STMicroelectronics SM6HT27A

Overview

SM6HT27A from STMicroelectronics is a unidirectional high-temperature Transil™ TVS diode designed for automotive circuit protection, featuring 27 V breakdown voltage (VBR), 37.5 V clamping voltage (VCL) at 44 A IPP, 600 W peak pulse power (10/1000 µs), and ≤5 µA leakage current at 150 °C. It operates in voltage regulation mode with planar junction technology and is qualified for under-hood applications requiring robust surge suppression.

For engineers reviewing the SM6HT27A datasheet, SM6HT27A pinout, SM6HT27A application, or SM6HT27A equivalent, this device serves as a high-reliability transient voltage suppressor for 12 V automotive power rails, ECU input protection, and CAN bus interface surge hardening - where low clamping factor, high-temperature stability, and JEDEC DO-214AA surface-mount compatibility are critical selection criteria.

Technical Context

The SM6HT27A employs a planar silicon junction structure optimized for stable voltage regulation under sustained thermal stress up to 175 °C junction temperature. Its unidirectional configuration provides forward conduction capability while maintaining precise reverse standoff (VRM = 23.1 V) and sharp avalanche turn-on at nominal VBR = 27 V.

Thermal design is supported by Rth(j-l) = 20 °C/W and Rth(j-a) = 100 °C/W on recommended FR4 pad layout, enabling reliable power dissipation of 6 W at 50 °C ambient. The device exhibits αT = 10⁻⁴ /°C temperature coefficient for VBR drift, ensuring predictable clamping behavior across automotive temperature ranges.

Key Specifications

Pinout & Package

SM6HT27A uses the SMB (DO-214AA) surface-mount package: molded plastic body with solderable planar terminals, cathode indicated by a band, UL94V-0 flammability rating, and RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transient voltage suppression applications.

Compared with SMAJ28A and 1.5SMC27A, the SM6HT27A delivers superior high-temperature reliability (≤5 µA IR at 150 °C), tighter VBR tolerance (±5%), and lower clamping ratio (1.39 vs. ≥1.54), making it the only choice for mission-critical automotive power rail protection where thermal margin and clamping precision are non-negotiable.

Availability

SM6HT27A is available at Aetrix Electronics and suitable for engine control units, body electronics power distribution, and CAN physical layer protection requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SM6HT27A 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The SM6HT series belongs to ST's automotive-grade Transil™ TVS portfolio, engineered specifically for high-temperature transient suppression in engine bay and powertrain applications where conventional TVS devices fail prematurely.

FAQ

Is SM6HT27A suitable for bidirectional transient protection?

No. SM6HT27A is a unidirectional TVS diode, intended for DC power rail protection where polarity is fixed. For bidirectional signal-line protection (e.g., USB, RS-485), ST offers the SMBJ series or dedicated bidirectional Transil™ variants like SM6HTxxCA. Using SM6HT27A in reverse-biased signal paths risks permanent breakdown due to lack of symmetrical avalanche characteristics.

What is the maximum continuous power dissipation for SM6HT27A at 100°C ambient?

At 100 °C ambient, SM6HT27A's continuous power dissipation is approximately 2.4 W, calculated using its Rth(j-a) = 100 °C/W and Tj(max) = 175 °C: P = (Tj − Tamb)/Rth(j-a) = (175 − 100)/100 = 0.75 W - however, ST specifies 6 W at Tamb = 50 °C with infinite heatsink, and derating follows linear thermal rules per Figure 2 in the datasheet.

Does SM6HT27A meet AEC-Q200 stress test requirements?

While SM6HT27A is designed for automotive applications and qualified to operate at 175 °C junction temperature, it is not formally AEC-Q200-qualified as a discrete component. ST positions it as a high-temperature Transil™ for automotive use, but system-level qualification per AEC-Q200 must be performed by the end customer based on full assembly testing and lifetime validation.

Can SM6HT27A replace SM6HT24A in an existing design?

Yes, with circuit review. SM6HT27A has higher VBR (27 V vs. 24 V) and VCL (37.5 V vs. 33.2 V), offering greater margin against normal operating voltage but reduced clamping sensitivity. Verify that downstream components tolerate the higher clamping level and that the increased standoff voltage does not delay transient response in fast-rising surge events such as ESD.