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Analog Devices Inc. LT4275CIDD#PBF
- Part No.:
- LT4275CIDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT4275CIDD#PBF.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:371
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Product details
Overview
LT4275CIDD#PBF from Analog Devices (formerly Linear Technology) is an IEEE 802.3af-compliant Type 1 Powered Device (PD) controller for Power over Ethernet systems, delivering up to 13W at the RJ45 connector. It integrates a precision 24.4kΩ signature resistor, supports N-channel MOSFET hot-swap control, and operates across –40°C to +85°C junction temperature. Used in low-power PoE endpoints such as VoIP phones and wireless access points.
For engineers reviewing the LT4275CIDD#PBF datasheet, LT4275CIDD#PBF pinout, LT4275CIDD#PBF application, or LT4275CIDD#PBF equivalent, key selection criteria include IEEE 802.3af compliance, 100V absolute maximum input voltage, programmable inrush current, integrated thermal protection, and DFN-10 (3mm × 3mm) package compatibility with space-constrained PoE designs.
Technical Context
The LT4275CIDD#PBF implements IEEE 802.3af detection, classification, and powered-on operation using a 25kΩ signature resistance (24.4kΩ ±0.7kΩ), 12.5V–21V classification voltage range, and 35V/30V hot-swap turn-on/turn-off thresholds. It drives an external N-channel MOSFET via HSGATE with 10–18V open-circuit gate drive and supports auxiliary supply override via AUX pin with 6.3V threshold.
Unlike LT4275A/B variants, the LT4275C disables RCLASS++ and T2P functionality-RCLASS++ is unconnected and T2P is NC-limiting operation strictly to Type 1 (13W) classification. Its internal charge pump enables efficient N-MOSFET control without requiring P-channel devices, reducing power loss and thermal load during inrush and steady-state operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| IEEE Standard | Complies with IEEE 802.3af Type 1 PD specification for 13W delivery at RJ45 port. |
| Max Input Voltage | 100V absolute maximum VPORT rating ensures robustness against cable surge and transient events. |
| Signature Resistance | 24.4kΩ ±0.7kΩ between VPORT–GND enables reliable 25kΩ detection by PSEs per IEEE 802.3af. |
| Hot Swap Thresholds | VHSON = 35V / VHSONOFF = 30V (IEEEUVLO grounded); provides controlled MOSFET turn-on after detection. |
| Junction Temp Range | –40°C to +85°C operating range supports commercial indoor PoE applications including IP cameras and sensors. |
| Inrush Control | Adjustable via external CGATE capacitor; enables precise 100mA inrush current design per IEEE requirement. |
| Power Good Output | PWRGD open-drain signal asserts high only after HSGATE reaches ~7V above HSSRC, enabling safe isolated supply startup. |
Pinout & Package
LT4275CIDD#PBF uses a 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11) electrically connected to GND and required to be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1: IEEEUVLO | Hot swap UVLO threshold select | Grounded to enable IEEE-compliant 35V/30V turn-on/turn-off; left open for lower thresholds. |
| Pin 2: AUX | Auxiliary supply sense input | Sinks 4–8µA when below 6.3V threshold; triggers auxiliary mode, disconnects signature, floats PWRGD. |
| Pin 3: RCLASS | Classification resistor connection | Accepts 49.9Ω (Class 3, 13W) or open (Class 0) to set PD power level per IEEE 802.3af Table 1. |
| Pin 4: RCLASS++ | LTPoE++ classification pin | No-connect on LT4275C; not used in IEEE 802.3af-only operation. |
| Pin 5: GND | Analog/digital reference ground | Primary return path; must be tied to PCB GND and connected to exposed pad. |
| Pin 6: T2P | PSE type indicator output | No-connect on LT4275C; unused since T2P signaling applies only to Type 2/LTPoE++ PSE identification. |
| Pin 7: PWRGD | Power good status indicator | Open-drain output pulled low until HSGATE ≥7V above HSSRC; synchronizes isolated supply enable. |
| Pin 8: HSSRC | MOSFET source reference | Connects to source of external N-channel MOSFET; defines gate drive reference point. |
