EL452-G Jerin 4-Pin SOP Babban Karfin Lantarki Photodarlington Optocoupler Datasheet - Kunshin 4.4x7.4x2.0mm - VCEO 350V - CTR 1000% - Takardun Fasaha na Hausa

1. Bayanin Samfur EL452-G jerin babban karfin lantarki photodarlington optocoupler ne wanda aka tsara don ingantaccen watsa siginar tsakanin da'irori na yuwuwar daban-daban. Yana haɗa diode mai fitar da infrared wanda aka haɗa ta hanyar haske zuwa babban karfin lantarki darlington phototransistor. An sanya na'urar a cikin ƙunƙuntaccen kunshin 4-pin Small Outline Package (SOP) tare da ƙananan bayanin martaba na 2.0mm, yana mai da shi dacewa da aikace-aikacen hawa saman da ke da ƙarancin sarari. Babban aikinsa shine samar da keɓewar lantarki yayin watsa siginar sarrafawa ko bayanai, yana kare da'irar da ke da hankali daga saurin canjin babban karfin lantarki da matsalolin madauki na ƙasa.

1.1 Fa'idodi na Asali da Kasuwar da Ake Nufi Fa'idodin mahimmanci na wannan ɓangaren sun haɗa da babban ƙimar karfin lantarki na mai tara-emitter na 350V (VCEO), wanda yake da mahimmanci don haɗawa da da'irori masu amfani da wutar lantarki ko tuƙin mota. Yana ba da babban rabon canja wurin halin yanzu (CTR) tare da mafi ƙarancin 1000% a daidaitattun yanayin gwaji, yana tabbatar da ingantattun matakan siginar fitowa daga ingantaccen halin yanzu na shigarwa. Na'urar tana alfahari da babban karfin lantarki na keɓewa na 3750Vrms tsakanin bangarorinta na shigarwa da fitarwa, yana cika ƙa'idodin aminci masu tsauri. Hakanan ba shi da halogen kuma ya bi ka'idojin RoHS da umarnin marasa gubar. Waɗannan fasalulluka sun sa ya zama manufa don aikace-aikace a cikin kayan aikin sadarwa (tarho, musanya), masu sarrafa jerin masana'antu, kayan aikin tsarin, kayan aikin aunawa, da kowane yanayi da ke buƙatar amintaccen watsa sigina a cikin yankunan karfin lantarki daban-daban.

2. Bincike Mai zurfi na Sigogi na Fasaha Wannan sashe yana ba da cikakken fassara na haƙiƙa na ƙayyadaddun lantarki, haske, da zafin jiki na na'urar kamar yadda aka ayyana a cikin matsakaicin matsakaicin ƙimar sa da halayen lantarki da haske.

