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Isolated Input

Specification of the isolated GPIO input ports

Simplified schematic

The input port implements an isolated current-sense input.

DC characteristics

Parameter Conditions Min. Typ. Max. Units
Differential voltage   -30   +30 V
Input current threshold     1   mA
Differential voltage @1 mA 1.5 1.65 1.9 V
Input current @(VIN+ - VIN-) = 1.65 V   1   mA
@(VIN+ - VIN-) = 2.5 V   2   mA
@(VIN+ - VIN-) = 5 V   2.3   mA
@(VIN+ - VIN-) = 12 V   3   mA
@(VIN+ - VIN-) = 30 V     5 mA
@(VIN+ - VIN-) < 1 V     10 µA
DC isolation voltage   250     V
AC isolation voltage   170     VRMS
Input Current vs. Input Voltage Characteristics

AC characteristics

Parameter Min. Typ. Max. Units
Pulse width 10     µs
Pulse rate 0   50 kHz

Logical map

The state of the port is reported as follows:

Input currentLogical State
IIN > 1 mAHIGH
IIN < 1 mALOW
Unconnected input portLOW

Compatible drivers and receivers

The following drivers are compatible with the isolated current-sense inputs:

  • Totem-pole LVTTL, TTL, 5 V CMOS drivers
  • RS-422 Differential line drivers
  • Potential free contact, solid-state relay, or opto-isolators
  • 12 V and 24 V signaling voltages are also accepted

Note: The +12 V power supply on the I/O connector(s) can be used for powering drivers requiring a power supply.
Note: No external resistors are required. However, to obtain the best noise immunity with 12 V and 24 V signaling, it is recommended to insert a series resistor in the circuit. The recommended resistor values are: 4.7kOhms for 12 V signaling and 10kOhms for 24 V signaling.