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Analog Devices Inc. LT4275AIDD#PBF
- Part No.:
- LT4275AIDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT4275AIDD#PBF.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,031
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Product details
Overview
LT4275AIDD#PBF from Analog Devices (formerly Linear Technology) is an LTPoE++/IEEE 802.3at/af powered device (PD) controller for PoE-powered equipment. It supports up to 90W delivered power at the RJ45 connector, features integrated signature resistor and N-channel MOSFET gate drive, operates from 23V to 60V input, and delivers power-good signaling and thermal protection. It is used in high-power outdoor security cameras requiring robust PoE interface with auxiliary supply override.
For engineers reviewing the LT4275AIDD#PBF datasheet, LT4275AIDD#PBF pinout, LT4275AIDD#PBF application, or LT4275AIDD#PBF equivalent, key selection criteria include LTPoE++ 90W classification capability, 100V absolute maximum input voltage, –40°C to 85°C operating temperature range, DFN-10 (3mm × 3mm) package with exposed GND pad, and compatibility with external low-RDS(ON) N-channel MOSFETs for high-efficiency hot-swap control.
Technical Context
The LT4275AIDD#PBF implements a dual-stage classification architecture: IEEE 802.3af/at 2-event detection plus proprietary LTPoE++ multi-level classification via RCLASS and RCLASS++ pins. It uses an internal charge pump to drive an external N-channel MOSFET, eliminating need for P-channel devices while maintaining <3V gate drive headroom across full input range.
Its control logic integrates undervoltage lockout (VHSON = 35V, VHSOFF = 30V), programmable inrush current via external CGATE capacitor, and open-drain T2P output that toggles at 690–990Hz to signal LTPoE++ PSE presence. The AUX pin enables auxiliary supply takeover with 6.3V threshold and hysteresis current of 4–8µA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max Delivered Power | 90W at PD RJ45 connector - enables high-power wireless access points and PTZ cameras without separate AC wiring |
| Input Voltage Range | 23V to 60V - supports full IEEE 802.3af/at and LTPoE++ PSE output ranges after diode bridge drop |
| Absolute Max Input | 100V - withstands transient surges on Ethernet cabling without external clamping degradation |
| Operating Temp | –40°C to 85°C - suitable for commercial indoor and outdoor enclosures without derating |
| Signature Resistance | 24.4kΩ ±0.7kΩ - precision temperature-compensated value meets IEEE 25kΩ detection requirement including bridge loss |
| T2P Output Frequency | 690–990Hz - modulated open-drain signal uniquely identifies LTPoE++ PSE to host microcontroller |
| Package | 10-Lead DFN (3mm × 3mm) with exposed GND pad - provides low θJC = 5°C/W for thermal management in sealed housings |
Pinout & Package
LT4275AIDD#PBF is housed in a 10-lead plastic DFN package (3mm × 3mm) with exposed GND pad (Pin 11) that must be soldered to PCB ground plane for thermal and electrical integrity. The package supports reflow assembly per JEDEC J-STD-020 and has 0.5mm pitch leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (IEEEUVLO) | Hot-swap UVLO threshold select | GND connection sets IEEE-compliant 35V turn-on / 30V turn-off; floating enables lower thresholds for non-standard PoE |
| Pin 2 (AUX) | Auxiliary supply enable input | Sinks 4–8µA below 6.3V threshold to initiate auxiliary power takeover and disable classification |
| Pin 3 (RCLASS) | IEEE classification resistor node | Connects to GND via 49.9Ω for 90W LTPoE++ or 34.8Ω for 25.5W PoE+, enabling multi-standard compliance |
| Pin 4 (RCLASS++) | LTPoE++ extended classification node | Required for >38.7W LTPoE++ levels; connects to GND via 118Ω for 90W mode (LT4275A only) |
| Pin 5 (GND) | Analog/digital reference and thermal path | Primary ground return; exposed pad (Pin 11) is electrically tied to this pin and must be soldered |
| Pin 6 (T2P) | PSE type indicator output | Open-drain output toggling at 690–990Hz signals LTPoE++ PSE; pulls low for PoE+; floats for PoE (Type 1) |
| Pin 7 (PWRGD) | Power-good status output | Open-drain signal held low until HSGATE reaches ~7V above HSSRC, enabling safe isolated supply startup |
| Pin 8 (HSSRC) | External MOSFET source reference | Connects to source of N-channel MOSFET; defines gate drive reference for low-side switching topology |
