HSDL-4250 Infrared LED Datasheet - T-1 3/4 Package - Wavelength 870nm - Forward Voltage 1.6V - Power Dissipation 190mW - Technical Documentation

1. Product Overview

HSDL-4250 is a high-performance infrared light-emitting diode designed for applications requiring fast data transmission and reliable optical signals. This device utilizes advanced aluminum gallium arsenide semiconductor technology, aiming to provide high radiant intensity and excellent response speed. Its primary function is to convert electrical signals into modulated infrared light, serving as a transmitter in optical communication links.

The core advantage of this device lies in its combination of high speed and efficient optical output. Fast rise and fall times enable it to support high-data-rate communication protocols. Furthermore, its low forward voltage characteristic is a significant advantage for system design, especially in portable or battery-powered applications where power consumption is critical. It employs the industry-standard T-1 3/4 through-hole package, compatible with common PCB assembly processes.

The target market for this infrared LED is broad, covering consumer electronics and industrial electronics fields. It is a key component for systems requiring wireless, line-of-sight data transmission.

2. Bincike Mai zurfi na Sigogi na Fasaha

This section provides a detailed and objective interpretation of the key electrical, optical, and thermal parameters in the datasheet. Understanding these values is crucial for proper circuit design and reliable operation.

2.1 Halayen Gani

Optical performance defines the effectiveness of an LED as a light source.

• Peak Wavelength (λ_pk):870 nanometers. This places its emission strictly within the near-infrared spectrum, invisible to the human eye but efficiently detectable by silicon photodiodes and other common infrared sensors. The 870nm wavelength offers a good balance between device (detector) availability and atmospheric transmission performance.
• Axial Radiant Intensity (I_E):At a forward current (I_F) of 100mA, the typical value is 180 milliwatts per steradian. This parameter measures the optical power emitted per unit solid angle along the LED's central axis. A higher value indicates a more concentrated and powerful beam, which is crucial for achieving longer transmission distances or stronger signal strength.
• Viewing Angle (2θ_1/2):15 digiri. Wannan shine cikakken kusurwa lokacin da ƙarfin radiation ya ragu zuwa rabin ƙimar axial. Ƙunƙarar haske mai 15 digiri tana da madaidaiciyar alkibla, tana rage yawan rikicewar gani, kuma tana mai da hankali kan makamashi a kan mai karɓar manufa, don haka yana haɓaka sigina zuwa amo, amma yana buƙatar daidaitaccen daidaitawa.
• Faɗin bakan (Δλ):Cikakken faɗin rabin tsayi shine 45 nm. Wannan yana nuna kewayon tsayin raƙuman da LED ke fitarwa kusa da kololuwar tsayin raƙuman sa. Don aikace-aikacen da suke da hankali ga takamaiman tsayin raƙuman, ana fifita ƙunƙuntaccen faɗin bakan.
• Lokacin tashi/faduwar gani (T_r/T_f):40 ns. Wannan shine ma'auni mai mahimmanci na sadarwar dijital. Yana ayyana saurin canjin fitowar haske daga 10% zuwa 90% na ƙarfinsa mafi girma (tashi) da kuma akasin haka (faduwa). Ƙayyadaddun 40ns yana ba shi damar tallafawa ka'idojin canja wurin bayanai mai sauri.
• Ma'aunin zafin ƙarfi (ΔI_E/ΔT):-0.43 %/°C. Wannan ma'auni mara kyau yana nufin cewa ƙarfin fitowar haske yana raguwa yayin da zafin haɗin gwiwa ya ƙaru. Dole ne a yi la'akari da wannan tasiri a cikin sarrafa zafi da ƙirar kewayawa, don tabbatar da daidaiton aiki a cikin kewayon zafin aiki.

2.2 Halayen Lantarki

These parameters determine the LED's electrical interface and power requirements.

