January 1995

31

Philips Semiconductors

Objective specification

processor

TDA8366

22. The timing pulses for the vertical ramp generator are obtained from the horizontal oscillator via a divider circuit. This

divider circuit has 3 modes of operation:

a) Search mode ‘large window’.

This mode is switched on when the circuit is not synchronized or when a non-standard signal (number of lines per

frame in the 50 Hz mode is between 311 and 314 and in the 60 Hz mode between 261 and 264). In the search mode

the divider can be triggered between line 244 and line 361 (approximately 45 to 64.5 Hz).

b) Standard mode ‘narrow window’.

This mode is switched on when more than 15 succeeding vertical sync pulses are detected in the narrow window.

When the circuit is in the standard mode and a vertical sync pulse is missing the retrace of the vertical ramp generator

is started at the end of the window. Consequently, the disturbance of the picture is very small. The circuit will switch

back to the search window when, for 6 successive vertical periods, no sync pulses are found within the window.

c) Standard TV-norm (divider ratio 525 (60 Hz) or 625 (50 Hz).

When the system is switched to the narrow window it is checked whether the incoming vertical sync pulses are in

accordance with the TV-norm. When 15 standard TV-norm pulses are counted the divider system is switched to the

standard divider ratio mode. In this mode the divider is always reset at the standard value even if the vertical sync

pulse is missing.

When 3 vertical sync pulses are missed the system switches back to the narrow window and when also in this

window no sync pulses are found (condition 3 missing pulses) the system switches over to the search window.

The vertical divider needs some waiting time during channel-switching of the tuner. When a fast reaction of the

divider is required during channel-switching the system can be forced to the search window by means of the NCIN bit

in subaddress 08.

23. Conditions: frequency is 50 Hz; normal mode; VS = 1F.

24. At a chrominance input voltage of 660 mV (p-p) (colour bar with 75% saturation i.e. burst signal amplitude

300 mV (p-p)) the dynamic range of the ACC is +6 and

−20 dB.

25. All frequency variations are referenced to 3.58 or 4.43 MHz carrier frequency.

All oscillator specifications are measured with the Philips crystal series 9922 520.

If the spurious response of the 4.43 MHz crystal is lower than

−1 dB with respect to the fundamental frequency for a

damping resistance of 1 k

Ω, oscillation at the fundamental frequency is guaranteed.

The spurious response of the 3.58 MHz crystal must be lower than

−1 dB with respect to the fundamental frequency

for a damping resistance of 1.5 k

Ω.

The catching and detuning range are measured for nominal crystal parameters. These are:

off chip.

Philips Components has developed a special crystal which is tuned to the correct frequency in an application without

series capacitance (code number 9922 520 0038X; see Table 43). This has the advantage that the tuning (catching)

range is increased with approximately 50% without negative effects on spurious responses. When the catching range

of 300 Hz is considered too low this special crystal is a suitable alternative.

condition the colour killer is not active so that the frequency off-set is visible on the screen. When two crystals are

connected to the IC the circuit must be forced to one of the crystals during this test to prevent the oscillator switching

continuously between the two frequencies.