TDA8501 Datasheet, PDF (9/30 Pages) NXP Semiconductors – PAL/NTSC encoder

Philips Semiconductors
PAL/NTSC encoder
Preliminary specification
TDA8501
Fig.7 Band pass filter nominal frequency
response (NTSC mode).
Y +SYNC, CVBS AND CHROMINANCE OUTPUTS
The Y signal from the matrix, or the Y signal from pin 5,
(selected via the switch) is added with the composite sync
signal of the sync separator (dependent on pin 17
conditioning). The output of the adder, nominal 1 V
(peak-to-peak), is connected to pin 22 (see Fig.1). Pin 22
is connected to an external delay line.
The delay line is necessary for correct timing of the
Y + SYNC signal with the chrominance signal. The output
resistor of the delay line is connected to V_REF (pin 13). The
output of the external delay line is connected to (input)
pin 20.
The Y +SYNC (delayed) input signal at pin 20 is amplified
via a buffer to a level of 2 V (peak-to-peak) nominal and
connected to pin 19 (Y + SYNC output).
The Y + SYNC (delayed) input signal at pin 20 is also
connected via an internal resistor of 2 kΩ to the input of the
CVBS adder stage. After the internal resistor of 2 kΩ, and
before the input of the CVBS adder, an external notch filter
can be connected via pin 18.
The chrominance output of the bandpass filter is added
with Y +SYNC signal via the CVBS adder. The CVBS
(combined video and blanking signal) output of the adder
is connected to pin 16 with a nominal amplitude of 2 V
(peak-to-peak).
The chrominance output of the bandpass filter is amplified
via a buffer and connected to pin 14. The chrominance
amplitude corresponds with the value of Y + SYNC signal
output at pin 19. Together both outputs give the
Y +C (SVHS) signals.
BLACK AND BLANKING LEVELS IN PAL AND NTSC MODES
PAL mode: Fig.9 illustrates the nominal Y + SYNC signal
at pin 22, the difference between black and blanking level
is 0 mV.
NTSC mode: Fig.10 illustrates the nominal Y + SYNC
signal at pin 22, the difference between black and blanking
level is 53 mV.
Because of the difference between the black and blanking
level in the NTSC mode, there are two options for NTSC.
(1) frequency response.
(2) group delay.
Fig.8 Band pass filter nominal frequency/group
delay response (NTSC mode).
April 1993
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