SMDJ18 Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SMDJ18 is a unidirectional transient voltage suppressor diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This part operates with an 18V reverse standoff voltage and delivers 3000W peak pulse power in a DO-214AB (SMC) package. The SMDJ18 is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Active alternatives with identical or compatible electrical characteristics are available from multiple manufacturers.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	18	V
Voltage - Breakdown (Min)	18.95	V
Voltage - Clamping (Max) @ Ipp	30.66	V
Current - Peak Pulse (10/1000µs)	102.7	A
Power - Peak Pulse	3000	W
Operating Temperature Range	-65 to 150	°C (TJ)
Package / Case	DO-214AB, SMC	—
Mounting Type	Surface Mount	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution for the SMDJ18 is determined by the following critical parameters:

Voltage Rating: Reverse standoff voltage of 18V and breakdown voltage minimum of 18.95V
Peak Pulse Current: 102.7A at 10/1000µs pulse width
Peak Pulse Power: 3000W (3kW)
Package: DO-214AB (SMC) surface-mount form factor
Unidirectional Configuration: Single-channel zener-type TVS diode

Substitute parts are grouped into two categories based on peak pulse current capability:

Category A - Full Current Rating (≥102.7A): Parts with peak pulse current of 102.7A or greater maintain identical power dissipation and transient protection performance. These include SMDJ18A, SMLJ18A, SMLJ18A-TP, TV30C180J-G, and SMCJ18AE3/TR13.

Category B - Reduced Current Rating (51.4A): Parts with peak pulse current of approximately 51.4A deliver 1500W peak pulse power, representing a 50% reduction in transient energy handling. These include SMCJ18A, SMCJ18A-TP, and TV15C180J-G. These are suitable only for applications with lower transient energy requirements.

All substitute parts maintain the 18V reverse standoff voltage, 20V minimum breakdown voltage, and 29.2V maximum clamping voltage within acceptable engineering tolerances.

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Clamping (Max) @ Ipp (V)	Current - Peak Pulse (A)	Power - Peak Pulse (W)	Operating Temp (°C)	Product Status	Package
SMDJ18	Littelfuse Inc.	18	30.66	102.7	3000	-65 to 150	Obsolete	DO-214AB, SMC
SMDJ18A	Alpha & Omega Semiconductor Inc.	18	29.2	102.8	3000	-55 to 150	Active	DO-214AB, SMC
SMCJ18A	MDD	18	29.2	51.4	1500	-50 to 150	Active	DO-214AB, SMC
SMCJ18A-TP	Micro Commercial Co	18	29.2	51.4	1500	-55 to 175	Active	DO-214AB, SMC
SMCJ18AE3/TR13	Microchip Technology	18	29.2	51.4	1500	-65 to 150	Active	DO-214AB, SMC
SMLJ18A	Bourns Inc.	18	29.2	102.8	3000	-55 to 150	Active	DO-214AB, SMC
SMLJ18A-TP	Micro Commercial Co	18	29.2	102.8	3000	-55 to 175	Active	DO-214AB, SMC
TV15C180J-G	Comchip Technology	18	29.2	51.37	1500	-55 to 150	Active	DO-214AB, SMC
TV30C180J-G	Comchip Technology	18	29.2	102.74	3000	-55 to 150	Active	DO-214AB, SMC

Engineering Selection Recommendations

Primary Substitutes (Full Electrical Equivalence)

SMDJ18A, SMLJ18A, SMLJ18A-TP, TV30C180J-G, and SMCJ18AE3/TR13 are direct functional equivalents with peak pulse current ratings of 102.7A to 102.8A and 3000W peak pulse power. These parts maintain the original SMDJ18 transient protection capability and are suitable for direct replacement in applications requiring full 3kW energy dissipation.

SMDJ18A (Alpha & Omega Semiconductor Inc.) is an active product with identical electrical performance and is available in high volume (3967 pcs in stock). Operating temperature range is -55°C to 150°C, which is narrower than the original -65°C to 150°C specification.

SMLJ18A (Bourns Inc.) and SMLJ18A-TP (Micro Commercial Co) deliver equivalent 3000W peak pulse power with peak pulse currents of 102.8A. SMLJ18A-TP extends the upper operating temperature to 175°C. Both are actively produced and widely available.

TV30C180J-G (Comchip Technology) provides 102.74A peak pulse current and 3000W power dissipation with -55°C to 150°C operating range. This part is actively produced and available in stock.

SMCJ18AE3/TR13 (Microchip Technology) delivers 51.4A peak pulse current and 1500W power, representing a reduced-power variant. Operating temperature range extends to -65°C, matching the original SMDJ18 lower limit.

Secondary Substitutes (Reduced Power Rating)

SMCJ18A (MDD), SMCJ18A-TP (Micro Commercial Co), and TV15C180J-G (Comchip Technology) are suitable only for applications where transient energy is limited to 1500W. These parts deliver approximately 51.4A peak pulse current, representing a 50% reduction from the original specification. Selection of these parts requires confirmation that the application circuit can tolerate reduced transient protection capability.

All substitute parts are ROHS3 compliant and carry REACH Unaffected or REACH Affected status as specified. Moisture sensitivity level is MSL 1 (Unlimited) for all alternatives.

Frequently Asked Questions (FAQ)

Q: Can SMCJ18A replace SMDJ18 directly?

A: SMCJ18A is electrically compatible in terms of voltage rating (18V reverse standoff, 29.2V clamping) and package (DO-214AB, SMC). However, SMCJ18A delivers 1500W peak pulse power compared to SMDJ18's 3000W. Direct replacement is possible only if the application circuit does not require the full 3kW transient energy handling capability. Verify circuit transient energy requirements before substitution.

Q: What is the difference between SMLJ18A and SMCJ18A?

A: Both parts share the same 18V voltage rating and DO-214AB package. The primary difference is peak pulse power: SMLJ18A delivers 3000W (102.8A peak pulse current), while SMCJ18A delivers 1500W (51.4A peak pulse current). SMLJ18A is the appropriate choice for applications requiring full transient protection equivalent to SMDJ18.

Q: Are all substitute parts available in tape and reel packaging?

A: Most substitute parts are available in tape and reel (TR) packaging for automated assembly. SMCJ18A (MDD) and TV15C180J-G (Comchip Technology) do not specify packaging format in the available data. Confirm packaging availability with the supplier before design finalization.

Q: What is the operating temperature range difference between SMDJ18 and its substitutes?

A: SMDJ18 operates from -65°C to 150°C. Most substitutes operate from -55°C to 150°C, representing a 10°C reduction in the lower temperature limit. SMCJ18A-TP and SMLJ18A-TP extend the upper limit to 175°C. For applications requiring -65°C operation, select SMCJ18AE3/TR13 (Microchip Technology) or confirm that -55°C minimum is acceptable.

Q: Are all substitute parts RoHS3 compliant?

A: Yes, all substitute parts listed are ROHS3 compliant. SMLJ18A (Bourns Inc.) carries REACH Affected status, while all other substitutes are REACH Unaffected. Verify REACH compliance requirements for your specific application and supply chain.

Q: What is the clamping voltage difference between SMDJ18 and substitutes?

A: SMDJ18 specifies 30.66V maximum clamping voltage at peak pulse current. All substitute parts specify 29.2V maximum clamping voltage, representing a 1.46V reduction. This difference is within typical engineering tolerance for TVS diode applications and does not affect functional compatibility for general-purpose overvoltage protection.

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