NXP Semiconductors BT1308-400D,412

Overview

BT1308-400D from NXP Semiconductors is a passivated sensitive-gate triac in SOT54 (TO-92) package, rated for 400 V repetitive peak off-state voltage (V_DRM), 0.8 A RMS on-state current (I_T(RMS)), and ≤5 mA gate trigger current (I_GT). It enables direct logic-level interfacing and is used in low-power AC fan speed control and general-purpose phase-control circuits.

For engineers reviewing the BT1308-400D datasheet, BT1308-400D pinout, BT1308-400D application, or BT1308-400D equivalent, key selection criteria include quadrants-triggering capability (T2−G+ to T2+G−), dV/dt immunity (≥45 V/µs), thermal resistance (R_th(j-lead) = 60 K/W), and compatibility with low-power gate drive circuits without external amplification.

Technical Context

The BT1308-400D operates as a bidirectional thyristor switch with four-quadrant gate triggering-supporting all combinations of main terminal polarity and gate polarity (T2+/G+, T2+/G−, T2−/G−, T2−/G+). Its sensitive gate design allows triggering with ≤5 mA across three quadrants and ≤7 mA in T2−/G+ mode.

It features a maximum junction temperature of 125 °C, non-repetitive surge rating of 9 A (20 ms), and commutating dV/dt capability of 5 V/µs. The device uses passivated silicon die for enhanced reliability in humid or contaminated environments and is optimized for through-hole mounting on PCBs with 4 mm lead length.

Key Specifications

Pinout & Package

SOT54 (TO-92) plastic single-ended leaded through-hole package with 3 leads; standardized outline per IEC 60134, JEDEC TO-92, and JEITA SC-43A.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triac switching applications.

Compared with BT131-600D and MAC97A6, the BT1308-400D delivers the lowest gate drive requirement (≤5 mA) and highest dV/dt immunity (≥45 V/µs) within its 400 V class-making it the preferred choice for noise-prone, microcontroller-driven AC control where minimal external components are critical.

Availability

BT1308-400D is available at Aetrix Electronics and suitable for AC fan speed control, light dimming circuits, small appliance motor control, and heater power regulation requiring stable component supply and long-term manufacturability.

Supply support for BT1308-400D 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, automotive ICs, and power management devices.

The BT1308 series belongs to NXP's logic-level triac product line, designed specifically for cost-sensitive, low-power AC switching applications where direct microcontroller interfacing and high noise immunity are essential.

FAQ

What is the maximum gate trigger current specification for BT1308-400D?

The BT1308-400D has a maximum gate trigger current (I_GT) of 5 mA in T2+/G+, T2+/G−, and T2−/G− quadrants, and 7 mA in the T2−/G+ quadrant. This low I_GT enables direct drive from standard 3.3 V or 5 V logic outputs without external amplification, making BT1308-400D ideal for microcontroller-based AC control designs.

Can BT1308-400D be used in 230 V AC mains applications?

Yes, BT1308-400D is rated for 400 V repetitive peak off-state voltage (V_DRM), which corresponds to safe operation on 230 V RMS mains (peak ≈ 325 V) with adequate safety margin. However, designers must verify actual line transients and ensure dV/dt stress remains below 45 V/µs; use of RC snubbers may be required in high-noise environments. BT1308-400D remains valid for this use case when properly applied.

What is the thermal resistance from junction to lead for BT1308-400D?

The BT1308-400D has a maximum thermal resistance from junction to lead (R_th(j-lead)) of 60 K/W. This value defines the temperature rise at the die per watt of power dissipated into the PCB copper or chassis. For example, at 0.8 A RMS and 1.5 V on-state drop (1.2 W), junction-to-lead temperature rise is ≤72 °C-critical for estimating safe operating area without heatsinking. BT1308-400D's R_th(j-lead) is confirmed in Table 4 of the NXP datasheet.

Does BT1308-400D support all four triggering quadrants?

Yes, BT1308-400D supports gate triggering in all four quadrants (T2+/G+, T2+/G−, T2−/G−, T2−/G+), as explicitly stated in the NXP datasheet Section 1.2 Features and verified in Table 5 (IGT values per quadrant). This enables flexible gate drive design-no polarity inversion circuitry is needed-and ensures reliable turn-on regardless of AC half-cycle polarity. BT1308-400D's full-quadrant capability is a core functional differentiator versus simpler two-quadrant triacs.

What is the non-repetitive peak on-state current rating for BT1308-400D?

The BT1308-400D is rated for a non-repetitive peak on-state current (I_TSM) of 9 A for a pulse width of 20 ms, and 10 A for 16.7 ms (one 60 Hz half-cycle), per Table 3 in the NXP datasheet. This rating supports inrush currents from motors, lamps, or transformers without device failure. BT1308-400D's I_TSM is validated under T_j = 25 °C prior to surge and must be applied with appropriate thermal recovery time between surges.