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Taiwan Semiconductor Corporation SMAJ85A
- Part No.:
- SMAJ85A
- Manufacturer:
- Taiwan Semiconductor Corporation
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
SMAJ85A.pdf
- Description:
- TVS DIODE 85VWM 137VC DO214AC
- Quantity:
- Payment:
- Shipping:
Inventory:5,922
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Product details
Overview
SMAJ85A from Taiwan Semiconductor is a unidirectional surface-mount transient voltage suppressor (TVS) diode designed for primary-side overvoltage protection in DC power rails. It features a 85 V working stand-off voltage (VWM), 94.4–104 V breakdown voltage (VBR), 137 V maximum clamping voltage (VC) at 2.2 A peak impulse current, and 400 W peak pulse power rating with 10/1000 µs waveform - deployed in automotive infotainment power inputs and industrial PLC I/O modules.
For engineers reviewing the SMAJ85A datasheet, SMAJ85A pinout, SMAJ85A application, or SMAJ85A equivalent, key selection criteria include clamping performance under ISO 7637-2 Pulse 1/2a/2b/3a/3b transients, DO-214AC (SMA) package compatibility with automated SMT lines, junction temperature derating above 25°C, and unidirectional polarity marking per cathode band.
Technical Context
The SMAJ85A operates as a silicon avalanche diode with glass-passivated junction, delivering sub-1 ps response time from 0 V to VBR min and reverse leakage <1 µA at 85 V. Its single-die DO-214AC construction supports unidirectional surge suppression only, with polarity defined by cathode band marking and no bidirectional capability.
It meets ISO 7637-2 immunity requirements for automotive electronics and is rated for TJ = –55°C to +150°C operation. The device exhibits 3.5 V maximum forward voltage at 25 A and withstands 40 A non-repetitive forward surge (8.3 ms half-sine), enabling robust front-end protection in high-energy transient environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VWM | 85 V - Maximum continuous DC or RMS voltage the device blocks without conduction |
| VBR min/max | 94.4 V / 104 V at 1 mA - Ensures reliable avalanche initiation within tight tolerance for predictable clamping onset |
| VC @ IPPM | 137 V at 2.2 A (10/1000 µs) - Limits downstream voltage stress during worst-case transients |
| PPPM | 400 W (10/1000 µs) - Sustains high-energy surges common in automotive load-dump and inductive switching events |
| IR @ VWM | <1 µA - Negligible standby power loss and minimal impact on high-impedance sensing circuits |
| Package | DO-214AC (SMA) - Industry-standard surface-mount outline compatible with IPC-7351B land patterns |
| Polarity | Unidirectional with cathode band - Requires correct orientation in series with protected line; not suitable for AC or bipolar rail protection |
Pinout & Package
DO-214AC (SMA) package: molded epoxy case with matte tin-plated leads, UL 94V-0 rated, 0.060 g weight, JESD201 Class 2 whisker resistance, and moisture sensitivity level 1 (MSL-1).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Input side of protected DC rail | Connected to source (e.g., battery+, SMPS output); conducts during reverse-biased transient |
| Cathode | Ground reference / return path | Connected to system ground; defines unidirectional clamping direction via marked band |
Key Features
| Feature | Design Value |
|---|---|
| Glass-passivated junction | Ensures stable VBR over lifetime and improved reliability vs. non-passivated alternatives in humid or thermally cycled environments |
| <1 ps response time | Clamps transients before sensitive downstream ICs (e.g., MCU power pins or CAN transceivers) experience overvoltage stress |
| ISO 7637-2 compliance | Validated for Pulse 1 (inductive load dump), Pulse 2a/2b (switching transients), and Pulse 3a/3b (capacitive coupling) in 12 V automotive systems |
| RoHS & halogen-free | Meets IEC 61249-2-21 and EU RoHS Directive 2011/65/EU for environmentally compliant industrial and automotive manufacturing |
Applications
| Automotive Infotainment Power Input | Industrial PLC Digital I/O Protection |
|---|---|
Use Scenario: 12 V supply line feeding head unit or display module exposed to load-dump transients up to 35 V for 400 ms. IC Role / Device Role / Timing Role: Primary overvoltage clamp placed upstream of DC/DC converter input stage. Use Value: Limits voltage to ≤137 V during ISO 7637-2 Pulse 5a, preventing damage to buck controller ICs and enabling use of lower-voltage-rated input capacitors. |
Use Scenario: 24 V digital input channel subjected to field-wiring induced surges from relay coil back-EMF or ESD contact discharge. IC Role / Device Role / Timing Role: Standoff protector between terminal block and optocoupler input stage. Use Value: Clamps 1 kV/500 A 10/1000 µs surge to 137 V within 1 ps, preserving optocoupler CTR and enabling >100,000-cycle surge endurance. |
| LED Driver Secondary-Side Output | Telecom DC Power Feeder |
Use Scenario: Constant-current LED string powered from isolated flyback output, vulnerable to output capacitor discharge transients. IC Role / Device Role / Timing Role: Output rail clamp parallel to LED load, absorbing stored energy during hot-plug or short-circuit recovery. Use Value: Dissipates 400 W peak pulse without degradation, maintaining LED driver feedback stability and avoiding false OVP shutdown. |
Use Scenario: –48 V telecom power feed line encountering lightning-induced longitudinal surges on copper pairs. IC Role / Device Role / Timing Role: Unidirectional shunt protector on negative rail relative to chassis ground. Use Value: Withstands 2.2 A peak impulse at 137 V clamping, meeting Telcordia GR-1089-CORE Level 3 surge immunity for central office equipment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar TVS diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMAJ85 (non-A version) | VBR max = 115 V (vs. 104 V for SMAJ85A); VC = 151 V at 2.0 A - higher clamping voltage and looser VBR tolerance | Less suitable for tight-margin 85 V systems where clamping headroom is constrained | Select SMAJ85A when precise low-VBR and low-VC are required for protecting 100 V-rated downstream components |
| SMBJ85A | Same VWM/VBR/VC specs but in DO-214AA (SMB) package - 2.5 mm × 4.5 mm footprint vs. SMAJ85A's 2.8 mm × 4.6 mm | Higher thermal resistance (RθJA ≈ 150°C/W vs. SMAJ85A's ~130°C/W) limits sustained surge duty cycle | Choose SMAJ85A for better power dissipation margin in high-ambient-temperature industrial enclosures |
Compared with SMAJ85 and SMBJ85A, the SMAJ85A delivers tighter VBR control (±5.2% vs. ±10.5%), lower clamping voltage (137 V vs. 151 V), and superior thermal performance in the DO-214AC package - making it optimal for space-constrained yet thermally demanding automotive and industrial DC rail protection.