• Forward Voltage (V_F):Ranges from 1.4V (min) to 1.9V (max) depending on current. Typical value is 1.6V at 20mA and 1.9V at 100mA. This low voltage is a key feature, reducing the voltage headroom required from the power supply and enabling efficient operation, especially when multiple LEDs are connected in series.
• Series Resistance (R_S):Typical value 2.5 ohms. This internal resistance causes V_Fto increase linearly with current beyond a certain point. This is important for predicting voltage drop under different driving conditions.
• Reverse Voltage (V_R):Maximum 5V. Exceeding this voltage under reverse bias will permanently damage the LED. Circuit protection (such as a series resistor or parallel protection diode) is typically required if reverse voltage conditions are possible.
• Diode Capacitance (C_O):Typical value 75 pF. This parasitic capacitance affects the RC time constant of the drive circuit, thereby limiting the maximum achievable switching speed in extremely high-frequency applications.
• Forward Voltage Temperature Coefficient (ΔV/ΔT):-1.44 mV/°C. The forward voltage decreases as temperature increases. This characteristic can be used for temperature sensing in certain circuits, but primarily indicates that constant current drive is crucial for stable light output, as constant voltage drive leads to increased current with rising temperature (and may cause thermal runaway).

2.3 Matsakaicin Matsakaici na Cikakke da Halayen Zafi

These are the stress limits that must not be exceeded to ensure device reliability and lifetime.

• Continuous Forward Current (I_FDC):Maximum 100 mA.
• Peak Forward Current (I_FPK):500 mA, but only under pulse conditions (20% duty cycle, 100µs pulse width). Pulsing allows higher instantaneous light output without overheating the junction.
• Power Dissipation (P_DISS):190 mW. This is the maximum electrical power that can be converted into heat (and light) without exceeding the maximum junction temperature.
• Junction Temperature (T_J):Maximum 110 °C. The temperature of the semiconductor chip itself must be kept below this limit.
• Junction-to-Ambient Thermal Resistance (R_θJA):300 °C/W. This parameter defines the efficiency of heat transfer from the semiconductor junction to the ambient air. A lower value is better. 300°C/W means that for every watt of power dissipated, the junction temperature will rise by 300°C above the ambient temperature. This highlights the importance of reducing operating current at higher ambient temperatures, as shown in the derating curve (Figure 6 in the original datasheet).
• Storage Temperature:-40 to +100 °C.
• Operating Temperature:-40 to +85 °C.

3. Grading System Description

The provided HSDL-4250 datasheet does not explicitly detail a commercial binning structure for parameters such as wavelength or intensity. In high-volume LED manufacturing, components are typically binned based on measured performance to ensure consistency within a specific order. While not specified here, designers should note that key parameters such as Radiant Intensity (I_E) and Forward Voltage (V_FThere will be a minimum/typical/maximum distribution range. For critical applications, it is recommended to consult the manufacturer for available binning options, or to design circuits that can tolerate the specified parameter ranges.

4. Performance Curve Analysis

The datasheet references several graphs that graphically represent device characteristics. Although the exact curves are not reproduced here, their significance is explained.

• Forward Current vs. Forward Voltage (I-V Curve):This curve (refer to Figure 2, Figure 3) shows the exponential relationship between current and voltage. It is used to determine the drive voltage required for a desired operating current and to understand the influence of series resistance (R_S).
• Derating Curve (Power/Temperature):Figure 6 is crucial for reliable design. It shows how the maximum allowable power dissipation (or forward current) must be reduced as the ambient operating temperature increases. Ignoring this curve may lead to LED overheating and premature failure.
• Relative Intensity vs. Temperature:This indicates a coefficient of -0.43%/°C, showing a linear decrease in light output with increasing temperature.
• Spectral Distribution:Figure 1 will show the shape of the emission spectrum, centered at 870nm with a full width at half maximum of 45nm.
• Angular Distribution Diagram:Figure 7 will describe the angular distribution of the emitted light, defining the beam profile at a half-angle of 15 degrees.

