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onsemi 1SMA20AT3
- Part No.:
- 1SMA20AT3
- Manufacturer:
- onsemi
- Category:
- TVS Diodes
- Package:
- DO-214AC, SMA
- Datasheet:
-
1SMA20AT3.pdf
- Description:
- TVS DIODE 20VWM 32.4VC SMA
- Quantity:
- Payment:
- Shipping:
Inventory:7,155
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Product details
Overview
1SMA20AT3 from ON Semiconductor is a unidirectional 400 W peak power Zener transient voltage suppressor (TVS) designed for clamping overvoltage transients in DC power lines and signal paths. It features a 20 V working peak reverse voltage (VRWM), 22.2–24.5 V breakdown voltage (VBR) at 1 mA test current, 32.4 V clamping voltage (VC) at 12.3 A peak pulse current (IPP), and sub-1 ns response time. It is used in automotive power supply protection and industrial control I/O interfaces.
For engineers reviewing the 1SMA20AT3 datasheet, pinout, applications, or equivalent options, key selection criteria include VRWM margin vs. operating voltage, clamping ratio (VC/VBR), surge current capability under 10/1000 µs waveform, and SMA package thermal performance on FR-4 PCBs with minimum footprint.
Technical Context
The 1SMA20AT3 operates as a unidirectional avalanche diode, conducting only during reverse overvoltage events above its VBR threshold while presenting high impedance under normal bias. Its low zener impedance and fast <1 ns response enable effective suppression of ESD and lightning-induced surges without affecting steady-state circuit operation.
It is rated for 400 W non-repetitive peak pulse power (10/1000 µs waveform), 0.5 W DC power dissipation at 25°C ambient, and 1.5 W at 75°C lead temperature. Thermal resistance from junction to ambient is 250°C/W, and junction-to-lead is 20°C/W - confirming reliance on PCB copper area for heat sinking.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRWM | 20 V - Maximum continuous reverse voltage before clamping begins; must exceed system's max operating voltage. |
| VBR @ IT=1 mA | 22.2–24.5 V - Breakdown tolerance defines clamping onset precision; tighter spread improves design margin predictability. |
| VC @ IPP=12.3 A | 32.4 V - Clamping voltage limits protected circuit stress; lower VC reduces risk of downstream component damage. |
| PPK | 400 W @ 1 ms - Peak surge energy handling capacity; validates suitability for IEC 61000-4-5 Level 4 (4 kV) testing. |
| Response Time | <1 ns - Ensures suppression initiates before transient propagates into sensitive ICs or microcontrollers. |
| ESD Rating | Class 3 (>16 kV HBM) - Confirms robustness against human-body model ESD events in handling and assembly. |
Pinout & Package
SMA package (Case 403D-02), surface-mount, unidirectional polarity indicated by cathode band. Low-profile plastic housing with flat handling surface for accurate placement and top/bottom board mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Anode | Forward conduction terminal / Surge return path | Connected to ground or low-impedance return plane; carries full IPP during clamping. |
| Cathode | Protected line connection / High-side clamp node | Connected to line being protected (e.g., 24 V rail); reverse-biased during normal operation. |
Key Features
| Feature | Design Value |
|---|---|
| 400 W peak pulse power | Supports IEC 61000-4-5 surge immunity up to 4 kV on 2 Ω source impedance without failure. |
| Clamping ratio (VC/VBR) ≈ 1.46 | Low ratio ensures minimal overvoltage overshoot during transient events, protecting 3.3 V/5 V logic interfaces. |
| Pb-free SMA package (1SMA20AT3G variant) | Complies with RoHS Directive 2011/65/EU; compatible with standard reflow profiles up to 260°C for 10 s. |
| Flat handling surface | Enables consistent pick-and-place accuracy and solder joint reliability in automated SMT assembly. |
Applications
| Automotive Power Rail Protection | Industrial PLC Digital Input Protection |
|---|---|
Use Scenario: 12 V/24 V battery-fed ECUs exposed to load dump and ISO 7637-2 pulses. IC Role / Device Role / Timing Role: Primary overvoltage clamp on main power input, placed upstream of DC-DC converters and LDOs. Use Value: Limits transient voltage to ≤32.4 V, preventing damage to 36 V-rated regulators and MCU power pins. |
Use Scenario: 24 V digital input channels in programmable logic controllers subject to field-wiring induced surges. IC Role / Device Role / Timing Role: Input-stage TVS diode across optocoupler input terminals. Use Value: Absorbs 12.3 A surge current without degradation, preserving signal integrity and optocoupler lifetime. |
| Medical Equipment Power Supply Filtering | Telecom Line Card Surge Suppression |
Use Scenario: Auxiliary 5 V/12 V rails in diagnostic imaging systems requiring IEC 60601-1 compliance. IC Role / Device Role / Timing Role: Secondary protection after primary MOVs, providing precise clamping near IC voltage ratings. Use Value: Sub-1 ns response ensures fast intervention before transient couples into analog front-end or ADC reference circuits. |
Use Scenario: Ethernet or RS-485 interface power rails in outdoor base station line cards. IC Role / Device Role / Timing Role: DC bias rail protector adjacent to isolation transformers and PHY ICs. Use Value: 400 W rating handles repeated lightning-induced surges per Telcordia GR-1089-CORE, reducing field failure rates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar unidirectional TVS applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SMBJ20A (Bourns) | Same VRWM (20 V), higher PPK = 600 W, larger SMB package (case 403A), 38.9 V VC @ 15.4 A IPP. | Higher surge margin but requires more PCB area; better for repeated surge environments. | Select when 600 W peak power and enhanced thermal mass are required, and SMB footprint is acceptable. |
| P6SMB20A (Littelfuse) | Identical VRWM (20 V), same SMA package, 38.9 V VC @ 15.4 A IPP, 600 W PPK, tighter VBR tolerance (22.2–24.4 V). | Higher clamping voltage increases protected circuit stress; requires verification of downstream voltage margin. | Choose if sourcing flexibility is needed and clamping voltage margin allows; verify VC compatibility with load ICs. |
Compared with 1SMA20AT3, SMBJ20A offers greater surge endurance in a larger package, while P6SMB20A provides identical form factor but higher clamping voltage - making 1SMA20AT3 optimal where precise low-VC clamping and SMA space constraints are critical.
