My Inquiry
My Account
STMicroelectronics XL0840
,TO-226_straightlead.jpg)
- Part No.:
- XL0840
- Manufacturer:
- STMicroelectronics
- Category:
- SCRs
- Package:
- TO-226-3, TO-92-3 (TO-226AA)
- Datasheet:
-
XL0840.pdf
- Description:
- SCR 400V 800MA TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:7,332
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
XL0840 from STMicroelectronics is an asymmetric sensitive-gate silicon-controlled rectifier (SCR) rated for 0.8 A RMS on-state current and 400 V repetitive peak off-state voltage, with gate trigger current as low as 200 µA at 25 °C and dV/dt immunity of 75 V/µs at 125 °C; it is designed for low-power AC load switching in decorative lighting control circuits.
For engineers reviewing the XL0840 datasheet, XL0840 pinout, XL0840 application, or XL0840 equivalent, key selection considerations include sensitive gate drive capability, thermal resistance (Rth(j-a) = 150 °C/W), junction temperature range (–40 to +125 °C), and TO-92 package compatibility with through-hole board assembly.
Technical Context
The XL0840 operates as an asymmetrical SCR-blocking forward voltage only (not reverse), enabling simplified half-wave AC control without external reverse-blocking diodes. Its sensitive gate allows direct drive from microcontroller GPIOs or optocouplers with minimal current budget (≤200 µA).
It features high dV/dt immunity (75 V/µs at 125 °C) and low holding current (max. 5 mA), supporting stable latching in noisy, low-current-trigger environments such as seasonal light strings where EMI and limited gate drive are typical.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| IT(RMS) | 0.8 A - maximum continuous RMS load current at TC = 55 °C, defining safe steady-state power handling |
| VDRM | 400 V - peak repetitive off-state voltage, sets maximum AC line voltage compatibility (e.g., 230 VAC RMS) |
| IGT | 200 µA max at 25 °C - minimum gate current required for reliable turn-on, enabling direct MCU/opto drive |
| dV/dt | 75 V/µs min at 125 °C - immunity to false triggering from fast transients in noisy AC environments |
| Rth(j-a) | 150 °C/W - junction-to-ambient thermal resistance (DC), determines self-heating under load without heatsink |
| IDRM | 100 µA max at 125 °C - peak off-state leakage, critical for low-power standby integrity |
| VTM | 1.95 V max at ITM = 1.6 A - on-state voltage drop, directly impacts conduction loss and thermal rise |
Pinout & Package
XL0840 is housed in a standard TO-92 plastic package with axial leads, optimized for manual or automated through-hole insertion and compatible with FR4 PCB layouts per ST's recommended pad dimensions.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode (A) | Main current entry terminal | Carries full load current into device; must connect to AC line phase or switched hot side |
| Cathode (K) | Main current exit terminal | Connects to load return path; referenced for gate drive and defines SCR polarity |
| Gate (G) | Control input terminal | Triggers conduction when ≥200 µA applied relative to cathode; sensitive enough for direct optocoupler output |
Key Features
| Feature | Design Value |
|---|---|
| Sensitive gate triggering | IGT ≤ 200 µA enables direct drive from low-current sources like microcontroller pins or PC817 outputs |
| High dV/dt immunity | 75 V/µs at 125 °C prevents spurious turn-on during AC zero-crossing noise or dimmer harmonics |
| Low leakage at high temperature | IDRM ≤ 100 µA at 125 °C ensures reliable off-state blocking in enclosed, thermally stressed fixtures |
| Asymmetric blocking | Blocks only forward voltage (VDRM = 400 V), eliminating need for reverse parallel diode in half-wave applications |
Applications
| Christmas Light Strings | LED Night Light Dimming |
|---|---|
Use Scenario: Sequential or grouped illumination of incandescent/LED mini-lights powered from 120/230 VAC mains. IC Role / Device Role / Timing Role: Asymmetric SCR acting as half-wave AC switch, triggered once per half-cycle by low-current gate pulse. Use Value: Eliminates need for reverse-blocking components while maintaining robust noise immunity in unshielded wiring bundles. | Use Scenario: Mains-powered LED night lights with simple brightness control via phase-cut dimming. IC Role / Device Role / Timing Role: Sensitive-gate SCR providing zero-crossing–referenced turn-on for smooth, flicker-free dimming. Use Value: Enables use of passive RC timing networks instead of active drivers, reducing BOM cost and component count. |
| AC Fan Speed Control | Low-Power Appliance Power Switching |
Use Scenario: Single-speed or stepped speed control of shaded-pole fans in small appliances. IC Role / Device Role / Timing Role: Half-wave AC switch triggered by optocoupler-isolated gate signal synchronized to AC phase. Use Value: Supports operation at <5 mA holding current, ensuring stable latching even with inductive kickback and low gate drive margin. | Use Scenario: Mains isolation and on/off control of auxiliary circuits (e.g., indicator lamps, solenoid buzzers) in industrial panels. IC Role / Device Role / Timing Role: Solid-state replacement for electromechanical relays, driven by logic-level signals. Use Value: Reduces mechanical wear and contact arcing while maintaining compatibility with existing 5 V/3.3 V control interfaces. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar sensitive-gate SCR applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BT169G | Higher IGT (50 µA typ. but 200 µA max), same VDRM (400 V), TO-92 package | Lower dV/dt immunity (60 V/µs typ.), less suited for noisy decorative lighting wiring | Preferable where tighter gate current tolerance is needed, but verify noise environment |
| TYN104 | Higher IT(RMS) (1 A), higher IGT (50 µA typ., 200 µA max), same TO-92 footprint | Higher thermal mass and Rth(j-a) (125 °C/W), requires larger copper area for same power dissipation | Choose when future-proofing for higher load current or improved surge rating (ITSM = 10 A) |
Compared with BT169G and TYN104, XL0840 offers superior dV/dt immunity and lower thermal resistance for compact designs, making it optimal for space-constrained, noise-prone seasonal lighting where gate drive margin is minimal.