2.1 Matsakaicin Matsayin Matsakaici Matsakaicin matsakaicin ƙimar yana ayyana iyakokin damuwa waɗanda sama da su lalacewar dindindin na na'urar na iya faruwa. Halin yanzu na gaba (IF) an ƙididdige shi a 60mA ci gaba, tare da ɗan gajeren lokaci kololuwar halin yanzu na gaba (IFP) na 1A na 10µs. Jimlar ɓarnawar wutar lantarki (PT) bai kamata ya wuce 170mW ba. Mahimmin sigar fitowa shine karfin lantarki na mai tara-emitter (VCEO) na 350V, wanda shine matsakaicin karfin lantarki da transistor ɗin fitowa zai iya toshe lokacin da LED ɗin shigarwa ya kashe. Karfin lantarki na keɓewa (VISO) na 3750Vrms na minti ɗaya yana ƙayyadadden ƙarfin dielectric na shinge na ciki. Na'urar tana aiki a cikin kewayon zafin jiki daga -55°C zuwa +110°C._CEO2.2 Halayen Lantarki da Haske Halayen lantarki da haske suna ayyana aikin na'urar a ƙarƙashin yanayin aiki na yau da kullun a 25°C._{2.2.1 Halayen Shigarwa (Bangaren LED) Karfin lantarki na gaba (VF) na infrared LED yawanci 1.2V ne tare da matsakaicin 1.4V a halin yanzu na gaba na 10mA. Wannan ƙananan VF yana ba da gudummawar ƙananan amfani da wutar lantarki a bangaren shigarwa. Halin yanzu na juyawa (IR) shine matsakaicin 10µA a 4V juyawa mai karkata.}2.2.2 Halayen Fitowa (Bangaren Phototransistor) Halin yanzu na duhu na mai tara-emitter (ICEO), wanda shine halin yanzu na jiyya lokacin da LED ya kashe, an ƙayyade shi a matsakaicin 100nA a VCE=200V. Karfin lantarki na rushewar mai tara-emitter (BVCEO) shine mafi ƙarancin 350V, yana tabbatar da ƙarfin babban karfin lantarki. Karfin lantarki na cikakken mai tara-emitter (VCE(sat)) yawanci 1.2V ne (matsakaici 1.5V) lokacin da na'urar ta kasance cikakke (IF=20mA, IC=100mA), yana nuna raguwar karfin lantarki a cikin fitowa a cikin yanayin gudanarwa.

2.2.3 Halayen Canja wuri Rarrabawar Canja wurin Halin yanzu (CTR) shine mafi mahimmancin siga, wanda aka ayyana azaman rabon halin yanzu na mai tara fitowa zuwa halin yanzu na gaba na shigarwa, wanda aka bayyana azaman kashi. Ga EL452-G, CTR shine mafi ƙarancin 1000%, yawanci 2000%, a IF=1mA da VCE=2V. Wannan babban CTR na musamman halayen tsarin darlington ne, wanda ke ba da babban ribar halin yanzu, yana ba da damar ƙananan halayen shigarwa don sarrafa manyan halayen fitowa yadda ya kamata. Saurin sauyawa yana siffanta ta hanyar lokacin tashi (tr) na yawanci 80µs (matsakaici 250µs) da lokacin faɗuwa (tf) na yawanci 10µs (matsakaici 100µs). Waɗannan lokutan suna da sannu a hankali saboda tsarin darlington da kuma ajiyar caji na asali a cikin phototransistors, yana mai da na'urar ta dace da sauyawa mai ƙarancin mitar zuwa matsakaici da aikace-aikacen analog na layi, amma ba don keɓewar dijital mai sauri ba. Mitar yanke (fc) yawanci 7kHz ne. Resistance na keɓewa (RIO) shine mafi ƙarancin 5×10¹⁰Ω, yana nuna ingantaccen keɓewar DC.

3. Bincike na Lanƙwan Ayyuka Yayin da PDF ke nuna kasancewar lanƙwasa halayen lantarki da haske na yau da kullun, takamaiman jadawali (misali, CTR vs. Halin yanzu na Gaba, CTR vs. Zazzabi, Halin yanzu na Mai tara vs. Karfin lantarki na Mai tara-Emitter) ba a bayar da su a cikin abun cikin rubutu ba. A cikin cikakken takardar bayanai, waɗannan lanƙwan suna da mahimmanci don zane. Yawanci suna nuna yadda CTR ke raguwa tare da haɓakar zafin jiki, yadda halin yanzu na fitowa ya cika a manyan halayen shigarwa ko ƙananan karfin lantarki na mai tara-emitter, da kuma alaƙar tsakanin karfin lantarki na gaba da halin yanzu don LED. Dole ne masu zane su tuntubi waɗannan jadawali don fahimtar halayen na'urar a cikin cikakken kewayon aiki, ba kawai a wurin yau da kullun na 25°C ba.

