User`s manual

28 Configuring the Agilent E1330B Digital I/O
Chapter 2
Using with External Pull-ups
The Digital I/O module data lines can be used in an open collector
configuration. Connections for open collector require the use of external
power supplies and pull-up resistors. The internal pull-up mode of the
Digital I/O module should be disabled for open collector output. Figure 2-10
shows a single data line connection. The value of the pull-up resistor is
calculated as follows:
The value of TTL high with the 200 Ω pull-up resistor is calculated as
follows:
Figure 2-10. Typical Open Collector Data Line
Vcc 5.0 Vdc=
Imax Iout
Low
safety_factor
×
48mA 0.52
×
25mA===
R
Vcc
Imax
------------
5
0.025
-------------
200Ω== =
V
High
Vcc
6200
6200 200+
---------------------------
× 4.84Vd
c
==