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Analog Devices Inc. LTC4268IDKD-1
- Part No.:
- LTC4268IDKD-1
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 32-WFDFN Exposed Pad
- Datasheet:
-
LTC4268IDKD-1.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 32DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,773
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Product details
Overview
LTC4268IDKD-1 from Analog Devices (formerly Linear Technology) is a high-power IEEE 802.3af Powered Device (PD) controller with integrated synchronous flyback regulator, designed for PoE applications up to 35W. It features a rugged 750mA internal MOSFET, precision dual-level current limiting (750mA operational / 300mA inrush), No-Opto isolated feedback, and operates from –57V input. It powers WAPs, PTZ cameras, and RFID readers.
For engineers reviewing the LTC4268IDKD-1 datasheet, LTC4268IDKD-1 pinout, LTC4268IDKD-1 application, or LTC4268IDKD-1 equivalent, key selection criteria include its –40°C to +85°C industrial temperature grade, 32-pin 7mm × 4mm DFN package with exposed thermal pad, dual PWRGD outputs (active-high referenced to VNEG and active-low referenced to VPORTN), and programmable classification current up to 75mA.
Technical Context
The LTC4268IDKD-1 implements a current-mode synchronous flyback controller with patented No-Opto feedback, eliminating optocouplers while maintaining full IEEE 802.3af isolation. Its dual current limit architecture enforces 300mA inrush during detection/classification and transitions to 750mA operational mode after startup.
It integrates a robust power path with 0.6Ω typical RON, supports adjustable switching frequency from 50kHz to 250kHz via external capacitor, and delivers tight multi-output regulation using load compensation via RCMP/CCMP pins. The device includes complete thermal and overcurrent protection with automatic recovery.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | –1.5V to –57V (negative supply referenced to VPORTP; compatible with standard PoE polarity protection diode bridges) |
| Max Output Power | 35W (supports high-power PoE applications such as dual-radio WAPs and PTZ security cameras) |
| Current Limit Modes | 750mA (high-level operational), 300mA (low-level inrush), and 1.45A safeguard mode when ILIM_EN is disabled |
| Oscillator Frequency | 84–110kHz (adjustable via external COSC capacitor; typical 100kHz with 100pF) |
| Signature Resistance | 23.25–26kΩ (meets IEEE 802.3af two-point measurement requirement with onboard 25kΩ resistor) |
| Operating Temp Range | –40°C to +85°C (industrial-grade rating; marked "I" in part number suffix) |
| Package | 32-pin DFN (7mm × 4mm, exposed thermal pad soldered to GND plane for θJA = 49°C/W) |
Pinout & Package
The LTC4268IDKD-1 is housed in a 32-lead plastic DFN package (7mm × 4mm) with an exposed thermal pad (Pin 33) that must be soldered to a GND-connected heatsinking plane. Pin count, layout, and thermal design are optimized for high-current PoE front-end integration.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VPORTN (Pins 5,6,7) | Primary negative input rail | Connects to PD input through diode bridge; three pins paralleled for low-inductance, high-current return path |
| VPORTP (Pin 32) | Positive input reference | Return node for input diode bridge; used as voltage reference for all VPORTN-referenced pins |
| PWRGD (Pins 29,30) | Dual power-good indicators | Pin 29: Active-high open-collector output referenced to VNEG; Pin 30: Active-low open-drain output referenced to VPORTN |
| PG (Pin 24) | Primary gate driver | Drives external N-channel MOSFET on primary side; high-current capability with fast rise/fall times (≤15ns into 1nF) |
| SG (Pin 9) | Secondary gate driver | Drives synchronous rectifier on secondary side; enables high-efficiency flyback operation without Schottky losses |
| RCLASS (Pin 3) | Classification current programming | Sets IEEE 802.3af class current (0–75mA) via resistor to VPORTN; supports Class 0–5 |
| ILIM_EN (Pin 4) | Input current limit control | Floating = 750mA mode; tied to VPORTN = disable limit (1.45A safeguard); enables flexible inrush vs. steady-state trade-offs |
| GND (Pin 33) | Signal and gate drive ground | Must be connected to VNEG; serves as reference for all analog and digital circuitry and gate drivers |
Key Features
| Feature | Design Value |
|---|---|
| No-Opto feedback topology | Eliminates optocoupler and TL431, reducing BOM cost and board space while maintaining ±1% output regulation across line/load/temperature |
