1SMA4740 Zener Diode Equivalent & Substitute Parts

Part Overview

The 1SMA4740 is a 10 V, 1.25 W surface mount zener diode manufactured by Taiwan Semiconductor Corporation in the DO-214AC (SMA) package. This component is classified as Active product status with full RoHS3 compliance and unlimited moisture sensitivity rating (MSL 1). The 1SMA4740 is suitable for voltage regulation and protection circuits requiring surface mount implementation.

Substitute parts become necessary when the primary part number experiences inventory constraints, discontinuation, or when design requirements permit operation with alternative electrical or mechanical specifications within acceptable tolerances.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	10	V
Tolerance	±5%	%
Power - Max	1.25	W
Impedance (Max)	7	Ohms
Current - Reverse Leakage @ Vr	5	µA @ 7.6 V
Operating Temperature	-55 to 175	°C
Mounting Type	Surface Mount	—
Package / Case	DO-214AC, SMA	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the 1SMA4740 is determined by the following critical parameters:

Primary Substitution Criteria:

Voltage - Zener (Nom): 10 V (exact match required)
Tolerance: ±5% (exact match required)
Package / Case: DO-214AC or SMA (mechanical compatibility)
Mounting Type: Surface Mount (assembly compatibility)
RoHS Status: ROHS3 Compliant (regulatory compliance)

Secondary Substitution Parameters:

Power - Max: 1.25 W or greater (equal or higher power rating acceptable)
Impedance (Max): 7 Ohms or lower (lower impedance acceptable)
Current - Reverse Leakage: 5 µA @ 7.6 V or lower (lower leakage acceptable)
Operating Temperature: Must encompass or exceed -55°C to 175°C range

Substitute parts are grouped into two categories: Parametric Equivalents (identical electrical specifications with packaging variations) and Similar Parts (matching core voltage and tolerance with variations in power rating, impedance, or temperature range).

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance	Power (W)	Zzt (Ohms)	Ir @ Vr (µA)	Temp Range (°C)	Package	Status
1SMA4740	Taiwan Semiconductor	10	±5%	1.25	7	5 @ 7.6V	-55 to 175	DO-214AC	Active
1PGSMA4740HR3G	Taiwan Semiconductor	10	±5%	1.25	7	5 @ 7.6V	-55 to 175	DO-214AC	Discontinued
1SMA5925BT3G	onsemi	10	±5%	1.5	4.5	2.5 @ 8V	-65 to 150	DO-214AC	Active
3SMAJ5925B-TP	Micro Commercial Co	10	±5%	3	4.5	5 @ 8V	-55 to 150	DO-214AC	Active
SMAJ4740A-TP	Micro Commercial Co	10	±5%	1	7	10 @ 7.6V	-65 to 150	DO-214AC	Active
SMAZ10-TP	Micro Commercial Co	10	±5%	1	4	1 @ 7.6V	-65 to 150	DO-214AC	Active
SZ1SMA5925BT3G	onsemi	10	±5%	1.5	4.5	2.5 @ 8V	-65 to 150	DO-214AC	Active

Engineering Selection Recommendations

Parametric Equivalent (Direct Replacement):

The 1PGSMA4740HR3G is a parametric equivalent with identical electrical specifications (10 V, 1.25 W, ±5%, 7 Ohms impedance). However, this part is discontinued at DiGi Electronics and carries automotive qualification (AEC-Q101). Selection of this part is limited to applications where automotive-grade components are required and inventory availability is confirmed through alternative distribution channels.

Higher Power Rating Substitutes (1.5 W and 3 W):

The 1SMA5925BT3G and SZ1SMA5925BT3G (both 1.5 W, onsemi) are suitable substitutes when circuit design permits higher power dissipation capability. Both parts feature lower impedance (4.5 Ohms) and reduced reverse leakage current (2.5 µA @ 8 V). The SZ1SMA5925BT3G carries automotive qualification (AEC-Q101). Operating temperature range is -65°C to 150°C, which does not extend to the upper 175°C limit of the 1SMA4740.

