LTR-3208E Infrared Phototransistor Datasheet - 3.0x2.8x1.5mm Package - Vce 30V - Collector Current up to 3.6mA - Dark Epoxy Package - Technical Documentation

1. Product Overview

LTR-3208E is a discrete infrared (IR) phototransistor component, specifically designed for sensing applications within the infrared spectrum. Its primary function is to convert incident infrared light into a corresponding current at its collector terminal. This device belongs to the broader family of optoelectronic components and is suitable for systems requiring reliable and cost-effective infrared detection.

1.1 Core Advantages and Product Positioning

LTR-3208E is positioned as a general-purpose infrared detector suitable for cost-sensitive applications. Its key advantages stem from its specific packaging and electrical characteristics. The device utilizes a special dark plastic encapsulation. This material is designed to attenuate or cut off visible light wavelengths, thereby specifically enhancing its sensitivity and signal-to-noise ratio for infrared signals (typically around 940nm). This makes it ideal for environments where ambient visible light is present, but only infrared signals need to be detected. Furthermore, it offers a wide collector current operating range, enabling it to interface with various circuit designs without requiring highly precise biasing. The use of standard plastic encapsulation helps reduce costs, making it an attractive choice for high-volume consumer electronics.

The primary target markets for the LTR-3208E include consumer electronics and basic industrial control systems. It is designed for applications requiring reliable infrared detection without the extreme performance demands of more specialized components, such as ultra-high speed or ultra-low noise. Its most common application is as a detector in infrared remote control systems for televisions, audio equipment, and other household appliances. It is also suitable for simple infrared wireless data transmission links, security alarm systems that detect infrared beam interruption, and various proximity or object sensing scenarios. Its robustness and simplicity make it a staple component in entry-level to mid-range electronic designs requiring infrared sensing capabilities.

1.2 Target Markets and Applications

2. In-depth Technical Parameter Analysis

Sehemu hii inafafanua kwa kina na kwa uwazi vigezo vya umeme na vya nuru vilivyobainishwa katika maelezo ya udhibiti, na kuelezea umuhimu wake katika usanidi wa saketi.

2.1 Absolute Maximum Ratings

Viwango hivi vinabainisha mipaka ya mkazo ambayo inaweza kusababisha uharibifu wa kudumu wa kifaa. Hivi sio hali za kawaida za uendeshaji.

• Matumizi ya nguvu (P_D):100 mW. Hii ndiyo nguvu ya juu kabisa ambayo kifaa kinaweza kutolea kama joto, inayotokana hasa na I_C* V_CEUamuzi. Kuzidi kikomo hiki kuna hatari ya kudhibitiwa kwa joto na kushindwa.
• Voltage ya kolekta-emiteri (V_CEO):30 V. Voltage ya juu zaidi inayoweza kutumiwa kati ya vituo vya kolekta na emiteri wakati msingi (ingizo la mwanga) umefunguliwa. Kuzidi thamani hii kunaweza kusababisha kuvunjika kwa theluji.
• Voltage ya emiteri-kolekta (V_ECO):5 V. Voltage ya juu zaidi ya nyuma inayoweza kutumiwa kati ya emiteri na kolekta. Hii kwa kawaida ni chini sana kuliko V_CEO.
• Joto la uendeshaji na uhifadhi:They are -40°C to +85°C and -55°C to +100°C, respectively. These define the environmental limits for reliable operation and non-operating storage.
• Pin Soldering Temperature:260°C for 5 seconds at a distance of 1.6mm from the package body. This is critical for wave soldering or reflow processes to prevent package damage.

2.2 Tabia za Umeme na Mwangaza

These parameters are measured under specific test conditions (T_A=25°C) and define the device's performance.

