SMF24AT1G Equivalent & Substitute Parts

Part Overview

The SMF24AT1G is a unidirectional transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. This component features a 24V reverse standoff voltage with a 38.9V maximum clamping voltage and 5.1A peak pulse current capability in a SOD-123FL package. The part is currently listed as obsolete, necessitating identification of active equivalent and substitute components that maintain electrical compatibility or provide suitable alternatives for circuit protection requirements.

Key Parameters

Parameter	SMF24AT1G
Manufacturer	Littelfuse Inc.
Product Status	Obsolete
Type	Zener TVS Diode
Unidirectional Channels	1
Voltage - Reverse Standoff (Typ)	24V
Voltage - Breakdown (Min)	26.7V
Voltage - Clamping (Max) @ Ipp	38.9V
Current - Peak Pulse (10/1000µs)	5.1A
Power - Peak Pulse	200W
Operating Temperature	-55°C ~ 150°C (TJ)
Mounting Type	Surface Mount
Package / Case	SOD-123F
RoHS Status	ROHS3 Compliant
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the SMF24AT1G is determined by the following critical electrical parameters:

Voltage - Reverse Standoff (Typ): The nominal voltage at which the TVS diode remains non-conducting. Substitutes must match or closely approximate this value to maintain circuit protection thresholds.
Voltage - Clamping (Max) @ Ipp: The maximum voltage clamped at peak pulse current. This parameter directly affects the protection level provided to downstream components.
Current - Peak Pulse (10/1000µs): The maximum transient current the diode can safely dissipate. Substitutes must meet or exceed this specification.
Power - Peak Pulse: The maximum peak power dissipation capability, fixed at 200W across the SMF series.
Package / Case: Physical form factor compatibility. The SOD-123F package is standard across all listed substitutes.
Operating Temperature Range: The thermal operating window must encompass the application requirements.

Substitutes are categorized into two groups:

Direct Equivalents maintain identical or near-identical electrical specifications and are pin-compatible replacements.

Voltage-Variant Alternatives provide different voltage ratings within the SMF series, suitable for applications requiring different protection thresholds while maintaining the same package, power rating, and general-purpose protection function.

Parameter Comparison

Part Number	Manufacturer	Status	Vwm (Typ)	Vbr (Min)	Vc (Max)	Ipp (A)	Package	Temp Range
SMF24AT1G	Littelfuse Inc.	Obsolete	24V	26.7V	38.9V	5.1A	SOD-123F	-55°C ~ 150°C
SMF24A	MDD	Active	24V	26.7V	38.9V	5.1A	SOD-123F	-55°C ~ 150°C
SMF24A-T13	Littelfuse Inc.	Active	24V	26.7V	38.9V	5.1A	SOD-123F	-55°C ~ 150°C
SMF20A	MDD	Active	20V	22.2V	32.4V	6.2A	SOD-123F	-55°C ~ 150°C
SMF22A	MDD	Active	22V	24.4V	35.5V	5.6A	SOD-123F	-55°C ~ 150°C
SMF26A	EVVO Semi	Active	26V	28.9V	42.1V	4.8A	SOD-123F	-55°C ~ 150°C
SMF28A	MDD	Active	28V	31.1V	45.4V	4.4A	SOD-123F	-55°C ~ 150°C
SMF30A	MDD	Active	30V	33.3V	48.4V	4.1A	SOD-123F	-55°C ~ 150°C
SMF33A	Diotec Semiconductor	Active	33V	36.7V	53.3V	3.75A	SOD-123F	-50°C ~ 150°C
SMF36A	MDD	Active	36V	40V	58.1V	3.44A	SOD-123F	-55°C ~ 150°C
SMF43A	Diotec Semiconductor	Active	43V	47.8V	69.4V	2.88A	SOD-123F	-50°C ~ 150°C

Engineering Selection Recommendations

Direct Replacement (Identical Specifications)

SMF24A (MDD) and SMF24A-T13 (Littelfuse Inc.) are direct functional equivalents to the obsolete SMF24AT1G. Both maintain identical electrical parameters: 24V reverse standoff voltage, 38.9V clamping voltage, and 5.1A peak pulse current. Both are active products with ROHS3 compliance and MSL 1 rating. SMF24A-T13 is manufactured by the original equipment supplier (Littelfuse Inc.) and represents the most direct replacement path. SMF24A is available from MDD with higher inventory levels (27,619 units).

