Analog Devices Inc. LTC1731ES8-4.1#TRPBF

Overview

LTC1731ES8-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a single-cell lithium-ion linear battery charger controller with internal 4.1V float voltage regulation, ±1% output accuracy, 5% charge current setting via external sense resistor, and automatic trickle-to-CC-to-CV charging sequence. It operates from 4.5V to 12V input and supports programmable C/10 termination and timer-based safety cutoff for portable power management in handheld devices.

For engineers reviewing the LTC1731ES8-4.1#TRPBF datasheet, LTC1731ES8-4.1#TRPBF pinout, LTC1731ES8-4.1#TRPBF application, or LTC1731ES8-4.1#TRPBF equivalent, key selection criteria include its 4.1V fixed float voltage, 7µA sleep-mode battery drain, MSOP-8/SO-8 package compatibility, PROG-pin programmable current control, and CHRG open-drain status signaling with C/10 detection.

Technical Context

The LTC1731ES8-4.1#TRPBF implements a dual-loop linear control architecture: a current amplifier servoing an external P-channel MOSFET or PNP pass device via the DRV pin, and a voltage amplifier regulating BAT pin potential against an internal 2.457V reference and precision resistor divider. Its charge sequencing includes automatic 10% trickle mode below 2.457V battery voltage, transitioning to constant-current mode upon threshold crossing.

Termination logic combines analog C/10 current detection (via internal comparator) with a capacitor-programmable timer (tTIMER = CTIMER × 3h / 0.1µF), both independently disableable via TIMER pin configuration. Sleep mode activates when VCC drops ≤54mV above VBAT or during input removal, reducing ICC to 7µA while disconnecting the internal voltage divider to minimize battery leakage.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (Small Outline, narrow 0.150") with standard JEDEC MO-153 footprint; RoHS-compliant, Pb-free, #TRPBF suffix indicates tape-and-reel packaging.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear battery charger controller applications.

Compared with LTC1731ES8-4.1#TRPBF, the -4.2 variant offers identical architecture with higher float voltage for standard Li-ion, while MAX1555ESA+ trades external component flexibility for monolithic simplicity at lower current capability - choice depends on voltage requirement, current demand, and BOM optimization goals.

Availability

LTC1731ES8-4.1#TRPBF is available at Aetrix Electronics and suitable for portable medical instruments, industrial handheld scanners, USB-powered audio devices, and consumer electronics requiring stable component supply with guaranteed long-term availability.

Supply support for LTC1731ES8-4.1#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 legacy Linear parts including the LTC1731 series.

The LTC1731 product line was designed specifically for cost-sensitive, space-constrained portable electronics needing fully autonomous linear Li-ion charging with hardware-based safety - targeting cellular phones, handheld computers, and charging docks before widespread adoption of switch-mode solutions.

FAQ

What is the exact float voltage of the LTC1731ES8-4.1#TRPBF?

The LTC1731ES8-4.1#TRPBF has a factory-trimmed internal float voltage of 4.1V with ±1% accuracy over the full –40°C to 85°C operating temperature range. This value is fixed and non-adjustable; it is implemented using a precision internal resistor divider referenced to a 2.457V bandgap, ensuring stable termination without external components. The 4.1V setting is optimized for lithium-ion cells requiring lower float voltage to extend cycle life.

Can the LTC1731ES8-4.1#TRPBF charge NiMH or NiCd batteries?

Yes, the LTC1731ES8-4.1#TRPBF can charge NiMH or NiCd batteries in constant-current-only mode by connecting the TIMER pin to VCC, which disables the voltage regulation loop and timer. In this configuration, the IC functions as a programmable current source with C/10 detection still active. External methods such as temperature monitoring or ΔV detection must be used for final termination, as the LTC1731ES8-4.1#TRPBF does not provide built-in NiMH/NiCd-specific algorithms.

How does the CHRG pin indicate charge status on the LTC1731ES8-4.1#TRPBF?

The CHRG pin on the LTC1731ES8-4.1#TRPBF provides three distinct states: actively pulled low by an internal N-channel MOSFET during constant-current or constant-voltage charging; switched to a 100µA current sink when charge current falls to C/10 (indicating near-full state); and placed in high-impedance when the timer expires or shutdown occurs. This allows direct LED drive or microprocessor polling without additional logic, enabling simple visual or digital status feedback in the LTC1731ES8-4.1#TRPBF-based design.

What is the minimum battery voltage that triggers trickle charge on the LTC1731ES8-4.1#TRPBF?

The LTC1731ES8-4.1#TRPBF initiates trickle charge when the battery voltage at the BAT pin is below 2.457V, with a tolerance of ±0.103V over temperature. During trickle mode, the charge current is automatically set to 10% of the full-scale programmed current. If the battery remains below this threshold for one quarter of the total timer duration, the LTC1731ES8-4.1#TRPBF terminates charging and places the CHRG pin in high-impedance to indicate a potentially defective cell.

Does the LTC1731ES8-4.1#TRPBF require external compensation components?

No, the LTC1731ES8-4.1#TRPBF is internally compensated and stable without external compensation when used with a P-channel MOSFET as the pass element. A 10µF capacitor is recommended at the BAT pin for stability when the battery is disconnected. If a PNP transistor is used instead, a 1000pF capacitor from DRV to VCC is required to stabilize the voltage loop, in addition to the BAT bypass capacitor - these are application-specific recommendations, not compensation network components.