S125U Schottky Diode Equivalent & Substitute Parts

Part Overview

The S125U is a Schottky rectifier diode manufactured by SMC Diode Solutions, rated for 250 V DC reverse voltage and 1 A average rectified current in a surface mount SMAF package. This component is classified as obsolete, necessitating identification of active equivalent parts for new designs and ongoing production requirements. The S125U features fast recovery characteristics suitable for high-frequency switching applications with a maximum forward voltage of 920 mV at 1 A.

Key Parameters

Parameter	Value
Manufacturer Part Number	S125U
Manufacturer	SMC Diode Solutions
Category	Diodes, Rectifiers
Technology	Schottky
Voltage - DC Reverse (Vr) (Max)	250 V
Current - Average Rectified (Io)	1 A
Voltage - Forward (Vf) (Max) @ If	920 mV @ 1 A
Speed	Fast Recovery ≤ 500 ns, > 200 mA (Io)
Current - Reverse Leakage @ Vr	50 µA @ 250 V
Capacitance @ Vr, F	28 pF @ 4 V, 1 MHz
Mounting Type	Surface Mount
Package / Case	DO-221AC, SMA Flat Leads
Supplier Device Package	SMAF
Operating Temperature - Junction	-55°C ~ 150°C
Product Status	Obsolete
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the S125U is determined by the following critical electrical and mechanical parameters:

Electrical Compatibility Criteria:

Technology type: Schottky rectifier diode
Current rating: 1 A average rectified current (Io)
Reverse voltage rating: Must equal or exceed 250 V
Forward voltage characteristics: Maximum 920 mV @ 1 A
Recovery speed: Fast recovery ≤ 500 ns, > 200 mA
Reverse leakage current: 50 µA @ rated voltage
Junction capacitance: 28 pF @ 4 V, 1 MHz

Mechanical Compatibility Criteria:

Mounting type: Surface mount
Package designation: DO-221AC with SMA flat leads
Supplier device package: SMAF

The S120U qualifies as a manufacturer-recommended substitute despite a reduced reverse voltage rating of 200 V. This substitution is valid for applications where the circuit design operates at or below 200 V DC reverse voltage. The S120U maintains identical current rating, forward voltage characteristics, recovery speed, reverse leakage current, capacitance, package configuration, and operating temperature range as the S125U.

Parameter Comparison

Parameter	S125U (Main Part)	S120U (Substitute)
Manufacturer	SMC Diode Solutions	SMC Diode Solutions
Technology	Schottky	Schottky
Voltage - DC Reverse (Vr) (Max)	250 V	200 V
Current - Average Rectified (Io)	1 A	1 A
Voltage - Forward (Vf) (Max) @ If	920 mV @ 1 A	900 mV @ 1 A
Speed	Fast Recovery ≤ 500 ns, > 200 mA (Io)	Fast Recovery ≤ 500 ns, > 200 mA (Io)
Current - Reverse Leakage @ Vr	50 µA @ 250 V	50 µA @ 200 V
Capacitance @ Vr, F	28 pF @ 4 V, 1 MHz	28 pF @ 4 V, 1 MHz
Mounting Type	Surface Mount	Surface Mount
Package / Case	DO-221AC, SMA Flat Leads	DO-221AC, SMA Flat Leads
Supplier Device Package	SMAF	SMAF
Operating Temperature - Junction	-55°C ~ 150°C	-55°C ~ 150°C
Product Status	Obsolete	Active
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)
REACH Status	REACH Affected	REACH Affected
ECCN	EAR99	EAR99
HTSUS	8541.10.0080	8541.10.0080

Engineering Selection Recommendations

The S120U is the manufacturer-recommended substitute for the obsolete S125U. Selection of the S120U is appropriate for applications where the maximum reverse voltage requirement does not exceed 200 V DC. The S120U offers the following advantages:

Product Status: The S120U maintains active product status with 966 units in stock, ensuring supply chain continuity and long-term availability compared to the obsolete S125U.

Compliance: The S120U is RoHS3 compliant, providing enhanced environmental and regulatory compliance for new designs. Both parts maintain identical REACH affected status and EAR99 export classification.

Electrical Performance: The S120U delivers equivalent or superior electrical characteristics within its voltage rating, including a marginally lower forward voltage of 900 mV @ 1 A compared to 920 mV @ 1 A for the S125U.

Mechanical Compatibility: Identical package configuration (DO-221AC, SMAF) and mounting type ensure direct PCB layout compatibility without redesign.

Thermal and Environmental: Matching operating temperature range (-55°C ~ 150°C) and moisture sensitivity level (MSL 1) maintain equivalent reliability characteristics.

For applications requiring the full 250 V reverse voltage rating of the S125U, alternative Schottky diodes with equivalent current and package specifications must be sourced from the manufacturer or alternative suppliers.

Frequently Asked Questions (FAQ)

Q: Can the S120U be used as a direct replacement for the S125U in all applications?

A: The S120U is a direct mechanical and electrical substitute only for applications where the circuit design operates at or below 200 V DC reverse voltage. Applications requiring the full 250 V reverse voltage rating of the S125U cannot use the S120U without circuit redesign or voltage derating analysis.

Q: What is the primary difference between the S125U and S120U?

A: The primary difference is the maximum reverse voltage rating: S125U is rated for 250 V, while S120U is rated for 200 V. All other electrical parameters, including current rating, forward voltage, recovery speed, and reverse leakage current, are equivalent or superior in the S120U.

Q: Are the S125U and S120U pin-compatible?

A: Yes. Both parts use the DO-221AC package with SMA flat leads (SMAF supplier device package), ensuring identical pinout and PCB footprint compatibility.

Q: Why is the S125U classified as obsolete?

A: The S125U is listed as obsolete by the manufacturer. The S120U is the active replacement part recommended by SMC Diode Solutions for new designs and production applications.

Q: Does the S120U meet RoHS compliance requirements?

A: Yes. The S120U is RoHS3 compliant. The S125U does not specify RoHS compliance status.

Q: What is the moisture sensitivity level for both parts?

A: Both the S125U and S120U have a moisture sensitivity level (MSL) of 1, indicating unlimited shelf life without moisture control requirements.

Q: Are there any differences in operating temperature range between the two parts?

A: No. Both parts operate across the identical junction temperature range of -55°C to 150°C.

Q: What is the forward voltage difference between the S125U and S120U?

A: The S125U has a maximum forward voltage of 920 mV @ 1 A, while the S120U has a maximum forward voltage of 900 mV @ 1 A. The S120U exhibits slightly lower forward voltage drop.

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