Voltage-Variant Alternatives

For applications where the exact 24V protection threshold is not critical, the SMF series offers voltage alternatives within the same 200W power class and SOD-123F package:

SMF20A: Lower voltage protection (20V standoff). Suitable for circuits requiring lower overvoltage thresholds with increased peak pulse current capability (6.2A).
SMF22A: Intermediate voltage (22V standoff) with 5.6A peak pulse current, positioned between SMF20A and SMF24A specifications.
SMF26A: Higher voltage protection (26V standoff) with 4.8A peak pulse current, appropriate for circuits tolerating higher transient voltages.
SMF28A, SMF30A, SMF33A, SMF36A, SMF43A: Progressive voltage ratings from 28V to 43V standoff, each with correspondingly reduced peak pulse current. Selection depends on the specific overvoltage threshold required by the protected circuit.

All voltage-variant alternatives maintain ROHS3 compliance, MSL 1 rating (except SMF33A and SMF43A with MSL Not Applicable), and the SOD-123F package form factor. Operating temperature ranges are -55°C to 150°C for most variants, with SMF33A and SMF43A rated to -50°C minimum.

Frequently Asked Questions (FAQ)

Q: Can SMF24A directly replace SMF24AT1G without circuit modification?

A: Yes. SMF24A maintains identical electrical specifications: 24V reverse standoff voltage, 38.9V clamping voltage, 5.1A peak pulse current, and 200W peak power dissipation. The SOD-123F package is pin-compatible. No circuit modifications are required.

Q: What is the difference between SMF24A and SMF24A-T13?

A: Both parts are electrically identical with matching specifications. SMF24A-T13 is manufactured by Littelfuse Inc. (the original SMF24AT1G supplier) and is supplied in Tape & Reel packaging. SMF24A is supplied by MDD, also in Tape & Reel format. Selection may depend on supplier availability and procurement preferences.

Q: Can I use SMF26A or SMF28A as substitutes for SMF24A?

A: SMF26A and SMF28A are not direct replacements. They provide higher voltage protection thresholds (26V and 28V standoff respectively) compared to the 24V specification of SMF24AT1G. Use these alternatives only if your circuit design permits higher transient voltage clamping levels. Peak pulse current capability is also reduced (4.8A and 4.4A respectively versus 5.1A).

Q: Are all SMF series diodes compatible with the SOD-123F package footprint?

A: Yes. All listed substitute parts use the SOD-123F package form factor, ensuring mechanical and electrical compatibility with existing PCB layouts designed for SMF24AT1G.

Q: What is the impact of selecting a lower voltage rating like SMF20A?

A: SMF20A provides protection at a lower 20V standoff threshold with increased peak pulse current (6.2A). This is suitable only for circuits designed to tolerate lower overvoltage protection levels. The clamping voltage is reduced to 32.4V. Verify that your protected circuit components can withstand this lower clamping voltage before substitution.

Q: Do all substitute parts meet RoHS3 compliance?

A: Yes. All listed substitute parts are ROHS3 compliant. Moisture sensitivity levels are MSL 1 (Unlimited) for most variants, with SMF33A and SMF43A rated as MSL Not Applicable.

Q: What is the minimum operating temperature for SMF33A and SMF43A?

A: SMF33A and SMF43A are rated to -50°C minimum operating temperature, compared to -55°C for other variants. If your application requires operation below -50°C, select alternatives with -55°C minimum rating.

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