Analog Devices Inc. LTC4120IUD-4.2#PBF

Overview

LTC4120IUD-4.2#PBF from Analog Devices is a fixed 4.2V float voltage wireless power receiver and synchronous buck battery charger IC. It delivers up to 400mA constant-current/constant-voltage charging for single-cell Li-Ion/Polymer batteries, integrates Dynamic Harmonization Control (DHC) for air-gap–robust resonant power regulation, and operates across 12.5V–40V input range in a thermally enhanced 3mm × 3mm QFN package. It enables sealed-environment charging in medical sensors and industrial IoT nodes.

For engineers reviewing the LTC4120IUD-4.2#PBF datasheet, LTC4120IUD-4.2#PBF pinout, LTC4120IUD-4.2#PBF application, or LTC4120IUD-4.2#PBF equivalent, key selection criteria include its fixed 4.2V float voltage accuracy (±0.039V), DHC input regulation at 14V, ±1% feedback voltage reference, 50–400mA programmable charge current via single resistor, and NTC-qualified thermal safety with auto-recharge on 2.2% battery voltage drop.

Technical Context

The LTC4120IUD-4.2#PBF implements a synchronous buck topology with integrated high-side and low-side MOSFETs (R_DS(ON) = 0.8Ω / 0.5Ω), supports 750kHz or 1.5MHz switching via FREQ pin, and uses BATSNS pin for direct battery voltage sensing-eliminating external feedback dividers. Its DHC pin modulates receiver tank resonance by dynamically adjusting impedance when input voltage falls below 14V, enabling stable wireless power transfer across variable coupling distances.

It features precision analog control loops: a dedicated 2.4V internal reference (V_FB(REG)) for the LTC4120 variant is replaced by fixed 4.2V regulation (V_FLOAT = 4.188–4.227V) in this -4.2 variant, with ±0.5% total float voltage accuracy over –40°C to 125°C. Charge termination uses dual criteria: timer (1.3–2.8 hours) and C/10 current threshold, while low-battery preconditioning activates below 2.21V with 6–16mA linear current.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4120IUD-4.2#PBF, LTC4125IDDB#PBF serves only as a transmitter companion, while BQ51013BRGER offers Qi compatibility but sacrifices DHC-based coupling robustness and industrial input voltage range - making LTC4120IUD-4.2#PBF uniquely suited for non-standard, high-reliability wireless charging in sealed industrial systems.

Availability

LTC4120IUD-4.2#PBF is available at Aetrix Electronics and suitable for handheld medical sensors, industrial rotating equipment, and harsh-environment IoT nodes requiring stable component supply with guaranteed long-term availability.

Supply support for LTC4120IUD-4.2#PBF 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.

The LTC4120 product line was designed specifically for contactless battery charging in sealed, rotating, or sanitary environments - combining wireless power reception with precision Li-Ion charging and robust thermal management in miniature QFN packages.

FAQ

What is the exact float voltage tolerance of the LTC4120IUD-4.2#PBF over temperature?

The LTC4120IUD-4.2#PBF guarantees a float voltage of 4.188V minimum to 4.227V maximum across –40°C to 125°C junction temperature, representing ±0.039V absolute tolerance and ±0.5% relative accuracy. This is confirmed in the Electrical Characteristics table (Rev. G, page 3) under V_FLOAT parameter, and validated by typical performance curves showing <10mV drift over full temperature range.

Does the LTC4120IUD-4.2#PBF require external feedback resistors for voltage regulation?

No, the LTC4120IUD-4.2#PBF does not require external feedback resistors. Unlike the programmable LTC4120 variant, it uses the dedicated BATSNS pin to directly sense battery voltage and regulate to a factory-trimmed 4.2V float point. This eliminates resistor-divider errors, temperature drift, and layout sensitivity - simplifying design and improving long-term stability.

How does Dynamic Harmonization Control (DHC) function in the LTC4120IUD-4.2#PBF?

In the LTC4120IUD-4.2#PBF, DHC regulates input voltage by modulating the resonant receiver tank's impedance when VIN falls below 14V. The DHC pin switches between high-impedance (VIN > 14V) and low-impedance (VIN < 14V) states, altering tank Q-factor to maintain stable power transfer across coupling variations from 0.4cm to 1.8cm spacing - verified in Figure TA01b of the datasheet.

What is the minimum recommended inductor value for the LTC4120IUD-4.2#PBF buck converter?

The LTC4120IUD-4.2#PBF datasheet specifies a minimum inductance of 15µH (SLF4075 series) for reliable operation at 400mA charge current and 750kHz switching frequency. Lower values risk peak current limit triggering (750mA typical) and reduced efficiency; the 33µH inductor shown in Figure 1 is recommended for optimal ripple and thermal performance.

Can the LTC4120IUD-4.2#PBF operate without an NTC thermistor?

Yes, the LTC4120IUD-4.2#PBF can operate without an NTC thermistor: tie the NTC pin to GND to disable thermal qualification. In this configuration, the device performs full CC/CV charging without temperature monitoring. However, safety-critical applications (e.g., medical, industrial) must retain NTC functionality to comply with UL/IEC battery charging standards.