Analog Devices Inc. LTC4120IUD

Overview

LTC4120IUD from Analog Devices is a monolithic wireless power receiver IC with integrated 400mA Li-ion battery charger, autoresonant synchronous rectifier, and programmable charge termination. It operates at 125kHz resonant frequency, supports up to 2W received power across 3–10mm air gaps, and delivers regulated 4.2V charging with ±0.5% voltage accuracy for single-cell batteries. It is used in sealed medical devices, wearable sensors, and rotating industrial tools requiring contactless recharging.

For engineers reviewing the LTC4120IUD datasheet, LTC4120IUD pinout, LTC4120IUD application, or LTC4120IUD equivalent, key selection criteria include its 400mA constant-current/constant-voltage charging capability, integrated NTC thermistor interface for temperature monitoring, 125kHz autoresonant rectification, and compatibility with LTC4125-based transmitters in Qi-adjacent wireless power systems.

Technical Context

The LTC4120IUD implements a full-bridge synchronous rectifier driven by an internal autoresonant controller that locks to the transmitter's LC tank frequency (typically 103–125kHz), eliminating need for external timing components. Its charge management engine integrates CC/CV regulation, end-of-charge detection via timer or voltage plateau, and thermal foldback using an external NTC thermistor.

It features a dedicated BOOST pin enabling high-efficiency buck-boost conversion of rectified AC to stable DC output, and uses BAT and BATSNS pins for precise battery voltage sensing with Kelvin connection support. The device requires no communication link with the transmitter-power delivery and foreign object detection are handled entirely by the LTC4125 side.

Key Specifications

Pinout & Package

Package: 16-pin 3 mm × 3 mm QFN with exposed thermal pad (UD package suffix). RoHS-compliant, moisture-sensitive level 3.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ51221RGER and MP-A21, the LTC4120IUD provides autonomous analog-based charging with integrated NTC bias and Kelvin sensing-enabling robust, certification-free operation in medical and industrial settings where communication overhead and layout complexity must be minimized.

Availability

LTC4120IUD is available at Aetrix Electronics and suitable for implantable sensors, sealed industrial tools, rotating IoT endpoints, disposable wearables, and sterilizable medical devices requiring stable component supply and long-lifecycle assurance.

Supply support for LTC4120IUD 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, Inc. is a global semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial, automotive, and healthcare applications.

The LTC4120IUD belongs to Analog Devices' Power by Linear™ wireless power product line, designed specifically for self-contained, communication-free wireless battery charging in safety-critical and environmentally constrained applications.

FAQ

What is the maximum received power the LTC4120IUD can handle?

The LTC4120IUD is rated for up to 2W of received power from the transmitter coil. This enables full 400mA constant-current charging across air gaps up to 10mm and coil misalignments up to ±15°, as validated in reference designs paired with the LTC4125 transmitter. Power handling is thermally limited by the QFN-16 package; sustained 2W operation requires ≥2 cm² of 2-oz copper on the thermal pad layer.

Does the LTC4120IUD require communication with the transmitter?

No, the LTC4120IUD operates autonomously without any digital or analog communication link to the transmitter. It relies solely on autoresonant rectification synchronized to the incoming 125kHz magnetic field. All charge control-including current regulation, voltage termination, and thermal cutoff-is performed locally using internal circuits and external components like the PROG capacitor and NTC thermistor.

Can the LTC4120IUD charge batteries other than 4.2V Li-ion?

The LTC4120IUD is factory-trimmed for 4.2V ±0.5% constant-voltage termination and is not user-adjustable. It is intended exclusively for single-cell Li-ion or Li-polymer batteries. Charging LiFePO4 (3.6V) or other chemistries requires a different IC-such as the LT3652HV in conjunction with discrete rectification-as the LTC4120IUD lacks voltage programming capability.

How does the NTC interface on the LTC4120IUD work?

The LTC4120IUD provides a precise 10 µA current source on the NTC pin to bias a standard 10 kΩ @ 25°C NTC thermistor. The resulting voltage is monitored internally to suspend charging outside the JEITA-defined 0°C–45°C window. No external ADC or MCU is needed-the IC handles threshold detection and charge enable/disable autonomously.

What is the purpose of the BATSNS pin on the LTC4120IUD?

The BATSNS pin provides Kelvin (4-wire) sensing of the battery voltage at the cell terminals, separate from the main BAT pin carrying charge current. This compensates for voltage drop across PCB traces or protection FETs, ensuring the LTC4120IUD regulates battery voltage to exactly 4.2V ±0.5% at the cell itself-even with up to 200 mV IR loss in the power path.