4. Bayanin Injiniya da Kunshi

4.1 Girman Kunshi da Tsarin Pin Na'urar tana amfani da kunshin 4-pin SOP. Girman jikin kunshin yana kusan 4.4mm a tsayi da 7.4mm a faɗi, tare da bayanin martaba na 2.0mm. Tsarin pin daidai ne ga irin waɗannan optocouplers: Pin 1 shine LED Anode, Pin 2 shine LED Cathode, Pin 3 shine Phototransistor Emitter, kuma Pin 4 shine Phototransistor Collector. An ba da shimfidar kushin da aka ba da shawarar don hawa saman don tabbatar da ingantaccen solder da kwanciyar hankali na injiniya._F4.2 Alamar Na'ura An yiwa na'urar alama a saman saman tare da lamba. Alamar ta haɗa da "EL" (lambar masana'anta), "452" (lambar sashi), lambar shekara mai lamba ɗaya, lambar mako mai lamba biyu, da zaɓi "V" don nuna amincewar VDE. Wannan alamar tana ba da damar gano ranar ƙirƙira da yarda._FM5. Jagororin Solder da Haɗawa_TOT5.1 Yanayin Solder na Reflow Takardar bayanai tana ba da cikakkun ƙayyadaddun bayanan bayanan solder na reflow don hana lalacewar zafi. Bayanin ya bi IPC/JEDEC J-STD-020D. Mahimman sigogi sun haɗa da: matakin preheat daga 150°C zuwa 200°C sama da 60-120 seconds, matsakaicin zafin jiki (Tp) bai wuce 260°C ba, da lokacin sama da ruwa (217°C) tsakanin 60-100 seconds. Na'urar na iya jure matsakaicin zagaye uku na reflow. Yin bin wannan bayanin yana da mahimmanci don kiyaye ingancin rufaffen epoxy na ciki da haɗin waya._CEO6. Bayanin Kunshi da Oda_ISO6.1 Tsarin Lambar Sashen Oda Lambar sashi tana bin tsari: EL452(Y)-VG. Matsayin "Y" yana nuna zaɓin tef da reel (TA, TB, ko babu don kunshin bututu). "V" yana nuna cewa naúrar ta sami amincewar aminci ta VDE. Maɗaukakin "G" yana nuna samfurin ba shi da halogen. Misali, EL452TA-VG yana nufin na'urar da aka kawo akan tef da reel na TA, tare da amincewar VDE, kuma ba shi da halogen._{6.2 Ƙayyadaddun Tape da Reel Na'urar tana samuwa a cikin daidaitaccen tef ɗin mai ɗaukar kaya don haɗawa ta atomatik. Akwai hanyoyin ciyarwa guda biyu: Zaɓi TA da Zaɓi TB. Faɗin tef ɗin (W) shine 16.0mm, filin aljihu (P0) shine 4.0mm, kuma reel yawanci yana riƙe da raka'a 3000. An ba da cikakkun girman tef (A, B, D0, da sauransu) don saitin mai ciyarwa.}7. Shawarwarin Aikace-aikace

7.1 Daidaitattun Da'irori na Aikace-aikace EL452-G ya dace da tuƙi triacs, thyristors, ko MOSFETs a cikin da'irorin sarrafa AC mains (misali, relays na ƙwaƙƙwaran jiki) saboda babban VCEO. Ana iya amfani da shi don canza matakin karfin lantarki a cikin musaya microcontroller, samar da keɓewa don siginar firikwensin analog, da ƙirƙirar madaukai na amsawa a cikin hanyoyin watsa wutar lantarki. Babban CTR ɗin sa yana ba shi damar tuƙi kai tsaye daga filayen GPIO na microcontroller (tare da resistor mai iyakance halin yanzu) ba tare da buƙatar ƙarin transistor direba don LED ba.

