Professional IC Distribution & Technical Solutions

ELM611(TA) Manufacturer: EVERLIGHT

Specifications:

• Type: Infrared Emitting Diode (IR LED)
• Wavelength: 940 nm (typical)
• Forward Voltage (Vf): 1.35 V (typical at 20 mA)
• Forward Current (If): 50 mA (maximum)
• Radiant Intensity (Ie): 20 mW/sr (minimum at 20 mA)
• Viewing Angle: 30° (typical)
• Package Type: 3 mm (T-1) through-hole LED
• Operating Temperature Range: -40°C to +85°C
• Storage Temperature Range: -40°C to +100°C

Descriptions:

The ELM611(TA) is a high-efficiency infrared LED designed for applications requiring reliable IR emission. It operates at a peak wavelength of 940 nm, making it suitable for remote control systems, optical sensors, and other IR-based applications. The device features a standard 3 mm T-1 package with a narrow 30° viewing angle for focused emission.

Features:

• High radiant intensity output
• Low forward voltage for energy efficiency
• Wide operating temperature range
• RoHS compliant
• Lead-free and halogen-free

This LED is commonly used in consumer electronics, industrial automation, and communication devices.

(Note: Always refer to the official datasheet for detailed technical parameters and application guidelines.)

# ELM611(TA) Phototransistor: Technical Analysis and Implementation

## Practical Application Scenarios

The ELM611(TA) from EVERLIGHT is a high-sensitivity silicon NPN phototransistor designed for optoelectronic applications. Its primary use cases include:

1. Optical Switching Systems

The component excels in object detection (e.g., vending machines, printers) due to its fast response time (t_r/t_f ≈ 15μs). Its 940nm peak sensitivity aligns with IR emitter wavelengths, enabling reliable interruption-based sensing.

2. Ambient Light Sensing

In IoT devices and smart lighting, the ELM611(TA) provides analog light-level feedback. Designers leverage its linear current output (I_C ≈ 1–5mA at 10mW/cm²) for adaptive brightness control.

3. Industrial Encoders

The phototransistor’s 60° half-angle sensitivity supports rotary encoder designs where precise alignment is challenging. Its epoxy resin package ensures stability in dusty environments.

## Common Design Pitfalls and Mitigation

1. Saturation in High-Irradiance Conditions

Excessive light exposure drives the transistor into saturation, distorting output signals. *Solution:* Implement a current-limiting resistor (R_L) calculated via:

\[

R_L = \frac{V_{CC} - V_{CE(sat)}}{I_C}

\]

where \(V_{CE(sat)}\) ≈ 0.4V (datasheet value).

2. Electrical Noise Coupling

Long PCB traces between the ELM611(TA) and amplification stages introduce noise. *Solution:*

• Place a 100nF decoupling capacitor near the collector pin
• Use shielded cables for >5cm trace lengths

3. Thermal Drift

The device’s dark current (I_D) doubles per 10°C rise, causing false triggers. *Solution:*

• For precision applications, pair with a temperature-compensated comparator (e.g., LM393)
• Derate maximum operating current by 20% above 50°C

## Key Technical Considerations

1. Spectral Matching

Ensure IR emitter wavelength (e.g., EVERLIGHT’s EL-5mm series) matches the 940nm peak responsivity (λ_p) of the ELM611(TA). Mismatches reduce SNR by up to 60%.

2. Load Resistance Selection

Optimal R_L balances speed and sensitivity:

• High R_L (10kΩ+): Increases voltage swing but slows response
• Low R_L (1kΩ): Improves speed at cost of output amplitude

3. Mechanical Layout

The 3mm lead spacing requires ≥2.5mm creepage distance in high-humidity environments per IPC-2221 standards.

For pulsed operation, stay below the absolute maximum rating of 100mA collector current (I_C) to prevent junction degradation. The 5mW power dissipation limit necessitates heatsinking in continuous-duty applications.

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*Note: All specifications reference EVERLIGHT’s ELM611(TA) datasheet (Rev 1.2, 2023).*