Version 1.0 rev 14 Aug 2019
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While waiting on the trigger event, the sensor is put into a “continuous global clear”. On detection of the trigger event,
the Global Clear is pulsed to clear the charge from the sensor. The exposure period lasts for the width of the External
Trigger. During the exposure period, a reference frame is read immediately as the system has no method to know how
long the External Trigger will be HIGH. This means that as the exposure time increases the time between the reference
and signal frame increases which results in a increase in the read noise. Please note that separation of the reference and
signal frames is kept to a minimum in modes with a known exposure time. When the external trigger input goes LOW,
the exposure ends by transferring the charge in all pixels simultaneously to the measurement node. A signal frame read
out then begins. The period of the external trigger pulse defines the overall cycle time. If the width of the trigger event is
less than the frame read out time, the falling edge will be missed and a subsequent falling edge will be required to end
the exposure.
Figure 25: Global Shutter External Exposure Triggering.
Table 16: Global Shutter External Exposure Triggering – Timing Parameters.
Parameter
Minimum
Maximum
Exposure (EXT Trig Pulse Width)
1 Frame + 16 Rows
600 s
Cycle Time ( EXT Trig Period)
EXT Trig Pulse Width + 1 Frame + 7
Rows
-
External Delay
1 Row
2 Rows
EXT Trig Pulse Width
1 Frame + 4 Rows
NOTE: Recommended maximum exposure due to read noise dependency.
