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Home > Products > Discrete Semiconductor Products > Transistors > FETs, MOSFETs > FETs, MOSFETs

STMicroelectronics STB85NF3LLT4

Name: STB85NF3LLT4
Brand: STMicroelectronics
SKU: STB85NF3LLT4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STB85NF3LLT4

Manufacturer:: STMicroelectronics

Category:: FETs, MOSFETs

Package:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Datasheet:: STB85NF3LLT4.pdf

Description:: MOSFET N-CH 30V 85A D2PAK

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Product details

Overview

STB85NF3LLT4 from STMicroelectronics is an N-channel 30V, 85A D²PAK Power MOSFET with R_DS(on) = 6 mΩ @ V_GS = 10 V and total gate charge Q_g = 30 nC @ V_DD = 24 V. It delivers ultra-low conduction and switching losses in high-frequency synchronous buck converters for PC motherboards and VRMs.

For engineers reviewing the STB85NF3LLT4 datasheet, STB85NF3LLT4 pinout, STB85NF3LLT4 application, or STB85NF3LLT4 equivalent, key selection criteria include its 0.36 °C/W R_thJC, 340 A pulsed drain current capability, and optimized R_DS(on) × Q_g trade-off at 4.5 V gate drive - critical for high-efficiency, high-density DC-DC regulation.

Technical Context

This STripFET™ II device uses a single-feature-size strip-based process to achieve best-in-class on-resistance versus gate charge balance. Its low 6 mΩ R_DS(on) at 10 V and 7.5 mΩ at 4.5 V enables high-current operation with minimal I²R loss, while 30 nC Q_g supports fast switching at >500 kHz frequencies.

The MOSFET integrates a robust body diode with t_rr = 65 ns and Q_rr = 105 µC under 100 A/µs di/dt, enabling efficient synchronous rectification and hard-switched inductive load handling in buck and half-bridge topologies.

Key Specifications

Parameter	Value and Actual Design Meaning
V_DS	30 V - Supports 24 V input rails with margin for transient spikes in VRM and server power stages
R_DS(on) @ 10 V	6 mΩ - Enables ≤ 43 W conduction loss at 85 A continuous drain current (T_C = 25°C)
Q_g	30 nC - Allows fast turn-on with low gate driver power dissipation in high-frequency PWM control
I_D (cont.)	85 A @ T_C = 25°C - Sustains full-load current in CPU/GPU VRMs without forced airflow
R_thJC	0.36 °C/W - Permits >100 W power dissipation with <36°C junction-to-case temperature rise
t_rr	65 ns - Minimizes reverse recovery energy loss during synchronous rectification transitions

Pinout & Package

STB85NF3LLT4 is housed in a surface-mount D²PAK (TO-263) package with three terminals: Gate (G), Drain (D), and Source (S). The exposed drain pad provides low-inductance, high-current path and thermal conduction to PCB copper.

Pin/Terminal	Circuit Role	Design Meaning
G	Gate control input	Accepts 0–16 V logic-level drive; 1 V threshold enables compatibility with 3.3 V and 5 V controllers
D	Drain connection	Exposed metal pad - electrically connected to drain, serves as primary heat sink interface
S	Source return path	Common reference for gate drive and current sensing; tied to low-side switch source or ground plane

Key Features

Feature	Design Value
Optimized R_DS(on) × Q_g	6 mΩ × 30 nC = 180 mΩ·nC - industry-leading figure-of-merit for 30 V MOSFETs driving >50 A loads
Low gate threshold voltage	V_GS(th) = 1 V - ensures reliable turn-on with standard 3.3 V PWM controllers and reduces gate drive complexity
High pulsed current rating	I_DM = 340 A - withstands inrush and overload transients in server VRMs without SOA violation
ECOPACK® lead-free construction	RoHS-compliant D²PAK with lead-free second-level interconnect - meets JEDEC JESD97 environmental requirements

Applications

PC Motherboard VRM

Server CPU Power Stage

Use Scenario: High-current, multi-phase buck converter supplying core voltage to Intel/AMD CPUs.

IC Role / Device Role / Timing Role: Low-side synchronous rectifier MOSFET in 300–600 kHz phase-leg configuration.

Use Value: 6 mΩ R_DS(on) and 30 nC Q_g reduce combined conduction + switching loss by >25% vs. prior-gen 30 V MOSFETs at 85 A.

Use Scenario: Single-phase or interleaved VRM delivering >200 A to Xeon or EPYC processors.

IC Role / Device Role / Timing Role: High-current, low-R_DS(on) power switch operating with adaptive gate drive timing.

Use Value: 0.36 °C/W R_thJC enables direct thermal coupling to heatsink-equipped PCBs, sustaining >100 W dissipation without derating.

GPU Power Delivery

Industrial DC-DC Converter

Use Scenario: Compact, high-efficiency power stage for discrete graphics cards with dynamic GPU load profiles.

IC Role / Device Role / Timing Role: Primary output switch in 400–800 kHz buck regulator with tight transient response requirements.

Use Value: 65 ns reverse recovery time minimizes shoot-through risk and improves efficiency during light-load discontinuous conduction mode.

Use Scenario: 24 V input to 5/3.3 V isolated or non-isolated converter in programmable logic controllers and motor drives.

IC Role / Device Role / Timing Role: Main power switch in industrial-grade buck or buck-boost topology requiring long-term reliability.

