Taiwan Semiconductor Corporation SMDJ85A

Overview

SMDJ85A from Taiwan Semiconductor is a unidirectional 3000W surface-mount transient voltage suppressor (TVS) diode in DO-214AB (SMC) package, with 85V working stand-off voltage (VWM), 94.4–104V breakdown voltage (VBR), and 137V maximum clamping voltage (VC) at 21.9A peak pulse current - designed to protect power rails and I/O lines in industrial motor drives against ISO 7637-2 Pulse 1/2a/2b/3a/3b transients.

For engineers reviewing the SMDJ85A datasheet, SMDJ85A pinout, SMDJ85A application, or SMDJ85A equivalent, key selection criteria include clamping performance under 10/1000µs surge, thermal resistance (R_θJA = 75°C/W), unidirectional polarity marking, and compatibility with automated SMT placement per J-STD-002 solderability standards.

Technical Context

The SMDJ85A employs a glass-passivated silicon junction optimized for fast transient response (<1.0ps), enabling effective suppression of ESD and load-switching spikes before sensitive downstream circuitry is stressed. Its single-die unidirectional configuration provides asymmetric conduction: low forward voltage (VF = 3.5V @ 100A) during fault conditions and sub-1µA reverse leakage at 85V.

Thermally, it sustains 175°C junction temperature with 6.5W steady-state dissipation and relies on PCB copper area for heat spreading; its R_θJL = 15°C/W indicates efficient lead-to-board conduction, critical for high-reliability automotive and industrial power supply designs where ambient temperatures exceed 85°C.

Key Specifications

Pinout & Package

Package: DO-214AB (SMC), surface-mount, matte tin-plated leads, cathode band marked on case for polarity identification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SAC85 and 1.5KE85A, the SMDJ85A delivers full 3000W surge immunity in a compact SMT package with industry-standard moisture sensitivity level 1 - making it the preferred choice for automotive and industrial designs requiring automated manufacturing and validated ISO 7637-2 compliance.

Availability

SMDJ85A is available at Aetrix Electronics and suitable for industrial motor drives, automotive body control modules, telecom power supplies, and renewable energy inverters requiring stable component supply across multi-year production cycles.

Supply support for SMDJ85A 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

Taiwan Semiconductor Corporation (TSC) is a vertically integrated analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, specializing in TVS diodes, rectifiers, and power MOSFETs since 1979.

The SMDJ series was developed specifically for high-power, surface-mount transient suppression in automotive and industrial environments - emphasizing robustness, AEC-Q200 alignment, and seamless integration into automated SMT lines.

FAQ

What is the maximum clamping voltage of the SMDJ85A under a 10/1000µs surge?

The SMDJ85A has a maximum clamping voltage (VC) of 137 V when subjected to its rated peak pulse current of 21.9 A under the standardized 10/1000µs waveform. This value is measured per JEDEC standards and defines the upper voltage limit imposed on protected circuitry during surge events. Designers must ensure downstream components tolerate this clamped voltage with appropriate safety margin. The SMDJ85A achieves this performance while maintaining low leakage and fast response.

Is the SMDJ85A suitable for bidirectional transient protection?

No, the SMDJ85A is a unidirectional TVS diode and is not rated for bidirectional operation. It features a cathode band marking and conducts only in reverse breakdown above VBR. For bidirectional protection, the SMDJ85CA variant must be used - which shares the same package and stand-off voltage but provides symmetrical clamping in both polarities. Using SMDJ85A in bidirectional applications risks failure during positive-going transients.

Does the SMDJ85A meet automotive transient immunity standards?

Yes, the SMDJ85A meets ISO 7637-2 requirements for Pulse 1, 2a, 2b, 3a, and 3b, making it suitable for 12V and 24V automotive subsystems including body control modules and infotainment power supplies. Its 3000W peak power rating and 137V clamping voltage align with load-dump and inductive switching test profiles. However, full AEC-Q200 qualification requires verification of the specific lot and packaging - consult TSC's qualified parts list for certified batches.

What is the thermal resistance from junction to ambient for the SMDJ85A?

The SMDJ85A has a junction-to-ambient thermal resistance (R_θJA) of 75°C/W under standard JEDEC test conditions (single-layer 1 in² copper pad). This value assumes minimal PCB copper; actual thermal performance improves significantly with enhanced heatsinking - such as internal ground planes or thermal vias. For sustained surge duty cycles, designers should verify junction temperature using R_θJA, power dissipation, and ambient conditions to ensure operation remains below 175°C. The SMDJ85A's R_θJL = 15°C/W further supports efficient conduction to PCB traces.

Can the SMDJ85A be used in RoHS-compliant and halogen-free assemblies?

Yes, the SMDJ85A is fully RoHS compliant and halogen-free per IEC 61249-2-21. Its molding compound meets UL 94V-0 flammability rating, and terminals are matte tin plated per J-STD-002 for lead-free solder compatibility. These attributes make the SMDJ85A suitable for consumer electronics, medical devices, and industrial equipment subject to strict environmental regulations. No exemptions or special handling are required for compliance reporting - the SMDJ85A carries full material declarations per IPC-1752.