| Dual-level current limiting | Enforces 300mA inrush during IEEE 802.3af detection/classification, then transitions to 750mA for full 35W operation - ensures interoperability and power headroom |
| Programmable classification current | Supports IEEE 802.3af Class 0–5 (up to 75mA) via single external resistor on RCLASS pin - simplifies PoE negotiation without firmware |
| Integrated thermal protection | Automatically disables MOSFET, clears classification load, and asserts invalid PWRGD on junction >150°C; resumes normal operation after cooldown |
| Adjustable flyback timing | Independent programming of minimum on-time (tON), enable delay (ENDLY), and PG turn-on delay (PGDLY) optimizes efficiency and EMI in diverse transformer designs |
Applications
| Wireless Access Points (WAPs) | PTZ Security Cameras |
|---|---|
|
Use Scenario: Dual-radio 802.11ac WAP requiring 24W+ continuous power and stable 5V/3.3V rails under variable RF load. IC Role / Device Role / Timing Role: PD controller and primary-side flyback regulator; manages PoE handshaking, inrush control, and synchronous rectification timing. Use Value: Delivers 35W at >88% peak efficiency with no optocoupler, enabling compact, fanless enclosure design and reduced thermal stress. |
Use Scenario: Outdoor pan-tilt-zoom camera with motorized optics, IR illumination, and video streaming - demanding burst power and thermal resilience. IC Role / Device Role / Timing Role: High-current PD interface with dual PWRGD signaling; coordinates gate timing between primary switch (PG) and synchronous rectifier (SG). Use Value: Sustains 750mA continuous input current with 0.6Ω RON, minimizing conduction loss and enabling reliable operation at –40°C ambient. |
| RFID Readers | Industrial Control Gateways |
|
Use Scenario: Multi-protocol UHF RFID reader powering antenna arrays and host MCU, requiring precise 12V/5V/3.3V rails and low standby current. IC Role / Device Role / Timing Role: IEEE 802.3af-compliant PD with programmable classification and soft-start (SFST pin) for controlled inrush during hot-plug events. Use Value: Onboard 25kΩ signature resistor and ±3.5% classification accuracy ensure plug-and-play compatibility with enterprise PoE switches. |
Use Scenario: DIN-rail mounted industrial gateway aggregating Modbus, CAN, and Ethernet - needing robust PoE input with wide temperature tolerance. IC Role / Device Role / Timing Role: Industrial-grade PD controller (–40°C to +85°C) with UVLO referenced to input (not VCC) and dual PWRGD fault signaling. Use Value: Independent VPORTN-referenced UVLO and thermal shutdown prevent latch-up in brownout or overload conditions common in factory environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Powered Device controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4269IDKD-1 | Supports IEEE 802.3at (PoE+) up to 60W; adds 2-event classification, higher 950mA current limit, and enhanced surge protection | Required for PoE+ infrastructure; not drop-in compatible due to different classification timing and higher power path ratings | Select LTC4269IDKD-1 only when upgrading to PoE+ or needing >35W; retains same DFN package and pinout but requires updated layout for higher current |
| MAX5974AETJ+ | Fixed 100kHz oscillator; no No-Opto topology - requires optocoupler and TL431; lower max power (25W); 20-pin TQFN | Suitable for cost-sensitive, lower-power PoE devices where isolation certification allows optocoupler use | Choose MAX5974AETJ+ for legacy designs or budget-constrained 802.3af systems; expect larger footprint and reduced efficiency vs. LTC4268IDKD-1 |
Compared with LTC4269IDKD-1, the LTC4268IDKD-1 offers optimal 35W performance with simpler classification and lower BOM cost; versus MAX5974AETJ+, it delivers higher efficiency, smaller size, and true optocoupler-free isolation - making it ideal for space-constrained, thermally demanding industrial PoE endpoints.
Availability
LTC4268IDKD-1 is available at Aetrix Electronics and suitable for wireless access points, PTZ security cameras, RFID readers, industrial gateways, and high-efficiency 802.3af systems requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC4268IDKD-1 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-performance analog and power management portfolio. Linear's legacy ICs emphasize precision, reliability, and system-level integration for demanding industrial and communications applications.
