Analog Devices Inc. LTC4267IGN-3#TRPBF

Overview

LTC4267IGN-3#TRPBF from Analog Devices (formerly Linear Technology) is an IEEE 802.3af-compliant Powered Device (PD) interface IC with integrated 300kHz current-mode switching regulator, designed for PoE-powered endpoints. It integrates 25kΩ signature resistor, programmable classification (Class 0–4), dual-level inrush current limiting (90–450mA), thermal overload protection, and power-good signaling. It drives external 6V N-channel MOSFETs in isolated or nonisolated flyback topologies for IP phones, wireless access points, and security cameras.

For engineers reviewing the LTC4267IGN-3#TRPBF datasheet, LTC4267IGN-3#TRPBF pinout, LTC4267IGN-3#TRPBF application, or LTC4267IGN-3#TRPBF equivalent, key selection criteria include its –40°C to +85°C industrial temperature range, 16-pin narrow SSOP package, integrated error amplifier and 0.8V reference, and dual-level input current limit optimized for legacy and IEEE-compliant PSE compatibility.

Technical Context

The LTC4267IGN-3#TRPBF implements a two-stage PD interface: first, a detection/classification block with precision 25kΩ signature resistor (±3.5% accuracy), programmable classification current via RCLASS, and UVLO thresholds (–36V turn-on / –30.5V turn-off); second, a constant-frequency 300kHz current-mode flyback controller with soft-start, programmable slope compensation, and NGATE driver capable of 1A peak output.

Its architecture supports both isolated and nonisolated configurations via integrated error amplifier and 0.8V feedback reference. The device features thermal shutdown at 140°C, precision dual-level inrush limiting (low: 90–205mA; high: 350–450mA), and PWRGD open-drain output referenced to VPORTN - all operating across –40°C to +85°C ambient.

Key Specifications

Pinout & Package

The LTC4267IGN-3#TRPBF is housed in a 16-lead narrow plastic SSOP package (GN package), with exposed pad not present (unlike DFN variant). Pin 1 is ITH/RUN; pins 1, 8, 9, and 16 are PGND; pin 17 does not exist in SSOP. Thermal resistance θ_JA = 90°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Powered Device interface applications.

Compared with LTC4267IGN-3#TRPBF, the LTC4275CDHC-3#TRPBF offers superior thermal dissipation in a smaller footprint but sacrifices industrial temperature range, while the MAX5984DEEE+T eliminates external MOSFETs at the cost of design flexibility and IEEE Class configurability.

Availability

LTC4267IGN-3#TRPBF is available at Aetrix Electronics and suitable for IP phone power management, wireless access point power supplies, and security camera PoE interfaces requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for LTC4267IGN-3#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 LTC portfolio.

The LTC4267IGN-3#TRPBF belongs to Linear's Power over Ethernet PD controller family, engineered specifically to simplify IEEE 802.3af-compliant endpoint designs with integrated signature, classification, and high-efficiency DC-DC control.

FAQ

What is the operating temperature range for the LTC4267IGN-3#TRPBF?

The LTC4267IGN-3#TRPBF is rated for –40°C to +85°C ambient operation, confirmed by manufacturer datasheet specifications for the "I" grade variant in narrow SSOP packaging. This industrial temperature range ensures reliable performance in outdoor security cameras, ceiling-mounted access points, and factory-floor IoT devices where ambient conditions exceed commercial limits. The LTC4267IGN-3#TRPBF maintains full electrical functionality-including signature detection, classification accuracy, and current limiting-across this entire range.

How does the LTC4267IGN-3#TRPBF implement dual-level inrush current limiting?

The LTC4267IGN-3#TRPBF uses an internal state machine that initiates low-level current limiting (90–205mA) during initial capacitor charging, then automatically transitions to high-level limiting (350–450mA) once POUT voltage exceeds the power-good threshold (~1.5V above VPORTN). This prevents PSE shutdown during cold start while enabling full Class 3 power delivery (up to 13W) after stabilization. The LTC4267IGN-3#TRPBF achieves this without external timers or logic, using only internal voltage comparators and sequencing circuitry.

Can the LTC4267IGN-3#TRPBF be used in isolated flyback topologies?

Yes, the LTC4267IGN-3#TRPBF supports isolated flyback designs via its integrated error amplifier and precise 0.8V feedback reference (0.780–0.812V). When configured with an optocoupler and secondary-side sensing, the VFB pin closes the regulation loop across isolation barriers. The LTC4267IGN-3#TRPBF requires no external amplifier or reference IC in such configurations, reducing component count and improving stability. Its 300kHz oscillator frequency also minimizes transformer size in isolated implementations.

What is the purpose of the SIGDISA pin on the LTC4267IGN-3#TRPBF?

The SIGDISA pin on the LTC4267IGN-3#TRPBF enables active invalidation of the 25kΩ signature resistor: tying SIGDISA to VPORTP reduces the effective signature to ~9kΩ, which fails IEEE 802.3af detection and keeps the PD inactive. This allows selective power-up in multi-PD systems or firmware-controlled wake-up sequences. When unused, SIGDISA must be tied to VPORTN to enable normal operation. The LTC4267IGN-3#TRPBF maintains this behavior across its full –40°C to +85°C range.

Does the LTC4267IGN-3#TRPBF require an external MOSFET, and what are its drive specifications?

Yes, the LTC4267IGN-3#TRPBF requires an external N-channel MOSFET driven by its NGATE pin, which delivers 1A peak current with 40ns rise/fall times into 3000pF load. It is optimized for 6V-rated FETs and includes programmable slope compensation via the SENSE pin to stabilize current-mode control. The LTC4267IGN-3#TRPBF's integrated 100V MOSFET (POUT) handles input switching but does not replace the external FET needed for transformer primary drive in flyback topologies.