Keithley DAS-4300 Series, Руководство пользователя, Страница: 53 / 94

Configuring the Board 3-19
Figure 3-3. Clock I/O and Trigger I/O Circuitry
Setting the 50
Ω
Termination Resistor for the Trigger Input Signal
The trigger input signal of the Trg IO connector has a jumper-selectable
50
Ω
termination to ground for signals driving long lines or lines that are
driving many devices. Insert a jumper into jumper block J502 to provide
the 50
Ω
termination resistor. The 50
Ω
resistor is provided in the
solderless component jack, R507. By default, the jumper is removed.
Note:
To prevent excessive loading of the signal, do not use the 50
Ω
termination resistor when the board is providing the trigger output signal
on the Trg IO connector.
U515
74ABT125
1
6
J508
4 5 7 8 9 10 3 2
Trigger
In/Out
(TTL)
1
6
J507
4 5 7 8 9 10 3 2
Clock
In/Out
(TTL)
1
2
R501
2.00 k
+5 V
R503
49.9
J500
1
2
1 2
D500
1N4149
+
5 V
1
2
2
1
R502
20
D501 1N4149
2
1
U514
74ABT125
ENEXTCLK-L
U514
74ABT125
9
8
10
1 12
GND
VCC
Out
+
5 V
U514
74ABT125
2 3
1
13
6
U514
74ABT125
Master 100
MHz Clock
ENINTCLK-L
U513
100 MHz
8
7
14
4
5
U515
74ABT125
4
5
6
1
2
3
10
8
9
U515
74ABT125
Trigger Out
ENTRIGOUT-L
Trigger In
J502
1
2
2 1
R507
49.9
R505
20
J501
1
2
2
1
R504
100
+5 V
D502
1N4149
+
5 V
2
1
D503 1N4149
2
1
2
1
+5 V
R506
2.00 k