SA18C Transient Voltage Suppressor Equivalent & Substitute Parts

Part Overview

The SA18C is an 18V Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., housed in a DO-204AC (DO-15) axial through-hole package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The SA18C provides 30.66V maximum clamping voltage at peak pulse current with 500W peak pulse power handling capability, suitable for general-purpose transient voltage suppression applications across industrial and commercial electronics.

Key Parameters

Parameter	Value
Voltage - Reverse Standoff (Typ)	18V
Voltage - Breakdown (Min)	18.95V
Voltage - Clamping (Max) @ Ipp	30.66V
Current - Peak Pulse (10/1000µs)	17.5A
Power - Peak Pulse	500W
Operating Temperature Range	-55°C ~ 175°C (TJ)
Package / Case	DO-204AC, DO-15, Axial
Mounting Type	Through Hole
Type	Zener
Bidirectional Channels	1

Substitute Part Grouping Explanation

Substitution eligibility for the SA18C is determined by the following critical parameters:

Voltage - Reverse Standoff (Typ): 18V (all substitutes must match)
Voltage - Breakdown (Min): minimum 18.95V (all substitutes meet or exceed this)
Current - Peak Pulse (10/1000µs): 17.5A minimum (all substitutes meet or exceed this)
Power - Peak Pulse: 500W (all substitutes match)
Operating Temperature Range: -55°C ~ 175°C (all substitutes match)
Package / Case: DO-204AC, DO-15, Axial (all substitutes match)
Mounting Type: Through Hole (all substitutes match)
Type: Zener, Bidirectional Channels: 1 (all substitutes match)

The substitute parts SA18CA, SA18CA-AP, SA18CA-BP, and SA18CA-TP all maintain the core electrical specifications required for direct substitution. Variations in clamping voltage (29.2V to 39.4V) remain within acceptable operating parameters for general-purpose transient suppression applications.

Parameter Comparison

Parameter	SA18C (Littelfuse)	SA18CA (Taiwan Semiconductor)	SA18CA-AP (Micro Commercial Co)	SA18CA-BP (Micro Commercial Co)	SA18CA-TP (Micro Commercial Co)
Voltage - Reverse Standoff (Typ)	18V	18V	18V	18V	18V
Voltage - Breakdown (Min)	18.95V	20V	20V	20V	20V
Voltage - Clamping (Max) @ Ipp	30.66V	39.4V	29.2V	29.2V	29.2V
Current - Peak Pulse (10/1000µs)	17.5A	17.9A	17.5A	17.5A	17.5A
Power - Peak Pulse	500W	500W	500W	500W	500W
Operating Temperature Range	-55°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 175°C
Package / Case	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial	DO-204AC, DO-15, Axial
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	ROHS3 Compliant	ROHS3 Compliant	Not specified	Not specified	Not specified

Engineering Selection Recommendations

All four substitute parts (SA18CA, SA18CA-AP, SA18CA-BP, SA18CA-TP) are active products with current manufacturing status, addressing the obsolescence of the original SA18C. Selection among these substitutes should be based on the following factors:

SA18CA (Taiwan Semiconductor Corporation): Active product status with ROHS3 compliance confirmation. Supplied in Tape & Reel packaging with 2145 units in stock. Clamping voltage of 39.4V represents the highest specification among substitutes.

SA18CA-AP, SA18CA-BP, SA18CA-TP (Micro Commercial Co): All three variants maintain identical electrical specifications with 29.2V clamping voltage and 17.5A peak pulse current. These parts are supplied in bulk packaging with inventory levels of 756, 847, and 1139 units respectively. REACH compliance status is confirmed as unaffected for all three variants.

Product availability and packaging format should guide final selection. All substitutes maintain compliance certifications (ECCN: EAR99, HTSUS: 8541.10.0080) consistent with the original SA18C.

Frequently Asked Questions (FAQ)

Q: Can SA18CA, SA18CA-AP, SA18CA-BP, and SA18CA-TP be used interchangeably with SA18C?

A: Yes. All four substitute parts maintain the critical electrical parameters: 18V reverse standoff voltage, 500W peak pulse power, 17.5A or higher peak pulse current, and identical operating temperature range (-55°C ~ 175°C). All are housed in DO-204AC (DO-15) axial through-hole packages with identical mounting characteristics.

Q: What is the difference between SA18CA and the SA18CA variants (AP, BP, TP)?

A: SA18CA is manufactured by Taiwan Semiconductor Corporation and supplied in Tape & Reel packaging. SA18CA-AP, SA18CA-BP, and SA18CA-TP are manufactured by Micro Commercial Co and supplied in bulk packaging. Electrically, SA18CA has a 39.4V clamping voltage, while the Micro Commercial variants specify 29.2V clamping voltage. All meet the minimum electrical requirements for SA18C substitution.

Q: Does packaging format affect substitution compatibility?

A: Packaging format (Tape & Reel versus bulk) does not affect electrical or mechanical compatibility. The choice between formats depends on procurement workflow and assembly process requirements. All substitute parts use identical DO-204AC (DO-15) axial through-hole package geometry.

Q: Are all substitute parts RoHS compliant?

A: SA18C and SA18CA are confirmed ROHS3 compliant. SA18CA-AP, SA18CA-BP, and SA18CA-TP do not specify RoHS status in the provided data. Compliance verification should be obtained directly from Micro Commercial Co if RoHS certification is a design requirement.

Q: What is the inventory status for each substitute?

A: SA18CA: 2145 units (Taiwan Semiconductor). SA18CA-AP: 756 units (Micro Commercial Co). SA18CA-BP: 847 units (Micro Commercial Co). SA18CA-TP: 1139 units (Micro Commercial Co). All parts are listed as new original stock.

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