5. Mechanical and Package Information

The HSDL-4250 employs a T-1 3/4 (5mm) radial lead package. Key dimensional specifications in the datasheet include:

• Sai dai idan an faɗi daban, duk ma'aunin girma yana cikin milimita, kuma madaidaicin ƙa'idar girma shine ±0.25mm.
• Matsakaicin fitowar resin a ƙarƙashin flange shine 1.5mm.
• Ana auna tazarar igiyoyin a wurin da igiyoyin suka fita daga jikin encapsulation.
• Encapsulation ya ƙunshi fili ko wasu siffofi don nuna igiyar cathode (negative), yawanci igiya mafi guntu ko kuma igiya mafi kusa da filin flange na ruwan tabarau. A lokacin haɗawa, gano polarity daidai yana da mahimmanci.

Ƙirar ramukan buɗe ido na buƙatar daidaitaccen girman ramin PCB da siffar filaye, don tabbatar da daidaitaccen shigarwa da haɗawa.

6. Soldering and Assembly Guide

Takaddar ƙayyadaddun ta ba da cikakkun bayanai na walda don hana lalacewar zafi:

• Zazzabin walda na igiyoyin haɗi:Igiyoyin haɗi na iya jure zafin 260°C, na tsawon dakika 5. Ana yin wannan ma'auni a nisan milimita 1.6 (0.063 inci) daga jikin kewayon.
• Abubuwan da ake kula da tsarin aiki:Don walda ta guguwa ko walda da hannu, bin wannan lanƙwasa na lokaci da zafi daidai yana da mahimmanci. Yawan zafi ko tsawon lokacin haɗuwa zai narke epoxy na ciki, lalata igiyoyin haɗin gwiwa, ko rage aikin kayan semiconductor.
• Yanayin ajiya:Baya ga kewayon zafin ajiya, ko da yake ba a bayyana shi a sarari ba, LED yakamata a ajiye su a cikin yanayi mai bushewa, mai hana tashin wutar lantarki, don hana ɗaukar danshi (wanda zai iya haifar da "bushewar gasa" a lokacin sake walda) da lalacewa ta hanyar fitar da wutar lantarki.

7. Shawarwarin Aikace-aikace

7.1 Yanayin Aikace-aikace na Al'ada

The datasheet lists several key applications that leverage the LED's high-speed and infrared output characteristics:

• High-Speed Infrared Data Links:Infrared LANs, wireless data transfer between computers and peripherals (e.g., infrared adapters), and modern infrared communication modules. The 40ns rise time supports protocols like IrDA for serial data transmission.
• Portable Infrared Instruments:Devices utilizing active infrared sensing, such as non-contact thermometers, gas analyzers, and distance sensors.
• Consumer Electronics:One very common application is as an emitter in infrared remote controls for televisions, audio systems, and other home appliances. It is also suitable for components in optical computer mice, used to illuminate surfaces for tracking.

7.2 Abubuwan Lura na Ƙira

• Drive Circuit:Always use a series current-limiting resistor. For optimal stability and to prevent thermal runaway, especially when operating near the maximum current or under extreme temperatures, a constant current drive circuit should be considered instead of a simple resistor with a constant voltage source.
• Thermal Management:Due to the relatively high thermal resistance (300°C/W), ensure sufficient airflow or consider heat sinking if operating at high ambient temperatures or high duty cycles. Strictly adhere to the derating curve.
• Optical Design:A narrow 15-degree beam requires careful mechanical alignment with the receiver (photodiode or sensor). Lenses or mirrors can be used to further collimate or shape the beam for specific applications. For remote controls, a wider, more diffuse spot is typically generated by the plastic housing of the remote itself.
• Modulation:For data transmission, the LED is typically driven by a modulated signal (e.g., PWM) at a carrier frequency (such as 38kHz used by many remote controls) to distinguish it from ambient infrared light and improve noise immunity.

