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PRELIMINARY
3.2.3 TTL Trigger Source
If the external trigger source is a TTL level, the signal needs to be converted to a LVDS
signal before sending it to the camera. An example of this circuit is illustrated below:
EXSYNC +
EXSYNC -
EXT. TRIGGER
U1
SN65LVDS3487/SO
5
6
8 13
14
16
2
3
10
11
1
7
9
15
4
12
DO2-
DO2+
GND DO4-
DO4+
VCC
DO1+
DO1-
DO3+
DO3-
DI1
DI2
DI3
DI4
EN1/2
EN3/4
+3.3
C1
.1uF
TTL TRIGGER SOURCE
J5
DSUB 15-P
4
12
3.4 Frame Grabber Receives Trigger
When using the frame grabber to provide an EXSYNC to the camera, the frame grabber
receives the external trigger source and it generates the EXSYNC. The EXTERNAL
TRIGGER input signal will depend on what brand of frame grabber is used to interface to
the camera. Consult the manufacturer’s data sheet for the available types of signal level.
The following illustration shows the EXSYNC connection between the National Instrument’s
frame grabber and the camera control input DB15 connector. The frame grabber receives
the TTL external trigger on pin 95 and generates an EXSYNC (LVDS level) on pins 33 and
pin 34. This signal is then sent to the camera via twisted pair wires.
In order to have the frame grabber generate EXSYNC signal, some software programming
using National Instrument’s Labview application software is required.
This circuit is illustrated on the following page.
Fairchild Imaging • CAM/CCD-2KLV.TDI & CAM/CCD-4KLV.TDI Line Scan Camera User’s Manual • Rev 073004 • 19 of 38