Availability
1SMA20AT3 is available at Aetrix Electronics and suitable for automotive electronics, industrial PLCs, medical power supplies, and telecom infrastructure requiring stable component supply and long-term obsolescence management.
Supply support for 1SMA20AT3 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
ON Semiconductor (now onsemi) is a global semiconductor manufacturer specializing in power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud power applications.
The 1SMAxxAT3 series was developed to deliver cost-effective, high-reliability transient suppression in compact SMA packages for DC power rail and signal line protection across harsh environments.
FAQ
What is the maximum working peak reverse voltage (VRWM) of the 1SMA20AT3?
The 1SMA20AT3 has a VRWM of 20 V, meaning it remains non-conductive up to this reverse voltage under normal operation. This value is selected to be equal to or slightly greater than the system's maximum continuous operating voltage - for example, matching a nominal 24 V rail with 20 % tolerance (28.8 V max) would require a higher VRWM device. The 1SMA20AT3 is appropriate for 12–16 V systems where 20 V provides sufficient margin.
What clamping voltage does the 1SMA20AT3 exhibit during a surge event?
The 1SMA20AT3 exhibits a maximum clamping voltage (VC) of 32.4 V at 12.3 A peak pulse current (IPP), measured using the standard 10/1000 µs waveform. This VC value defines the highest voltage imposed on the protected circuit during a surge. For instance, when used on a 24 V supply line, the 1SMA20AT3 limits transient excursions to ≤32.4 V - well within the absolute maximum rating of most 36 V tolerant DC-DC controllers and microcontrollers.
Is the 1SMA20AT3 unidirectional or bidirectional, and how is polarity identified?
The 1SMA20AT3 is a unidirectional TVS diode, intended for DC line protection where polarity is fixed. Polarity is marked by a cathode band on the SMA package body - the banded end is the cathode and connects to the line being protected, while the anode connects to ground. Bidirectional variants (e.g., 1SMA20CAT3) exist but are distinct part numbers; the "A" suffix in 1SMA20AT3 explicitly denotes unidirectional configuration.
What is the thermal performance of the 1SMA20AT3 on a standard PCB?
The 1SMA20AT3 has a thermal resistance from junction to ambient (RJA) of 250°C/W when mounted on an FR-4 board using ON Semiconductor's minimum recommended footprint. At 25°C ambient, its DC power dissipation is limited to 0.5 W; this derates linearly above 25°C. Effective thermal design requires adequate copper pour on both sides of the PCB connected to the anode and cathode pads - the 1SMA20AT3 relies entirely on PCB conduction for heat removal, not package convection.
Does the 1SMA20AT3 meet industry-standard ESD and surge immunity requirements?
Yes, the 1SMA20AT3 meets Class 3 ESD immunity (>16 kV per Human Body Model) and supports IEC 61000-4-5 surge testing up to Level 4 (4 kV, 2 Ω source impedance) due to its 400 W peak pulse rating and sub-1 ns response time. These characteristics make the 1SMA20AT3 suitable for end-equipment compliance in automotive (ISO 7637-2), industrial (IEC 61000-4-4/5), and medical (IEC 60601-1) applications - provided layout practices (short traces, low-inductance grounding) are followed.
1SMA20AT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Package/Case:
- DO-214AC, SMA
- Series:
- -
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Zener
- Unidirectional Channels:
- 1
- Bidirectional Channels:
- -
- Voltage - Reverse Standoff (Typ):
- 20V
- Voltage - Breakdown (Min):
- 22.2V
- Voltage - Clamping (Max) @ Ipp:
- 32.4V
- Current - Peak Pulse (10/1000µs):
- 12.3A
- Power - Peak Pulse:
- 400W
- Power Line Protection:
- No
- Applications:
- General Purpose
- Capacitance @ Frequency:
- 585pF @ 1MHz
- Operating Temperature:
- -65°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SMA
1SMA20AT3 FAQ
1.How can I place an order for 1SMA20AT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for 1SMA20AT3 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 1SMA20AT3 reliable?
The price and inventory of 1SMA20AT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 1SMA20AT3 is usually 5 days.
3.What payment methods are accepted for 1SMA20AT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 1SMA20AT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 1SMA20AT3?
1SMA20AT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 1SMA20AT3 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 1SMA20AT3?
For technical support, including 1SMA20AT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 1SMA20AT3 requirements.
6.How does Aetrix verify that 1SMA20AT3 is sourced from the original manufacturer or authorized distributors?
All 1SMA20AT3 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 1SMA20AT3 meets industry standards.
7.What is the process for return or replacement of 1SMA20AT3?
All 1SMA20AT3 units undergo pre-shipment inspection (PSI). If there is an issue with 1SMA20AT3, 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 1SMA20AT3 part is unused and in its original packaging.
Return procedure for 1SMA20AT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
1SMA20AT3 Tags
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