1SMB5944H Zener Diode Equivalent & Substitute Parts

Part Overview

The 1SMB5944H is a 62 V, 3 W surface mount zener diode manufactured by Taiwan Semiconductor Corporation in DO-214AA (SMB) package. This component is classified as an active product with AEC-Q101 automotive qualification and ROHS3 compliance. Substitute parts are identified based on matching or compatible electrical specifications, package compatibility, and operational parameters that permit direct functional replacement in circuit applications.

Key Parameters

Parameter	Value
Voltage - Zener (Nom)	62 V
Tolerance	±5%
Power - Max	3 W
Impedance (Max)	100 Ohms
Current - Reverse Leakage @ Vr	1 µA @ 47.1 V
Operating Temperature	-55°C ~ 150°C
Package / Case	DO-214AA, SMB
Mounting Type	Surface Mount
Grade	Automotive
Qualification	AEC-Q101
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the 1SMB5944H are categorized based on the following substitution criteria:

Direct Electrical Equivalents (62 V, 3 W): Parts with identical zener voltage (62 V) and power rating (3 W) provide direct functional replacement with no circuit redesign required. These include the 1SMB5944BT3G from onsemi, which maintains the same electrical specifications and package format.

Voltage-Adjacent Substitutes (68 V, 3 W): Parts with higher zener voltage (68 V) and matching 3 W power rating are classified as voltage-adjacent substitutes. These include 1SMB5945BT3G and SZ1SMB5945BT3G from onsemi. These parts operate within the same power envelope but provide different voltage regulation characteristics and are suitable for applications where the higher voltage threshold is acceptable.

Higher Power Alternatives (60 V / 68 V, 5 W): Parts with increased power dissipation capability (5 W) and voltage specifications near the original (60 V or 68 V) are classified as higher power alternatives. These include SMBJ5371B-TP (60 V, 5 W) and SMBJ5373B-TP (68 V, 5 W) from Micro Commercial Co. These parts accommodate higher current or power dissipation requirements while maintaining compatible package and mounting specifications.

All substitute parts share the following compatibility criteria with the main part:

Surface mount technology
DO-214AA / SMB package format
±5% tolerance
ROHS3 compliance
Tape & Reel packaging
Active product status

Parameter Comparison

Part Number	Manufacturer	Voltage - Zener (Nom)	Power - Max	Impedance (Max)	Current - Reverse Leakage @ Vr	Operating Temperature	Package / Case	Grade	Qualification
1SMB5944H	Taiwan Semiconductor Corporation	62 V	3 W	100 Ohms	1 µA @ 47.1 V	-55°C ~ 150°C	DO-214AA, SMB	Automotive	AEC-Q101
1SMB5944BT3G	onsemi	62 V	3 W	100 Ohms	1 µA @ 47.1 V	-65°C ~ 150°C	DO-214AA, SMB	Standard	Not specified
1SMB5945BT3G	onsemi	68 V	3 W	120 Ohms	1 µA @ 51.7 V	-65°C ~ 150°C	DO-214AA, SMB	Standard	Not specified
SMBJ5371B-TP	Micro Commercial Co	60 V	5 W	40 Ohms	500 nA @ 45.5 V	-55°C ~ 150°C	DO-214AA, SMB	Standard	Not specified
SMBJ5373B-TP	Micro Commercial Co	68 V	5 W	44 Ohms	500 nA @ 51.7 V	-55°C ~ 150°C	DO-214AA, SMB	Standard	Not specified
SZ1SMB5945BT3G	onsemi	68 V	3 W	120 Ohms	1 µA @ 51.7 V	-65°C ~ 150°C	DO-214AA, SMB	Automotive	AEC-Q101

Engineering Selection Recommendations

For Direct Replacement (No Circuit Modification): The 1SMB5944BT3G from onsemi is the primary direct electrical equivalent, offering identical 62 V zener voltage and 3 W power rating. This part extends the lower operating temperature limit to -65°C compared to the original -55°C specification. Both parts maintain ROHS3 compliance and identical package specifications.