| Pin 9 (HSGATE) | N-channel MOSFET gate driver | Charge-pump-driven output sourcing 18–27µA; ramps external MOSFET gate to control inrush current |
| Pin 10 (VPORT) | PD input power rail | Accepts 23–60V from Ethernet magnetics; carries full PD current and interfaces to TVS clamp (e.g., SMAJ58A) |
Key Features
| Feature | Design Value |
|---|---|
| LTPoE++ 90W classification support | Enables single-cable delivery of full 90W to high-performance edge AI cameras and beamforming APs |
| Integrated 24.4kΩ signature resistor | Eliminates external precision resistor and reduces BOM count while meeting IEEE 25kΩ detection spec |
| Charge-pump N-MOSFET gate drive | Supports low-RDS(ON) discrete FETs (e.g., FDMC86102) to achieve >95% system efficiency and reduce thermal load |
| Programmable auxiliary supply takeover | Allows seamless switchover to 9–60V DC or 24V AC auxiliary input when PoE is unavailable or insufficient |
| Open-drain T2P signaling | Provides unambiguous PSE type identification (PoE/PoE+/LTPoE++) to host MCU without additional level-shifting circuitry |
Applications
| High-Power Wireless Access Point | Outdoor PTZ Security Camera |
|---|---|
Use Scenario: Enterprise-grade Wi-Fi 6E access point deployed in ceiling plenums with no local AC outlet, requiring full 90W for RF amplification and cooling fans. IC Role / Device Role / Timing Role: PD controller managing PoE negotiation, inrush limiting, and power-good sequencing for isolated DC/DC converters powering RF front-end and baseband SoC. Use Value: Enables single-cable installation with guaranteed 90W delivery and LTPoE++ backward compatibility with legacy 802.3at switches. | Use Scenario: IP-based pan-tilt-zoom camera mounted on building exterior, exposed to wide ambient temperature swings and requiring heater operation in sub-zero conditions. IC Role / Device Role / Timing Role: Primary PoE interface IC providing IEEE-compliant detection/classification, thermal shutdown at 150°C junction, and auxiliary 24VAC takeover during winter low-light operation. Use Value: Maintains continuous operation using PoE by day and auxiliary AC at night, with no firmware intervention or manual switching required. |
| Commercial Digital Signage Display | Industrial IoT Gateway |
Use Scenario: 55-inch LCD display in airport terminal powered exclusively via PoE, driving backlight LEDs and video processing unit with peak 70W demand. IC Role / Device Role / Timing Role: PD controller executing LTPoE++ 70W classification (RCLASS = 76.8Ω, RCLASS++ = 64.9Ω), controlling inrush into bulk capacitance, and asserting PWRGD to enable display power-up sequence. Use Value: Eliminates need for local power supply and associated safety certifications, reducing total cost of ownership and simplifying maintenance logistics. | Use Scenario: DIN-rail mounted gateway aggregating Modbus RTU sensors in factory automation, requiring PoE for primary power and 12V auxiliary for isolated RS-485 transceivers. IC Role / Device Role / Timing Role: Dual-role PD controller supporting both IEEE 802.3at 25.5W classification and auxiliary 12VDC override via resistive divider on AUX pin. Use Value: Ensures uninterrupted operation during PoE brownouts by automatically engaging auxiliary supply without host MCU involvement. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar powered device controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4265 | IEEE 802.3at-only PD controller; no LTPoE++ support; internal 100V/1A switch instead of external MOSFET drive | Supports only up to 25.5W; lacks RCLASS++ pin and T2P modulation; not suitable for 38.7W+ LTPoE++ systems | Select LTC4265 only for cost-sensitive PoE+ designs where 90W capability is unnecessary and integrated switch suffices |
| LT4276A | Successor device with enhanced surge immunity (IEC 61000-4-5 Level 4), same pinout, identical LTPoE++ classification but improved AUX hysteresis accuracy | Direct upgrade path with identical functionality; requires no PCB changes but offers higher reliability in harsh ESD environments | Choose LT4276A for new designs targeting industrial or outdoor deployments where long-term field reliability is critical |
Compared with LTC4265, LT4275AIDD#PBF delivers 3.5× more power and supports multi-standard negotiation; compared with LT4276A, it lacks IEC 61000-4-5 Level 4 surge rating but remains qualified for commercial indoor/outdoor use with proper TVS protection.
