips Semiconductors, TDA9809 Datasheet - Page 6

• Manufacturer Part Number: TDA9809
• Description: Single standard multimedia IF-PLL and FM radio demodulator
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Frequency Phased-Locked Loop detector (FPLL)
The VIF amplifier output signal is fed, via a limiting
amplifier, to a frequency and phase detector. During
acquisition, the frequency detector generates a DC current
that is proportional to the difference in frequency between
the input signal and the VCO signal.
After frequency lock-in, the phase detector generates a
DC current proportional to the phase difference between
the input signal and the VCO signal. The DC current
generated by the frequency or phase detector is converted
to a DC voltage via the loop filter, which controls the VCO
frequency.
VCO, TWD and TV AFC
The VCO operates with a resonance circuit (with L and C
in parallel) at double the Picture Carrier (PC) frequency.
The VCO is controlled by two integrated variable
capacitors. The control voltage required to tune the VCO
from its free-running frequency to double the PC frequency
is generated by the FPLL and fed via the loop filter to the
first variable capacitor. This control voltage is amplified
and converted into a current which represents the AFC
output signal. At the centre frequency, the AFC output
current is zero.
The TWD divides the oscillator signal by 2 and generates
two differential output signals with a 90 phase difference
independent of frequency.
Video demodulator and amplifier
Video demodulation is realized by a multiplier designed for
low distortion and wide bandwidth. The vision IF input
signal and the ‘in-phase’ signal of the travelling wave
divider output are multiplied together.
The demodulated output signal is fed to the video amplifier
via an integrated low-pass filter used to attenuate the
carrier harmonics. This is an operational amplifier with
internal feedback and wide bandwidth. A low-pass filter is
integrated to attenuate the carrier harmonics. The video
output signal at V
modulation, in order to achieve 1 V (p-p) at the sound trap
output.
1998 Jan 08
Single standard multimedia IF-PLL and FM
radio demodulator
o(vid)
is 1.1 V (p-p) for nominal vision IF
6
Intercarrier mixer
The intercarrier mixer is realized by a multiplier.
The sound IF signal passes through the vision IF SAW
filter and the composite IF signal is then fed to the
intercarrier mixer. Here, the IF signal is multiplied by the
90 TWD output signal to convert the sound IF to the
intercarrier frequency. By using this quadrature detection,
the low frequency video signals are removed. The mixer
output signal is fed, via a high-pass filter used to attenuate
the video signal components, at output pin 10.
RIF amplifier and AGC detector
The radio IF amplifier amplifies the 10.7 MHz radio IF
signal. This signal is supplied by the tuner and is fed to the
RIF input (pin 4) via a matching circuit and a ceramic
band-pass filter. This amplifier contains two stages.
The first stage, a conventional 0 dB differential amplifier
designed for optimal dynamic range, is followed by a
switchable differential amplifier stage with a gain of 10 dB.
Either the radio IF or the TV IF signal can be selected at
the output (pin 10).
The RIF output signal is fed via ceramic band-pass filters
to the FM-PLL demodulator and the radio IF AGC detector.
The AGC threshold is very high and is designed to obtain
some adjacent channel protection. The AGC detector
output is fed to the tuner AGC output stage (pin 12) to
control the tuner.
FM-PLL demodulator, level detector and radio AFC
The FM-PLL demodulator consists of a limiter and an FM
phase-locked loop. The 8-stage internally AC-coupled
limiter amplifies and limits the TV FM sound intercarrier or
the radio FM intermediate frequency signal prior to
demodulation. The limiter is designed for high sensitivity
and AM suppression with low DC offset and needs no
external pins for DC coupling.
Furthermore, the AF output signal can be force muted by
connecting a resistor between pin 11 and ground. The soft
mute function can be disabled by connecting a resistor
between pin 11 and the power supply. See the application
circuit in Fig.16.
Preliminary specification
TDA9809M