onsemi H22A4

Overview

H22A4 from Fairchild Semiconductor is a slotted optical switch with phototransistor output, designed for object detection and position sensing in industrial and consumer equipment. It features a 0.125-inch wide slot, 70% minimum current transfer ratio (CTR), 30 V collector-emitter breakdown voltage, and operates across -40°C to +85°C ambient temperature.

For engineers reviewing the H22A4 datasheet, pinout, applications, or equivalent options, key selection considerations include slot width tolerance, CTR stability over temperature, dark current specification, and compatibility with 5 V logic-level interfacing circuits.

Technical Context

The H22A4 integrates an infrared LED emitter and NPN silicon phototransistor in a single molded package with a fixed 0.125-inch gap. Detection occurs when an opaque object interrupts the optical path, causing phototransistor conduction to cease. The device operates in DC-coupled mode with no internal signal conditioning.

It requires external current-limiting on the anode side and load resistance on the collector side. No internal hysteresis or Schmitt-trigger functionality is present - output state transitions are determined solely by optical coupling efficiency and bias conditions.

Key Specifications

Pinout & Package

Package: 4-pin DIP (dual in-line package) with through-hole mounting and integrated slot geometry. Body width accommodates standard PCB slot-cutting tooling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar slotted optical switch applications.

Compared with H22A4, ELCSL813 offers superior mechanical stability but reduced slot clearance, while TCST1103 provides higher CTR and identical footprint - both require validation of dark current and thermal derating in target enclosure conditions.

Availability

H22A4 is available at Aetrix Electronics and suitable for printer paper detection, industrial limit switching, automated vending machine validation, and conveyor belt object counting requiring stable component supply and long-term obsolescence management.

Supply support for H22A4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Fairchild Semiconductor was a U.S.-based analog and discrete semiconductor manufacturer, acquired by ON Semiconductor in 2016. Its legacy optocoupler and optoswitch portfolio remains widely deployed in industrial control systems.

The H22A4 belongs to Fairchild's slotted optical switch family, engineered for cost-sensitive, high-reliability object-sensing tasks in electromechanical systems where precise mechanical alignment is impractical.

FAQ

What is the maximum forward current rating for the H22A4 LED emitter?

The H22A4 LED emitter has an absolute maximum forward current rating of 60 mA. Continuous operation above 10 mA requires thermal consideration; typical design uses 10–20 mA with appropriate series resistance. Exceeding 60 mA risks irreversible LED degradation. The H22A4 datasheet specifies derating curves for ambient temperatures above 25°C, and all designs must respect the 60 mA limit to ensure H22A4 reliability over its intended service life.

Does the H22A4 include built-in hysteresis or signal conditioning?

No, the H22A4 does not include hysteresis, Schmitt-triggering, or any internal signal conditioning. It is a basic DC-coupled phototransistor-output slotted switch. Output state depends directly on optical coupling and external bias conditions. System-level noise immunity must be achieved via external RC filtering, comparator hysteresis, or firmware debouncing. This behavior is consistent across all documented H22A4 test data and applies identically to every unit of the H22A4.

Can the H22A4 operate from a 3.3 V supply on the collector side?

Yes, the H22A4 phototransistor can operate with a 3.3 V collector supply, provided the load resistor is selected to ensure sufficient saturation voltage margin (typically <0.4 V). At 3.3 V, the 30 V V_CEO rating provides ample headroom. However, CTR performance must be verified at lower V_CE; the H22A4 maintains usable gain down to 2 V, making it compatible with 3.3 V logic interfaces when properly biased.

What is the typical dark current specification for the H22A4 at room temperature?

The H22A4 has a maximum dark current of 100 nA at V_CE = 20 V and T_A = 25°C. Typical values are below 10 nA under these conditions. Dark current increases with temperature and collector-emitter voltage - at 85°C and 20 V, it may reach 500 nA. This parameter directly impacts false-trigger risk in high-impedance pull-up configurations and must be accounted for in H22A4 system-level noise budgets.

Is the H22A4 RoHS compliant and lead-free?

Yes, the H22A4 was manufactured in RoHS-compliant, lead-free versions prior to Fairchild's acquisition by ON Semiconductor. Legacy production lots meet EU RoHS Directive 2011/65/EU requirements, with lead content below 0.1% by weight. Aetrix Electronics supplies only RoHS-compliant H22A4 units, and full material declarations are available upon request for the specific H22A4 batch received.