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NXP Semiconductors BT149B,126
,TO-226_straightlead.jpg)
- Part No.:
- BT149B,126
- Manufacturer:
- NXP Semiconductors
- Category:
- SCRs
- Package:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Datasheet:
-
BT149B,126.pdf
- Description:
- SCR 200V 800MA TO92-3
- Quantity:
- Payment:
- Shipping:
Inventory:8,688
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Product details
Overview
BT149B,126 from NXP Semiconductors is a passivated, sensitive-gate logic-level thyristor in SOT54 (TO-92) package, designed for direct interfacing with microcontrollers and low-power gate drivers. It supports 200 V repetitive peak off-state voltage (VDRM/VRRM), 0.8 A RMS on-state current (IT(RMS)), and 8 A non-repetitive surge current (ITSM), enabling reliable AC phase control and switching in compact consumer and industrial power circuits.
For engineers reviewing the BT149B,126 datasheet, BT149B,126 pinout, BT149B,126 application, or BT149B,126 equivalent, this page delivers verified electrical parameters, validated SOT54 pin mapping, real-world switching use cases, and two confirmed alternative thyristors with documented functional trade-offs for design-in validation.
Technical Context
The BT149B,126 operates as a silicon-controlled rectifier (SCR) with sensitive gate triggering-requiring only 50–200 µA gate trigger current (IGT) at 25 °C and maintaining latching/holding currents of 2–6 mA and 2–5 mA respectively. Its low VGT (0.5–0.8 V) and high dVD/dt immunity (500–800 V/µs with 1 kΩ gate resistor) enable robust noise-immune turn-on in noisy low-voltage control environments.
Thermal performance is defined by junction-to-lead thermal resistance (Rth(j-lead) ≤ 60 K/W) and junction-to-ambient (Rth(j-a) ≤ 150 K/W on PCB with 4 mm leads), supporting continuous operation up to 125 °C junction temperature while dissipating ≤ 0.8 W at rated IT(AV) = 0.5 A.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VDRM / VRRM | 200 V - maximum repetitive blocking voltage before unintended conduction; defines safe AC mains interface capability for 115 V RMS systems. |
| IT(RMS) | 0.8 A - RMS current handling under full-conduction-angle conditions; sets thermal limits for continuous load switching without heatsinking. |
| IGT | 50–200 µA - gate trigger current range at 12 V anode-cathode voltage; enables direct drive from GPIO pins or open-collector logic outputs. |
| VT | 1.25–1.7 V - on-state voltage drop at 1.2 A; determines conduction loss (≤ 2.04 W max) and self-heating during active conduction. |
| dVD/dt (RGK = 1 kΩ) | 500–800 V/µs - critical rate-of-rise immunity with gate resistor; prevents false triggering from EMI or fast transients in motor or lamp dimmer circuits. |
| tq | 100 µs - circuit-commutated turn-off time at 125 °C; defines minimum off-time required for reliable commutation in phase-control topologies. |
| Rth(j-lead) | ≤ 60 K/W - thermal resistance from junction to lead; enables accurate thermal modeling when leads are used as heat paths to PCB copper. |
Pinout & Package
SOT54 (TO-92) plastic single-ended leaded through-hole package with epoxy meeting UL94 V-0 flammability rating; 5.2 mm × 4.8 mm × 14.5 mm body, 2.54 mm lead pitch, and 1.27 mm inner lead spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | cathode (K) | Reference terminal for gate trigger reference and load return path; must be connected to lowest potential side of controlled AC load. |
| 2 | gate (G) | Control input requiring low-current pulse (≥50 µA) to initiate conduction; referenced to cathode; sensitive to ESD and transient overvoltage. |
| 3 | anode (A) | High-side terminal carrying full load current; blocks up to 200 V in reverse or off-state; connects to AC line or positive DC rail. |
Key Features
| Feature | Design Value |
|---|---|
| Logic-level gate sensitivity | Triggers reliably with <200 µA gate current-eliminates need for discrete gate driver stages when interfacing with 3.3 V/5 V MCUs. |
| Passivated junction | Enhanced reliability and moisture resistance per JEDEC JESD22-A110, supporting long-term operation in humid or thermally cycled environments. |
| High dVD/dt immunity | 800 V/µs with 1 kΩ gate resistor-prevents spurious turn-on in high-noise applications like universal motor speed controls or fan regulators. |
| Low holding current | 2–5 mA at 125 °C-ensures stable latched conduction even under light loads or elevated temperatures without gate retriggering. |
Applications
| AC Lamp Dimmer | Small Appliance Motor Control |
|---|---|
Use Scenario: Phase-angle dimming of incandescent or halogen lamps in residential lighting modules. IC Role / Device Role / Timing Role: Main AC power switch controlling conduction angle via zero-crossing synchronized gate pulses. Use Value: Enables smooth brightness adjustment using low-power MCU timing without external amplification, leveraging 50 µA IGT and 200 V VDRM. |
Use Scenario: Speed regulation of shaded-pole or universal motors in coffee makers, blenders, and exhaust fans. IC Role / Device Role / Timing Role: Bidirectional AC switch activated at precise phase points to modulate average motor torque. Use Value: Delivers 0.8 A IT(RMS) handling with 100 µs tq-supporting rapid on/off cycling and stable commutation at 50/60 Hz line frequencies. |
| Industrial Solenoid Driver | AC Power Sequencer |
Use Scenario: Controlled energization of 24–120 V AC solenoids in vending machines or HVAC actuators. IC Role / Device Role / Timing Role: High-voltage, low-duty-cycle switch triggered by logic-level signals to manage inductive load activation. Use Value: Withstands 8 A ITSM surges and maintains 2 mA IH at 125 °C-ensuring reliable pull-in and hold under varying ambient conditions. |
Use Scenario: Staged power-up of multiple AC subsystems (e.g., sensors, displays, pumps) in test equipment or lab instruments. IC Role / Device Role / Timing Role: Isolated, sequenced AC switching element controlled by microcontroller GPIO with minimal BOM overhead. Use Value: Direct microcontroller compatibility (no level-shifting) and 0.5 A IT(AV) rating allow clean sequencing of sub-500 mW loads without auxiliary drivers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar thyristor switching applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| BT134-600E,127 | 600 V VDRM/VRRM, 4 A IT(RMS), TO-92 package; higher voltage rating but requires ~5 mA IGT-needs gate buffer for MCU drive. | Supports 230 V AC mains directly; unsuitable for low-power logic-driven designs where gate sensitivity is critical. | Select when higher blocking voltage and surge current are prioritized over gate drive simplicity. |
| MAC97A6,127 | 600 V VDRM/VRRM, 0.8 A IT(RMS), TO-92; IGT = 10–50 mA-requires dedicated gate driver stage for 3.3 V/5 V logic. | Offers same RMS current as BT149B,126 but lacks logic-level sensitivity; better suited for buffered or transformer-isolated gate drive. | Choose when system already includes gate drive circuitry and higher voltage margin is needed over gate efficiency. |
Compared with BT149B,126, BT134-600E,127 provides higher voltage headroom at the cost of gate drive complexity, while MAC97A6,127 trades gate sensitivity for broader voltage compatibility-making BT149B,126 optimal for direct-MCU, low-voltage AC switching where minimal component count and low IGT are essential.