For Automotive Applications with Extended Temperature Range: The SZ1SMB5945BT3G from onsemi provides automotive-grade qualification (AEC-Q101) matching the original part's grade status. This part operates at 68 V with a -65°C lower temperature limit, suitable for automotive environments requiring higher voltage regulation and extended cold-temperature performance.

For Higher Power Dissipation Requirements: The SMBJ5371B-TP and SMBJ5373B-TP from Micro Commercial Co offer 5 W power ratings, doubling the dissipation capability of the original 3 W part. The SMBJ5371B-TP maintains 60 V operation close to the original specification, while SMBJ5373B-TP provides 68 V operation. Both parts maintain the same operating temperature range as the original (-55°C ~ 150°C) and ROHS3 compliance.

All substitute parts are active products with ROHS3 compliance and REACH unaffected status, matching the regulatory compliance profile of the original 1SMB5944H.

Frequently Asked Questions (FAQ)

Q: Can the 1SMB5944BT3G directly replace the 1SMB5944H without circuit modification?

A: Yes. The 1SMB5944BT3G maintains identical electrical specifications: 62 V zener voltage, 3 W power rating, 100 Ohms maximum impedance, and 1 µA reverse leakage current. Both parts use the DO-214AA (SMB) package and surface mount technology. The primary difference is the extended lower operating temperature limit (-65°C versus -55°C) on the onsemi part, which does not restrict compatibility.

Q: What is the difference between the 3 W and 5 W zener diode options?

A: Power rating indicates maximum continuous power dissipation capability. The 3 W parts (1SMB5944H, 1SMB5944BT3G, 1SMB5945BT3G, SZ1SMB5945BT3G) are suitable for applications with lower current or power dissipation requirements. The 5 W parts (SMBJ5371B-TP, SMBJ5373B-TP) accommodate higher current loads or continuous power dissipation. Selection depends on circuit current requirements and thermal management capabilities.

Q: Are the 68 V zener diodes (1SMB5945BT3G, SMBJ5373B-TP, SZ1SMB5945BT3G) compatible with circuits designed for 62 V operation?

A: Voltage-adjacent substitutes operate at different regulation thresholds. A 68 V zener will not conduct until the reverse voltage reaches 68 V, compared to 62 V for the original part. These substitutes are compatible only in applications where the higher voltage threshold is acceptable or required by circuit design. Direct voltage equivalence is not maintained.

Q: What is the significance of AEC-Q101 qualification on the 1SMB5944H and SZ1SMB5945BT3G?

A: AEC-Q101 qualification indicates the part meets automotive industry reliability and quality standards established by the Automotive Electronics Council. Both the original 1SMB5944H and the SZ1SMB5945BT3G carry this automotive-grade designation. Non-qualified parts (1SMB5944BT3G, 1SMB5945BT3G, SMBJ5371B-TP, SMBJ5373B-TP) are standard-grade components suitable for non-automotive applications.

Q: Do all substitute parts use the same DO-214AA (SMB) package?

A: Yes. All listed substitute parts use the DO-214AA (SMB) surface mount package, ensuring mechanical and electrical compatibility with PCB layouts designed for the 1SMB5944H. Package compatibility permits direct board-level substitution without layout modification.

Q: What is the difference in impedance specifications between the substitute parts?

A: Impedance (Zzt) values range from 40 Ohms (SMBJ5371B-TP) to 120 Ohms (1SMB5945BT3G, SZ1SMB5945BT3G). Lower impedance values indicate better voltage regulation stability at higher currents. The original 1SMB5944H specifies 100 Ohms. Impedance differences affect transient response and regulation characteristics in dynamic load conditions.

Q: Are all substitute parts ROHS3 compliant?

A: Yes. All listed substitute parts carry ROHS3 compliance status, matching the regulatory requirement of the original 1SMB5944H. All parts are also REACH unaffected, indicating no restricted substances of concern.

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