7.2 Abubuwan Ɗauka da Kula da Zane Bangaren Shigarwa: Dole ne a ko da yaushe a yi amfani da resistor na jerin tare da LED don iyakance halin yanzu na gaba zuwa ingantaccen ƙima, yawanci tsakanin 1mA da 20mA dangane da CTR da saurin da ake buƙata. LED yana da hankali ga karfin lantarki na baya; idan da'irar tuƙi na iya sanya jujjuyawar baya, ana ba da shawarar diode ɗin kariya a layi daya tare da LED. Bangaren Fitowa: Photodarlington na iya nutsewa cikin halin yanzu (har zuwa 150mA). Dole ne a haɗa resistor ɗin kaya tsakanin mai tara da layin wadata mai kyau don saita motsin karfin lantarki na fitowa da iyakance ɓarnawar wutar lantarki. Saboda tsarin darlington, karfin lantarki na cikakken (VCE(sat)) ya fi na transistor guda ɗaya, wanda ke rage motsin karfin lantarki na fitowa a aikace-aikacen sauyawa. Dole ne masu zane su yi la'akari da lalacewar CTR akan zafin jiki da tsawon rayuwa; gefen zane na 20-50% yana da kyau. Saurin sauyawa sannu a hankali yana hana amfani da shi a cikin PWM mai girma ko sadarwar bayanai sama da kilohertz kaɗan.

8. Kwatancen Fasaha da Bambance-bambance EL452-G ya bambanta kansa a kasuwa ta hanyar haɗuwa da babban karfin lantarki (350V), babban CTR (1000% min), da ƙunƙuntaccen kunshin SOP. Idan aka kwatanta da daidaitattun masu haɗawa na phototransistor (waɗanda ƙila suna da CTR na 50-600%), tsarin darlington yana ba da mafi girman hankali. Idan aka kwatanta da wasu photodarlingtons, ƙimar keɓewar 3750Vrms da yawancin amincewar aminci na duniya (UL, CUL, VDE, SEMKO, da sauransu) sun sa ya zama zaɓi mai ƙarfi don aikace-aikacen aminci mai mahimmanci da na masana'antu. Rashin halogen da bin RoHS sun yi daidai da ƙa'idodin muhalli na zamani.

