Analog Devices Inc. LTC4057ES5-4.2#TRMPBF

Overview

LTC4057ES5-4.2#TRMPBF from Analog Devices (formerly Linear Technology) is a monolithic linear Li-ion battery charger IC designed for single-cell 4.2V batteries in USB-powered portable devices. It integrates a P-channel power MOSFET, thermal regulation, ±1% float voltage accuracy, programmable charge current up to 800mA via external resistor, and operates without external sense resistor or blocking diode. It delivers constant-current/constant-voltage charging directly from 4.25–6.5V sources such as USB ports.

For engineers reviewing the LTC4057ES5-4.2#TRMPBF datasheet, LTC4057ES5-4.2#TRMPBF pinout, LTC4057ES5-4.2#TRMPBF application, or LTC4057ES5-4.2#TRMPBF equivalent, key selection considerations include thermal regulation behavior at 120°C junction limit, PROG-pin-based current programming and monitoring, shutdown mode supply current (25µA), trickle-charge threshold (2.9V), and SOT-23-5 package compatibility with high-density PCB layouts.

Technical Context

The LTC4057ES5-4.2#TRMPBF implements a fully integrated constant-current/constant-voltage (CC/CV) charge algorithm with internal thermal feedback that dynamically reduces charge current when die temperature approaches 120°C. Its architecture eliminates external power FETs and current-sense resistors by embedding a 600mΩ R_DS(ON) P-MOSFET between VCC and BAT pins.

Charge termination is externally programmable via the PROG pin (1.0V reference), enabling precise current setting using a single resistor; the same pin provides real-time current monitoring via V_PROG/R_PROG × 1000. Trickle charging activates below 2.9V battery voltage, and undervoltage lockout (UVLO) engages at 3.8V with 200mV hysteresis to prevent reverse current flow.

Key Specifications

Pinout & Package

Package: 5-lead TSOT-23 (S5), 1mm profile, JEDEC MO-193 compliant. Exposed pad not present; thermal path relies on copper layout on PCB.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear Li-ion charging applications.

Compared with LTC4057ES5-4.2#TRMPBF, LTC4054ES5-4.2#TRMPBF offers simpler autonomous operation but no current control or monitoring, while LTC4053EDD-4.2#TRMPBF adds USB-aware power management at the expense of increased complexity and package size-making LTC4057ES5-4.2#TRMPBF optimal for cost-sensitive, MCU-managed USB-charged portable devices needing programmability and telemetry.

Availability

LTC4057ES5-4.2#TRMPBF is available at Aetrix Electronics and suitable for smartphone charging circuits, USB-powered portable medical devices, wearable fitness trackers, Bluetooth headset battery management, and other compact Li-ion applications requiring stable component supply and long-term manufacturability.

Supply support for LTC4057ES5-4.2#TRMPBF 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 its precision analog and power management portfolio. Linear's legacy engineering rigor continues in all former Linear products, including the LTC series.

The LTC4057ES5-4.2#TRMPBF belongs to Linear's ThinSOT™ linear battery charger family, engineered specifically for space-constrained, USB-powered portable electronics requiring high integration, thermal robustness, and ±1% voltage accuracy without external discrete components.

FAQ

What is the maximum programmable charge current for the LTC4057ES5-4.2#TRMPBF?

The LTC4057ES5-4.2#TRMPBF supports a maximum programmable charge current of 800mA, achieved using a 1.25kΩ resistor from PROG to GND. This value assumes adequate PCB thermal design (θ_JA ≤ 125°C/W) and ambient temperature ≤ 48°C. At higher temperatures or poorer thermal layouts, the internal thermal regulation circuit will reduce current to maintain junction temperature ≤ 120°C.

Does the LTC4057ES5-4.2#TRMPBF require an external blocking diode?

No, the LTC4057ES5-4.2#TRMPBF does not require an external blocking diode. Its internal P-channel MOSFET architecture prevents reverse current flow from the battery to the input supply. When VCC drops near the battery voltage (within ~30mV), the device automatically enters shutdown mode, reducing battery drain to less than 2µA.

How is charge current monitored on the LTC4057ES5-4.2#TRMPBF?

Charge current is monitored in real time via the PROG pin on the LTC4057ES5-4.2#TRMPBF. The voltage at this pin remains at 1.0V during constant-current charging, and battery current is calculated using I_BAT = (V_PROG/R_PROG) × 1000. For example, with R_PROG = 2kΩ and V_PROG = 1.0V, I_BAT = 500mA. This enables host MCU-based charge telemetry without additional sensing components.

What happens when the battery voltage falls below 2.9V on the LTC4057ES5-4.2#TRMPBF?

When the BAT pin voltage falls below 2.9V, the LTC4057ES5-4.2#TRMPBF initiates trickle charging at approximately 1/10 the programmed full-scale current (e.g., ~50mA for a 500mA setup). This low-current mode safely raises the battery voltage to a level where full-rate constant-current charging can resume, protecting deeply discharged Li-ion cells from damage.

Can the LTC4057ES5-4.2#TRMPBF operate from a 4.5V input supply?

Yes, the LTC4057ES5-4.2#TRMPBF operates from 4.25V to 6.5V, so a 4.5V supply is fully supported. At 4.5V input and 3.7V battery voltage, power dissipation is (4.5V – 3.7V) × I_BAT. With proper PCB thermal design (e.g., θ_JA = 130°C/W), it can sustain ~600mA before thermal regulation activates-making it suitable for USB 2.0 and many regulated 4.5V adapter applications.