1.5KE Series TVS Diode EOL Cross-Reference and Equivalent Replacements

Bottom Line: The 1.5KE series is a JEDEC-standardized 1500 W peak pulse power TVS diode family manufactured by STMicroelectronics, Vishay, Littelfuse, and others. When a specific voltage variant goes end-of-life (EOL) in your distributor's catalog, you can almost always qualify a pin-compatible equivalent by matching four parameters: standoff voltage (V_WM), peak pulse power rating (1500 W at 10/1000 µs), axial DO-201AD package, and polarity suffix (unidirectional "A" or bidirectional "CA"). This guide decodes the 1.5KE part-numbering system, explains the most common EOL patterns in this family, and provides a practical cross-reference table with confirmed active-stock alternatives available through FindMyChip's 200+ verified distributor network.

Understanding the 1.5KE Part Number System

The 1.5KE part number compresses all critical electrical parameters into a compact alphanumeric string. Engineers unfamiliar with this convention often struggle to identify equivalents because the "standoff voltage" number in the part number does not directly match the component's nominal breakdown voltage. Breaking down 1.5KE36A character by character:

• 1.5K — Peak pulse power rating: 1500 W (K = 1000, so 1.5 × 1000 = 1500 W). This rating is defined at the industry-standard 10/1000 µs unidirectional surge waveform per IEC 60825. Note that some datasheets also specify an 8/20 µs current rating that can be significantly higher (up to 10 kW), but cross-reference comparisons should always use the 10/1000 µs figure.
• E — Package and series designation. The "E" identifies the DO-201AD through-hole axial package standardized by JEDEC. This is a large-body glass-passivated junction diode package, approximately 9.5 mm long with 1.0 mm diameter leads on a standard 10 mm board pitch.
• 36 — Nominal standoff voltage (V_WM) in volts. For 1.5KE36A, V_WM = 30.8 V, which is roughly 85% of the nominal voltage step. The discrepancy between the number "36" and the actual V_WM value (30.8 V) exists because the number refers to the nominal breakdown voltage step, while V_WM is the maximum continuous reverse working voltage — always lower than V_BR to provide noise margin.
• A — Unidirectional polarity suffix. A device with an "A" suffix conducts current in only one direction (like a standard Zener diode) and is intended for DC rail protection. Omitting "A" and using "CA" instead designates a bidirectional (complementary anti-parallel) device that clamps transients of either polarity.

For 1.5KE100CA: the standoff voltage is nominally 85 V (actual V_WM), it is rated at 1500 W peak pulse, it comes in a DO-201AD package, and the "CA" suffix means it is bidirectional — protecting both positive and negative transients on a signal or power rail.

Why 1.5KE Variants Go EOL: Understanding the Discontinuation Patterns

The 1.5KE family spans standoff voltages from 5 V to 376 V across more than 30 voltage steps in both unidirectional and bidirectional variants, giving the full product matrix well over 60 individual part numbers. Manufacturers periodically rationalize this catalog, discontinuing variants with insufficient annual production volume. Understanding the patterns helps engineers anticipate which parts are at risk and plan design-in alternatives proactively.

Low-demand high-voltage steps are the most common EOL candidates. Variants above 150 V — such as 1.5KE200A (171 V standoff) — are used primarily in industrial power-line protection, motor drive clamping, and telecom equipment. Annual demand for a single voltage step at this level is a fraction of the volume for common 12 V or 36 V variants, making dedicated mask and assembly runs economically marginal.

Package migration toward SMD is a structural industry trend. The DO-201AD is a legacy through-hole package with significant board real-estate requirements. Many designs that previously used 1.5KE through-hole parts have migrated to SMA, SMB, or SMC surface-mount equivalents (P4SMA, P6SMB, SMBJ series). As demand for DO-201AD declines, fabs consolidate production runs, which can lead to longer lead times and eventual PDN (Product Discontinuation Notice) issuance even for otherwise-healthy voltage steps.

Single-source voltage steps are vulnerable whenever the sole qualified manufacturer changes process nodes or closes a fab line. The 1.5KE standard is JEDEC-defined (JESD77), meaning any manufacturer can produce a compliant part, but in practice, several voltage steps in the 150–376 V range have historically been produced by only one or two vendors. A single fab process change can remove those variants from active production.

A PDN does not mean the component is immediately unavailable. Authorized distributors may maintain stock for 12–36 months after the official discontinuation date, and the spot market often carries additional inventory. However, relying on aging stock without a qualified alternative creates supply chain risk, especially for programs with 5–10 year production runs.

Key Parameters for Cross-Reference Qualification

Standoff Voltage (V_WM)

The standoff voltage is the maximum reverse voltage the TVS may sustain indefinitely without entering avalanche conduction. An equivalent must have V_WM equal to or slightly above the original part's V_WM. Substituting a part with lower V_WM will cause false triggering at normal operating voltage; substituting with significantly higher V_WM may leave the clamping voltage (V_C) above the protected IC's absolute maximum input rating.

