Equivalent & Substitute Parts for 18TQ045

Part Overview

The 18TQ045 is a Schottky rectifier diode manufactured by Vishay General Semiconductor - Diodes Division, rated for 45 V DC reverse voltage and 18 A average rectified current in a Through Hole TO-220AC package. This part is classified as Obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The 18TQ045 operates across a junction temperature range of -55°C to 175°C with fast recovery characteristics (≤500 ns) and forward voltage of 600 mV at 18 A. The part is RoHS non-compliant and carries Moisture Sensitivity Level 1 (Unlimited).

Key Parameters

Parameter	Value
Voltage - DC Reverse (Vr) (Max)	45 V
Current - Average Rectified (Io)	18 A
Voltage - Forward (Vf) (Max) @ If	600 mV @ 18 A
Speed	Fast Recovery ≤ 500 ns, > 200 mA (Io)
Current - Reverse Leakage @ Vr	2.5 mA @ 45 V
Mounting Type	Through Hole
Package / Case	TO-220-2
Operating Temperature - Junction	-55°C ~ 175°C
Technology	Schottky

Substitute Part Grouping Explanation

Substitution of the 18TQ045 is determined by the following critical parameters:

Voltage Rating: All substitute parts must maintain the 45 V DC reverse voltage specification to ensure circuit protection and reliability.

Current Rating: Substitute parts must support the 18 A average rectified current requirement. Parts rated at or above 18 A are acceptable; parts rated below 18 A are not suitable for direct substitution.

Package Type: All substitutes must use Through Hole mounting in TO-220-2 or TO-220-3 package configurations to ensure mechanical and electrical compatibility with existing PCB layouts.

Technology: All substitutes employ Schottky diode technology with fast recovery characteristics (≤500 ns) to maintain switching performance.

Temperature Range: Operating temperature ranges must encompass or exceed the -55°C to 175°C junction temperature specification.

The following substitute parts meet these criteria with varying current ratings, forward voltage characteristics, and product status classifications.

Parameter Comparison

Parameter	18TQ045 (Vishay)	DSS25-0045A (IXYS)	MBR1645-BP (Micro Commercial Co)	MBR1645G (onsemi)	STPS2045CT (STMicroelectronics)
Voltage - DC Reverse (Vr) (Max)	45 V	45 V	45 V	45 V	45 V
Current - Average Rectified (Io)	18 A	25 A	16 A	16 A	10 A (per Diode)
Voltage - Forward (Vf) (Max) @ If	600 mV @ 18 A	690 mV @ 25 A	Not Specified	630 mV @ 16 A	570 mV @ 10 A
Speed	Fast Recovery ≤ 500 ns, > 200 mA (Io)	Fast Recovery ≤ 500 ns, > 200 mA (Io)	Fast Recovery ≤ 500 ns, > 200 mA (Io)	Fast Recovery ≤ 500 ns, > 200 mA (Io)	Fast Recovery ≤ 500 ns, > 200 mA (Io)
Current - Reverse Leakage @ Vr	2.5 mA @ 45 V	1 mA @ 45 V	200 µA @ 45 V	200 µA @ 45 V	100 µA @ 45 V
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	TO-220-2	TO-220-2	TO-220-2	TO-220-2	TO-220-3
Operating Temperature - Junction	-55°C ~ 175°C	-55°C ~ 175°C	-55°C ~ 150°C	-65°C ~ 175°C	Max 175°C
Product Status	Obsolete	Active	Active	Active	Active
RoHS Status	RoHS Non-Compliant	ROHS3 Compliant	Not Specified	ROHS3 Compliant	ROHS3 Compliant

Engineering Selection Recommendations

DSS25-0045A (IXYS): This part provides the highest current rating at 25 A, exceeding the 18 A requirement of the 18TQ045. It maintains identical voltage specifications and temperature range (-55°C to 175°C). The part is Active status with ROHS3 compliance, making it suitable for new designs and long-term availability. The higher current rating provides design margin for applications requiring sustained 18 A operation.

MBR1645G (onsemi): This part operates at 16 A, which is below the 18 A specification of the original part. However, it offers the widest operating temperature range (-65°C to 175°C) and is ROHS3 compliant with Active product status. This part is suitable only for applications where the actual operating current does not exceed 16 A, despite the 18 A design specification of the original circuit.

MBR1645-BP (Micro Commercial Co): This part also operates at 16 A and includes a reduced maximum junction temperature of 150°C compared to the original 175°C specification. This part is suitable only for applications where operating current remains below 16 A and where the lower temperature maximum does not constrain thermal design.

STPS2045CT (STMicroelectronics): This part is a diode array configuration (1 Pair Common Cathode) in TO-220-3 package, rated at 10 A per diode. The package configuration differs from the original TO-220-2, requiring PCB layout modification. This part is suitable only for applications where the circuit topology accommodates a common cathode configuration and where current requirements do not exceed 10 A per diode.

Frequently Asked Questions (FAQ)

Q: Can the DSS25-0045A directly replace the 18TQ045 in existing designs?

A: Yes. The DSS25-0045A maintains the same 45 V voltage rating, TO-220-2 package configuration, and operating temperature range. The higher 25 A current rating is compatible with circuits designed for 18 A operation. No PCB modifications are required.

Q: Why is the MBR1645G not a direct replacement despite being from a major manufacturer?

A: The MBR1645G is rated at 16 A, which is below the 18 A specification of the 18TQ045. While it shares the same voltage rating and package type, it cannot reliably handle the full 18 A current requirement. This part is suitable only for circuits where actual operating current does not exceed 16 A.

Q: What is the significance of the STPS2045CT being a diode array?

A: The STPS2045CT contains two diodes in a common cathode configuration within a single TO-220-3 package, whereas the 18TQ045 is a single diode in TO-220-2 package. This configuration difference requires circuit topology changes and is not suitable for direct pin-for-pin replacement in single diode applications.

Q: How do reverse leakage currents compare across substitute options?

A: The 18TQ045 specifies 2.5 mA reverse leakage at 45 V. The DSS25-0045A provides lower leakage at 1 mA, while MBR1645-BP, MBR1645G, and STPS2045CT all provide significantly lower leakage in the range of 100-200 µA. Lower reverse leakage improves circuit efficiency and reduces standby power consumption.

Q: Are all substitute parts RoHS compliant?

A: The DSS25-0045A, MBR1645G, and STPS2045CT are ROHS3 compliant. The MBR1645-BP RoHS status is not specified in the provided data. The original 18TQ045 is RoHS non-compliant. For applications requiring RoHS compliance, DSS25-0045A, MBR1645G, or STPS2045CT are appropriate selections.

Q: What is the impact of forward voltage differences on circuit performance?

A: Forward voltage varies across substitutes: 18TQ045 at 600 mV @ 18 A, DSS25-0045A at 690 mV @ 25 A, MBR1645G at 630 mV @ 16 A, and STPS2045CT at 570 mV @ 10 A. Higher forward voltage increases power dissipation; lower forward voltage reduces it. Circuit thermal design must account for these differences when selecting substitutes.

Q: Can the MBR1645-BP be used in high-temperature applications?

A: The MBR1645-BP specifies a maximum junction temperature of 150°C, which is 25°C lower than the original 18TQ045 specification of 175°C. This part is not suitable for applications requiring operation near or above 150°C junction temperature.

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