Load Short-Circuit Protection And Line Disconnection Detection For Cj-Series Basic I/O Units; A-4-1 Load Short-Circuit Protection And Line Disconnection Detection For Cj1W-Od202 - Omron NJ501-1 Series User Manual

Appendices
A-4 Load Short-circuit Protection and
Line Disconnection Detection for CJ-
series Basic I/O Units
A-4-1 Load Short-circuit Protection and Line Disconnection Detection
for CJ1W-OD202
This section describes the load short-circuit protection and line disconnection detection of the CJ1W-
OD202 Output Units.
As shown below, normally when the output bit (OUT) turns ON, the transistor will turn ON and then out-
put current (Iout) will flow.
Figure 1 Normal Operation
ON
OUT
OFF
ON
I
OUT
OFF
ON
ERR
OFF
If the output current (Iout) exceeds the detection current (Ilim) when an overload or short-circuit occurs,
the output current (Iout) will be limited as shown in figure below. When the junction temperature (Tj) of
the output transistor reaches the thermal shutdown temperature (Tstd), the output will turn OFF to pro-
tect the transistor from being damaged, and the alarm output bit will turn ON to light the ERR indicator.
When the junction temperature (Tj) of the transistor drops down to the reset temperature (Tr), the ERR
indicator will be automatically reset and the output current will start flowing.
Figure 2 Operation for Overload or Short Circuit
ON
OUT
OFF
I
lim
ON
I
OUT
OFF
ON
ERR
OFF
If the line is disconnected and the output current (Iout) drops below the line disconnection detection cur-
rent (IOL), the ERR indicator will light as shown in the following figure.
A-96
OUT: Output bit
I
OUT
ERR: Alarm output, ERR indicator
I
lim
I
OL
T
T
T
Tj =Tstd Tj =Tr
: Output current
: Short-circuit detection current
: Disconnection detection current
: Junction temperature of transistor
j
: Thermal shutdown temperature
std
: Reset temperature
r
NJ-series CPU Unit Hardware User's Manual (W500)