Equivalent & Substitute Parts for 18TQ050 Schottky Diode

Part Overview

The 18TQ050 is a Schottky rectifier diode manufactured by Vishay General Semiconductor - Diodes Division, rated for 50 V DC reverse voltage and 18 A average rectified current in a Through Hole TO-220AC package. This part is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design requirements and procurement needs. Equivalent parts maintain identical electrical and mechanical specifications, while substitute parts provide functional alternatives with modified parameters within acceptable application ranges.

Key Parameters

Parameter	Value	Unit
Voltage - DC Reverse (Vr) (Max)	50	V
Current - Average Rectified (Io)	18	A
Voltage - Forward (Vf) (Max) @ If	600 mV @ 18 A	mV
Speed	Fast Recovery ≤ 500ns, > 200mA (Io)	ns
Current - Reverse Leakage @ Vr	2.5	mA @ 50 V
Technology	Schottky	—
Mounting Type	Through Hole	—
Package / Case	TO-220-2	—
Operating Temperature - Junction	-55°C ~ 175°C	°C

Substitute Part Grouping Explanation

Substitution of the 18TQ050 is determined by the following critical parameters: voltage rating (Vr), current capacity (Io), forward voltage drop (Vf), reverse leakage current, package type, and operating temperature range.

Parametric Equivalent Classification: Parts maintaining identical voltage, current, forward voltage, and leakage specifications with the same TO-220AC package qualify as direct equivalents.

Functional Substitute Classification: Parts with reduced current ratings (10 A or 16 A versus 18 A) or slightly reduced voltage ratings (45 V versus 50 V) are classified as functional substitutes. These parts operate within the same application envelope but with modified performance margins. Substitution is valid when the application circuit design accommodates the reduced current or voltage specification.

Key Parameters Determining Substitution:

Voltage - DC Reverse (Vr) (Max): 45 V minimum for 50 V applications; 50 V for full compatibility
Current - Average Rectified (Io): 7.5 A to 18 A range; lower ratings acceptable if circuit design permits
Voltage - Forward (Vf) (Max) @ If: 600 mV to 950 mV range; higher values acceptable with thermal management consideration
Package / Case: TO-220-2 required for mechanical compatibility
Mounting Type: Through Hole required for PCB compatibility

Parameter Comparison

Part Number	Manufacturer	Vr (Max)	Io	Vf (Max) @ If	Reverse Leakage @ Vr	Package	Product Status	RoHS Status
18TQ050	Vishay General Semiconductor	50 V	18 A	600 mV @ 18 A	2.5 mA @ 50 V	TO-220-2	Obsolete	Non-compliant
VS-18TQ050PBF	Vishay General Semiconductor	50 V	18 A	600 mV @ 18 A	2.5 mA @ 50 V	TO-220-2	Active	ROHS3 Compliant
MBR1645G	onsemi	45 V	16 A	630 mV @ 16 A	200 µA @ 45 V	TO-220-2	Active	ROHS3 Compliant
MBR1645-BP	Micro Commercial Co	45 V	16 A	—	200 µA @ 45 V	TO-220-2	Active	—
MBR1050	Fairchild Semiconductor	50 V	10 A	950 mV @ 10 A	100 µA @ 50 V	TO-220-2	Active	—
MBR750	Fairchild Semiconductor	50 V	7.5 A	750 mV @ 7.5 A	500 µA @ 50 V	TO-220-2	Active	—

Engineering Selection Recommendations

Primary Equivalent: VS-18TQ050PBF is the direct parametric equivalent to the obsolete 18TQ050. This part maintains identical electrical specifications (50 V, 18 A, 600 mV forward voltage) and mechanical compatibility while offering Active product status and ROHS3 compliance. Selection of VS-18TQ050PBF eliminates substitution risk and ensures design continuity.

