Specifications

2–28 Selecting Your Hardware Components
Publication 1747-6.2
To reduce the possibility of inadvertent operation of devices
connected to transistor outputs, adhere to the following guidelines:
• Either ensure that any programmable device connected to the
transistor output is programmed to ignore all output signals until
after the transient pulse has ended,
• or add an external resistor in parallel to the load to increase the
on-state load current. The duration of the transient pulse is
reduced when the on-state load current is increased.
The duration of the transient pulse is proportional to the load
impedance. This is illustrated in the following graph.
0
On-State Load Current (mA)
1000
1
2
3
4
5
6
7
8
9
10
1 100 200
300
400 500 600 700 800 900
Duration of Transient (ms)
Time
Example
Increasing the load current by 100 mA decreases the transient time
from approximately 7 ms to less than 2.5 ms. To calculate the size of
the resistor added in parallel to increase the current, use the
following information:
R (Ohms)
V (Volts)
I (Amps)
Resistor value (Ohms) = Applied voltage (Volts) / Desired current (Amps)
= 24 / 0.1 = 240 (Ohms)
P (Watts) = I
2
(Amps) x R (Ohms)
Actual Power (Watts) = (Desired Current)
2
x Resistor Value
Resistor size = 2 x Actual power (Watts) = 4.8W ≅ 5W
=
24V = your applied voltage
Need 100 mA of load current to reduce the transient to < 2.5 ms. (taken from graph above)
= (0.1)
2
x 240 = 2.4 (Watts)
Use a resistor rated for 240 Ohms at 5 Watts to decrease the transient
time from approximately 7 ms to less than 2.5 ms.