SA18A Transient Voltage Suppressor (TVS) Diode - Equivalent & Substitute Parts

Part Overview

The SA18A is a unidirectional Zener-type transient voltage suppressor diode manufactured by onsemi, designed for general-purpose overvoltage protection applications. Packaged in DO-15 (DO-204AC) through-hole configuration, it provides 18V reverse standoff voltage with 29.2V maximum clamping voltage at 17.2A peak pulse current. The SA18A is classified as obsolete, making identification of active equivalent and substitute parts essential for ongoing design support and procurement continuity.

Key Parameters

Parameter	Value	Unit
Manufacturer Part Number	SA18A	—
Manufacturer	onsemi	—
Category	Transient Voltage Suppressors (TVS)	—
Type	Zener	—
Unidirectional Channels	1	—
Voltage - Reverse Standoff (Typ)	18	V
Voltage - Breakdown (Min)	20	V
Voltage - Clamping (Max) @ Ipp	29.2	V
Current - Peak Pulse (10/1000µs)	17.2	A
Power - Peak Pulse	500	W
Mounting Type	Through Hole	—
Package / Case	DO-204AC, DO-15, Axial	—
Product Status	Obsolete	—

Substitute Part Grouping Explanation

Substitution of the SA18A is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff (Typ): 18V
Voltage - Clamping (Max) @ Ipp: 29.2V
Current - Peak Pulse (10/1000µs): 17.2A
Power - Peak Pulse: 500W
Mounting Type: Through Hole
Package / Case: DO-15 (DO-204AC) or compatible axial package

Substitute Categories:

Direct Equivalents (DO-15 Package, Identical Electrical Specifications): Parts maintaining the same reverse standoff voltage (18V), clamping voltage (29.2V), peak pulse current (17.2A), and 500W power rating in DO-15 packaging:

P5KE18A-AP (Micro Commercial Co)
P5KE18A-BP (Micro Commercial Co)
P5KE18A-TP (Micro Commercial Co)
SAC18 (Littelfuse)

Functional Equivalents (DO-201 Package, Enhanced Performance): Parts with matching reverse standoff voltage (18V) and clamping voltage (29.2V) but in DO-201 package with higher peak pulse current and power ratings:

LCE18A (Littelfuse)

Related Voltage Ratings (DO-15 Package):

P6KE22A (Fairchild Semiconductor) - 18.8V standoff, 30.6V clamp, 20A peak pulse, 600W power

Related Voltage Ratings (DO-201 Package):

LCE15A (Littelfuse) - 15V standoff, 24.4V clamp, 61A peak pulse, 1500W power
LCE16A (Littelfuse) - 16V standoff, 26V clamp, 57A peak pulse, 1500W power
LCE17A (Littelfuse) - 17V standoff, 27.6V clamp, 54A peak pulse, 1500W power

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (Typ) [V]	Voltage - Clamping (Max) @ Ipp [V]	Current - Peak Pulse (10/1000µs) [A]	Power - Peak Pulse [W]	Package / Case	Product Status
SA18A	onsemi	18	29.2	17.2	500	DO-15	Obsolete
P5KE18A-AP	Micro Commercial Co	18	29.2	17.2	500	DO-15	Active
P5KE18A-BP	Micro Commercial Co	18	29.2	17.2	500	DO-15	Active
P5KE18A-TP	Micro Commercial Co	18	29.2	17.2	500	DO-15	Active
SAC18	Littelfuse	18	28.8	15	500	DO-15	Active
LCE18A	Littelfuse Inc.	18	29.2	51	1500	DO-201	Active
P6KE22A	Fairchild Semiconductor	18.8	30.6	20	600	DO-15	Active
LCE15A	Littelfuse Inc.	15	24.4	61	1500	DO-201	Active
LCE16A	Littelfuse Inc.	16	26	57	1500	DO-201	Active
LCE17A	Littelfuse Inc.	17	27.6	54	1500	DO-15	Active

Engineering Selection Recommendations

For Direct Replacement (Same Electrical and Package Specifications):

The P5KE18A series (P5KE18A-AP, P5KE18A-BP, P5KE18A-TP) manufactured by Micro Commercial Co provides identical electrical performance to the SA18A with active product status. These parts maintain 18V reverse standoff voltage, 29.2V clamping voltage, 17.2A peak pulse current, and 500W power dissipation in DO-15 packaging. All variants are REACH compliant and classified under ECCN EAR99.

