onsemi H22B1

Overview

H22B1 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; it delivers 0.5 mA on-state collector current at 2 mA input, 1.0 V saturation voltage, and 45 µs turn-on time for position sensing in mechanical encoders.

For engineers reviewing the H22B1 datasheet, pinout, applications, or equivalent options, key selection criteria include its 30 V V_CEO, -55°C to +100°C operating temperature range, opaque housing for ambient light rejection, and mechanical gap-based switching architecture requiring physical interruption.

Technical Context

The H22B1 operates as a through-beam optical interrupter: infrared light from the GaAs emitter is detected by the integrated photodarlington, which provides high DC current gain (I_C(ON) = 0.5 mA @ I_F = 2 mA) and open-collector output behavior. Its photodarlington structure enables direct interface with TTL/CMOS logic without external amplification.

It features a fixed 0.035" aperture gap optimized for mechanical resolution and ambient light rejection; electrical isolation between input and output exceeds 5000 V_RMS (per Fairchild's standard test protocol for this family), and thermal derating begins at 25°C with 1.67 mW/°C linear power reduction.

Key Specifications

Pinout & Package

Package: 4-pin DIP plastic housing with 0.3" row spacing and 0.1" pin pitch; body dimensions 0.433" × 0.249" × 0.110" (11.0 mm × 6.35 mm × 2.8 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with H22B1, LTH-1550 trades current gain for speed and requires higher input drive, while TCST2103 offers footprint reduction but lacks the H22B1's 30 V V_CEO margin and extended temperature range - making H22B1 preferable for industrial 24 V control and wide-temperature deployments.

Availability

H22B1 is available at Aetrix Electronics and suitable for industrial limit switches, rotary encoders, printer jam detection, and automotive throttle position sensing requiring stable component supply across long production lifecycles.

Supply support for H22B1 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; known for high-reliability optocouplers and power management ICs.

The H22B1 belongs to Fairchild's photodarlington optical interrupter family designed specifically for robust, non-contact position and presence sensing in harsh industrial and automotive environments.

FAQ

What is the maximum forward current rating for the H22B1 emitter diode?

The H22B1 emitter has an absolute maximum continuous forward current (I_F) of 50 mA per its datasheet Absolute Maximum Ratings table. Operation above this value risks permanent degradation of the GaAs LED. For typical use, I_F = 2–10 mA is recommended to achieve specified I_C(ON) while maintaining long-term reliability. The H22B1 must always be driven with a series current-limiting resistor.

Does the H22B1 require an external pull-up resistor on its output?

Yes, the H22B1 output is an open-collector photodarlington configuration - Pin 3 (collector) must be pulled up to a positive supply (e.g., 5 V or 24 V) via an external resistor to generate a valid logic HIGH signal. The value depends on load current and speed requirements; 1–10 kΩ is typical. Without this resistor, the H22B1 cannot assert a HIGH state, and the output remains floating or LOW.

What is the isolation voltage rating of the H22B1?

The H22B1 provides 5000 V_RMS input-to-output isolation, as confirmed by Fairchild's standard safety testing protocol for this photointerrupter family. This rating applies to the internal dielectric barrier between the GaAs emitter and silicon photodarlington, enabling safe interfacing between low-voltage control circuits and higher-voltage industrial loads - a critical specification for the H22B1 in PLC and motor-control applications.

Can the H22B1 operate reliably at 100°C ambient temperature?

Yes, the H22B1 is fully rated for continuous operation from -55°C to +100°C ambient temperature. However, power dissipation must be derated linearly at 1.67 mW/°C above 25°C. At 100°C, the maximum allowable power dissipation drops to ~125 mW (combined emitter + detector). Thermal design must ensure junction temperatures remain within limits - confirming this behavior is essential for H22B1 deployment in under-hood automotive or enclosed motor-drive applications.

How does the H22B1 differ from the H22B2 and H22B3 variants?

The H22B1, H22B2, and H22B3 share identical packaging, pinout, and absolute maximum ratings, but differ in coupled current transfer ratio: H22B1 delivers ≥0.5 mA I_C(ON) at I_F = 2 mA, H22B2 ≥1.0 mA, and H22B3 ≥2.0 mA. This grading allows designers to select the appropriate gain variant based on drive capability and noise immunity needs - the H22B1 is optimized for low-power microcontroller drive, while H22B3 suits noisy industrial environments requiring higher output margin.