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Analog Devices Inc. LT4276AHUFD#TRPBF
- Part No.:
- LT4276AHUFD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LT4276AHUFD#TRPBF.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:7,232
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Product details
Overview
LT4276AHUFD#TRPBF from Analog Devices (formerly Linear Technology) is a high-power LTPoE++/PoE+/PoE Powered Device (PD) controller with integrated forward/flyback switching regulator control, supporting up to 90W delivered power at the RJ45 port, operating across –40°C to 125°C junction temperature, and featuring external N-channel Hot Swap MOSFET drive for >94% end-to-end efficiency when paired with LT4321. It is used in outdoor security cameras and commercial displays requiring robust PoE power negotiation and isolated DC-DC conversion.
For engineers reviewing the LT4276AHUFD#TRPBF datasheet, LT4276AHUFD#TRPBF pinout, LT4276AHUFD#TRPBF application, or LT4276AHUFD#TRPBF equivalent, this page delivers verified technical context, validated pin functions, confirmed LTPoE++ 90W classification behavior, exact package mapping to 28-lead 4mm × 5mm QFN, and two rigorously cross-checked alternative parts with documented functional and application-level differences.
Technical Context
The LT4276AHUFD#TRPBF implements IEEE 802.3af/at-compliant detection/classification plus proprietary LTPoE++ signaling via dual-class resistor inputs (RCLASS and RCLASS++) and T2P pin modulation at fT2P = fSW/256. Its current-mode switching regulator supports both flyback (no opto-isolator required, third-winding feedback on FB31 = 3.17V) and forward topologies via FFSDLY pin voltage selection.
It integrates a buck-based VCC generation path (SWVCC/VIN), programmable soft-start via SFST capacitor, and inverted ITHB-controlled peak current sensing with ΔVSENSE/ΔVITHB = –111 mV/V and VITHB(OS) = 3.17V. The device uses external Hot Swap MOSFET control (HSGATE/HSSRC/VPORT) with VHSON = 37V and VHSON–VHSOFF = 3V hysteresis, enabling precise inrush current control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max Delivered Power | 90W at RJ45 port per LTPoE++ Class 4, backward-compatible with IEEE 802.3at (25.5W) and 802.3af (13W) |
| Operating Junction Temp | –40°C to 125°C (H-grade), enabling deployment in outdoor enclosures and industrial environments |
| VPORT Absolute Max | 100V - provides margin against surge events per IEEE 802.3 standard compliance |
| Switching Frequency | 214kHz default (ROSC open); adjustable to 300kHz with 45.3kΩ to GND - sets transformer size and EMI profile |
| FB31 Regulation Voltage | 3.17V ±6mV - defines output voltage setpoint in flyback mode without opto-isolator |
| VITHB Offset Voltage | 3.17V - establishes baseline for inverted current sense threshold scaling |
| Overcurrent Threshold | 140mV (VISEN+–VISEN–) - triggers fault shutdown with tFAULT = 86ms delay |
Pinout & Package
LT4276AHUFD#TRPBF is housed in a 28-lead 4mm × 5mm plastic QFN (UFD package) with exposed thermal pad (Pin 29) soldered to PCB ground. Pin functions are validated per Linear Technology's LT4276FA datasheet Rev. D and confirmed for LT4276A grade.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 19, 29) | Device ground reference and thermal path | Exposed pad (Pin 29) must be electrically and thermally connected to PCB GND plane for thermal reliability |
| RCLASS++ (Pin 3) | LTPoE++ classification select input | Required only for LT4276A; connects to GND via precision 1% resistor to enable 38.7W/52.7W/70W/90W classes |
| AUX (Pin 2) | Auxiliary supply enable threshold input | Senses auxiliary input via resistor divider; asserts below VAUXT = 6.25V to disable classification and disconnect signature resistor |
| RCLASS (Pin 4) | IEEE 802.3 classification select input | Connects to GND via 1% resistor per Table 1 to define Type 1/2 power class (e.g., 35.7Ω = 25.5W) |
| T2P (Pin 5) | PSE type indicator output | Pulls up to VCC for Type 2; alternates between pull-up and float at fT2P for LTPoE++; not connected on LT4276C |
| FFSDLY (Pin 12) | Flyback/forward topology select & gate delay control | Pull to GND → flyback mode; pull to VCC → forward mode; resistor value sets tPGDELAY (45–391ns range) |
| FB31 (Pin 14) | Flyback third-winding feedback input | 3.17V reference enables isolated regulation without opto-isolator; tied to GND in forward mode |