The LTC4268-1 product line was engineered specifically for high-efficiency, high-power PoE endpoints requiring integrated PD control and synchronous flyback regulation - targeting applications where size, thermal performance, and IEEE compliance are critical.
FAQ
What is the operating temperature range for the LTC4268IDKD-1?
The LTC4268IDKD-1 is rated for –40°C to +85°C ambient operation, confirmed by its "I" temperature grade designation and validated across all electrical specifications in the datasheet. This industrial-grade rating ensures reliable performance in outdoor security cameras, factory-floor gateways, and uncontrolled-environment WAP deployments where thermal margins are critical. The LTC4268IDKD-1 incorporates junction temperature monitoring and automatic thermal shutdown at 150°C.
Does the LTC4268IDKD-1 require an optocoupler for feedback isolation?
No, the LTC4268IDKD-1 uses Linear Technology's patented No-Opto feedback topology, which eliminates the need for an optocoupler and TL431. It achieves full IEEE 802.3af isolation by sensing flyback voltage via a third winding and compensating for leakage inductance using the ENDLY pin. This reduces component count, improves reliability, and saves board space - a key advantage over alternatives like MAX5974AETJ+ that require external isolation components.
How does the dual current limit function work on the LTC4268IDKD-1?
The LTC4268IDKD-1 enforces a 300mA inrush current limit during IEEE 802.3af detection and classification phases to ensure interoperability with legacy switches, then automatically transitions to a 750mA operational limit after successful handshaking. This behavior is controlled internally - no external configuration is needed. If ILIM_EN is tied to VPORTN, the device enters a 1.45A safeguard mode, intended only for fault analysis and requiring careful thermal design.
What are the key differences between the LTC4268IDKD-1 and LTC4268CDKD-1?
The LTC4268IDKD-1 and LTC4268CDKD-1 share identical functionality and pinout but differ in temperature grade: "I" denotes –40°C to +85°C industrial operation, while "C" specifies 0°C to +70°C commercial range. Electrical parameters such as RON, current limits, and oscillator stability are fully specified across the respective ranges. For outdoor or industrial deployments, the LTC4268IDKD-1 is mandatory; the "C" version is suitable only for climate-controlled indoor applications.
Can the LTC4268IDKD-1 support IEEE 802.3at (PoE+)?
No, the LTC4268IDKD-1 is designed exclusively for IEEE 802.3af (Type 1) PoE, supporting up to 35W. It lacks 2-event classification, higher current capability (>950mA), and enhanced surge protection required for 802.3at compliance. For PoE+ applications, Analog Devices recommends the pin-compatible LTC4269IDKD-1, which extends functionality while retaining the same 32-pin DFN package and core architecture - though layout revisions may be needed for higher current paths.
LTC4268IDKD-1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 32-WFDFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Controller (PD), DC/DC
- Number of Channels:
- 1
- Power - Max:
- 35 W
- Internal Switch(s):
- No
- Auxiliary Sense:
- No
- Standards:
- 802.3af (PoE)
- Voltage - Supply:
- 57V (Max)
- Current - Supply:
- 3mA (Max)
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-DFN (7x4)
LTC4268IDKD-1 FAQ
1.How can I place an order for LTC4268IDKD-1 through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC4268IDKD-1 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 LTC4268IDKD-1 reliable?
The price and inventory of LTC4268IDKD-1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC4268IDKD-1 is usually 5 days.
3.What payment methods are accepted for LTC4268IDKD-1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC4268IDKD-1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC4268IDKD-1?
LTC4268IDKD-1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC4268IDKD-1 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 LTC4268IDKD-1?
For technical support, including LTC4268IDKD-1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC4268IDKD-1 requirements.
6.How does Aetrix verify that LTC4268IDKD-1 is sourced from the original manufacturer or authorized distributors?
All LTC4268IDKD-1 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 LTC4268IDKD-1 meets industry standards.
7.What is the process for return or replacement of LTC4268IDKD-1?
All LTC4268IDKD-1 units undergo pre-shipment inspection (PSI). If there is an issue with LTC4268IDKD-1, 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 LTC4268IDKD-1 part is unused and in its original packaging.
Return procedure for LTC4268IDKD-1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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