Use Value: 175 °C max junction temperature and –65 °C to 175 °C storage range support operation in extended-temperature industrial enclosures.

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel 30 V power MOSFET applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
IRF8726PbF	R_DS(on) = 5.2 mΩ @ 10 V; Q_g = 22 nC; TO-252 package	Lower R_DS(on) but higher thermal resistance (R_thJC = 2.5 °C/W); unsuitable for >40 A continuous without large copper area	Select when board space allows DPAK footprint and lower gate charge is prioritized over thermal performance
IXTP85N30L2	R_DS(on) = 7.5 mΩ @ 10 V; Q_g = 48 nC; TO-220 package	Higher switching loss due to 60% greater Q_g; through-hole mounting limits high-frequency layout density	Select only for legacy through-hole designs where D²PAK rework is not feasible

Compared with IRF8726PbF and IXTP85N30L2, STB85NF3LLT4 uniquely balances ultra-low R_DS(on), moderate Q_g, and superior thermal performance in a surface-mount D²PAK - making it optimal for high-power-density, high-reliability motherboard and server VRMs.

Availability

STB85NF3LLT4 is available at Aetrix Electronics and suitable for PC motherboard VRMs, server CPU power stages, GPU power delivery systems, and industrial DC-DC converters requiring stable component supply and long-lifecycle support.

Supply support for STB85NF3LLT4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The STB85NF3LL belongs to ST's STripFET™ II Power MOSFET product line, engineered specifically for high-efficiency, high-frequency DC-DC conversion in computing and communications infrastructure.

FAQ

What is the maximum safe operating frequency for STB85NF3LLT4 in a synchronous buck converter?

STB85NF3LLT4 supports stable operation up to 1 MHz in well-designed layouts, based on its 30 nC Q_g, 130 ns rise time, and 36.5 ns fall time at V_GS = 4.5 V and R_G = 4.7 Ω. Practical limit is ~800 kHz for thermally constrained 2-layer PCBs; 1 MHz requires 4+ layer boards with enhanced thermal vias and gate drive optimization.

Can STB85NF3LLT4 be used as a high-side switch in a buck-boost topology?

Yes - its ±16 V V_GS rating and 30 V V_DS support high-side use in non-isolated buck-boost configurations with bootstrap gate drive. However, the body diode's 1.3 V forward voltage and 65 ns t_rr make it less ideal than dedicated high-side switches for continuous conduction mode; best suited for discontinuous or boundary-mode operation.

Does STB85NF3LLT4 require a gate resistor for EMI suppression?

A gate resistor of 2.2–4.7 Ω is recommended to dampen ringing and reduce dv/dt-induced EMI, especially in high-current (>50 A) applications. The device's low 138 pF Crss and 30 nC Q_g allow fast switching without excessive overshoot when properly terminated - confirmed by Figure 12 test circuit in the datasheet.

Is STB85NF3LLT4 qualified for automotive applications?

No - STB85NF3LLT4 is not AEC-Q101 qualified and lacks automotive-grade screening, temperature cycling, or humidity testing. ST explicitly states in the datasheet that non-automotive-grade products are not recommended for automotive use. For automotive VRMs, consider ST's AEC-Q101-certified STD85N3LH5 or similar.

STB85NF3LLT4 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: STripFET™ II

Package/Case:: TO-263-3, D2PAK (2 Leads + Tab), TO-263AB

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

FET Type:: N-Channel

Technology:: MOSFET (Metal Oxide)

Drain to Source Voltage (Vdss):: 30 V

Current - Continuous Drain (Id) @ 25°C:: 85A (Tc)

Drive Voltage (Max Rds On, Min Rds On):: 4.5V, 10V

Rds On (Max) @ Id, Vgs:: 8mOhm @ 40A, 10V

Vgs(th) (Max) @ Id:: 1V @ 250µA

Gate Charge (Qg) (Max) @ Vgs:: 40 nC @ 4.5 V

Vgs (Max):: ±16V

Input Capacitance (Ciss) (Max) @ Vds:: 2210 pF @ 25 V

FET Feature:: -

Power Dissipation (Max):: 110W (Tc)

Operating Temperature:: -65°C ~ 175°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: D2PAK

STB85NF3LLT4 FAQ

1.How can I place an order for STB85NF3LLT4 through Aetrix?

Please submit a Request for Quotation (RFQ) for STB85NF3LLT4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for STB85NF3LLT4 reliable?

The price and inventory of STB85NF3LLT4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STB85NF3LLT4 is usually 5 days.

3.What payment methods are accepted for STB85NF3LLT4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STB85NF3LLT4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STB85NF3LLT4?

STB85NF3LLT4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STB85NF3LLT4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for STB85NF3LLT4?

For technical support, including STB85NF3LLT4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STB85NF3LLT4 requirements.

6.How does Aetrix verify that STB85NF3LLT4 is sourced from the original manufacturer or authorized distributors?

All STB85NF3LLT4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that STB85NF3LLT4 meets industry standards.

7.What is the process for return or replacement of STB85NF3LLT4?

All STB85NF3LLT4 units undergo pre-shipment inspection (PSI). If there is an issue with STB85NF3LLT4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The STB85NF3LLT4 part is unused and in its original packaging.

Return procedure for STB85NF3LLT4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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