9. Tambayoyin da ake yawan yi (FAQ) Q: Zan iya tuƙi LED kai tsaye daga fitarwar dabaru na 5V? A: Ee, amma dole ne ku ƙididdige resistor na jerin. Misali, tare da VF na yau da kullun na 1.2V da IF da ake so na 5mA daga wadata 5V: R = (5V - 1.2V) / 0.005A = 760Ω. Yi amfani da daidaitaccen resistor 750Ω. Q: Menene matsakaicin mitar sauyawa? A: Matsakaicin mitar sauyawa yana iyakance ta hanyar lokutan tashi da faɗuwa. Ƙididdiga mai ra'ayin mazan jiya don murabba'in murabba'i shine 1/(tr+tf) ≈ 1/(250µs+100µs) ≈ 2.9kHz. Don aiki mai aminci, ƙira don mitoci ƙasa da 1kHz. Q: Ta yaya zafin jiki ke shafar aiki? A: CTR yawanci yana raguwa tare da haɓakar zafin jiki. Halin yanzu na duhu (ICEO) yana ƙaruwa tare da zafin jiki. Karfin lantarki na gaba na LED yana raguwa tare da zafin jiki. Dole ne a yi la'akari da waɗannan tasirin don kwanciyar hankali aiki a cikin cikakken kewayon zafin jiki. Q: Shin akwai haɗin tushe na waje don haɓaka sauri? A: A'a. Wannan daidaitaccen photodarlington ne ba tare da jagorar tushe na waje ba. Ba za a iya inganta saurin sauyawa ta hanyar abubuwan haɗin waje ba._F10. Nazarin Aikin Zane na Aiki Yanayi: Keɓe siginar microcontroller 3.3V don sarrafa coil ɗin relay 24V DC. Ai: Pin ɗin GPIO na microcontroller (3.3V) yana tuƙi LED ta hanyar resistor 470Ω, yana saita IF ≈ (3.3V - 1.2V)/470Ω ≈ 4.5mA. An haɗa coil ɗin relay (24V, coil 50Ω ≈ 480mA) tsakanin wadata 24V da mai tara na EL452-G. An haɗa emitter zuwa ƙasa. Dole ne a sanya diode na flyback a gefen coil ɗin relay don danne ƙwanƙwaran karfin lantarki lokacin da photodarlington ya kashe. A shigarwar 4.5mA, CTR yana tabbatar da cikakkiyar fitowa mai iya nutsewar halin yanzu na relay, tare da VCE(sat) yana haifar da ƙaramin raguwar karfin lantarki. 350V VCEO yana ba da isasshen gefe a kan wadata 24V da duk wani ƙwanƙwasa na inductive._F11. Ka'idar Aiki Na'urar tana aiki akan ka'idar haɗin haske. Lokacin da halin yanzu ke gudana ta cikin infrared Light Emitting Diode (LED) na shigarwa, yana fitar da photons. Waɗannan photons suna tafiya a kan tazara mai banƙyama ta keɓewa kuma suna buga yankin tushe na nau'in darlington phototransistor na fitowa. Photons ɗin da aka ɗauka suna haifar da nau'ikan lantarki-ramuka, suna haifar da halin yanzu na tushe wanda ke kunna nau'in darlington transistor. Wannan yana ba da damar babban halin yanzu don gudana daga mai tara zuwa emitter, daidai da halin yanzu na LED (wanda aka ayyana ta CTR). Mahimmanci shine cewa ana watsa siginar ta hanyar haske, yana samar da cikakkiyar keɓewar galvanic tsakanin da'irorin shigarwa da fitarwa, saboda babu haɗin lantarki—hanya ta haske kawai ta hanyar kayan keɓewa._R12. Trends da Ci gaban Masana'antu Kasuwar optocoupler na ci gaba da haɓakawa. Trends sun haɓaka manyan masu keɓewa na dijital dangane da fasahar CMOS da RF, waɗanda ke ba da mafi girman sauri, amfani da wutar lantarki, da rashin tsangwama idan aka kwatanta da na'urorin haɗin gwiwa na gargajiya. Duk da haka, photodarlington da phototransistor optocouplers kamar EL452-G suna riƙe da matsayi mai ƙarfi a aikace-aikacen da ke buƙatar babban ƙarfin karfin lantarki, babban fitarwar halin yanzu, sauƙi, ƙarfi, da inganci don keɓewar mitar ƙasa zuwa matsakaici. Hakanan akwai ci gaba da turawa don ƙananan ƙira, haɗin kai mafi girma (misali, haɗa tashoshi da yawa), ingantaccen aminci, da ingantattun takaddun shaida don cika ƙa'idodin duniya masu tasowa. Matsi zuwa ga kayan da ba su da halogen da kayan muhalli, kamar yadda aka gani a cikin EL452-G, buƙatar masana'antu ce ta yau da kullun.

.2.2 Output Characteristics (Phototransistor Side)

The collector-emitter dark current (I_CEO), which is the leakage current when the LED is off, is specified at a maximum of 100nA at V_CE=200V. The collector-emitter breakdown voltage (BV_CEO) is a minimum of 350V, confirming the high-voltage capability. The collector-emitter saturation voltage (V_CE(sat)) is typically 1.2V (max 1.5V) when the device is fully on (I_F=20mA, I_C=100mA), indicating the voltage drop across the output in the conducting state.

.2.3 Transfer Characteristics

The Current Transfer Ratio (CTR) is the most critical parameter, defined as the ratio of output collector current to input forward current, expressed as a percentage. For the EL452-G, the CTR is a minimum of 1000%, typically 2000%, at I_F=1mA and V_CE=2V. This exceptionally high CTR is characteristic of a darlington configuration, which provides high current gain, allowing small input currents to control larger output currents effectively. The switching speed is characterized by rise time (t_r) of typically 80µs (max 250µs) and fall time (t_f) of typically 10µs (max 100µs). These times are relatively slow due to the darlington structure and the inherent charge storage in phototransistors, making the device suitable for low-to-moderate frequency switching and linear analog applications, but not for high-speed digital isolation. The cut-off frequency (f_c) is typically 7kHz. The isolation resistance (R_IO) is a minimum of 5×10¹⁰Ω, indicating excellent DC isolation.

