Omron CS1D DUPLEX SYSTEM - 10-2009 Operation Manual page 535

Specifications of Basic I/O Units and High-density I/O Units
Load Short-circuit Protection
CS1W-OD212/OD232/OD262/MD262
As shown below, normally when the output bit turns ON (OUT), the transistor will turn ON and then output cur-
rent (Iout) will flow. If the output (Iout) is overloaded or short-circuited exceeding the detection current (Ilim), the
output current (Iout) will be limited as shown in Figure 2 below. When the junction temperature (Tj) of the output
transistor reaches the thermal shutdown temperature (Tstd), the output will turn OFF to protect the transistor
from being damaged, and the alarm output bit will turn ON to light the ERR indicator. When the junction tem-
perature (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 1: Normal Condition
ON
OUT
OFF
ON
I
OUT OFF
ON
ERR
OFF
Figure 2: Overload or Short-circuit
Operating Restrictions for the CS1W-OD212/OD232/OD262/MD262
Although the CS1W-OD212/OD232/OD262/MD262 are provided with short-circuit protection, these are for pro-
tecting internal circuits against momentary short-circuiting in the load. As shown in Figure 2 below, the short-
circuit protection is automatically released when the Tj equals to Tr. Therefore, unless the cause of short-circuit
is removed, ON/OFF operations will be repeated in the output. Leaving short-circuits for any length of time will
cause internal temperature rise, deterioration of elements, discoloration of the case or PCBs, etc. Therefore,
observe the following restrictions.
Restrictions
If a short-circuit occurs in an external load, immediately turn OFF the corresponding output and remove the
cause. The CS1W-OD212/OD232/OD262/MD262 turn ON an alarm output bit that corresponds to the external
load output number. There is an alarm output bit for every common.
When an alarm output bit turns ON, use a self-holding bit for the alarm in the user program and turn OFF the
corresponding output.
The alarm output bit is allocated in the Basic I/O Unit Information Area (A050 to A089) for every Unit mounting
slot.
The following table shows the correspondence between output bits and bits in the Basic I/O Unit Information
Area.
Output bit
CS1W-OD212 Mounted in even slot
Mounted in odd slot
OUT: OUTPUT instruction
I : Output current
OUT
ERR: Alarm output, ERR indicator
I : Detection current
lim
Tj: Junction temperature of transistor
Tstd: Thermal shutdown temperature
Tr: Reset temperature
ON
OUT
OFF
Tj =Tstd Tj =Tr
I
lim
ON
I
OUT OFF
ON
ERR
OFF
m
0 to 7 8 to 15
0 1
8 9
m+1 m+2
0 to 15 0 to 15
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Appendix A
m+3
0 to 15
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