| Pin 9: HSGATE | MOSFET gate driver output | Provides 10–18V gate drive relative to HSSRC; controls external N-MOSFET turn-on timing and inrush rate. |
| Pin 10: VPORT | PD input power rail | Connects to Ethernet port power pair; handles up to 100V transient; feeds internal charge pump and logic. |
Key Features
| Feature | Design Value |
|---|---|
| N-channel MOSFET support | Integrated charge pump eliminates need for costly P-channel FET, reducing BOM cost and board area. |
| Programmable inrush current | External CGATE capacitor sets IINRUSH ≈ 100mA per IEEE 802.3af, ensuring compliant startup behavior. |
| Thermal protection | Automatic HSGATE/PWRGD pull-down when junction exceeds 150°C, preventing damage during abnormal conditions. |
| Integrated signature resistor | On-die 24.4kΩ resistor meets IEEE 802.3af detection accuracy and temperature stability requirements. |
| Auxiliary supply override | AUX pin enables seamless switchover to 9–60V auxiliary input, supporting hybrid PoE/DC-powered systems. |
Applications
| VoIP Phones | Wireless Access Points |
|---|---|
Use Scenario: Desktop or wall-mounted IP telephony device powered exclusively via Cat5e/Cat6 Ethernet cabling. IC Role / Device Role / Timing Role: IEEE 802.3af PD controller managing detection, classification, and hot-swap sequencing for 13W power delivery. Use Value: Enables single-cable deployment without local AC adapters; 100V input rating withstands typical PoE transients in office environments. |
Use Scenario: Indoor 802.11n/ac access point mounted on ceiling or wall with no nearby AC outlet. IC Role / Device Role / Timing Role: PD interface controlling power-up sequence, isolating inrush, and asserting PWRGD to enable DC/DC converter startup. Use Value: Supports full 13W operation for dual-band radios and integrated antennas while maintaining strict IEEE compliance. |
| Networked Sensors | Smart Building Controllers |
Use Scenario: Low-power environmental sensor node (temperature/humidity/motion) deployed in HVAC ducts or ceilings. IC Role / Device Role / Timing Role: Type 1 PD controller providing regulated 3.3V/5V rails via downstream isolated DC/DC after PoE handshaking. Use Value: Eliminates battery replacement cycles; –40°C to +85°C operation ensures reliability in unconditioned spaces. |
Use Scenario: DIN-rail mounted building automation controller receiving power and data over Ethernet backbone. IC Role / Device Role / Timing Role: PD interface with AUX pin support for failover to 24VAC auxiliary supply during PoE interruption. Use Value: Ensures continuous operation during network maintenance or PSE faults without system reboot or data loss. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Powered Device controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4257-1 | Integrates 100V/400mA internal switch; no external MOSFET required. Lacks AUX override and LTPoE++ compatibility. | Targeted at ultra-compact, low-current (<400mA) PoE endpoints where board space is critical. | Select LTC4257-1 when eliminating external MOSFET and gate driver components is prioritized over auxiliary supply flexibility. |
| LTC4265 | IEEE 802.3at (Type 2) compliant; supports 25.5W; includes 2-event classification and internal 1A switch. | Designed for higher-power applications like PTZ cameras or multi-radio APs requiring >13W. | Choose LTC4265 only if upgrading to PoE+ infrastructure is planned; not drop-in compatible with LT4275CIDD#PBF layout or firmware. |
Compared with LTC4257-1 and LTC4265, the LT4275CIDD#PBF offers optimal balance of external MOSFET efficiency control, AUX-supported redundancy, and strict IEEE 802.3af compliance-making it ideal for cost-sensitive, thermally constrained, and reliability-critical 13W PoE endpoints.
Availability
LT4275CIDD#PBF is available at Aetrix Electronics and suitable for VoIP phones, wireless access points, networked sensors, and smart building controllers requiring stable component supply and long-term industrial availability.