Availability
BT149B,126 is available at Aetrix Electronics and suitable for AC lamp dimmers, small appliance motor controllers, and industrial solenoid drivers requiring stable component supply across production lifecycles.
Supply support for BT149B,126 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
NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.
The BT149B,126 belongs to NXP's logic-level thyristor product line, engineered specifically for direct integration with low-power digital controllers in cost-sensitive AC power switching applications.
FAQ
What is the maximum junction temperature specification for BT149B,126?
The BT149B,126 has a maximum junction temperature (Tj) rating of 125 °C, as defined in the Absolute Maximum Ratings table. This limit applies under all operating conditions, including surge events. Exceeding this temperature risks permanent degradation of the passivated junction and reduced device lifetime. Thermal design must ensure Rth(j-lead) ≤ 60 K/W and proper lead-to-PCB thermal coupling to maintain safe operation within this bound.
Can BT149B,126 be driven directly from a 3.3 V microcontroller GPIO pin?
Yes, BT149B,126 can be driven directly from a 3.3 V microcontroller GPIO pin because its gate trigger current (IGT) is specified at 50–200 µA and gate trigger voltage (VGT) is 0.5–0.8 V at 25 °C. A series resistor of 2.2–4.7 kΩ limits gate current to safe levels while ensuring sufficient IGT margin-even at elevated temperatures where IGT increases. No external transistor or driver IC is required.
What is the non-repetitive peak on-state current (ITSM) rating for BT149B,126 at 10 ms pulse width?
The BT149B,126 has a non-repetitive peak on-state current (ITSM) rating of 8 A for a 10 ms half-sine pulse at Tj = 25 °C prior to surge, as stated in Table 3 of the NXP datasheet. This value decreases with increasing junction temperature and shorter pulse durations-designers must consult Figure 2 and Figure 3 to verify safe operation under actual thermal and waveform conditions.
Does BT149B,126 meet any flammability standards for its package material?
Yes, the SOT54 (TO-92) package of BT149B,126 uses epoxy that meets UL94 V-0 flammability requirements at 1/8 inch thickness, as confirmed in Section 7 of the NXP datasheet. This certification ensures self-extinguishing behavior and low flame spread-critical for compliance in consumer and industrial end-equipment safety certifications.
How does the holding current (IH) of BT149B,126 change with temperature?
The holding current (IH) of BT149B,126 increases with junction temperature: it ranges from 2–5 mA at 25 °C and rises to approximately 3× that value near 125 °C, as shown in Figure 11 of the datasheet. This positive temperature coefficient ensures stable latched conduction under thermal stress, preventing unintended turn-off during sustained load operation.
BT149B,126 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- TO-226-3, TO-92-3 (TO-226AA) Formed Leads
- Packaging:
- Tape & Box (TB)
- Product Status:
- Obsolete
- Voltage - Off State:
- 200 V
- Voltage - Gate Trigger (Vgt) (Max):
- 800 mV
- Current - Gate Trigger (Igt) (Max):
- 200 µA
- Voltage - On State (Vtm) (Max):
- 1.7 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):
- 100 µA
- Current - Non Rep. Surge 50, 60Hz (Itsm):
- 8A, 9A
- SCR Type:
- Sensitive Gate
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-92-3
BT149B,126 FAQ
1.How can I place an order for BT149B,126 through Aetrix?
Please submit a Request for Quotation (RFQ) for BT149B,126 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 BT149B,126 reliable?
The price and inventory of BT149B,126 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BT149B,126 is usually 5 days.
3.What payment methods are accepted for BT149B,126?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BT149B,126 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BT149B,126?
BT149B,126 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BT149B,126 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 BT149B,126?
For technical support, including BT149B,126 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BT149B,126 requirements.
6.How does Aetrix verify that BT149B,126 is sourced from the original manufacturer or authorized distributors?
All BT149B,126 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 BT149B,126 meets industry standards.
7.What is the process for return or replacement of BT149B,126?
All BT149B,126 units undergo pre-shipment inspection (PSI). If there is an issue with BT149B,126, 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 BT149B,126 part is unused and in its original packaging.
Return procedure for BT149B,126:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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