The 3SMAJ5925B-TP (3 W, Micro Commercial Co) provides the highest power rating among substitutes. This part maintains the -55°C to 150°C temperature range and is suitable for applications requiring enhanced thermal margin.

Lower Power Rating Substitute (1 W):

The SMAJ4740A-TP and SMAZ10-TP (both 1 W, Micro Commercial Co) are suitable only when circuit design confirms that 1 W power dissipation is sufficient. The SMAJ4740A-TP maintains identical impedance (7 Ohms) to the 1SMA4740 but exhibits higher reverse leakage (10 µA @ 7.6 V). The SMAZ10-TP features superior impedance (4 Ohms) and minimal reverse leakage (1 µA @ 7.6 V).

Compliance and Certification:

All substitute parts maintain RoHS3 compliance and REACH unaffected status. Automotive-qualified variants (SZ1SMA5925BT3G, 1PGSMA4740HR3G) carry AEC-Q101 certification for applications requiring automotive-grade reliability.

Frequently Asked Questions (FAQ)

Q: Can the 1SMA5925BT3G replace the 1SMA4740 in all applications?

A: The 1SMA5925BT3G is electrically compatible for the 10 V zener voltage and ±5% tolerance. However, the operating temperature range differs: 1SMA5925BT3G operates -65°C to 150°C, while 1SMA4740 operates -55°C to 175°C. Applications requiring operation above 150°C must use the original 1SMA4740 or equivalent parts with extended upper temperature limits.

Q: What is the difference between the 1SMA5925BT3G and SZ1SMA5925BT3G?

A: Both parts are manufactured by onsemi with identical electrical specifications (10 V, 1.5 W, ±5%). The SZ1SMA5925BT3G carries automotive qualification (AEC-Q101) and is suitable for automotive applications. The 1SMA5925BT3G is the standard commercial-grade variant. Selection depends on application requirements for automotive certification.

Q: Can I use the SMAJ4740A-TP or SMAZ10-TP as substitutes if my circuit only requires 1 W dissipation?

A: Both 1 W parts are mechanically and electrically compatible with the 1SMA4740 for 10 V zener voltage applications. The SMAZ10-TP offers superior performance characteristics with lower impedance (4 Ohms versus 7 Ohms) and minimal reverse leakage (1 µA versus 5 µA). The SMAJ4740A-TP maintains identical impedance but exhibits higher reverse leakage. Selection depends on circuit sensitivity to leakage current and impedance characteristics.

Q: Is the 1PGSMA4740HR3G a viable substitute despite being discontinued?

A: The 1PGSMA4740HR3G is a parametric equivalent with identical specifications and automotive qualification (AEC-Q101). Discontinuation at DiGi Electronics does not preclude availability through alternative distribution channels. This part is suitable only for applications where automotive-grade certification is required and inventory can be confirmed through secondary sources.

Q: What packaging differences exist among the substitute parts?

A: All substitute parts use DO-214AC or SMA package designations, which are mechanically compatible. The 1PGSMA4740HR3G is supplied in Cut Tape (CT) packaging, while the 1SMA4740 is supplied in Tape & Reel (TR). All other substitutes are supplied in Tape & Reel format. Packaging format affects handling and assembly processes but does not impact electrical performance.

Q: Can I use the 3SMAJ5925B-TP (3 W) in place of the 1SMA4740?

A: The 3SMAJ5925B-TP is electrically compatible for 10 V zener voltage and ±5% tolerance. The higher power rating (3 W versus 1.25 W) provides additional thermal margin and is acceptable for applications where circuit design permits. The operating temperature range (-55°C to 150°C) does not extend to 175°C, which may be a limitation for high-temperature applications.

Q: How do impedance differences affect circuit performance?

A: Impedance (Zzt) affects the dynamic resistance of the zener diode. Lower impedance values result in better voltage regulation under varying load conditions. Substitutes with lower impedance (4 to 4.5 Ohms) compared to the 1SMA4740 (7 Ohms) provide improved regulation characteristics. Substitutes with equal or higher impedance maintain equivalent performance.

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