For the 1.5KE family, V_WM is specified at 25°C. At elevated temperatures, the breakdown voltage increases slightly (positive temperature coefficient for voltages above ~6 V), which generally improves noise margin but should be verified in high-temperature applications.

Clamping Voltage (V_C) at Peak Pulse Current (I_PP)

The clamping voltage at rated I_PP is the maximum voltage across the TVS terminals during a full-rated surge event. For the 1.5KE series, V_C is typically 1.35–1.4× V_BR at I_PP. This value must remain below the absolute maximum voltage rating of every device connected to the protected node. For example, a 1.5KE36A with V_C = 58.1 V at I_PP must be used in circuits where all downstream ICs tolerate ≥ 58.1 V at their protected terminals.

Peak Pulse Power Rating (1500 W at 10/1000 µs)

All cross-reference candidates must be rated at ≥ 1500 W peak pulse power at the 10/1000 µs waveform. Do not substitute a 600 W P6KE-series or a 400 W 1N6267-series part without performing a full surge energy analysis. For IEC 61000-4-5 Level 3 and Level 4 protection (open-circuit test voltages of 2 kV and 4 kV respectively), the 1500 W peak pulse power rating provides the required energy absorption capacity when the circuit impedance is within the standard's defined range.

Package: DO-201AD Axial Through-Hole

The DO-201AD package is the mechanical standard for the 1.5KE family. Lead pitch and body dimensions are identical across STMicroelectronics, Vishay, Littelfuse, and ON Semiconductor versions. The Vishay -E3/54 suffix (e.g., 1.5KE36A-E3/54) indicates a RoHS-compliant matte-tin lead finish on the same DO-201AD body — it is a direct mechanical drop-in for any standard 1.5KExxA placement.

Polarity: Unidirectional (A) vs. Bidirectional (CA)

Polarity is a hard constraint. A unidirectional "A" part cannot replace a bidirectional "CA" part on AC lines, RS-485 buses, or motor braking rails where both positive and negative transients occur. The reverse is generally safe (a "CA" part can replace an "A" part on DC rails) but introduces marginally higher junction capacitance and reverse leakage, which may matter for high-speed signal lines or ultra-low-power standby circuits.

Junction Capacitance (C_J)

For TVS diodes on high-speed data interfaces (USB, Ethernet, CAN), junction capacitance is a critical parameter. The 1.5KE series exhibits relatively high C_J (typically 150–2000 pF depending on voltage), which limits its use on signals above ~1 MHz. If your cross-reference application involves a data interface rather than a power rail, verify C_J in the alternative part's datasheet before committing to a design-in.

Cross-Reference Table: EOL 1.5KE Parts to Active Equivalents

The following table maps the four target EOL variants to confirmed active-stock equivalents available through FindMyChip. All linked MPNs are verified catalog entries.

EOL / Target Part	V_WM	Polarity	Package	Active Equivalent	Manufacturer	Notes
1.5KE15A	12.8 V	Uni (A)	DO-201AD	1.5KE15A	STMicroelectronics	1500 W, V_C = 24.4 V
1.5KE36A	30.8 V	Uni (A)	DO-201AD	1.5KE36A	STMicroelectronics	1500 W, V_C = 58.1 V
1.5KE36A	30.8 V	Uni (A)	DO-201AD	1.5KE36A-E3/54	Vishay	RoHS matte-tin, drop-in
1.5KE200A	171 V	Uni (A)	DO-201AD	1.5KE200A	STMicroelectronics	1500 W, 10 kW at 8/20 µs
1.5KE200A	171 V	Uni (A)	DO-201AD	1.5KE200A-E3/54	Vishay	RoHS, confirmed active
1.5KE100CA	85 V	Bi (CA)	DO-201AD	1.5KE100CA	STMicroelectronics	Bidirectional, AC/RS-485

The Vishay -E3/54 variants are particularly useful as second-source alternatives because Vishay maintains active production of the DO-201AD package for the telecom and industrial markets where these parts are most used.

Selection Decision Flowchart

When selecting a replacement for an EOL 1.5KE part, follow this decision logic:

Step 1 — Identify V_WM. Look up the V_WM from the original part datasheet (not the part number nominal voltage). For 1.5KE15A, V_WM = 12.8 V. For 1.5KE36A, V_WM = 30.8 V. For 1.5KE200A, V_WM = 171 V. For 1.5KE100CA, V_WM = 85 V.

Step 2 — Confirm polarity requirement. If the protected rail is unidirectional DC and negative transients are not expected → use the "A" (unidirectional) variant. If the line is AC, RS-485, motor brake, or any bipolar application → use the "CA" (bidirectional) variant. Never substitute "A" for "CA."

