STMicroelectronics SM15T56AY

Overview

SM15T56AY from STMicroelectronics is an AEC-Q101-qualified unidirectional automotive TVS diode in SMC package, designed to clamp transient surges up to 77.4 V (10/1000 µs) at 20 A peak pulse current while maintaining low dynamic resistance (0.925 Ω) and leakage current (0.2 µA at 25 °C). It delivers 1500 W peak pulse power (10/1000 µs) and meets ISO 7637-2 Pulse 1 (−150 V), Pulse 3a (−220 V), and ISO 10605 ESD (±30 kV contact/air) for 12 V battery rail protection.

For engineers reviewing the SM15T56AY datasheet, SM15T56AY pinout, SM15T56AY application, or SM15T56AY equivalent, key selection criteria include clamping voltage at rated surge current, junction temperature derating above 25 °C, standoff voltage margin relative to system operating voltage, and SMC footprint compatibility with IPC7531-compliant PCB layout.

Technical Context

This unidirectional TVS operates as a voltage-clamping overvoltage protector placed across DC power rails-typically between battery and load-to shunt energy from ISO 7637-2 transients (Pulse 1, 2a, 3a, 3b) and IEC/ISO ESD events. Its planar silicon junction enables stable V_BR (56 V nominal) with ±5% tolerance and low temperature coefficient (10.3 × 10⁻⁴/°C).

Clamping behavior is defined by V_CL = V_BR(max) + R_D × I_PP, where R_D = 0.925 Ω at 10/1000 µs ensures predictable voltage limiting under surge conditions. Junction temperature range spans −55 °C to +150 °C, supporting operation in engine bay environments with validated power derating down to 1250 W at T_j = 150 °C.

Key Specifications

Pinout & Package

SM15T56AY uses the industry-standard SMC (DO-214AB) surface-mount package with two terminals: Cathode (marked end) and Anode. The package measures 5.55–6.25 mm × 7.75–8.15 mm × 2.45 mm max height and features matte tin-plated leads compliant with J-STD-002 and JEDEC registered outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SMAJ56A and 1.5KE56A, SM15T56AY provides 3.75× higher surge power handling, 16.2 V lower clamping voltage at rated current, and AEC-Q101 qualification-making it the sole option for new automotive designs requiring ISO 7637-2 Pulse 1/3a and ESD immunity in SMT form factor.

Availability

SM15T56AY is available at Aetrix Electronics and suitable for body control modules, infotainment power supplies, and ADAS camera systems requiring stable component supply with full automotive-grade traceability and long-term lifecycle support.

Supply support for SM15T56AY 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, specializing in automotive, industrial, and power management solutions with vertical manufacturing and design expertise.

The SM15TxxAY series belongs to ST's automotive-grade transient voltage suppression portfolio, engineered specifically for robust protection of 12 V battery-fed ECUs, sensors, and communication interfaces against ISO 7637-2 and ISO 10605 threats.

FAQ

What is the maximum clamping voltage of SM15T56AY under a 10/1000 µs surge?

The maximum clamping voltage is 77.4 V at 20 A peak pulse current for a 10/1000 µs waveform, measured at T_j = 25 °C. This value increases with junction temperature per the α_T coefficient (10.3 × 10⁻⁴/°C), reaching approximately 81.2 V at T_j = 150 °C.

Does SM15T56AY require heatsinking for 1500 W surge dissipation?

No external heatsink is required for single-event surge handling. The SMC package achieves sufficient thermal performance via copper pour under both terminals per IPC7531 footprint; Figure 12 confirms R_th(j-a) ≤ 40 °C/W with ≥2 cm² total copper area, enabling safe 1500 W pulse dissipation at T_amb ≤ 85 °C.

How does SM15T56AY differ from bidirectional SM15T56CAY in circuit implementation?

SM15T56AY is unidirectional and must be oriented with cathode toward ground; it blocks reverse voltage but clamps only positive transients. SM15T56CAY is bidirectional and symmetrical, clamping both polarities-used where AC-coupled signals or dual-rail protection is needed, such as in LIN bus termination networks.

Can SM15T56AY replace older P6SMB56A in existing automotive designs?

Yes, with validation: SM15T56AY offers identical V_BR (56 V) and superior specs-1500 W vs. 600 W peak power, 0.925 Ω vs. 1.2 Ω R_D, and AEC-Q101 qualification-while sharing the same SMC footprint. Layout compatibility is confirmed by identical mechanical dimensions in Table 3 of DS6928.