BYT03-400 Equivalent & Substitute Parts

Part Overview

The BYT03-400 is a general-purpose rectifier diode rated for 400 V DC reverse voltage and 3 A average rectified current, packaged in DO-201AD axial configuration. Manufactured by STMicroelectronics, this component is classified as obsolete, necessitating identification of active equivalent and substitute parts for new designs and ongoing production requirements. The fast recovery characteristic (≤500 ns) and 55 ns reverse recovery time define its operational profile for high-frequency rectification applications.

Key Parameters

Parameter	Value	Unit
Voltage - DC Reverse (Vr) Maximum	400	V
Current - Average Rectified (Io)	3	A
Voltage - Forward (Vf) Maximum @ If	1.5 V @ 3 A	V
Speed Classification	Fast Recovery ≤500 ns	—
Reverse Recovery Time (trr)	55	ns
Current - Reverse Leakage @ Vr	20	µA @ 400 V
Mounting Type	Through Hole	—
Package / Case	DO-201AD, Axial	—
Operating Temperature - Junction Maximum	150	°C
Product Status	Obsolete	—
RoHS Status	ROHS3 Compliant	—

Substitute Part Grouping Explanation

Substitution of the BYT03-400 is determined by the following critical parameters:

Mandatory Matching Parameters:

Voltage - DC Reverse (Vr) Maximum: 400 V
Current - Average Rectified (Io): 3 A
Mounting Type: Through Hole
Package / Case: DO-201AD or compatible axial configuration

Performance Considerations:

Speed classification (Fast Recovery vs. Standard Recovery) affects switching behavior
Reverse recovery time (trr) influences high-frequency performance
Forward voltage (Vf) and reverse leakage current impact thermal and efficiency characteristics
Operating temperature range affects reliability in thermal environments

Substitute parts are grouped into two categories:

Direct Equivalents (DO-201AD Package): Parts maintaining identical voltage, current, and package specifications with active product status.

Functional Equivalents (Alternative Packages): Parts meeting voltage and current requirements but utilizing different package configurations (DO-15, DO-27) or exhibiting different speed classifications (Standard Recovery vs. Fast Recovery).

Parameter Comparison

Part Number	Manufacturer	Vr (Max) V	Io (A)	Vf (Max) @ If	Speed	trr (ns)	Ir @ Vr (µA)	Package	Tj (Max) °C	Product Status
BYT03-400	STMicroelectronics	400	3	1.5 V @ 3 A	Fast Recovery ≤500 ns	55	20 @ 400 V	DO-201AD	150	Obsolete
STTH3R04RL	STMicroelectronics	400	3	1.5 V @ 3 A	Fast Recovery ≤500 ns	35	5 @ 400 V	DO-201AD	175	Active
STTH3R04QRL	STMicroelectronics	400	3	1.5 V @ 3 A	Fast Recovery ≤500 ns	35	5 @ 400 V	DO-15	175	Active
1N5404-E3/54	Vishay General Semiconductor	400	3	1.2 V @ 3 A	Standard Recovery >500 ns	—	5 @ 400 V	DO-201AD	150	Active
1N5404-G	Comchip Technology	400	3	950 mV @ 3 A	Standard Recovery >500 ns	—	5 @ 400 V	DO-201AD	125	Active
1N5404G	onsemi	400	3	1 V @ 3 A	Standard Recovery >500 ns	—	10 @ 400 V	DO-27	150	Not For New Designs
1N5404GP-AP	Micro Commercial Co	400	3	1.1 V @ 3 A	Standard Recovery >500 ns	—	5 @ 400 V	DO-201AD	150	Active
1N5404RLG	onsemi	400	3	1 V @ 3 A	Standard Recovery >500 ns	—	10 @ 400 V	DO-27	150	Not For New Designs
EGP20G	Fairchild Semiconductor	400	2	1.25 V @ 2 A	Fast Recovery ≤500 ns	50	5 @ 400 V	DO-15	150	Active
EGP30F	Fairchild Semiconductor	300	3	1.25 V @ 3 A	Fast Recovery ≤500 ns	50	5 @ 300 V	DO-201AD	150	Active

Engineering Selection Recommendations

Primary Recommendation: STTH3R04RL

The STTH3R04RL is the direct equivalent replacement for the BYT03-400. Both parts are manufactured by STMicroelectronics and maintain identical electrical specifications: 400 V reverse voltage, 3 A average rectified current, 1.5 V forward voltage at 3 A, and fast recovery characteristics. The STTH3R04RL offers improved performance with reduced reverse recovery time (35 ns vs. 55 ns), lower reverse leakage current (5 µA vs. 20 µA), and extended maximum junction temperature (175°C vs. 150°C). The part is active and ROHS3 compliant. Packaging is DO-201AD axial, identical to the original specification.

Secondary Recommendation: 1N5404-E3/54 (Vishay General Semiconductor)

The 1N5404-E3/54 provides functional equivalence with identical voltage and current ratings in DO-201AD packaging. This part is active and ROHS3 compliant. The primary distinction is speed classification: the 1N5404-E3/54 employs standard recovery (>500 ns) rather than fast recovery. This characteristic is suitable for applications where switching speed is not critical. Forward voltage is lower (1.2 V vs. 1.5 V), providing improved efficiency. Reverse leakage current is reduced to 5 µA.