• Breakdown Voltage (V_(BR)CEO, V_(BR)ECO):Typical values are 30V and 5V minimum, respectively. These confirm that the device can withstand the voltages listed in the absolute maximum ratings.
• Collector-Emitter Saturation Voltage (V_CE(SAT)):at I_C=100µA and E_e=1 mW/cm², the maximum is 0.4V. This low voltage indicates good efficiency when the transistor is fully "on" (saturated), thereby minimizing power loss.
• Rise and Fall Times (T_r, T_f):Under test conditions (V_CC=5V, I_C=1mA, R_L=1kΩ), the typical values are 10 µs and 15 µs, respectively. These specify the switching speed. The LTR-3208E is not a high-speed device; it is suitable for low to medium frequency signals, such as those from remote controls (typically up to several tens of kHz).
• Collector dark current (I_CEO):Under complete darkness and V_CE=10V, the maximum value is 100 nA. This is the leakage current flowing in the absence of light. A lower value is better for sensitivity, as it represents the detector's background noise.

3. Maelezo ya Mfumo wa Kugawa Daraja

The LTR-3208E grades its key parameter—the on-state collector current (I_C(ON)) – A binning system is employed. Binning is a manufacturing process that sorts components into different groups ("bins") based on measured performance to ensure consistency within a batch.

3.1 Kugawa Daraja la Mkondo wa Collector

The datasheet specifies I_C(ON)=5V, E_CE=1mW/cm², λ=940nm)._e. The devices are classified into bins from A to F, with each bin having defined minimum and typical current ranges.

• Bin A:0.64 to 1.68 mA
• Gear B:1.12 to 2.16 mA
• Gear C:1.44 to 2.64 mA
• Gear D:1.76 to 3.12 mA
• Gear E:2.08 to 3.60 mA
• Bin F:2.40 mA (Typical, maximum may be similar to Bin E)

Design Impact:This binning is critical for design. If a circuit requires a minimum photocurrent to trigger a logic level, the designer must select a bin that guarantees this current under worst-case conditions (minimum irradiance, highest temperature). Devices from Bin E or F offer higher signal strength, which can improve detection range or allow the use of higher-value load resistors for greater voltage swing. Conversely, for very sensitive circuits, even a device from Bin A may suffice. The bin code is typically part of the full ordering part number.

4. Uchambuzi wa Mviringo wa Utendaji

The datasheet contains several graphs depicting how key parameters vary with environmental and operating conditions.

4.1 Relationship Between Collector Dark Current and Ambient Temperature (Figure 1)

Mkunjo huu unaonyesha I_CEOinaongezeka kwa kasi ya kielelezo kadiri joto linavyoongezeka. Katika 85°C, mkondo wa giza unaweza kuwa wa mpangilio kadhaa juu kuliko katika 25°C. Hii ni sifa ya msingi ya semiconductor. Kwa matumizi yanayofanya kazi katika joto la juu, ongezeko hili la uvujaji la mkondo linaweza kuongeza kelele ya msingi, kupunguza usikivu, au kuhitaji fidia katika mzunguko wa usindikaji wa ishara (mfano, kizingiti cha juu cha kugundua).

4.2 Relationship Between Collector Power Dissipation and Ambient Temperature (Figure 2)

Mchoro huu unaonyesha dhana ya "kupunguza rating". Kadiri joto la mazingira (T_A) linavyoongezeka, matumizi ya juu ya nguvu yanayoruhusiwa (P_C) hupungua kwa mstari. Katika T_A=85°C, matumizi ya juu ya nguvu ni chini sana kuliko rating ya 100mW katika 25°C. Mbuni lazima akuhesabu nguvu halisi katika matumizi yake (I_C* V_CE), na kuhakikisha kuwa iko chini ya mkunjo wa kupunguza rating katika joto la juu la kufanya kazi lililotarajiwa, ili kuepuka mzigo wa kupita kiasi wa joto.

4.3 Relationship Between Rise/Fall Time and Load Resistance (Figure 3)

Mkunjo huu unaonyesha usawazishaji wa kawaida katika usanidi wa saketi ya fototransista. Muda wa kupanda na kushuka (T_r, T_f) huongezeka kadri upinzani wa mzigo (R_L) unavyoongezeka. R_Lkubwa hutoa mabadiliko makubwa ya voltage ya pato (ΔV = I_C* R_L), lakini hupunguza kasi ya kubadili, kwa sababu capacitance ya kiunganishi cha transistor inahitaji muda mrefu zaidi kujaza na kutolewa umeme kupitia upinzani mkubwa. Msanidi lazima achague R_Lili kusawazisha mahitaji ya ukubwa wa ishara na upana wa bendi unaohitajika na ishara ya infrared.