Availability
XL0840 is available at Aetrix Electronics and suitable for Christmas light control, LED night light dimming, AC fan speed regulation, and low-power appliance switching requiring stable component supply across seasonal production cycles.
Supply support for XL0840 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.
XL0840 belongs to ST's "Sensitive SCR" series, engineered specifically for low-current-trigger AC switching in cost-sensitive, high-volume lighting and appliance control applications.
FAQ
What is the maximum junction temperature for continuous operation of XL0840?
The XL0840 has a specified operating junction temperature range of –40 °C to +125 °C. Continuous operation must maintain Tj ≤ +125 °C, which requires derating IT(RMS) above TC = 55 °C per Figure 2 in the datasheet, and accounting for Rth(j-a) = 150 °C/W in still-air conditions.
Can XL0840 be used in full-wave AC switching applications?
No-XL0840 is an asymmetric SCR and blocks voltage only in the forward direction (A→K). It cannot block reverse voltage, so it is unsuitable for full-wave or bridge configurations without external reverse-blocking components such as a parallel diode.
Is XL0840 RoHS-compliant and lead-free?
Yes-XL0840 is manufactured in ECOPACK®2-compliant packaging with no RoHS exemptions, meeting EU Directive 2011/65/EU requirements including lead-free terminations and halogen-free molding compounds.
What is the minimum gate-cathode resistance required to ensure reliable turn-off?
A gate-cathode resistor ≤1 kΩ is recommended to ensure rapid discharge of gate capacitance and prevent false re-triggering. Figure 6 shows IH increases significantly above RGK = 1 kΩ; exceeding this value risks failure to latch or erratic commutation under load.
XL0840 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Voltage - Off State:
- 400 V
- Voltage - Gate Trigger (Vgt) (Max):
- 800 mV
- Current - Gate Trigger (Igt) (Max):
- 200 µA
- Voltage - On State (Vtm) (Max):
- 1.95 V
- Current - On State (It (AV)) (Max):
- 500 mA
- Current - On State (It (RMS)) (Max):
- 800 mA
- Current - Hold (Ih) (Max):
- 5 mA
- Current - Off State (Max):
- 1 µA
- Current - Non Rep. Surge 50, 60Hz (Itsm):
- 7A, 8A
- SCR Type:
- Sensitive Gate
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
XL0840 FAQ
1.How can I place an order for XL0840 through Aetrix?
Please submit a Request for Quotation (RFQ) for XL0840 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for XL0840 reliable?
The price and inventory of XL0840 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for XL0840 is usually 5 days.
3.What payment methods are accepted for XL0840?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for XL0840 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for XL0840?
XL0840 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your XL0840 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for XL0840?
For technical support, including XL0840 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your XL0840 requirements.
6.How does Aetrix verify that XL0840 is sourced from the original manufacturer or authorized distributors?
All XL0840 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that XL0840 meets industry standards.
7.What is the process for return or replacement of XL0840?
All XL0840 units undergo pre-shipment inspection (PSI). If there is an issue with XL0840, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The XL0840 part is unused and in its original packaging.
Return procedure for XL0840:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
XL0840 Tags
-
MCR12DSNT4G
Littelfuse Inc.
-
2N6404G
Littelfuse Inc.
-
S4015LTP
Littelfuse Inc.
-
VS-25TTS12HM3
Vishay General Semiconductor - Diodes Division
-
S4020LTP
Littelfuse Inc.
-
MCR12MG
Littelfuse Inc.
-
MCR69-3G
Littelfuse Inc.
-
S8025LTP
Littelfuse Inc.
-
CMA30E1600PN
IXYS
-
S8016RATP
Littelfuse Inc.
-
TXN625RG
STMicroelectronics
.jpg)
-
SK055RTP
Littelfuse Inc.
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
