Analog Devices Inc. LTC4120IUD-4.2#TRPBF

Overview

LTC4120IUD-4.2#TRPBF from Analog Devices is a fixed 4.2V float voltage wireless power receiver and synchronous buck battery charger IC, delivering up to 400mA charge current with ±1% feedback voltage accuracy, Dynamic Harmonization Control (DHC) for air-gap–robust resonant coupling, and integrated NTC temperature qualification - designed for sealed, rotating, or hygienic Li-ion battery-powered devices in industrial sensors and portable medical equipment.

For engineers reviewing the LTC4120IUD-4.2#TRPBF datasheet, LTC4120IUD-4.2#TRPBF pinout, LTC4120IUD-4.2#TRPBF application, or LTC4120IUD-4.2#TRPBF equivalent, this page delivers verified technical context, validated pin functions, confirmed 16-lead 3mm × 3mm QFN package mapping, real-world wireless charging efficiency curves, and two rigorously cross-checked alternative parts with documented functional and application-level differences.

Technical Context

The LTC4120IUD-4.2#TRPBF implements a synchronous buck topology with programmable switching frequency (750kHz/1.5MHz via FREQ pin), internal 0.8Ω top-switch and 0.5Ω bottom-switch R_DS(ON), and precise 4.2V ±0.012V regulated float voltage for Li-ion/Polymer batteries. Its DHC architecture dynamically modulates receiver tank resonance by controlling DHC pin impedance to maintain stable input regulation across variable coil spacing (tested up to 18mm).

It integrates full battery management logic: low-voltage preconditioning (2.21V threshold), auto-recharge at 2.2% battery voltage drop, 2-hour safety timer, bad-battery fault detection, and open-drain CHRG/FAULT status outputs. The device operates over –40°C to 125°C and enters <100µA sleep mode post-charge termination.

Key Specifications

Pinout & Package

Package: 16-lead (3mm × 3mm × 0.75mm) plastic QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad to PCB ground plane for θ_JA = 54°C/W and reliable thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar wireless battery charging applications.

Compared with LTC4120IUD-4.2#TRPBF, LTC4125IDDB#TRPBF serves the opposite side of the wireless link and cannot replace it directly, while BQ51221RGER trades industrial flexibility (DHC, wide input, NTC) for Qi ecosystem compatibility - making LTC4120IUD-4.2#TRPBF uniquely suited for rugged, non-standard, and safety-critical wireless charging deployments.

Availability

LTC4120IUD-4.2#TRPBF is available at Aetrix Electronics and suitable for industrial wireless sensors, sealed portable medical devices, and rotating equipment monitoring requiring stable component supply, long-lifecycle support, and guaranteed parametric performance across –40°C to 125°C.

Supply support for LTC4120IUD-4.2#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets with precision power, sensing, and connectivity solutions.

The LTC4120 product line was engineered specifically for contactless battery charging in harsh, sealed, or mechanically constrained environments - emphasizing robustness, self-regulating power transfer, and integrated safety features over consumer-oriented convenience.

FAQ

What is the primary function of the DHC pin on the LTC4120IUD-4.2#TRPBF?

The DHC pin on the LTC4120IUD-4.2#TRPBF enables Dynamic Harmonization Control by acting as a programmable impedance node that modulates the resonant frequency of the external receiver tank. When input voltage falls below 14V, the DHC pin transitions to low-impedance mode, allowing the LTC4120IUD-4.2#TRPBF to dynamically adjust coupling efficiency and maintain stable input regulation across variable air gaps - a core capability for rotating or misaligned wireless charging systems.

Does the LTC4120IUD-4.2#TRPBF require an external microcontroller to manage the charging cycle?

No, the LTC4120IUD-4.2#TRPBF does not require an external microcontroller. It implements a complete autonomous charging algorithm - including low-voltage preconditioning, constant-current/constant-voltage regulation, 2-hour safety timer, auto-recharge at 2.2% voltage drop, and NTC-qualified thermal management - using internal analog comparators and state machines. The LTC4120IUD-4.2#TRPBF communicates status via open-drain CHRG and FAULT pins, eliminating firmware dependencies.

How is battery voltage sensed in the LTC4120IUD-4.2#TRPBF compared to the standard LTC4120?

The LTC4120IUD-4.2#TRPBF uses dedicated BATSNS (Pin 10) for direct battery terminal sensing to enforce its fixed 4.2V float voltage, whereas the standard LTC4120 uses FB/FBG pins with an external resistor divider for programmable voltage. This eliminates external components and potential divider inaccuracies, ensuring tighter regulation and simplified layout - a key differentiator for production reliability in the LTC4120IUD-4.2#TRPBF variant.

What is the maximum recommended spacing between transmitter and receiver coils when using the LTC4120IUD-4.2#TRPBF?

The LTC4120IUD-4.2#TRPBF has been characterized for stable operation up to 1.8cm spacing in typical 9–11mm diameter coil configurations, with usable power transfer observed beyond 18mm in optimized setups. Performance depends on coil geometry, ferrite shielding, and transmitter drive strength; the DHC feature actively compensates for coupling variation, but efficiency declines gradually beyond 1.2cm - design validation at target spacing is recommended per application requirements.

Can the LTC4120IUD-4.2#TRPBF be used with battery chemistries other than Li-ion?

No - the LTC4120IUD-4.2#TRPBF is specifically configured for single-cell Li-ion and Li-polymer batteries with its fixed 4.2V float voltage and associated charge profile (including 2.21V low-voltage preconditioning and 4.2V CV termination). It is not suitable for LiFePO₄, NiMH, or lead-acid chemistries, which require different voltage thresholds and charge algorithms. For multi-chemistry support, the programmable LTC4120 (non-4.2 variant) must be used instead of the LTC4120IUD-4.2#TRPBF.