. Performance Curve Analysis

While the PDF indicates the presence of typical electro-optical characteristic curves, the specific graphs (e.g., CTR vs. Forward Current, CTR vs. Temperature, Collector Current vs. Collector-Emitter Voltage) are not provided in the text content. In a full datasheet, these curves are crucial for design. They typically show how CTR degrades with increasing temperature, how output current saturates at high input currents or low collector-emitter voltages, and the relationship between forward voltage and current for the LED. Designers must consult these graphs to understand device behavior across the full operating range, not just at the 25°C typical point.

. Mechanical and Package Information

.1 Package Dimensions and Pin Configuration

The device uses a 4-pin SOP package. The package body dimensions are approximately 4.4mm in length and 7.4mm in width, with a height profile of 2.0mm. The pin configuration is standard for such optocouplers: Pin 1 is the LED Anode, Pin 2 is the LED Cathode, Pin 3 is the Phototransistor Emitter, and Pin 4 is the Phototransistor Collector. A recommended pad layout for surface mounting is provided to ensure reliable soldering and mechanical stability.

.2 Device Marking

The device is marked on the top surface with a code. The marking includes "EL" (manufacturer code), "452" (part number), a one-digit year code, a two-digit week code, and an optional "V" to denote VDE approval. This marking allows for traceability of manufacturing date and compliance.

. Soldering and Assembly Guidelines

.1 Reflow Soldering Conditions

The datasheet provides detailed reflow soldering profile specifications to prevent thermal damage. The profile is compliant with IPC/JEDEC J-STD-020D. Key parameters include: a preheat stage from 150°C to 200°C over 60-120 seconds, a peak body temperature (T_p) not exceeding 260°C, and a time above liquidus (217°C) between 60-100 seconds. The device can withstand a maximum of three reflow cycles. Adherence to this profile is critical to maintain the integrity of the internal epoxy encapsulation and the wire bonds.

. Packaging and Ordering Information

.1 Ordering Part Number System

The part number follows the format: EL452(Y)-VG. The "Y" position indicates the tape and reel option (TA, TB, or none for tube packaging). The "V" denotes that the unit is VDE safety approved. The "G" suffix indicates the product is halogen-free. For example, EL452TA-VG refers to the device supplied on TA orientation tape and reel, with VDE approval, and is halogen-free.

.2 Tape and Reel Specifications

The device is available in standard embossed carrier tape for automated assembly. Two feed directions are available: Option TA and Option TB. The tape width (W) is 16.0mm, the pocket pitch (P₀) is 4.0mm, and the reel typically holds 3000 units. Detailed tape dimensions (A, B, D₀, etc.) are provided for feeder setup.

. Application Recommendations

.1 Typical Application Circuits

The EL452-G is well-suited for driving triacs, thyristors, or MOSFETs in AC mains control circuits (e.g., solid-state relays) due to its high V_CEO. It can be used for voltage level shifting in microcontroller interfaces, providing isolation for analog sensor signals, and creating isolated feedback loops in switch-mode power supplies. Its high CTR allows it to be driven directly from microcontroller GPIO pins (with a suitable current-limiting resistor) without needing an additional driver transistor for the LED.

.2 Design Considerations and Precautions

Input Side:A series resistor must always be used with the LED to limit the forward current to a safe value, typically between 1mA and 20mA depending on the required CTR and speed. The LED is sensitive to reverse voltage; if the driving circuit can impose a reverse bias, a protection diode in parallel with the LED is recommended.
Output Side:The photodarlington can sink significant current (up to 150mA). A load resistor must be connected between the collector and the positive supply rail to set the output voltage swing and limit power dissipation. Due to the darlington configuration, the saturation voltage (V_CE(sat)) is higher than for a single transistor, which reduces the output voltage swing in switching applications. Designers must account for the CTR degradation over temperature and lifetime; a design margin of 20-50% is advisable. The relatively slow switching speeds preclude its use in high-frequency PWM or data communication above a few kilohertz.

