1N746ATR Zener Diode Equivalent & Substitute Parts

Part Overview

The 1N746ATR is a 3.3 V Zener diode rated at 500 mW with ±5% tolerance, manufactured by onsemi in a through-hole DO-35 package. This component is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement. The 1N746ATR serves voltage regulation and protection applications requiring precise 3.3 V reference voltage with moderate power dissipation capability.

Key Parameters

Parameter	Value	Unit
Voltage - Zener (Nom)	3.3	V
Tolerance	±5%	%
Power - Max	500	mW
Impedance (Max)	28	Ohms
Current - Reverse Leakage @ Vr	10	µA @ 1 V
Voltage - Forward (Vf) (Max) @ If	1.5	V @ 200 mA
Operating Temperature	-65 to 200	°C
Mounting Type	Through Hole
Package / Case	DO-204AH, DO-35, Axial

Substitute Part Grouping Explanation

Substitution of the 1N746ATR is determined by the following critical parameters:

Primary Matching Criteria:

Voltage - Zener (Nom): 3.3 V (exact match required)
Tolerance: ±5% (acceptable tolerance band)
Power - Max: 500 mW (minimum power rating)
Mounting Type: Through Hole (form factor requirement)
Package / Case: DO-35 or DO-204AH (physical compatibility)

Secondary Compatibility Factors:

Impedance (Max): 28 Ohms (electrical performance characteristic)
Operating Temperature Range: -65°C minimum and 200°C maximum (thermal envelope)
Current - Reverse Leakage: specification dependent on application requirements

Substitute parts are grouped into two categories:

Direct Equivalents (Identical Electrical and Physical Specifications): Parts matching all primary criteria with identical impedance and forward voltage characteristics.

Parametric Equivalents (Functionally Compatible): Parts meeting primary criteria with minor variations in secondary parameters such as impedance, reverse leakage current, or forward voltage, while maintaining functional compatibility within the 3.3 V regulation application.

Parameter Comparison

Part Number	Manufacturer	Vz (V)	Tolerance (%)	Power (mW)	Zzt (Ohms)	Reverse Leakage (µA @ 1V)	Vf (V) @ 200mA	Temp Range (°C)	Package	Status
1N746ATR	onsemi	3.3	±5	500	28	10	1.5	-65 to 200	DO-35	Obsolete
1N5226B	Microchip Technology	3.3	±5	500	28	25	1.5	-65 to 175	DO-35	Active
1N5226BTR	Fairchild Semiconductor	3.3	±5	500	28	25	1.2	-65 to 200	DO-35	Active
BZX79C3V3	Taiwan Semiconductor Corporation	3.3	±5	500	95	25	1.5	-65 to 175	DO-35	Active
1N746A-1	Microchip Technology	3.3	±5	500	24	5	1.1	-65 to 175	DO-35	Active
1N746AE3	Microchip Technology	3.3	±5	500	28	5	1.1	-65 to 175	DO-35	Active
1N746	Microchip Technology	3.3	±10	500	28	10	1.1	-65 to 175	DO-35	Active
1N4728A	Lumimax Optoelectronic Technology	3.3	±5	1000	10	100	1.2	-65 to 200	DO-41	Active
1N5226B TR PBFREE	Central Semiconductor Corp	3.3	±5	500	28	25	1.1	-65 to 200	DO-35	Active
1N746A TR PBFREE	Central Semiconductor Corp	3.3	±5	500	28	10	1.5	-65 to 200	DO-35	Active

Engineering Selection Recommendations

Tier 1 - Direct Substitutes (Highest Compatibility):

1N5226BTR (Fairchild Semiconductor) and 1N746A TR PBFREE (Central Semiconductor Corp) are the primary substitutes. Both maintain identical electrical specifications (3.3 V, ±5%, 500 mW, 28 Ohms impedance) and support the full operating temperature range (-65°C to 200°C) of the original 1N746ATR. 1N5226BTR is active with extensive inventory availability. 1N746A TR PBFREE offers RoHS3 compliance and lead-free construction.

