Analog Devices Inc. LTC4125IUFD#TRPBF

Overview

LTC4125IUFD#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic 5W AutoResonant wireless power transmitter IC designed to drive a series LC tank in full-bridge configuration. It delivers up to 5W wirelessly, features integrated 100mΩ MOSFETs, operates from 3V–5.5V input, and implements real-time resonant frequency tracking and load-adaptive power search for medical, industrial handheld, and sensor applications.

For engineers reviewing the LTC4125IUFD#TRPBF datasheet, LTC4125IUFD#TRPBF pinout, LTC4125IUFD#TRPBF application, or LTC4125IUFD#TRPBF equivalent, key selection criteria include its 50kHz–250kHz AutoResonant switching range, programmable input current limit (via IMON), dual foreign object detection (FTH/NTC), thermally enhanced 4mm × 5mm QFN-20 package, and integrated full-bridge driver with pulse-width modulation control.

Technical Context

The LTC4125IUFD#TRPBF employs a patent-pending AutoResonant™ architecture that continuously locks switching frequency to the LC tank's natural resonance-enabling stable power delivery despite coil inductance drift or temperature variation. Its internal oscillator dynamically adjusts duty cycle via PTH1/PTH2 pins while monitoring FB voltage to detect receiver load saturation.

It integrates dual protection layers: analog-based foreign object detection using FTH (frequency threshold) and NTC (thermistor) inputs, plus digital fault handling for overtemperature, overvoltage (FB > VIN), and input current limit (ILIM = 1.20V at IMON). The device performs periodic transmit power sweeps with configurable CTD/CTS timing capacitors and halts output on any fault condition without external intervention.

Key Specifications

Pinout & Package

Package: 20-lead (4mm × 5mm) plastic QFN, 0.75mm profile, exposed thermal pad (Pin 21) requiring GND connection for electrical integrity and thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar wireless power transmitter applications.

Compared with MP-A21 and BQ500212A, the LTC4125IUFD#TRPBF offers superior design simplicity through monolithic integration, wider industrial temperature support, and adaptive resonance-reducing validation effort for medical and military applications where reliability outweighs protocol compliance.

Availability

LTC4125IUFD#TRPBF is available at Aetrix Electronics and suitable for medical equipment, industrial handhelds, and military sensor deployments requiring stable component supply, long-term lifecycle assurance, and guaranteed -40°C to +125°C operation.

Supply support for LTC4125IUFD#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 all Linear ICs including the LTC4125 family.

The LTC4125IUFD#TRPBF belongs to Linear's wireless power controller product line, engineered specifically for compact, high-efficiency, safety-certifiable transmitters in space-constrained and thermally demanding applications.

FAQ

What is the maximum wireless power output supported by the LTC4125IUFD#TRPBF?

The LTC4125IUFD#TRPBF is rated for up to 5W of wireless power delivery to a properly tuned receiver under optimal coupling conditions. This output assumes use of the full-bridge configuration (SW1–SW2), 3V–5.5V input, and appropriate LC tank design (e.g., 24µH coil with 100nF capacitor). Actual delivered power depends on coil geometry, air gap, and receiver efficiency-but the LTC4125IUFD#TRPBF's AutoResonant control ensures consistent peak power transfer across operational variables.

How does the LTC4125IUFD#TRPBF detect foreign objects during wireless power transmission?

The LTC4125IUFD#TRPBF implements two independent foreign object detection (FOD) methods: (1) FTH pin monitors resonant frequency-exceeding the programmed threshold indicates conductive object-induced inductance drop; (2) NTC pin reads thermistor voltage to halt transmission if coil or nearby components overheat. Both mechanisms trigger immediate power shutdown and high-impedance STAT output, satisfying IEC 62368-1 safety requirements without external circuitry.

Can the LTC4125IUFD#TRPBF operate in half-bridge mode, and what are the trade-offs?

Yes, the LTC4125IUFD#TRPBF supports half-bridge operation by connecting the SW1 pin to the LC tank and SW2 to GND. In this configuration, maximum output power is reduced versus full-bridge mode due to lower effective voltage swing across the tank. However, half-bridge simplifies layout and reduces component count for ≤2.5W applications. The AutoResonant and Optimum Power Search functions remain fully operational in either topology.

What is the role of the IMON pin on the LTC4125IUFD#TRPBF, and how is it configured?

The IMON pin on the LTC4125IUFD#TRPBF sources a current proportional to input current sensed across an external R_IS resistor. When paired with R_IMON, it generates a voltage used for two thresholds: 0.80V (V_ITH) pauses the power search, and 1.20V (V_ILIM) triggers immediate shutdown. Configuration uses R_IN and R_IMON values per the formula I_LIM = (R_IN/R_IMON) × 1.20V / R_IS, enabling precise, supply-independent current limiting critical for USB or battery-fed systems.

Is the LTC4125IUFD#TRPBF RoHS-compliant and lead-free?

Yes, the LTC4125IUFD#TRPBF is RoHS-compliant and features a lead-free finish, as confirmed by Analog Devices' official part marking and packaging documentation. The "#TRPBF" suffix explicitly denotes tape-and-reel packaging with lead-free termination. Full compliance data-including substance declarations and test reports-is available through Analog Devices' Quality & Reliability portal using the exact part number LTC4125IUFD#TRPBF.