STMicroelectronics SM15T24A

Overview

SM15T24A from STMicroelectronics is a unidirectional 1500 W transient voltage suppression diode in SMC package, designed for IEC 61000-4-2 ESD (30 kV air/contact) and IEC 61000-4-4 surge (4 kV level 4) protection of DC power rails and signal lines. It features 24 V standoff voltage (VRM = 24 V), 33.2 V clamping voltage at 1 A (VCL = 33.2 V), and 0.2 µA leakage at 25 °C - optimized for high-reliability SMPS and industrial control inputs.

For engineers reviewing the SM15T24A datasheet, SM15T24A pinout, SM15T24A application, or SM15T24A equivalent, key selection criteria include clamping performance under 10/1000 µs surges, junction temperature derating above 25 °C, low-leakage operation at elevated Tj, and SMC footprint compatibility with IPC7531-compliant PCB layouts.

Technical Context

This TVS diode uses planar silicon technology to achieve stable breakdown behavior across -55 °C to +150 °C junction temperature range, with thermal coefficient αT = 9.4 × 10⁻⁴ /°C for both VBR and VCL. Its unidirectional polarity enables asymmetric clamping on positive-going transients only, preserving reverse-bias integrity in DC supply paths.

The device delivers 1500 W peak pulse power at Tamb = 25 °C (10/1000 µs), derating to 1250 W at Tj = 150 °C. Dynamic resistance RD = 0.178 Ω ensures minimal voltage overshoot during fast 8/20 µs surges up to 42.8 A, while junction capacitance remains below 45 pF at VR = 0 V (f = 1 MHz).

Key Specifications

Pinout & Package

SM15T24A is housed in an SMC (DO-214AB) surface-mount package with two terminals: Cathode (marked side) and Anode. The package complies with JEDEC MO-136AC and IPC7531 footprints, featuring 7.75–8.15 mm body width (E), 5.55–6.25 mm length (D), and 1.90–2.45 mm height (A1). Lead finish is matte tin plating per J-STD-002.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar TVS diode applications.

Compared with SMBJ24A and P6SMB24A, SM15T24A offers superior surge energy handling (1500 W vs. 600 W), lower clamping impedance, and lowest leakage in its class - making it optimal for high-reliability 24 V industrial and automotive power rail protection where long-term stability matters.

Availability

SM15T24A is available at Aetrix Electronics and suitable for industrial power supplies, automotive body electronics, telecom remote units, and factory automation I/O requiring stable component supply across multi-year production cycles.

Supply support for SM15T24A 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 microcontrollers, power management ICs, sensors, and discrete protection devices for industrial, automotive, and consumer markets.

SM15T24A belongs to ST's high-power planar TVS diode family targeting robust, low-leakage transient suppression in harsh-environment power systems - engineered specifically for reliability-critical 24 V DC infrastructure.

FAQ

What is the maximum clamping voltage of SM15T24A under a 10/1000 µs surge?

The SM15T24A clamps to 33.2 V at 1 A (IPP = 1 A) for 10/1000 µs waveform per Table 2. At higher currents - e.g., 10 A - VCL rises to approximately 45 V due to dynamic resistance (RD = 0.178 Ω), calculated as VCL = 33.2 V + RD × (IPP − 1 A). This value is confirmed in Figure 5 of DS0683 Rev 8.

Can SM15T24A be used in bidirectional signal lines?

No - SM15T24A is unidirectional and only protects against positive transients relative to ground. For bidirectional protection (e.g., RS-485, CAN), the CA variant SM15T24CA must be used. Using SM15T24A on AC-coupled or floating lines risks reverse breakdown and permanent damage during negative excursions.

How does junction temperature affect breakdown voltage?

VBR increases with junction temperature at αT = 9.4 × 10⁻⁴ /°C. At Tj = 125 °C, VBR shifts from 22.8 V (typ.) at 25 °C to ~24.5 V - verified by the formula VBR(Tj) = VBR(25°C) × [1 + αT × (Tj − 25)]. This positive TC ensures safe margin expansion under thermal stress.

Is SM15T24A compatible with lead-free reflow processes?

Yes - SM15T24A meets J-STD-020 MSL level 1 and is qualified for lead-free reflow with peak temperature up to 245 °C (see Figure 21). Matte tin plating ensures reliable wetting, and the SMC package withstands ramp rates ≤3 °C/s and soak times ≤90 s without delamination or voiding.