Supply support for LT4275CIDD#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 its high-reliability analog IC portfolio. Linear pioneered precision PoE interface solutions with robust fault tolerance and thermal resilience.
The LT4275 family was designed specifically for IEEE-compliant Powered Device interfaces, emphasizing interoperability, efficiency, and ruggedness in commercial and light-industrial Ethernet-powered equipment.
FAQ
What IEEE standard does the LT4275CIDD#PBF support?
The LT4275CIDD#PBF supports IEEE 802.3af Type 1 Powered Device operation, delivering up to 13W at the PD port. It performs full detection, classification (Classes 0–3), and powered-on sequencing per the standard. Unlike LT4275A/B variants, it does not support IEEE 802.3at or LTPoE++, and RCLASS++ and T2P pins are unconnected in this grade. The LT4275CIDD#PBF is fully compliant and tested for interoperability with certified 802.3af PSEs.
Does the LT4275CIDD#PBF require an external MOSFET?
Yes, the LT4275CIDD#PBF requires an external N-channel MOSFET connected between VPORT (drain), HSSRC (source), and HSGATE (gate). Its internal charge pump generates gate drive voltage relative to HSSRC, enabling efficient low-RDS(ON) switching. This architecture avoids the larger size and higher conduction loss of P-channel alternatives. The LT4275CIDD#PBF does not integrate any power switch.
What is the function of the AUX pin on the LT4275CIDD#PBF?
The AUX pin on the LT4275CIDD#PBF enables auxiliary supply override: when driven above 6.3V, it disconnects the signature resistor, disables classification, pulls down HSGATE, and floats PWRGD-allowing seamless transition to an external 9–60V DC or 24VAC auxiliary source. This feature supports failover operation in mission-critical PoE endpoints. The LT4275CIDD#PBF uses IAUXH hysteresis current (4–8µA) to ensure clean switching.
Can the LT4275CIDD#PBF be used in industrial temperature applications?
The LT4275CIDD#PBF is rated for –40°C to +85°C operating junction temperature, making it suitable for commercial and light-industrial indoor environments. For extended temperature operation up to +125°C, the LT4275CHDD#PBF variant is available. The LT4275CIDD#PBF's thermal protection activates at 150°C junction, safeguarding against sustained overload but is not intended for continuous operation beyond its specified range.
How is inrush current controlled in the LT4275CIDD#PBF?
Inrush current in the LT4275CIDD#PBF is controlled by programming the external CGATE capacitor value. The internal IGPU current (18–27µA) charges CGATE, ramping HSGATE voltage and thereby controlling the slew rate of the external MOSFET. Using the formula IINRUSH = IGPU × CPORT/CGATE, designers set CGATE to achieve ~100mA inrush per IEEE 802.3af. A typical 47nF CGATE with 470µF CPORT yields compliant behavior, verified in LT4275CIDD#PBF reference schematics.
LT4275CIDD#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:
- 13 W
- Internal Switch(s):
- No
- Auxiliary Sense:
- Yes
- Standards:
- 802.3af (PoE)
- Voltage - Supply:
- 23V ~ 60V
- Current - Supply:
- 2mA (Max)
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT4275CIDD#PBF FAQ
1.How can I place an order for LT4275CIDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT4275CIDD#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 LT4275CIDD#PBF reliable?
The price and inventory of LT4275CIDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT4275CIDD#PBF is usually 5 days.
3.What payment methods are accepted for LT4275CIDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT4275CIDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT4275CIDD#PBF?
LT4275CIDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT4275CIDD#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 LT4275CIDD#PBF?
For technical support, including LT4275CIDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT4275CIDD#PBF requirements.
6.How does Aetrix verify that LT4275CIDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT4275CIDD#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 LT4275CIDD#PBF meets industry standards.
7.What is the process for return or replacement of LT4275CIDD#PBF?
All LT4275CIDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT4275CIDD#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 LT4275CIDD#PBF part is unused and in its original packaging.
Return procedure for LT4275CIDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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