4.4 Relationship Between Relative Collector Current and Irradiance (Figure 4)

Grafu hii inaonyesha uhusiano kati ya nguvu ya mwanga wa infrared inayoingia (mnururisho E_e) na mkondo wa kolekta unaotokana (I_C). Majibu kwa kawaida huwa ya mstari ndani ya safu fulani. Uwiano huu wa mstari ni muhimu sana kwa matumizi ya analogi ambapo nguvu ya ishara hubeba habari. Mteremko wa mstari huu unawakilisha usikivu wa transistor nyeti-kwa-mwanga (mA kwa kila mW/cm²). Grafu inathibitisha kuwa chini ya V_CEthabiti, mkondo wa pato ni sawia na mwingilio wa mwanga, ambayo ndiyo kanuni yake ya msingi ya kufanya kazi.

5. Taarifa za Mitambo na Ufungaji

5.1 Vipimo vya Nje na Uvumilivu

Kifaa hiki kinatumia ufungashaji wa kawaida wa aina ya transistor (huenda kifanane na T-1 au ufungashaji kama huo). Vipimo muhimu vinajumuisha ukubwa wa mwili, umbali wa pini, na urefu wa jumla. Isipokuwa imebainishwa vinginevyo, uvumilivu kwa kawaida ni ±0.25mm. Lenzi imeunganishwa ndani ya ufungashaji kwa lengo la kuzingatia mwanga wa infrared unaoingia, na kuongeza usikivu. Kipengele cha kipekee ni kuruhusu resin inayojitokeza hadi 1.5mm chini ya flange, ambayo ni muhimu kwa mpangilio wa PCB na nafasi.

5.2 Utambuzi wa Upeo

Phototransistor ina viungo vitatu: Collector (C), Emitter (E), na "Base" inayotumika kama mwanga. Ufungaji utakuwa na alama za kimwili, kama vile uso wa gorofa au kipande kilichoinuka, kutambua pini ya Emitter. Katika ufungaji wa kawaida wa pini tatu, Collector kwa kawaida ndio pini ya kati. Uelekezaji sahihi ni muhimu kwa ubiaji sahihi na uendeshaji wa saketi.

6. Mwongozo wa Uchomaji na Usanikishaji

Ingawa hakuna mkunjo wa kina wa reflow uliotolewa, viwango vya juu kabisa vinatoa mwongozo muhimu: Pini zinaweza kuunganishwa kwa joto la 260°C kwa sekunde 5 kwa upeo, kipimo kinachochukuliwa 1.6mm kutoka kwa mwili wa ufungaji. Hii ni kiwango cha kawaida cha ufungaji wa plastiki. Kwa reflow, kutumia mkunjo wa kawaida usio na risasi wenye kiwango cha juu cha joto cha takriban 260°C kunakubalika, mradi wakati juu ya mstari wa kioevu udhibitiwe. Kwa kuunganisha kwa mikono, chuma cha kuunganisha chenye udhibiti wa joto kinapaswa kutumiwa, na pini zinapaswa kupashwa joto haraka na kwa ufanisi ili kuepuka kupasha joto kwa muda mrefu mwili wa ufungaji wenyewe, ambayo kunaweza kuharibu muundo wa chip ndani au plastiki. Uhifadhi unapaswa kufanywa katika mazingira yaliyokauka na yaliyodhibitiwa kulingana na anuwai ya joto ya uhifadhi, ili kuzuia unyevunyevu ambao unaweza kusababisha "popcorn" wakati wa kuunganisha.