8. Kwatancen Fasaha da Bambance-bambance

Compared to standard, lower-speed infrared LEDs, the primary differentiation of the HSDL-4250 lies in itshigh-speed capability (40ns). This makes it unsuitable for simple on/off indicator lights but ideal for digital communication. Itslow forward voltageIs another advantage, reducing power consumption and simplifying power supply design in battery-powered devices such as remote controls.870nm wavelengthIs a universal standard, ensuring broad compatibility with off-the-shelf infrared photodetectors, which are typically most sensitive in the 850-950nm range.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED directly from a 3.3V or 5V microcontroller pin?
A: No. You must always use a series resistor (or an active current driver) to limit the current. The forward voltage is only about 1.6V, so connecting it directly to 3.3V without a resistor would cause excessive current, damaging the LED and potentially the microcontroller pin.

Q: What resistor value should I use for a 5V power supply and 20mA drive current?
A: Using Ohm's Law: R = (V_{Power supply}- V_F) / I_F. Assuming V_F~ 1.6V, then R = (5V - 1.6V) / 0.020A = 170 ohms. A standard 180-ohm resistor would be a safe choice, resulting in a current slightly below 20mA.

Q: Why is the peak current (500mA) so much higher than the continuous current (100mA)?
A: The peak current rating applies to very short pulses. The semiconductor junction can withstand high instantaneous power pulses before heat has time to accumulate and exceed T_JmaxThis is used in communication systems to send bright, short light pulses for better signal integrity.

Q: How does temperature affect performance?
A: Increasing temperature reduces forward voltage (by -1.44mV per °C) and optical output power (by -0.43% per °C). Therefore, constant current drive is crucial for maintaining stable light output. The maximum allowable current must also be derated as ambient temperature rises.

10. Practical Design and Usage Examples

Example 1: Simple Infrared Remote Control Transmitter.In a basic remote control, a microcontroller generates a modulated data stream (e.g., 38kHz carrier). This signal drives a transistor switch (like a BJT or MOSFET) in series with the HSDL-4250 LED and a current-limiting resistor. The resistor value is calculated based on the supply voltage (typically 3V from two AA batteries) and the desired pulse current (e.g., 100mA for a strong signal). The transistor allows the low-power microcontroller to control the higher LED current.

Example 2: High-Speed Serial Data Link (IrDA).For a bidirectional IrDA port, the HSDL-4250 would be part of the transmitter circuit. It would be driven by a dedicated IrDA encoder/transmitter IC that shapes the electrical pulses to meet IrDA physical layer specifications (like pulse width). The LED's fast rise/fall times are critical for achieving the required data rate (e.g., 115.2 kbps for IrDA 1.0). Careful PCB layout is needed to minimize parasitic capacitance that could slow down edge speeds.

11. Brief Introduction to Working Principles

An infrared light-emitting diode is a semiconductor p-n junction diode. When forward biased (positive voltage applied to the anode relative to the cathode), electrons from the n-type region and holes from the p-type region are injected into the junction area. When these carriers recombine, they release energy. In the specific aluminum gallium arsenide material used in the HSDL-4250, this energy is primarily released in the form of photons (light), with energy corresponding to the infrared spectrum (approximately 870nm wavelength). The intensity of the emitted light is proportional to the carrier recombination rate, which is controlled by the forward current flowing through the diode. The T-1 3/4 package contains an epoxy lens to shape the emitted beam.

12. Technical Trends and Development

While the basic principles of infrared LEDs remain stable, trends focus on improving efficiency, higher speeds, and greater integration. Modern devices may feature the following:

• Higher Power and Efficiency:New semiconductor materials and chip designs aim to convert more electrical input into light output (higher electro-optical conversion efficiency), reducing heat generation and power consumption.
• Surface-Mount Device Packaging:Although the HSDL-4250 is a through-hole component, the industry has largely shifted to SMD packages (e.g., 0805, 1206, or chip-on-board) to enable automated assembly and a smaller form factor. Equivalent high-speed infrared LEDs are also available in these package types.
• Integrated Solutions:For consumer applications like remote controls, it is common to see the LED and its driving transistor integrated into a tiny module. For advanced sensing, LEDs are being integrated with drivers, modulators, and sometimes even detectors on a single substrate or in multi-chip modules.
• Application-Specific Optimization:LEDs are being customized for specific uses, such as extremely narrow beam angles for distance sensing or specific peak wavelengths for gas sensing applications.