. Technical Comparison and Differentiation

The EL452-G differentiates itself in the market through its combination of high voltage (350V), very high CTR (1000% min), and compact SOP package. Compared to standard phototransistor couplers (which may have CTRs of 50-600%), the darlington configuration provides much higher sensitivity. Compared to some other photodarlingtons, its 3750Vrms isolation rating and multiple international safety approvals (UL, CUL, VDE, SEMKO, etc.) make it a robust choice for safety-critical and industrial applications. The halogen-free and RoHS compliance aligns with modern environmental regulations.

. Frequently Asked Questions (FAQ)

Q: Can I drive the LED directly from a 5V logic output?
A: Yes, but you must calculate the series resistor. For example, with a typical V_Fof 1.2V and a desired I_Fof 5mA from a 5V supply: R = (5V - 1.2V) / 0.005A = 760Ω. Use a standard 750Ω resistor.

Q: What is the maximum switching frequency?
A: The practical switching frequency is limited by the rise and fall times. A conservative estimate for a square wave is 1/(t_r+t_f) ≈ 1/(250µs+100µs) ≈ 2.9kHz. For reliable operation, design for frequencies below 1kHz.

Q: How does temperature affect performance?
A: CTR typically decreases with increasing temperature. The dark current (I_CEO) increases with temperature. The forward voltage of the LED decreases with temperature. These effects must be considered for stable operation over the full temperature range.

Q: Is an external base connection available for speed-up?
A: No. This is a standard photodarlington with no external base lead. Switching speed cannot be improved by external components.

. Practical Design Case Study

Scenario:Isolating a 3.3V microcontroller signal to control a 24V DC relay coil.
Implementation:The microcontroller GPIO pin (3.3V) drives the LED via a 470Ω resistor, setting I_F≈ (3.3V - 1.2V)/470Ω ≈ 4.5mA. The relay coil (24V, 50Ω coil ≈ 480mA) is connected between a 24V supply and the collector of the EL452-G. The emitter is connected to ground. A flyback diode must be placed across the relay coil to suppress voltage spikes when the photodarlington turns off. At 4.5mA input, the CTR ensures a saturated output capable of sinking the relay current, with V_CE(sat)causing a small voltage drop. The 350V V_CEOprovides ample margin against the 24V supply and any inductive spikes.

. Operating Principle

The device operates on the principle of optical coupling. When current flows through the input infrared Light Emitting Diode (LED), it emits photons. These photons travel across a transparent insulating gap and strike the base region of the output darlington phototransistor pair. The absorbed photons generate electron-hole pairs, creating a base current that turns on the darlington transistor pair. This allows a much larger current to flow from the collector to the emitter, proportional to the LED current (defined by the CTR). The key is that the signal is transmitted by light, providing complete galvanic isolation between the input and output circuits, as there is no electrical connection—only an optical path through an insulating material.

. Industry Trends and Developments

The optocoupler market continues to evolve. Trends include the development of higher-speed digital isolators based on CMOS and RF technology, which offer superior speed, power consumption, and noise immunity compared to traditional optocouplers. However, photodarlington and phototransistor optocouplers like the EL452-G retain strong positions in applications requiring high voltage capability, high current output, simplicity, robustness, and cost-effectiveness for low-to-medium frequency isolation. There is also a continuous push for miniaturization, higher integration (e.g., combining multiple channels), improved reliability, and enhanced safety certifications to meet evolving global standards. The move towards halogen-free and environmentally friendly materials, as seen in the EL452-G, is a standard industry requirement.