SAC18 manufactured by Littelfuse is an active alternative in DO-15 packaging with matching 18V standoff and 500W power rating. The clamping voltage is 28.8V and peak pulse current is 15A, representing a slight reduction in current handling capacity. This part is ROHS3 compliant with unlimited moisture sensitivity level.

For Enhanced Performance with Package Change:

LCE18A manufactured by Littelfuse provides identical electrical specifications (18V standoff, 29.2V clamp, 500W power) but in DO-201 package with significantly higher peak pulse current (51A) and power rating (1500W). This substitution requires mechanical redesign for board layout and mounting but offers superior transient protection capability. LCE18A is ROHS3 compliant and active.

For Voltage-Shifted Applications:

P6KE22A (Fairchild Semiconductor) in DO-15 packaging offers slightly higher voltage ratings (18.8V standoff, 30.6V clamp) with enhanced current handling (20A peak pulse, 600W power). This part is suitable where marginal voltage headroom improvement is acceptable.

LCE series parts (LCE15A, LCE16A, LCE17A) in DO-201 packaging provide lower voltage ratings with substantially higher current and power capabilities (54A–61A peak pulse, 1500W power). These are applicable only where circuit voltage requirements permit lower standoff voltages.

Frequently Asked Questions (FAQ)

Q: Can I use P5KE18A-AP, P5KE18A-BP, or P5KE18A-TP interchangeably with SA18A?

A: Yes. All three Micro Commercial Co variants (P5KE18A-AP, P5KE18A-BP, P5KE18A-TP) are direct electrical and mechanical equivalents to SA18A. They maintain identical reverse standoff voltage (18V), clamping voltage (29.2V), peak pulse current (17.2A), power rating (500W), and DO-15 packaging. The suffix designations (-AP, -BP, -TP) indicate different packaging or tape configurations but do not affect electrical performance.

Q: What is the difference between DO-15 and DO-201 packages?

A: DO-15 (DO-204AC) and DO-201 (DO-204AA) are both axial through-hole packages for diodes. DO-15 is smaller and more compact, while DO-201 is larger. Substituting SA18A (DO-15) with LCE18A (DO-201) requires board layout modification and different mounting hole spacing. Electrical performance remains equivalent.

Q: Why is SAC18 listed as a substitute if its peak pulse current is only 15A versus SA18A's 17.2A?

A: SAC18 maintains the same reverse standoff voltage (18V), clamping voltage (29.2V), and power rating (500W) as SA18A. The 15A peak pulse current represents a 12.8% reduction in current handling. SAC18 is suitable for applications where the transient current does not exceed 15A. For applications requiring the full 17.2A capability, P5KE18A variants are preferred.

Q: Can I use LCE18A as a drop-in replacement for SA18A?

A: LCE18A provides identical electrical specifications (18V standoff, 29.2V clamp) but is packaged in DO-201 instead of DO-15. This is not a mechanical drop-in replacement without board redesign. However, LCE18A offers superior performance with 51A peak pulse current and 1500W power rating, making it suitable for applications requiring enhanced transient protection if layout permits the larger package.

Q: Is SAC18 ROHS compliant?

A: Yes. SAC18 is ROHS3 compliant with unlimited moisture sensitivity level (MSL 1).

Q: What is the operating temperature range for substitute parts?

A: P5KE18A variants operate from -65°C to 175°C (TJ). SAC18 and LCE18A operate from -55°C to 175°C (TJ). Verify operating temperature requirements for your specific application.

Q: Are all substitute parts REACH compliant?

A: Yes. All listed substitute parts (P5KE18A-AP, P5KE18A-BP, P5KE18A-TP, SAC18, LCE18A, P6KE22A, LCE15A, LCE16A, LCE17A) are REACH unaffected or REACH compliant.

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