onsemi H22B2

Overview

H22B2 from Fairchild Semiconductor is a photodarlington optical interrupter switch comprising a GaAs infrared LED coupled to a silicon photodarlington in a plastic housing with 0.035" apertures, rated for 1.0 mA on-state collector current at I_F = 2 mA and V_CE = 1.5 V, 30 V V_CEO, and operating from −55°C to +100°C - used in position sensing and object detection in industrial encoders and printer paper-path monitors.

For engineers reviewing the H22B2 datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed I_C(ON) performance across temperature, mechanical aperture tolerance (±0.010"), saturation voltage under load, ambient light rejection via opaque housing, and compatibility with standard 750 Ω pull-up configurations.

Technical Context

The H22B2 operates as a current-transfer device where infrared emission from the GaAs diode optically triggers the silicon photodarlington output stage, delivering high DC current gain without external biasing. Its open-collector photodarlington output provides direct interface to TTL/CMOS logic with V_CE(SAT) ≤ 1.0 V at I_F = 10 mA and I_C = 1.8 mA.

Designed for mechanical interrupt detection, the H22B2 features a fixed 0.035" gap between emitter and detector, enabling precise edge-triggered switching when an opaque flag passes through. Ambient light rejection is achieved via molded opaque housing and spectral filtering inherent to the GaAs/silicon pairing.

Key Specifications

Pinout & Package

Package: 4-pin DIP plastic housing with side-entry optical gap; dimensions 0.472" × 0.249" × 0.125" (12.0 × 6.35 × 3.2 mm), lead pitch 0.100".

Key Features

Applications

Equivalent & Alternatives

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

Compared with H22B1 and H22B3, the H22B2 delivers optimal balance of sensitivity, speed, and thermal stability - making it the default choice for general-purpose industrial interrupt detection where 1 mA output drive and 250 µs turn-off meet timing requirements.

Availability

H22B2 is available at Aetrix Electronics and suitable for industrial encoder position sensing, printer paper path detection, automotive throttle position feedback, and conveyor belt object counting requiring stable component supply and long-term lifecycle continuity.

Supply support for H22B2 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 power IC manufacturer acquired by ON Semiconductor in 2016; known for high-reliability optocouplers and discrete power devices.

The H22B2 belongs to Fairchild's legacy photodarlington optical interrupter family, designed specifically for robust mechanical position and presence detection in cost-sensitive industrial and office equipment.

FAQ

What is the maximum continuous forward current rating for the H22B2 emitter LED?

The H22B2 emitter has a maximum continuous forward current (I_F) rating of 50 mA at T_A = 25°C. Derating applies above 25°C at 1.67 mW/°C. This rating ensures long-term reliability of the GaAs infrared diode while supporting pulsed operation up to 60 mA for improved signal-to-noise ratio in noisy environments. Always use a series current-limiting resistor sized for the target I_F and supply voltage when driving the H22B2.

Does the H22B2 require an external base connection for the photodarlington output stage?

No, the H22B2 photodarlington output stage is internally connected - no external base terminal is provided or required. Pin 3 is the collector and Pin 4 is the emitter; the device functions as a two-terminal photosensitive switch with open-collector output. This simplifies PCB layout and eliminates base biasing complexity, making the H22B2 compatible with standard logic-level pull-up configurations without additional components.

What is the guaranteed minimum on-state collector current for H22B2 at elevated temperature?

The H22B2 guarantees I_C(ON) ≥ 1.0 mA at I_F = 2 mA and V_CE = 1.5 V at 25°C, and Figure 2 shows normalized output current remains ≥85% at +75°C and ≥70% at +100°C. Therefore, minimum usable I_C(ON) at +100°C is approximately 0.7 mA - sufficient to drive standard 750 Ω pull-ups to valid logic LOW in most industrial control interfaces using the H22B2.

Can the H22B2 be used with a 24 V supply on the collector side?

Yes, the H22B2 supports V_CEO = 30 V, allowing safe operation with 24 V collector supplies when used with an appropriate pull-up resistor. Ensure the series resistor limits peak collector current to ≤40 mA (absolute max), and verify power dissipation in both the H22B2 (P_D ≤ 150 mW at T_C = 25°C) and the resistor under worst-case ON-state conditions. The H22B2 is commonly deployed in 24 V PLC input modules and industrial sensors.

How does the 0.035" aperture dimension affect mechanical design of the H22B2 mounting fixture?

The 0.035" (0.89 mm) aperture defines the physical gap between emitter and detector windows and sets the mechanical resolution limit for flag-based detection. Mounting fixtures must align the moving flag within ±0.005" lateral tolerance to ensure consistent interruption; wider flags (>0.045") guarantee full beam blockage, while narrower flags require tighter positional control. This dimension is critical when designing encoder wheels or paper-path levers intended for use with the H22B2.