Secondary Equivalent (Voltage-Matched): MBR1645G provides functional substitution with 45 V rating and 16 A current capacity. This part is suitable for applications where the 50 V rating margin is not critical. MBR1645G offers Active status, ROHS3 compliance, and extended operating temperature range (-65°C to 175°C). The 45 V rating reduces design margin by 5 V; circuit analysis is required to confirm acceptability.

Tertiary Substitute (Current-Reduced): MBR1050 maintains the 50 V voltage rating with reduced current capacity of 10 A. This part is applicable only to circuits where the load current does not exceed 10 A. Higher forward voltage (950 mV @ 10 A) increases thermal dissipation compared to the original specification.

Lower-Current Substitute: MBR750 provides 50 V rating with 7.5 A capacity. This part is suitable only for applications with significantly reduced current requirements.

Compliance Consideration: VS-18TQ050PBF is the only substitute offering ROHS3 compliance matching modern procurement requirements. MBR1645G also provides ROHS3 compliance. Selection should prioritize compliance status for new designs and long-term supply chain stability.

Frequently Asked Questions (FAQ)

Q: Can VS-18TQ050PBF directly replace the obsolete 18TQ050 without circuit modification?

A: Yes. VS-18TQ050PBF is a parametric equivalent with identical voltage (50 V), current (18 A), forward voltage (600 mV @ 18 A), and reverse leakage (2.5 mA @ 50 V) specifications. The TO-220-2 package and Through Hole mounting are identical. No circuit modification is required.

Q: What is the difference between MBR1645G and MBR1645-BP?

A: Both parts share the same base product number (MBR1645) with 45 V rating and 16 A current capacity. MBR1645G is manufactured by onsemi in Tube packaging with ROHS3 compliance and extended temperature range (-65°C to 175°C). MBR1645-BP is manufactured by Micro Commercial Co in Bulk packaging. Electrical specifications are equivalent; packaging and manufacturer differ.

Q: Can MBR1645G be used in a 50 V application?

A: MBR1645G has a maximum reverse voltage rating of 45 V. Use in a 50 V application reduces the design safety margin by 5 V. Circuit analysis is required to confirm that peak reverse voltages do not exceed 45 V under all operating conditions, including transient overvoltage events.

Q: Why does MBR1050 have higher forward voltage (950 mV) compared to the original 18TQ050 (600 mV)?

A: Forward voltage is a function of diode current and junction design. MBR1050 is rated for 10 A versus 18 A for the 18TQ050. At lower current levels, forward voltage characteristics differ. The 950 mV specification at 10 A reflects the MBR1050 junction design. This higher forward voltage increases power dissipation and thermal load in the application circuit.

Q: Is the TO-220AC package identical to TO-220-2?

A: TO-220AC and TO-220-2 refer to the same physical package with two leads. Both designations are used interchangeably in industry documentation. All substitute parts listed use this package and are mechanically compatible with the original 18TQ050.

Q: What is the significance of reverse leakage current differences between parts?

A: Reverse leakage current (Ir) increases with temperature and affects standby power consumption and circuit performance in high-impedance applications. The 18TQ050 specifies 2.5 mA @ 50 V, while MBR1645G specifies 200 µA @ 45 V. Lower leakage is generally preferable; however, the difference is significant only in applications sensitive to standby current or operating at elevated temperatures.

Q: Can multiple lower-current parts be paralleled to replace the 18TQ050?

A: Paralleling Schottky diodes is not recommended without detailed thermal and current-sharing analysis. Schottky diodes exhibit positive temperature coefficients in forward voltage, which can lead to unequal current distribution and thermal runaway in parallel configurations. Single-part substitution is the preferred approach.

Q: What is the impact of operating temperature range differences?

A: The 18TQ050 operates from -55°C to 175°C. MBR1050 and MBR750 operate from -55°C to 150°C, reducing the upper temperature limit by 25°C. MBR1645G extends to 175°C. For applications operating near 150°C, MBR1050 and MBR750 may not be suitable. Verify application thermal requirements before selection.

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