Analog Devices Inc. LTC4255CG#TRPBF

Overview

LTC4255CG#TRPBF from Analog Devices (formerly Linear Technology) is a quad –48V network power controller with independent relay drivers and I²C-compatible interface. It controls four isolated –48V power channels, each featuring programmable current limit (125–170 mV sense threshold), open-circuit detection (1–4.5 mV), short-circuit foldback protection, and Power_OK indication. Used in IP phone systems and DTE power distribution where precise fault management and software-controlled sequencing of PoE-like supplies are required.

For engineers reviewing the LTC4255CG#TRPBF datasheet, LTC4255CG#TRPBF pinout, LTC4255CG#TRPBF application, or LTC4255CG#TRPBF equivalent, key selection considerations include its 28-pin SSOP package, –48V negative supply capability (VEE to AGND = –80V max), I²C address programmability (5-bit, up to 32 devices), FAULT interrupt signaling, and independent per-channel ON/OFF, latchoff/autoretry, and timing configuration (tCL = 4.8–115.2 ms, tOCD = 50–649 ms).

Technical Context

The LTC4255CG#TRPBF implements a digitally controlled hot-swap architecture for telecom-grade –48V distribution, using external N-channel MOSFETs (e.g., FDC3612) driven via GATE pins with 13 V (typ) clamp above VEE and 50 µA pull-up. Each channel integrates independent analog current sensing (SENSEx), voltage monitoring (OUTx), and relay control (RELAYx) with internal 18 V Zener clamping for coil kickback suppression.

Its I²C interface supports standard-mode (400 kHz) operation with configurable slave address (AD0–AD4), enabling daisy-chained control of up to 128 channels across 32 devices. Fault handling is hardware-accelerated: FAULT pin asserts open-drain low on current-limit or open-circuit events, eliminating polling via interrupt-driven status register reads (Status Reg 1 & 2).

Key Specifications

Pinout & Package

Package: 28-lead plastic SSOP (5.3 mm wide), RoHS-compliant, moisture sensitivity level 3. Pin pitch: 0.65 mm; body dimensions: 9.9 × 7.4 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative-voltage hot-swap controller applications.

Compared with LT4250CS8#PBF and LTC4251CMS#TRMPBF, the LTC4255CG#TRPBF uniquely delivers quad-channel integration, programmable fault timing, relay + gate drive co-location, and full –80V VEE tolerance - making it the only option for scalable, interrupt-driven, multi-port telecom power control in SSOP format.

Availability

LTC4255CG#TRPBF is available at Aetrix Electronics and suitable for IP phone systems, DTE power distribution, and telecom line card protection requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC4255CG#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 LTC4255CG#TRPBF belongs to Linear's high-reliability hot-swap controller family, designed specifically for telecom infrastructure requiring robust –48V power management with digital configurability and fault resilience.

FAQ

What is the absolute maximum VEE rating for the LTC4255CG#TRPBF?

The LTC4255CG#TRPBF supports an absolute maximum VEE voltage of –80 V referenced to AGND. This rating provides design margin for telecom transients and ensures reliable operation under worst-case surge conditions on –48 V distribution systems. Operation beyond this limit risks permanent damage to the device.

Does the LTC4255CG#TRPBF support autoretry after a short-circuit fault?

Yes, the LTC4255CG#TRPBF supports programmable autoretry after short-circuit faults via the Setup Register (B1 bit). When enabled, it automatically restarts the affected channel after a configurable retry delay, with duty cycle selectable between 0.83% and 6% (B3 bit). The LTC4255CG#TRPBF also supports latchoff mode for safety-critical applications requiring manual reset.

How many LTC4255CG#TRPBF devices can be addressed on a single I²C bus?

Up to 32 LTC4255CG#TRPBF devices can be uniquely addressed on a single I²C bus using the five address pins AD0–AD4, which provide 32 distinct slave addresses. Each device controls four channels, enabling coordinated management of up to 128 independent –48V power ports with only two MCU I/O lines (SCL/SDA).

What is the purpose of the RELAYx pins on the LTC4255CG#TRPBF?

The RELAY1–RELAY4 pins on the LTC4255CG#TRPBF are open-collector NPN outputs capable of sinking 50 mA to within 0.3 V of DGND. They drive external relays (e.g., Tyco V23079 series) to physically connect/disconnect the –48V supply path, providing galvanic isolation and inrush current limiting. An internal 18 V Zener clamp protects against inductive kickback when the relay de-energizes.

Can the LTC4255CG#TRPBF detect open-circuit conditions, and how is it configured?

Yes, the LTC4255CG#TRPBF detects open-circuit conditions by monitoring the SENSEx pin voltage: if it remains below 1–4.5 mV for longer than the programmable open-circuit filter time (t_OCF = 9.6–28.8 ms), the channel shuts off. Detection is enabled via Setup Register bit B2 and delayed by t_OCD (50–649 ms) after Power_OK assertion to avoid false triggers during startup - a feature confirmed in the LTC4255CG#TRPBF datasheet.