onsemi SA17CA

Overview

SA17CA from Fairchild Semiconductor is a 500 W bidirectional transient voltage suppressor (TVS) diode in DO-15 package, with 170 V reverse stand-off voltage (VRWM), 189–209 V breakdown voltage (VBR), and 275 V clamping voltage (VC) at 18.1 A peak pulse current (IPPM) on 10/1000 μs waveform - used for surge protection in AC power inputs and telecom line interfaces.

For engineers reviewing the SA17CA datasheet, pinout, applications, or equivalent options, key selection criteria include clamping performance under 10/1000 μs surges, unidirectional vs. bidirectional polarity requirements, thermal derating above 75°C, and compliance with IEC 61000-4-5 Level 4 surge immunity testing.

Technical Context

The SA17CA is a glass-passivated, bipolar junction TVS diode optimized for high-energy transient suppression. Its bidirectional structure enables symmetrical clamping in both polarities, with low incremental surge resistance and sub-5 ns response time from 0 V to breakdown.

It operates with a maximum junction temperature of +175°C and supports non-repetitive peak forward surge currents up to 70 A (8.3 ms half-sine). The device exhibits <1.0 μA reverse leakage at VRWM = 170 V, meeting stringent standby power requirements in protected AC front-ends.

Key Specifications

Pinout & Package

DO-15 axial-leaded package with cathode band omitted (bidirectional configuration); leads are tinned copper, 0.375" length standard for 1.0 W steady-state dissipation at TA = 75°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SA17CA, SMBJ170CA offers superior thermal performance and automation readiness but demands layout change, while P6SMB170CA provides mechanical drop-in potential in some sockets but trades off leakage performance for broader channel availability.

Availability

SA17CA is available at Aetrix Electronics and suitable for AC power input protection, telecom line interface, and motor drive control boards requiring stable component supply and long-lifecycle support.

Supply support for SA17CA 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

Fairchild Semiconductor (now part of ON Semiconductor) is a global leader in power management and protection semiconductors, with decades of expertise in TVS, MOSFET, and analog IC design.

The SAxxCA series was engineered specifically for high-reliability industrial and telecom surge protection, emphasizing robustness under repetitive 10/1000 μs transients and extended thermal endurance.

FAQ

What is the clamping voltage of SA17CA at its rated peak pulse current?

The SA17CA has a maximum clamping voltage (VC) of 275 V when subjected to its rated peak pulse current (IPPM) of 18.1 A on a 10/1000 μs waveform. This value is measured per JEDEC standards and ensures predictable overvoltage limiting during surge events. The SA17CA maintains this clamping performance across its full operating temperature range and after repeated surge exposures, making it suitable for mission-critical AC input protection where voltage overshoot must remain bounded.

Is SA17CA unidirectional or bidirectional, and how does that affect circuit placement?

The SA17CA is a bidirectional TVS diode, indicated by the "CA" suffix, and functions identically in both polarities with no cathode marking. This allows direct placement across AC lines (e.g., L–N or Tip–Ring) without orientation concerns. Unlike unidirectional variants, the SA17CA clamps positive and negative transients symmetrically - critical for protecting balanced interfaces where polarity reversal or common-mode surges occur. Its DO-15 package supports through-hole mounting in legacy AC front-end designs.

Can SA17CA replace SA170A in an existing design?

No - SA17CA and SA170A are not interchangeable. SA170A is unidirectional (cathode-banded), while SA17CA is bidirectional (no band). Substituting SA17CA for SA170A in a DC-coupled circuit may cause unintended conduction during normal operation. The SA17CA is only a valid replacement where bidirectional clamping is explicitly required and the original design accommodates symmetrical surge paths. Always verify polarity requirements and schematic placement before substitution.

What is the maximum allowable ambient temperature for continuous operation of SA17CA?

The SA17CA supports continuous operation up to +75°C ambient temperature at full 1.0 W steady-state power dissipation, per its specified lead-length condition (0.375"). Above 75°C, derating is required - e.g., at 100°C ambient, maximum power drops to ~0.65 W. Its +175°C maximum junction temperature enables reliable function in thermally demanding enclosures, but system-level thermal design must ensure junction temperature remains within limit under worst-case surge and ambient conditions.

Does SA17CA meet IEC 61000-4-5 surge immunity requirements?

Yes - the SA17CA's 500 W peak pulse rating on the 10/1000 μs waveform directly supports compliance with IEC 61000-4-5 Level 4 (4 kV line-to-earth, 2 Ω source impedance). When used with appropriate series impedance (e.g., fuse, PTC, or current-limiting resistor), the SA17CA clamps transient voltage to ≤275 V, keeping downstream components within safe operating area. Its fast <5 ns response ensures protection activation prior to energy coupling into sensitive circuitry.