S4040NQTP Equivalent & Substitute Parts

Part Overview

The S4040NQTP is a 400V 40A standard recovery SCR (silicon-controlled rectifier) in TO-263 surface mount packaging manufactured by Littelfuse Inc. This thyristor is designed for power control and switching applications requiring reliable gate-triggered operation at moderate current levels. The part is currently listed as obsolete, making identification of active equivalent and substitute components essential for ongoing design support and procurement continuity.

Substiute Parts

S4040NQTP

Littelfuse Inc.In Stock: 930S4040NQTP Datasheet

Current PartRFQ

S4040NTP

Littelfuse Inc.In Stock: 862S4040NTP Datasheet

Parametric EquivalentRFQ

S4055NTP

Littelfuse Inc.In Stock: 1171S4055NTP Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution for the S4040NQTP is determined by the following critical parameters:

• Blocking Voltage (Voltage - Off State): Must be 400 V or higher
• RMS Current Rating (It (RMS)): Must be 40 A or higher to handle the same or greater load
• Gate Trigger Characteristics: Vgt (Max) 1.5 V and Igt (Max) 40 mA ensure compatible gate drive requirements
• On-State Voltage (Vtm): Maximum 1.8 V maintains thermal performance consistency
• Package Type: TO-263-3 / D2PAK surface mount configuration for PCB compatibility
• SCR Type: Standard Recovery classification for switching speed and recovery characteristics
• Operating Temperature: -40°C to 125°C range for thermal environment compatibility

Two substitute parts meet these criteria:

1. S4040NTP — Direct parametric equivalent with identical electrical specifications; differs only in packaging format (Tube vs. unspecified for main part) and active product status
2. S4055NTP — Higher current rating (55 A RMS vs. 40 A RMS) with proportionally increased surge current; maintains all other critical parameters and blocking voltage

Parameter Comparison

Engineering Selection Recommendations

S4040NTP is the primary direct replacement for S4040NQTP. Both parts share identical electrical specifications and thermal characteristics. S4040NTP holds active product status with ROHS3 compliance and unlimited moisture sensitivity rating, ensuring long-term availability and regulatory alignment. Selection of S4040NTP eliminates any performance variation while maintaining design integrity.

S4055NTP serves as a higher-capacity alternative when design margins or future current requirements justify increased rating. The 55 A RMS capability provides 37.5% additional current headroom over the original 40 A specification. Surge current ratings scale proportionally (550A/650A vs. 430A/520A). All other electrical parameters remain identical, including gate trigger thresholds and on-state voltage. S4055NTP is suitable for applications where the original design operates below maximum current limits and where thermal management can accommodate the higher-rated device. Both substitute parts maintain ROHS3 compliance and active product status.

Frequently Asked Questions (FAQ)

Q: Can S4040NTP be used as a direct drop-in replacement for S4040NQTP?

A: Yes. S4040NTP is electrically and mechanically identical to S4040NQTP. Both devices share the same 400V blocking voltage, 40A RMS current rating, gate trigger characteristics, on-state voltage, and TO-263 D2PAK package. The only difference is product status (S4040NTP is active; S4040NQTP is obsolete) and packaging format.

Q: What is the difference between S4040NTP and S4055NTP?

A: S4055NTP has a higher current rating: 55A RMS and 35A average versus 40A RMS and 25A average for S4040NTP. Surge current ratings also increase proportionally. All other parameters—blocking voltage, gate trigger thresholds, on-state voltage, temperature range, and package type—remain identical. S4055NTP is suitable when higher current capacity is required or desired.

Q: Are both substitute parts compatible with the original PCB layout?

A: Yes. Both S4040NTP and S4055NTP use the same TO-263-3 D2PAK surface mount package as S4040NQTP. No PCB modifications are required for either substitute.

Q: Do the substitute parts meet the same compliance standards?

A: Yes. Both S4040NTP and S4055NTP are ROHS3 compliant with MSL 1 (Unlimited) moisture sensitivity rating, matching the compliance profile of S4040NQTP.

Q: Which substitute should be selected for a new design?

A: S4040NTP is the recommended choice for designs requiring the original 40A RMS specification. S4055NTP should be selected when the application benefits from higher current capacity or when design margins justify the increased rating. Both parts are active and available.

Q: Can gate drive circuitry remain unchanged when substituting?

A: Yes. Both substitute parts maintain the same gate trigger voltage (1.5V max) and gate trigger current (40mA max) as the original S4040NQTP, ensuring compatibility with existing gate drive designs.