Takes a 24 V industrial field signal and turns it into a clean logic level for a controller, meeting the IEC 61131-2 Type 1, 2, and 3 digital-input specs so it behaves like a proper PLC input. A single external resistor sets the input current threshold, which cuts the power that a resistor-divider input would burn, and the input has defined switching thresholds and hysteresis for noisy field wiring. It pairs with an isolator for a fully isolated channel. A building block for PLC and industrial I/O modules.

Pinout

Pin	Name	Type	Function
1	VCC1	power_in	Power supply, side 1 (logic/controller side). Operating range 2.25V to 5.5V; supports 2.5V, 3.3V, and 5V controllers. Absolute max 6V.
2	EN	input	Output enable. OUT is enabled when EN is high or open; OUT is high-impedance when EN is low. In noisy applications, tie EN to VCC1.
3	OUT	output	Channel output (logic-side digital output representing the field-side input state). Push-pull, referenced to VCC1/GND1. IOH up to -4mA (VCC1=5V); IOL up to 4mA (VCC1=5V).
4	GND1	power_in	Ground connection for VCC1 (logic/controller side ground reference).
5	SUB	passive	Internal connection to input chip substrate. For good thermal performance, connect this pin to a small 2mm x 2mm floating plane on the board. Do NOT connect this floating plane to FGND or any other signal or plane.
6	FGND	power_in	Field-side ground reference for the isolated field input.
7	IN	input	Field-side current input. Accepts 9V to 300V DC/AC digital input signals through an external current-limit resistor; ±60V absolute rating with reverse polarity protection.
8	SENSE	input	Field-side voltage sense pin. Used together with IN pin and external resistors to set the accurate current limit for IEC 61131-2 Type 1/2/3 compliance. Minimum pulse width at SENSE is 150ns.

Key specifications

Parameter	Value
Type	Digital-input receiver (24 V field)
Standard	IEC 61131-2 Type 1 / 2 / 3
Current setting	Single external resistor
Input	Defined thresholds + hysteresis
Output	Logic level (OUT)
Supply	2.25-5.5 V (logic side)
Package	SOIC-8

Ordering variants

Same part, different packaging or reel option.

ISO1211DR (SOIC-8)
ISO1212DR (dual channel)

CAD (KiCad official)

Symbol: Isolator:ISO1211 (KiCad official)
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (47 pp, sha256 41e0bc7308dd4e0c, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF