TLC5733A

20 MSPS 3CHANNEL ANALOGTODIGITAL CONVERTER

WITH HIGHPRECISION CLAMP

SLAS104B − JULY 1995 − REVISED FEBRUARY 2001

9

POST OFFICE BOX 655303

detailed description (continued)

timing error of COMPOSITE SYNC

The internal counter resets to zero on the first falling edge of COMPOSITE SYNC. After that time, if there is a

missing COMPOSITE SYNC signal, then the internal logic waits an interval of 76 clocks (interval E) for NTSC

or 93 for PAL from the counter zero count and then generates an internal clamp pulse 54 clocks wide

(interval F).

This function maintains the synchronization pattern when COMPOSITE SYNC is not present.

summary of device operation with COMPOSITE SYNC

This internal timing allows the TLC5733A to correctly position the clamp pulse when an external COMPOSITE

SYNC input:

The device operation is summarized as follows for these improper external clamp conditions:

the proper time after the horizontal sync period as shown in Figure 1.

interval that the COMPOSITE SYNC input is missing.

1H

Missing COMPOSITE SYNC,

therefore, Noise Gate is Not

Generated

B

A

C

F

D

F

E

NTSC/PAL Counter Reset

NTSC/PAL Counter at

Max Count

COMPOSITE

SYNC

Noise Gate 1

Noise Gate 2

Internal Clamp

Pulse

Figure 1. COMPOSITE SYNC and Internal Clamp Timing