Tier 2 - Functional Equivalents (Compatible with Minor Variations):

1N5226B (Microchip Technology) and 1N5226B TR PBFREE (Central Semiconductor Corp) provide electrical equivalence with identical impedance and power rating. Operating temperature range is reduced to -65°C to 175°C. Both are active products with high inventory levels. 1N5226B TR PBFREE includes RoHS3 compliance.

1N746A-1 and 1N746AE3 (both Microchip Technology) offer improved reverse leakage characteristics (5 µA versus 10 µA) and lower forward voltage (1.1 V versus 1.5 V), with identical impedance specifications. Operating temperature is -65°C to 175°C. Both are active with RoHS compliance available.

Tier 3 - Alternative Package Option:

1N4728A (Lumimax Optoelectronic Technology) provides 3.3 V regulation with doubled power rating (1 W versus 500 mW) in a DO-41 package. This option is suitable for applications requiring higher power dissipation but requires physical board layout modification due to different package geometry.

Compliance Considerations:

For applications requiring RoHS compliance, select 1N746AE3 (RoHS3 Compliant), 1N5226B TR PBFREE (RoHS3 Compliant), or 1N746A TR PBFREE (RoHS3 Compliant). The original 1N746ATR is RoHS non-compliant.

For applications with extended temperature requirements to 200°C, select 1N5226BTR, 1N746A TR PBFREE, or 1N4728A.

Frequently Asked Questions (FAQ)

Q: Can 1N5226B directly replace 1N746ATR in all applications?

A: 1N5226B is electrically equivalent with identical 3.3 V nominal voltage, ±5% tolerance, 500 mW power rating, and 28 Ohms impedance. The operating temperature range is reduced from -65°C to 200°C to -65°C to 175°C. Substitution is valid for applications operating within the -65°C to 175°C range.

Q: What is the difference between 1N746A-1 and 1N746AE3?

A: Both parts are 3.3 V, 500 mW Zener diodes with ±5% tolerance from Microchip Technology. 1N746AE3 has lower reverse leakage current (5 µA versus unspecified for 1N746A-1) and is RoHS3 compliant. Impedance is 24 Ohms for 1N746A-1 and 28 Ohms for 1N746AE3. Both operate from -65°C to 175°C.

Q: Why is 1N4728A listed as an alternative if it has a different power rating?

A: 1N4728A provides 1 W power dissipation versus 500 mW for the 1N746ATR. It maintains the 3.3 V nominal voltage and ±5% tolerance. This part is suitable for applications requiring higher power handling. However, the DO-41 package differs from the DO-35 package, requiring physical board layout changes.

Q: Are all substitute parts available in the same DO-35 package?

A: All substitute parts except 1N4728A are available in DO-35 or DO-204AH packages, which are physically compatible. 1N4728A uses a DO-41 package and requires different board layout accommodation.

Q: What does "TR PBFREE" designation indicate?

A: "TR PBFREE" indicates tape and reel packaging with lead-free (PbFree) construction. These parts comply with RoHS3 standards and are suitable for applications requiring lead-free components.

Q: Which substitute offers the best reverse leakage performance?

A: 1N746A-1 and 1N746AE3 both specify 5 µA reverse leakage at 1 V, compared to 10 µA for the original 1N746ATR. These parts provide superior leakage characteristics for precision voltage regulation applications.

Q: Can I use BZX79C3V3 as a direct replacement?

A: BZX79C3V3 maintains 3.3 V nominal voltage, ±5% tolerance, and 500 mW power rating. However, impedance is 95 Ohms compared to 28 Ohms for the 1N746ATR. This higher impedance may affect voltage regulation performance in applications sensitive to dynamic impedance characteristics. Operating temperature is -65°C to 175°C.

Q: What is the inventory status of recommended substitutes?

A: 1N5226BTR has 55,759 pieces in stock. 1N746A TR PBFREE has 16,293 pieces. 1N5226B TR PBFREE has 6,767 pieces. 1N5226B has 1,590 pieces. All recommended Tier 1 and Tier 2 substitutes maintain active product status with substantial inventory availability.

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