Availability
LT4275AIDD#PBF is available at Aetrix Electronics and suitable for high-power wireless data systems, outdoor security camera equipment, commercial and public information displays, and high-temperature industrial applications requiring stable component supply and long lifecycle support.
Supply support for LT4275AIDD#PBF 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 all Linear-branded ICs including the LT4275 family.
The LT4275 product line was designed specifically for high-efficiency, high-power PoE-powered devices requiring backward compatibility across IEEE 802.3af/at and proprietary LTPoE++ standards, with emphasis on thermal resilience and auxiliary supply flexibility.
FAQ
What power standards does the LT4275AIDD#PBF support?
The LT4275AIDD#PBF supports LTPoE++ (38.7W, 52.7W, 70W, and 90W), IEEE 802.3at (25.5W), and IEEE 802.3af (up to 13W) standards. Its dual-resistor classification architecture (RCLASS and RCLASS++) enables simultaneous compliance with all three, allowing one hardware design to interoperate with legacy PoE switches, PoE+ infrastructure, and LTPoE++ PSEs such as the LTC4266A or LTC4274A.
How does the LT4275AIDD#PBF implement inrush current control?
The LT4275AIDD#PBF controls inrush current using an internal charge pump that sources 18–27µA into an external CGATE capacitor connected to the HSGATE pin. This linearly ramps the gate voltage of an external N-channel MOSFET, limiting dV/dt across the output bulk capacitor (CPORT). The inrush current is calculated as IINRUSH = IGPU × CPORT / CGATE, enabling precise tuning to meet IEEE's ~100mA requirement without active current sensing.
What is the function of the T2P pin on the LT4275AIDD#PBF?
The T2P pin on the LT4275AIDD#PBF is an open-drain output that signals PSE type to the host system. It floats for IEEE 802.3af (13W), pulls low for IEEE 802.3at (25.5W), and toggles at 690–990Hz with ~50% duty cycle when an LTPoE++ PSE is detected. This allows the host microcontroller to configure power budgeting, thermal management, and feature enablement based on actual PSE capability - a capability not present in earlier PD controllers like the LTC4265.
Can the LT4275AIDD#PBF operate with auxiliary power inputs?
Yes, the LT4275AIDD#PBF supports auxiliary power override via its AUX pin. When AUX voltage exceeds 6.3V threshold (VAUXT), the device disconnects the signature resistor, disables classification, pulls down HSGATE to isolate the PoE path, and floats PWRGD. This enables seamless transition to 9–60V DC or 24V AC auxiliary supplies - critical for outdoor cameras needing heater operation during PoE brownouts or nighttime low-light conditions.
What package and thermal characteristics apply to the LT4275AIDD#PBF?
The LT4275AIDD#PBF uses a 10-lead 3mm × 3mm plastic DFN package with exposed GND pad (Pin 11). Its thermal resistance is θJC = 5°C/W, enabling efficient heat transfer to the PCB ground plane. The device operates from –40°C to 85°C and includes overtemperature protection that pulls down HSGATE and PWRGD if junction temperature exceeds 150°C, safeguarding both the IC and external MOSFET during sustained overload.
LT4275AIDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Controller (PD)
- 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:
- 23V ~ 60V
- Current - Supply:
- 2mA (Max)
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT4275AIDD#PBF FAQ
1.How can I place an order for LT4275AIDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT4275AIDD#PBF 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 LT4275AIDD#PBF reliable?
The price and inventory of LT4275AIDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT4275AIDD#PBF is usually 5 days.
3.What payment methods are accepted for LT4275AIDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT4275AIDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT4275AIDD#PBF?
LT4275AIDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT4275AIDD#PBF 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 LT4275AIDD#PBF?
For technical support, including LT4275AIDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT4275AIDD#PBF requirements.
6.How does Aetrix verify that LT4275AIDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT4275AIDD#PBF 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 LT4275AIDD#PBF meets industry standards.
7.What is the process for return or replacement of LT4275AIDD#PBF?
All LT4275AIDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT4275AIDD#PBF, 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 LT4275AIDD#PBF part is unused and in its original packaging.
Return procedure for LT4275AIDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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