7. Vidokezo vya Matumizi na Mazingatio ya Ubunifu

7.1 Saketi ya Kawaida ya Matumizi

Usanidi wa kawaida wa saketi ni hali ya "Emitter ya pamoja". Collector imeunganishwa kupitia upinzani wa mzigo (R_CC) Inayounganishwa na voltage ya usambazaji chanya (V_L). Emitter imewekwa chini. Wakati mwanga wa infrared unapoingia kwenye transistor nyeti kwa mwanga, inafunguka, na kusababisha kushuka kwa voltage kwenye R_L. Ishara ya pato inachukuliwa kutoka kwenye nodi ya kolekta. Thamani ya R_Lhuchaguliwa kulingana na mabadiliko ya voltage ya pato yanayohitajika na upana wa bendi, kama inavyoonyeshwa kwenye safu ya utendaji. Capacitor ya bypass inaweza kuongezwa kwenye usambazaji wa nguvu au pato ili kuchuja kelele.

7.2 Mazingatio ya Ubunifu

• Upendeleo:Transistor nyeti kwa mwanga kimsingi inapendelewa na ishara ya mwanga. Hakuna upendeleo wa umeme wa nje unaotumika kwa msingi.
• Uchaguzi wa Upinzani wa Mzigo:Kama ilivyoelezwa hapo awali, hii ni usawazisho muhimu kati ya ukubwa wa ishara (mabadiliko ya voltage) na kasi (wakati wa kupanda/kushuka). Kwa matumizi ya udhibiti wa mbali (masafa ya chini), upinzani katika safu ya 1kΩ hadi 10kΩ ni ya kawaida.
• Ambient Light Suppression:The dark plastic package provides significant visible light suppression. However, strong ambient infrared sources (sunlight, incandescent bulbs) can still cause interference. Optical filtering (additional IR filters) or modulation/demodulation of the infrared signal (as used in remote controls) are common techniques to improve noise immunity.
• Logic Interface:The output is an analog voltage. To interface with a digital input (e.g., a microcontroller), a comparator or Schmitt trigger input should be used to provide a clean digital signal with hysteresis, preventing chatter due to noise or slowly changing light levels.

8. Ulinganishi wa Kiufundi na Tofauti

The primary differentiation of the LTR-3208E lies in itsdark plastic package. Compared to phototransistors with transparent or translucent packages, it performs better in suppressing visible ambient light, resulting in a better signal-to-noise ratio in environments with fluctuating visible light. Its performance parameters (speed, dark current) are typical for a general-purpose device, making it less suitable for ultra-high-speed data links or ultra-low-light detection compared to specialized PIN photodiodes or Avalanche Photodiodes (APDs). Its advantage lies in its simplicity, robustness, and cost-effectiveness for its target market segment. The binning system for collector current provides designers with a guaranteed performance level, which is a key advantage over unbinned or loosely specified components.

9. Maswali Yanayoulizwa Mara kwa Mara (Kulingana na Vigezo vya Kiufundi)

Swali: "E" katika LTR-3208E inawakilisha nini?
Jibu: Kwa kawaida inawakilisha toleo maalum au marekebisho. Katika muktadha huu, kwa uwezekano mkubwa inamaanisha toleo maalum la ufungaji wa plastiki nyeusi, kama ilivyoelezwa katika sifa.

Swali: Je, naweza kutumia phototransistor hii pamoja na LED ya infrared ya 940nm kutoka kwa mtengenezaji tofauti?
Jibu: Ndio, imejaribiwa mahsusi kwenye urefu wa wimbi la 940nm, ambao ndio urefu wa wimbi linalotumika zaidi katika matumizi ya infrared ya watumiaji. Hakikisha wigo wa mwanga wa LED unalingana vizuri na kilele cha usikivu cha phototransistor (kwa nyenzo hii, kwa kawaida pia karibu na 940nm).

Swali: Kwa nini ishara yangu ya pato inapungua kasi au kuharibika katika masafa ya juu?
Jibu: Angalia thamani ya upinzani wako wa mzigo (R_L). Kama inavyoonyeshwa kwenye Mchoro 3, R kubwa_LItaongeza wakati wa kupanda na kushuka, na kuzuia upana wa bendi. Kwa ishara za kasi zaidi, tumia R ndogo._L, na uwezekano wa kutumia hatua ya kifuatia ya kizidishio cha uendeshaji ili kukuza mwinuko mdogo wa voltage.

