onsemi CNY29

Overview

CNY29 from Fairchild Semiconductor is a photodarlington optical interrupter switch comprising a GaAs infrared LED emitter and a silicon photodarlington detector in a single 4-pin DIP plastic housing with 0.1" pin spacing and 0.133" aperture diameter. It delivers 2.5 mA on-state collector current at 20 mA input, 1.2 V saturation voltage, and 150 µs turn-on/turn-off times, used for position sensing in mechanical encoders and tape detection systems.

For engineers reviewing the CNY29 datasheet, pinout, applications, or equivalent options, key selection considerations include its 25 V BV_CEO, 7 V BVE_CO, 100 °C max operating temperature, opaque housing with 0.035" apertures, and compatibility with standard 0.1" pitch PCB layouts for industrial motion control interfaces.

Technical Context

The CNY29 integrates an infrared GaAs LED (λ_P ≈ 940 nm) optically coupled across a fixed air gap to a silicon NPN photodarlington output stage. Its photodarlington architecture provides high DC current gain (I_C(ON)/I_F ≈ 125 at I_F = 20 mA), enabling low-input-current switching with minimal external drive circuitry.

It operates as a digital optical interrupter: incident IR light triggers conduction between collector and emitter; interruption by opaque objects forces the output into cutoff. The device features 30 V V_CEO, 6 V V_ECO, and 100 nA I_CEO at 10 V, supporting reliable open-collector logic-level interfacing in noisy industrial environments.

Key Specifications

Pinout & Package

Package: 4-pin dual-in-line (DIP) plastic housing with 0.1" (2.54 mm) pin pitch, opaque black body, and side-entry optical path through 0.035" diameter apertures aligned between pins 1–2 (emitter) and 3–4 (detector).

Key Features

Applications

Equivalent & Alternatives

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

Compared with H11AA1 and PC817X, the CNY29 uniquely combines self-contained interrupter geometry, photodarlington sensitivity, and industrial temperature range-making it optimal for cost-sensitive, mechanically constrained encoder and flag-sensing roles where ambient light immunity and low-drive capability are critical.

Availability

CNY29 is available at Aetrix Electronics and suitable for rotary encoders, tape detection systems, and shaft speed monitoring requiring stable component supply, long-term lifecycle support, and traceable sourcing for industrial automation OEMs.

Supply support for CNY29 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 optoelectronics and power management solutions.

The CNY29 belongs to Fairchild's legacy photointerrupter product line, designed specifically for robust, low-cost position and presence sensing in industrial motion control and electromechanical systems.

FAQ

What is the maximum continuous forward current rating for the CNY29 emitter?

The CNY29 emitter has a maximum continuous forward current (I_F) rating of 50 mA per the Absolute Maximum Ratings table. Operation at 20 mA is typical for reliable long-life performance while delivering 2.5 mA output current. Derating is not required below 25 °C, but thermal management becomes critical above that ambient due to 1.67 mW/°C power dissipation derating slope.

Does the CNY29 require external biasing or pull-up resistors?

Yes, the CNY29 requires an external pull-up resistor on the collector (PIN 3) to establish a defined logic-high state when the photodarlington is off. A typical value is 4.7 kΩ for 5 V systems, yielding ~1 mA quiescent current. No base biasing is needed-the photodarlington is fully self-contained, and the CNY29 internal structure eliminates external base connections.

Can the CNY29 operate reliably at 100 °C ambient temperature?

Yes, the CNY29 is rated for operation from −55 °C to +100 °C per its Absolute Maximum Ratings. At 100 °C, its normalized output current drops to ~60% of 25 °C value (per Figure 2), and V_CE(SAT) increases slightly (per Figure 3), but remains within specification. Derating of input current may be applied for extended lifetime at max temperature.

What is the optical center wavelength and spectral response of the CNY29?

The CNY29 uses a gallium arsenide (GaAs) infrared LED emitter with peak emission at approximately 940 nm. The silicon photodarlington detector has peak responsivity near 850 nm and usable response from 400 nm to 1100 nm, optimized for coupling with the emitter's output spectrum. This matched pair ensures high effective coupling efficiency and rejection of visible ambient light.

Is the CNY29 RoHS compliant and lead-free?

The original CNY29 datasheet (DS300282, 2001) predates RoHS legislation and does not specify RoHS status. Legacy Fairchild CNY29 units were manufactured with leaded solder and may contain Pb in terminations and mold compound. For RoHS-compliant alternatives, consult ON Semiconductor's updated photointerrupter portfolio or verify current manufacturing lot documentation with Aetrix Electronics.