Alternative Recommendation: 1N5404GP-AP (Micro Commercial Co)

The 1N5404GP-AP maintains 400 V, 3 A specifications in DO-201AD packaging with active product status. Standard recovery speed applies. Forward voltage is 1.1 V at 3 A. This part is suitable for applications where fast recovery is not required and lower forward voltage drop is beneficial.

Package Alternative: STTH3R04QRL (STMicroelectronics)

For applications permitting DO-15 package substitution, the STTH3R04QRL provides identical electrical performance to STTH3R04RL with fast recovery characteristics, improved reverse recovery time (35 ns), and extended temperature rating (175°C). This part is active and ROHS3 compliant.

Not Recommended for New Designs:

Parts with "Not For New Designs" status (1N5404G, 1N5404RLG from onsemi) should not be selected for new product development, although they remain functionally equivalent for legacy system maintenance.

Voltage Derating Consideration:

The EGP30F (Fairchild Semiconductor) is rated for 300 V maximum reverse voltage, which is below the 400 V requirement of the BYT03-400. This part does not meet the mandatory voltage specification and is not suitable as a direct substitute.

Current Derating Consideration:

The EGP20G (Fairchild Semiconductor) is rated for 2 A average rectified current, which is below the 3 A requirement. This part does not meet the mandatory current specification and is not suitable as a direct substitute.

Frequently Asked Questions (FAQ)

Q: Can the STTH3R04RL directly replace the BYT03-400 without circuit modification?

A: Yes. The STTH3R04RL is a direct equivalent with identical voltage (400 V), current (3 A), forward voltage (1.5 V @ 3 A), and package (DO-201AD) specifications. The improved performance characteristics (lower reverse recovery time, reduced leakage current, higher temperature rating) provide enhanced reliability without requiring circuit changes.

Q: What is the difference between fast recovery and standard recovery diodes?

A: Fast recovery diodes exhibit reverse recovery time ≤500 ns, enabling operation at higher switching frequencies with reduced switching losses. Standard recovery diodes have reverse recovery time >500 ns and are suitable for lower-frequency applications. The BYT03-400 is fast recovery; most 1N5404 variants are standard recovery. Selection depends on circuit switching frequency requirements.

Q: Can I use a 1N5404 series diode as a substitute?

A: The 1N5404 series (1N5404-E3/54, 1N5404-G, 1N5404GP-AP, 1N5404RLG) meets the 400 V, 3 A electrical requirements and DO-201AD packaging specification. However, these parts employ standard recovery characteristics rather than fast recovery. Substitution is valid for applications where switching speed is not critical. Verify circuit operating frequency before selection.

Q: Why is the reverse leakage current specification important?

A: Reverse leakage current (Ir) determines the diode's blocking capability and contributes to circuit standby power consumption. The BYT03-400 specifies 20 µA at 400 V. Most substitute parts offer improved leakage (5 µA), reducing power dissipation in blocking mode. Lower leakage current is generally beneficial and does not create compatibility issues.

Q: Can I substitute a DO-15 package diode for the DO-201AD package?

A: Package substitution requires mechanical compatibility verification. The DO-15 (STTH3R04QRL) and DO-201AD (BYT03-400) are both axial through-hole packages but differ in physical dimensions. PCB layout, lead spacing, and mechanical clearance must be confirmed before substitution. Electrical specifications remain compatible.

Q: What does "ROHS3 Compliant" mean for component selection?

A: ROHS3 (Restriction of Hazardous Substances Directive 3) compliance indicates the component meets European environmental regulations restricting lead, cadmium, mercury, and other hazardous substances. All recommended substitute parts are ROHS3 compliant, ensuring regulatory compatibility for products destined for European markets.

Q: Is the BYT03-400 still available for purchase?

A: The BYT03-400 is classified as obsolete. While inventory may exist in distribution channels (1950 pcs reported in stock), long-term availability is not guaranteed. Transition to active equivalent parts (STTH3R04RL, 1N5404-E3/54, 1N5404GP-AP) is recommended for new designs and ongoing production planning.

Q: What is the significance of the maximum junction temperature rating?

A: The maximum junction temperature (Tj) defines the thermal operating limit. The BYT03-400 is rated to 150°C; STTH3R04RL extends this to 175°C. Higher ratings provide greater thermal margin in high-temperature environments and reduce thermal stress during transient overcurrent conditions. This improvement in STTH3R04RL enhances reliability.

Q: Can I use multiple lower-current diodes in parallel to replace a 3 A diode?

A: Parallel connection of diodes for current sharing is not recommended without additional design considerations (current-sharing resistors, matched forward voltage characteristics). Direct substitution with a single equivalent 3 A diode is the preferred engineering approach.

Q: How do I verify that a substitute part is compatible with my circuit?

A: Verify the following parameters match or exceed the original specification: (1) Voltage - DC Reverse (Vr) ≥ 400 V, (2) Current - Average Rectified (Io) ≥ 3 A, (3) Package / Case compatible with PCB layout, (4) Operating temperature range suitable for application environment. Confirm speed classification (fast vs. standard recovery) aligns with circuit switching frequency. Review datasheets for forward voltage and leakage current to assess thermal and efficiency impact.

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