SMS12T1 Transient Voltage Suppressor Diode Equivalent & Substitute Parts

Part Overview

The SMS12T1 is a unidirectional Zener transient voltage suppressor diode manufactured by onsemi, rated for 12V reverse standoff with 23V maximum clamping voltage and 15A peak pulse current (8/20µs). The device is packaged in SC-74 (SOT-457) surface mount configuration for general-purpose transient protection applications.

The SMS12T1 carries an obsolete product status. Locating active equivalent and substitute parts is necessary to maintain design continuity and ensure component availability for new production runs and field replacements.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	12V	V
Voltage - Breakdown (Min)	13.3V	V
Voltage - Clamping (Max) @ Ipp	23V	V
Current - Peak Pulse (10/1000µs)	15A (8/20µs)	A
Power - Peak Pulse	350W	W
Capacitance @ 1MHz	80pF	pF
Operating Temperature Range	-55°C to 150°C	°C
Mounting Type	Surface Mount	—
Package / Case	SC-74, SOT-457	—
Unidirectional Channels	4	—
Type	Zener	—

Substitute Part Grouping Explanation

Substitution of the SMS12T1 is determined by the following critical electrical and mechanical parameters:

Primary Substitution Criteria:

Voltage - Reverse Standoff: 12V nominal
Voltage - Clamping (Max) @ Ipp: 23V maximum
Current - Peak Pulse: 15A (8/20µs)
Power - Peak Pulse: 350W
Unidirectional Channels: 4
Type: Zener
Mounting Type: Surface Mount
Package / Case: SC-74 or SOT-457 compatible

Direct Equivalent: SMS12T1G (onsemi) is the direct active equivalent with identical electrical specifications and active product status. This part differs only in packaging format (Tape & Reel) and RoHS compliance status (ROHS3 Compliant vs. RoHS non-compliant).

Similar Substitutes: The Nexperia BZA420A and BZA456A series parts are listed as similar alternatives. However, these parts exhibit different voltage ratings and current specifications that deviate from the SMS12T1 parameters. The BZA420A series operates at 20V reverse standoff with 28V clamping voltage. The BZA456A series operates at 5.6V reverse standoff with 8V clamping voltage. These parts are not electrically equivalent and represent different protection voltage classes.

The Bourns CDSOT236-T12 provides closer electrical alignment with 12V reverse standoff, 19V clamping voltage, and 12A peak pulse current, though it operates at reduced current capacity compared to the SMS12T1.

Parameter Comparison

Parameter	SMS12T1	SMS12T1G	CDSOT236-T12	BZA420A,125	BZA456A,125
Manufacturer	onsemi	onsemi	Bourns Inc.	Nexperia USA Inc.	Nexperia USA Inc.
Product Status	Obsolete	Active	Active	Active	Active
Voltage - Reverse Standoff (Typ)	12V	12V	12V	20V	5.6V
Voltage - Breakdown (Min)	13.3V	13.3V	13.3V	—	—
Voltage - Clamping (Max) @ Ipp	23V	23V	19V	28V	8V
Current - Peak Pulse (10/1000µs)	15A (8/20µs)	15A (8/20µs)	12A (8/20µs)	—	3A (8/20µs)
Power - Peak Pulse	350W	350W	350W	19.6W	24W
Capacitance @ 1MHz	80pF	80pF	80pF	48pF	240pF
Operating Temperature Range	-55°C to 150°C	-55°C to 150°C	-55°C to 150°C	-65°C to 150°C	-65°C to 150°C
Package / Case	SC-74, SOT-457	SC-74, SOT-457	SOT-23-6	6-TSOP	6-TSOP
Unidirectional Channels	4	4	4	4	4
RoHS Status	RoHS non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

Primary Selection: SMS12T1G

SMS12T1G is the recommended direct replacement for SMS12T1. This part maintains identical electrical specifications across all critical parameters: 12V reverse standoff, 23V clamping voltage, 15A peak pulse current, and 350W peak pulse power. The part is in active production status with substantial inventory availability (92,790 pcs). SMS12T1G carries ROHS3 compliance, meeting current regulatory requirements. The only functional difference is packaging format (Tape & Reel vs. bulk), which does not affect electrical performance or circuit compatibility.