| HSGATE (Pin 26) | External Hot Swap MOSFET gate driver output | Sinks IGPU = –22µA to ramp external N-FET gate; controls inrush current (IINRUSH ≈ IGPU·CPORT/CGATE) |
| VPORT (Pin 28) | PoE interface supply and Hot Swap FET drain | Accepts 37–57V PoE input; withstands 100V absolute max - critical for surge immunity design |
Key Features
| Feature | Design Value |
|---|---|
| LTPoE++ 90W classification support | Enables highest PoE power tier while maintaining full IEEE 802.3af/at interoperability via dual-resistor (RCLASS/RCLASS++) scheme |
| No-opto flyback feedback | FB31 = 3.17V reference + fixed tFB sampling window eliminates opto-isolator, improving long-term stability and dynamic response |
| Inverted ITHB current sensing | VITHB(OS) = 3.17V with ΔVSENSE/ΔVITHB = –111 mV/V allows precise peak-current control using standard resistive dividers |
| Programmable topology selection | FFSDLY pin voltage (GND vs VCC) selects flyback or forward operation - simplifies platform reuse across power architectures |
| Integrated VCC buck controller | SWVCC/VIN pins drive external PNP transistor to generate regulated VCC - removes need for separate bias supply |
| High-temp H-grade operation | Rated for –40°C to 125°C TJ ensures reliability in uncooled outdoor enclosures and high-ambient industrial settings |
Applications
| Outdoor Security Cameras | Commercial Information Displays |
|---|---|
|
Use Scenario: IP camera deployed in unheated exterior housings with PoE-powered imaging, IR illumination, and video streaming. IC Role / Device Role / Timing Role: LT4276AHUFD#TRPBF acts as PD interface controller and isolated flyback DC-DC regulator, managing 90W LTPoE++ power negotiation and delivering stable 12V/5V rails. Use Value: Enables single-cable deployment with surge-tolerant 100V VPORT rating and –40°C to 125°C operation - eliminating local AC adapters and thermal derating concerns. |
Use Scenario: Large-format LCD/LED display in retail or transit hubs powered exclusively via PoE infrastructure. IC Role / Device Role / Timing Role: LT4276AHUFD#TRPBF serves as forward-mode PD controller and primary-side gate driver (PG/SG), regulating 24V/48V bus for backlight and logic. Use Value: Supports high-efficiency forward topology with >94% end-to-end efficiency (with LT4321 ideal bridge), reducing heat buildup in sealed display enclosures. |
| Industrial Wireless Access Points | High-Temperature Networked Sensors |
|
Use Scenario: Ruggedized Wi-Fi 6 AP mounted inside hot factory ceilings or near HVAC ducts. IC Role / Device Role / Timing Role: LT4276AHUFD#TRPBF performs IEEE 802.3at classification and drives synchronous forward converter for 5V/3.3V system rails. Use Value: H-grade thermal rating avoids forced cooling; auxiliary power override (AUX pin) enables seamless switchover to local 12V backup during PoE interruption. |
Use Scenario: Condition-monitoring sensor node in oil/gas pipeline monitoring cabinet with ambient temps up to 85°C. IC Role / Device Role / Timing Role: LT4276AHUFD#TRPBF executes LTPoE++ 70W classification and manages flyback-derived 3.3V rail for ultra-low-power MCU and RF transceiver. Use Value: 125°C junction rating ensures continuous operation without derating; superior surge protection (100V abs max) guards against field-induced transients. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PoE PD controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT4275AHUFD#TRPBF | Single-class resistor interface (RCLASS only); supports up to 60W LTPoE++ (Class 3), no RCLASS++ or T2P pin | Limited to 60W max; lacks LTPoE++ 90W capability and dual-event signaling for PSE type detection | Select when 60W suffices and board space/cost optimization favors simpler classification network |
| MAX5984AEUI+T | IEEE 802.3at-only (25.5W), no LTPoE++ support; integrated Hot Swap FET (no external MOSFET required) | Cannot negotiate >25.5W; lacks flyback/forward topology flexibility and auxiliary power override | Choose for cost-sensitive, lower-power indoor devices where integrated FET reduces BOM count and layout complexity |
Compared with LT4276AHUFD#TRPBF, LT4275AHUFD#TRPBF sacrifices 90W LTPoE++ capability and T2P signaling for reduced pin count and bill-of-materials simplicity, while MAX5984AEUI+T trades programmable topology and high-power classification for integrated Hot Swap FET convenience at the expense of scalability beyond PoE+.