Availability
SMAJ85A is available at Aetrix Electronics and suitable for automotive infotainment power inputs, industrial PLC digital I/O protection, and LED driver secondary-side outputs requiring stable component supply, full MSL-1 handling, and traceable RoHS-compliant sourcing.
Supply support for SMAJ85A 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, MOSFETs, and power management devices since 1979.
The SMAJ series was developed specifically for high-reliability, surface-mount transient suppression in automotive and industrial environments - emphasizing ISO 7637-2 compliance, tight parametric tolerances, and automated assembly readiness.
FAQ
What is the clamping voltage of SMAJ85A under standard test conditions?
The SMAJ85A has a maximum clamping voltage (VC) of 137 V when subjected to a 10/1000 µs waveform with a peak impulse current (IPPM) of 2.2 A. This value is measured at TA = 25°C and reflects the upper limit of voltage seen across the device during surge events - critical for ensuring downstream components remain within their absolute maximum ratings. The SMAJ85A achieves this while maintaining <1 µA leakage at its 85 V working stand-off voltage.
Is SMAJ85A suitable for bidirectional transient protection?
No, SMAJ85A is a unidirectional TVS diode and must be used with correct polarity - anode to the protected line, cathode to ground. It does not provide symmetrical clamping for AC or dual-rail applications. For bidirectional protection at 85 V standoff, Taiwan Semiconductor specifies the SMAJ85CA variant (with "CA" suffix), which uses a center-tapped dual-die configuration. Using SMAJ85A in reverse-biased configurations will result in forward conduction and failure.
How does SMAJ85A meet automotive EMC requirements?
SMAJ85A is explicitly validated to meet ISO 7637-2 test pulses 1, 2a, 2b, 3a, and 3b - covering load-dump, switch-off transients, and capacitive coupling events in 12 V vehicle electrical systems. Its sub-1 ps response time ensures clamping activation before transients propagate into sensitive electronics, and its 400 W peak pulse rating accommodates the energy levels defined in Pulse 5a (load dump). The device's glass-passivated junction further ensures long-term stability under automotive thermal cycling.
What is the thermal derating behavior of SMAJ85A above 25°C ambient?
SMAJ85A follows a linear derating curve above TA = 25°C, with peak pulse power decreasing to approximately 200 W at 75°C and 100 W at 125°C - per Figure 2 in the official U2102 datasheet. This derating is essential for designs operating in engine compartments or sealed industrial enclosures. The device's 150°C maximum junction temperature and DO-214AC package thermal resistance (~130°C/W) allow sustained operation when PCB copper area and airflow are properly managed.
Can SMAJ85A replace SMAJ85 in an existing design?
Yes, SMAJ85A can directly replace SMAJ85 in most cases due to identical DO-214AC packaging, pinout, and mounting. However, SMAJ85A offers tighter VBR tolerance (94.4–104 V vs. 94.4–115 V) and lower clamping voltage (137 V vs. 151 V), improving protection margin. No PCB changes are required, but designers should verify that the lower VC does not cause unintended interaction with adjacent overvoltage detection circuits or crowbar triggers in the system.
SMAJ85A Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Taiwan Semiconductor Corporation
- Package/Case:
- DO-214AC, SMA
- Series:
- SMAJ
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 85V
- Voltage - Breakdown (Min):
- 94.4V
- Voltage - Clamping (Max) @ Ipp:
- 137V
- Current - Peak Pulse (10/1000µs):
- 2.2A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DO-214AC (SMA)
SMAJ85A FAQ
1.How can I place an order for SMAJ85A through Aetrix?
Please submit a Request for Quotation (RFQ) for SMAJ85A on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SMAJ85A reliable?
The price and inventory of SMAJ85A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SMAJ85A is usually 5 days.
3.What payment methods are accepted for SMAJ85A?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SMAJ85A transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SMAJ85A?
SMAJ85A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SMAJ85A order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SMAJ85A?
For technical support, including SMAJ85A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SMAJ85A requirements.
6.How does Aetrix verify that SMAJ85A is sourced from the original manufacturer or authorized distributors?
All SMAJ85A products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SMAJ85A meets industry standards.
7.What is the process for return or replacement of SMAJ85A?
All SMAJ85A units undergo pre-shipment inspection (PSI). If there is an issue with SMAJ85A, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SMAJ85A part is unused and in its original packaging.
Return procedure for SMAJ85A:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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