Q: Kifaa hutoa joto wakati wa uendeshaji. Je, hii ni kawaida?
A: Kutokana na matumizi ya nguvu (P = V_CE* I_C), joto fulani ni kawaida. Tafadhali rejea Mchoro 2. Kokotoa matumizi yako halisi ya nguvu, na hakikisha kuwa ni chini ya mkunjo wa kupunguza kwa joto la mazingira yako. Ikiwa ni kubwa sana, punguza voltage ya usambazaji, mkondo wa kolekta, au boresha upoaji joto / mtiririko wa hewa.

10. Mfano wa Matumizi Halisi

Hali: Kubuni kichunguzi rahisi cha karibu cha infrared kwa ajili ya toy.
LED ya infrared inaendeshwa kwa msisitiko wa masafa ya chini (mfano 1kHz). LTR-3208E (chagua daraja D kwa usikivu mzuri) imewekwa karibu. Wakati kitu kinakaribia, kinarudisha msisitiko wa infrared kwenye kigunduzi. Mkondo wa kolekta wa fototransistor unyounganishwa na V kupitia upinzani wa 4.7kΩ._CC=5V, inazalisha voltage ya msukumo. Ishara hii inapelekwa kwenye kichujio cha kipitio cha mawimbi kilichowekwa kwenye 1kHz ili kukandamiza kelele ya mwanga wa mazingira, kisha inaingia kwenye kigunduzi cha kilele na kulinganisha. Wakati ishara ya kutafakari inazidi kizingiti, pato la kulinganisha linakuwa juu, ikionyesha uwepo wa kitu. Ufungaji wa rangi nyeusi wa LTR-3208E husaidia kukandamiza taa ya ndani, na kasi yake ya wastani inafaa kabisa kwa usimbaji wa 1kHz.

11. Utangulizi wa Kanuni ya Kazi

Kanuni ya uendeshaji ya transistor nyeti kwa mwanga ni sawa na transistor ya kawaida ya kiungo bipolar (BJT), lakini mkondo wa msingi wake unazalishwa na mwanga, sio muunganisho wa umeme. Kifaa hiki kimsingi ni transistor ambayo kiungo cha msingi-mkusanyaji kinachukua nafasi ya diodi ya mwanga. Wakati fotoni zenye nishati ya kutosha (hapa ni mwanga wa infrared) zinapogonga eneo la utumiaji la msingi-mkusanyaji, zinazalisha jozi za elektroni na mashimo. Mkondo huu unaozalishwa na mwanga huchukua nafasi ya mkondo wa msingi (I_B). Kwa sababu ya faida ya mkondo ya transistor (β au h_FE), mkondo huu mdogo wa msingi unakuza, ukizalisha mkondo mkubwa zaidi wa mkusanyaji (I_C= β * I_B). Faida hii ya ndani ndiyo sababu transistor nyeti kwa mwanga ina usikivu mkubwa kuliko diodi rahisi ya mwanga (bila faida), ingawa kwa kawaida hii huja na gharama ya muda wa kukabiliana polepole zaidi na mkondo mkubwa wa giza.

12. Mwelekeo na Mazingira ya Kiufundi

Discrete infrared phototransistors like the LTR-3208E represent a mature and stable technology. Their development focuses on cost reduction, package optimization (such as filtered packages), and achieving consistent manufacturing through binning. The trend in infrared sensing is moving towards integration. Many modern systems use integrated solutions that combine a photodiode, transimpedance amplifier, and sometimes a digital interface (like I2C) into a single package. These integrated sensors offer better performance, lower noise, and simpler design, but at a higher cost. Consequently, discrete components like the LTR-3208E maintain a strong position in applications with high volume, cost-driven requirements, where basic functionality is sufficient, and board space allows for discrete circuitry. The demand for reliable, low-cost infrared detection in IoT devices, smart home accessories, and basic industrial sensors ensures the continued relevance of such components.