Secondary Selection: CDSOT236-T12

CDSOT236-T12 (Bourns) provides an alternative for applications where the 12V protection voltage class is required. This part maintains the same 12V reverse standoff and 13.3V minimum breakdown voltage as the SMS12T1. The clamping voltage is reduced to 19V (compared to 23V), and peak pulse current is reduced to 12A (compared to 15A). These reductions result in lower peak pulse power (350W maintained). CDSOT236-T12 is in active production with ROHS3 compliance. The package format differs (SOT-23-6 vs. SC-74), requiring PCB layout modification. This option is suitable only when the reduced current and voltage specifications align with circuit requirements.

Not Recommended: BZA420A and BZA456A Series

The BZA420A series (20V reverse standoff, 28V clamping) and BZA456A series (5.6V reverse standoff, 8V clamping) operate in different voltage protection classes and are not electrically equivalent to the SMS12T1. These parts should not be used as substitutes unless the circuit design is modified to accommodate the different voltage ratings.

Frequently Asked Questions (FAQ)

Q: Can SMS12T1G be used as a direct replacement for SMS12T1 without circuit modification?

A: Yes. SMS12T1G is electrically identical to SMS12T1 across all critical parameters. The part is pin-compatible and maintains the same SC-74 package footprint. No circuit modification is required. The primary difference is packaging format (Tape & Reel) and RoHS compliance status.

Q: What is the difference between SMS12T1 and SMS12T1G?

A: SMS12T1 is obsolete and RoHS non-compliant. SMS12T1G is the active production equivalent with ROHS3 compliance. Electrical specifications are identical. SMS12T1G is supplied in Tape & Reel packaging format.

Q: Can CDSOT236-T12 replace SMS12T1 in all applications?

A: CDSOT236-T12 can replace SMS12T1 only in applications where the reduced specifications are acceptable. The clamping voltage is 4V lower (19V vs. 23V) and peak pulse current is 3A lower (12A vs. 15A). The package footprint differs (SOT-23-6 vs. SC-74), requiring PCB redesign. Verify that the lower voltage and current ratings meet circuit protection requirements before substitution.

Q: Why are BZA420A and BZA456A listed as substitutes if they have different voltage ratings?

A: BZA420A and BZA456A are listed in the SMS12T1 substitute field but represent different voltage protection classes. These parts are not electrically equivalent and should not be used as direct replacements. They are included for reference only when circuit design allows for different protection voltage specifications.

Q: What is the significance of the 12V reverse standoff voltage?

A: The 12V reverse standoff voltage defines the normal operating voltage at which the TVS diode remains non-conducting. The diode conducts only when transient voltages exceed the breakdown voltage (13.3V minimum). This voltage class is critical for protecting circuits operating at or near 12V nominal levels.

Q: Does package format affect electrical performance?

A: No. Package format (SC-74, SOT-23-6, 6-TSOP) does not affect electrical performance. However, package format determines PCB footprint compatibility. Substitution between different package formats requires PCB layout modification.

Q: Are all listed substitutes RoHS compliant?

A: SMS12T1G, CDSOT236-T12, BZA420A series, and BZA456A series are all ROHS3 compliant. The original SMS12T1 is RoHS non-compliant. For new designs and production, ROHS3-compliant alternatives are required.

Q: What is the operating temperature range for these TVS diodes?

A: SMS12T1 and SMS12T1G operate from -55°C to 150°C junction temperature. CDSOT236-T12 operates from -55°C to 150°C. BZA420A and BZA456A series operate from -65°C to 150°C, providing extended low-temperature performance.

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