Teledyne SP Devices ADQ7DC, Manual

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19-2233 PC2
2019-02-01
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ADQ7DC Manual
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4.7.2 External trigger SYNC connector
The block diagram for the SYNC input is shown in Figure 12 and related parameters are listed in
Table 3 . The user can control the SYNC function for adapting it to the system in the following ways:
• The input impedance can be set in 50

(default) or high impedance mode, see Section 4.7.3 .
• Configure the threshold level.
• Set the trigger edge to rising or falling to adjust to the polarity of the trigger signal.
4.7.3 Driving the external TRIG/SYNC signal by controlling input impedance
The TRIG/SYNC input impedance is by default 50

. The trigger is optimized for systems where the
trigger source output impedance is 50

and the cables has a characteristic impedance of 50

. This
setup results in an optimal high-frequency response and low reflections, which is important for precise
timing.
However, in a high fan-out situation, where a trigger source has to drive many nodes, the load can be
too high. The trigger input can then be set in a high impedance mode and a bussed connection can be
used,
Figure 13 . In Figure 13 (a) an external source is driving the array of ADQ digitizers. In Figure 13
(b) one of the ADQ digitizer is used as a master and is driving signals to the array of ADQ digitzers.One
has to be careful with the trigger distribution network to handle the reflections. If the trigger is periodic,
reflections are less critical and can be handled. For more information on reflections, see application
note
[9] .
# DESCRIPTION USER COMMAND REF
a The input is available on an SMA connector on the front panel.
b The input impedance can be set as 50 ohm (default) or high
impedance. SetTriggerInputImpedance 4.7.3
c The trigger threshold is 0.5 V (default) and user-controlled. SetExtTrigThreshold
d High speed comparator.
e Select rising or falling edge. SetExternTrigEdge
Figure 12: Using SYNC as trigger input.
"*+
(,
-. /
01 01 01 01 01
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