Availability
LT4276AHUFD#TRPBF is available at Aetrix Electronics and suitable for outdoor security camera systems, commercial digital signage, and industrial wireless access points requiring stable component supply across extended temperature ranges and high-reliability PoE power delivery.
Supply support for LT4276AHUFD#TRPBF 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
Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT4276 family.
The LT4276 series was designed specifically for high-power, multi-standard PoE Powered Devices requiring flexible isolated DC-DC conversion, robust surge tolerance, and seamless interoperability across legacy and proprietary PSE infrastructures.
FAQ
What PoE standards does the LT4276AHUFD#TRPBF support?
The LT4276AHUFD#TRPBF supports IEEE 802.3af (13W), 802.3at (25.5W), and Linear Technology's proprietary LTPoE++ up to 90W. It achieves this through dual classification resistors (RCLASS and RCLASS++) and T2P pin signaling. The LT4276AHUFD#TRPBF is fully backward-compatible with existing PSEs while enabling higher power delivery where LTPoE++ infrastructure is deployed.
How does the LT4276AHUFD#TRPBF implement no-opto flyback regulation?
The LT4276AHUFD#TRPBF uses FB31 pin with a precise 3.17V internal reference and fixed tFB sampling window (550ns) to monitor the transformer's third winding voltage. This eliminates the need for an opto-isolator by directly sensing reflected output voltage during the off-time, improving long-term stability and transient response. The LT4276AHUFD#TRPBF requires no external compensation network on FB31 in standard implementations.
What is the function of the ITHB pin on the LT4276AHUFD#TRPBF?
The ITHB pin on the LT4276AHUFD#TRPBF provides inverted current threshold control: VSENSE = VITHB(OS) + (VITHB − VITHB(OS)) × (ΔVSENSE/ΔVITHB), where VITHB(OS) = 3.17V and ΔVSENSE/ΔVITHB = –111 mV/V. This allows direct programming of peak switch current using a simple resistor divider, enabling accurate overcurrent protection and load regulation without additional op-amps or DACs.
Can the LT4276AHUFD#TRPBF operate in forward topology, and how is it configured?
Yes, the LT4276AHUFD#TRPBF supports forward topology by connecting FFSDLY (Pin 12) to VCC via a resistor (10.5kΩ–52.3kΩ). This configures PG/SG timing for active-clamp forward operation, with tPGDELAY and tPGSG scaled linearly versus resistance. In forward mode, FB31 must be tied to GND, and SG drives the clamp FET through a level shifter - a configuration validated in Linear's LT4276FA datasheet Figure 11.
What thermal considerations apply to the LT4276AHUFD#TRPBF in high-power designs?
The LT4276AHUFD#TRPBF is rated for –40°C to 125°C junction temperature (H-grade) and features θJC = 3.4°C/W. To maintain reliability at 90W, the exposed pad (Pin 29) must be soldered to a low-thermal-resistance PCB ground plane with ≥4 thermal vias. Layout must minimize trace inductance on VPORT/HSSRC/HSGATE paths to reduce switching losses that contribute to die heating.
LT4276AHUFD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Controller (PD), DC/DC
- Number of Channels:
- 1
- Power - Max:
- 90 W
- Internal Switch(s):
- No
- Auxiliary Sense:
- Yes
- Standards:
- 802.3at (PoE+), 802.3af (PoE), LTPoE++
- Voltage - Supply:
- 60V (Max)
- Current - Supply:
- 2mA (Max)
- Operating Temperature:
- -40°C ~ 125°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LT4276AHUFD#TRPBF FAQ
1.How can I place an order for LT4276AHUFD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT4276AHUFD#TRPBF 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 LT4276AHUFD#TRPBF reliable?
The price and inventory of LT4276AHUFD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT4276AHUFD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT4276AHUFD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT4276AHUFD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT4276AHUFD#TRPBF?
LT4276AHUFD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT4276AHUFD#TRPBF 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 LT4276AHUFD#TRPBF?
For technical support, including LT4276AHUFD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT4276AHUFD#TRPBF requirements.
6.How does Aetrix verify that LT4276AHUFD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT4276AHUFD#TRPBF 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 LT4276AHUFD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT4276AHUFD#TRPBF?
All LT4276AHUFD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT4276AHUFD#TRPBF, 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 LT4276AHUFD#TRPBF part is unused and in its original packaging.
Return procedure for LT4276AHUFD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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