Step 3 — Verify peak pulse power. Confirm your surge specification requires ≤ 1500 W at 10/1000 µs. If your application sees 8/20 µs surges (typical in lightning protection), check the 8/20 µs rating (often 10 kW for the 1.5KE family) against your IEC 61000-4-5 test level.

Step 4 — Search active stock. Search FindMyChip by MPN to see real-time inventory across 200+ verified distributors. The cross-reference table above lists confirmed active alternatives. For the 1.5KE200A in particular — a high-voltage variant with limited second-source availability — the Vishay 1.5KE200A-E3/54 is the primary active replacement.

Step 5 — Request multi-line cross-reference. If your BOM contains several EOL 1.5KE variants, submit a quote request with your full part list and target quantities. FindMyChip's sourcing team will identify the best cross-reference options across verified distributors and apply 5-point authenticity verification before shipment.

FAQ

What does the "CA" suffix mean on a 1.5KE TVS diode?

The "CA" suffix (as in 1.5KE100CA) designates a bidirectional TVS diode. Two avalanche junctions are connected back-to-back inside the single DO-201AD package, allowing the device to clamp voltage transients of either polarity. This makes CA-suffix parts essential for AC power-line protection, RS-485 and CAN bus interfaces, and motor drive braking outputs where both positive and negative overvoltage events occur. A unidirectional "A" part will conduct in only one direction and cannot protect against reverse-polarity transients.

Is a Vishay 1.5KE36A-E3/54 a drop-in replacement for STMicroelectronics 1.5KE36A?

Yes. The Vishay 1.5KE36A-E3/54 is electrically and mechanically equivalent to the STMicroelectronics 1.5KE36A. The -E3/54 suffix indicates a RoHS-compliant matte-tin lead finish on the identical DO-201AD package body. Both parts meet the same JEDEC JESD77 electrical specification: V_WM = 30.8 V, V_C = 58.1 V at I_PP, 1500 W peak pulse power at 10/1000 µs. They share the same PCB footprint and require no BOM or layout changes.

What is the difference between 1500 W and 600 W TVS ratings?

The wattage rating describes peak pulse power dissipation capacity at the standard 10/1000 µs surge waveform. A 600 W TVS (e.g., P6KE series) will be destroyed or degraded when subjected to the same surge that a 1500 W TVS would safely absorb. For IEC 61000-4-5 Level 4 telecom and industrial surge protection (4 kV open-circuit, 2 kA short-circuit), the 1500 W rating is typically required when the circuit impedance results in peak pulse power approaching the rated maximum.

Why does the standoff voltage number in the part number not match V_WM?

For "A" suffix parts, the number in the part name (e.g., "36" in 1.5KE36A) refers to the JEDEC nominal breakdown voltage step, while V_WM is set approximately 15% below V_BR min to guarantee that the device does not conduct during normal steady-state operation. For 1.5KE36A, the "36" references a nominal V_BR near 36 V, while V_WM = 30.8 V — the maximum operating voltage where leakage remains within spec. This margin ensures TVS devices do not clamp legitimate voltage peaks within the normal signal range.

How do I find active stock for EOL 1.5KE parts?

The fastest path is to search FindMyChip by exact MPN. FindMyChip aggregates real-time inventory from 200+ verified distributors globally, including authorized representatives and factory-direct sources. For multi-line BOMs or time-sensitive shortages, submit a quote request with your target MPNs, quantities, and date-code requirements. Our sourcing team responds within 24 hours with pricing, cross-reference options, and counterfeit-screening status for every line item.

Conclusion and Sourcing Guidance

The 1.5KE TVS diode family remains a robust, cost-effective choice for 1500 W surge protection across a wide voltage range. When individual variants go EOL, the cross-reference process is systematic: confirm V_WM, verify polarity (A vs. CA), match peak pulse power (≥ 1500 W at 10/1000 µs), and select an active equivalent in the same DO-201AD package. The Vishay -E3/54 variants — including 1.5KE36A-E3/54 and 1.5KE200A-E3/54 — are confirmed active second-source options that are electrically and mechanically interchangeable with STMicroelectronics' standard lineup.

For the four variants covered in this guide:

• 1.5KE15A — Active stock available; check inventory.
• 1.5KE36A — Active from ST; Vishay 1.5KE36A-E3/54 confirmed as drop-in alternative.
• 1.5KE200A — Limited second-source; Vishay 1.5KE200A-E3/54 is the primary active cross-reference.
• 1.5KE100CA — Bidirectional; confirm "CA" suffix match in any replacement.

To check real-time stock, compare pricing across distributors, or submit a cross-reference RFQ for your full BOM, visit FindMyChip search or request a quote.