Analog Devices Inc. LTC1731EMS8-8.2#PBF

Overview

LTC1731EMS8-8.2#PBF from Analog Devices (formerly Linear Technology) is a complete constant-current/constant-voltage linear charger controller for 2-cell lithium-ion batteries, featuring 8.2V regulated float voltage, ±1% output voltage accuracy, 7% charge current programming accuracy via external R_PROG/R_SENSE, and automatic trickle-charge initiation below 4.95V battery voltage - used in handheld computing and charging cradles requiring precise dual-cell Li-Ion management.

For engineers reviewing the LTC1731EMS8-8.2#PBF datasheet, LTC1731EMS8-8.2#PBF pinout, LTC1731EMS8-8.2#PBF application, or LTC1731EMS8-8.2#PBF equivalent, key selection considerations include its MSOP-8 package, C/10 end-of-charge detection, programmable timer termination, sleep-mode battery drain of 15µA, and compatibility with external P-channel MOSFET or high-gain PNP pass devices.

Technical Context

The LTC1731EMS8-8.2#PBF implements a dual-loop linear control architecture: a current amplifier servoing the DRV pin to maintain precise charge current through R_SENSE, and a voltage amplifier regulating BAT pin potential to 8.2V using an internal 2.457V reference and precision resistor divider. It operates only within V_CC = 8.8V–12V and enters sleep mode when V_CC – V_BAT falls below 54mV.

Charge sequencing includes automatic low-voltage trickle mode (10% of full-scale current), transition to constant-current mode above 4.95V, then constant-voltage regulation until C/10 detection or timer expiry. The PROG pin enables shutdown via floating (2.5µA pull-up), while TIMER pin configures termination time (3 hours per 0.1µF) or forces constant-current-only operation when tied to V_CC.

Key Specifications

Pinout & Package

Package: 8-lead plastic MSOP (MS8), 3.0mm × 3.0mm body, 0.65mm pitch, exposed pad not electrically connected. Thermal resistance θ_JA = 200°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1731EMS8-8.4#PBF, the LTC1731EMS8-8.2#PBF provides lower float voltage for older 2S Li-Ion cells, while versus LTC1732EMS8#PBF it trades integrated features for superior voltage accuracy and deterministic C/10 signaling - making it optimal for MCU-managed, high-precision charging systems.

Availability

LTC1731EMS8-8.2#PBF is available at Aetrix Electronics and suitable for handheld computers, charging docks and cradles, and legacy cellular phones requiring stable component supply, long-lifecycle support, and guaranteed traceability.

Supply support for LTC1731EMS8-8.2#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for all Linear-branded parts including the LTC1731 series.

The LTC1731EMS8-8.2#PBF belongs to Linear's precision linear battery charger controller family, designed specifically for space-constrained, high-accuracy 2-cell Li-Ion applications where external pass devices and programmable termination are preferred over integrated-FET solutions.

FAQ

What is the exact float voltage regulation accuracy of the LTC1731EMS8-8.2#PBF?

The LTC1731EMS8-8.2#PBF regulates battery voltage to 8.2V with ±1% accuracy over the full –40°C to +85°C operating temperature range, achieved via an internal 2.457V precision reference and trimmed resistor divider - confirmed in Electrical Characteristics table under V_BAT parameter for LTC1731-8.2.

Can the LTC1731EMS8-8.2#PBF be used with NiMH batteries?

Yes, the LTC1731EMS8-8.2#PBF can charge NiMH batteries in constant-current-only mode by connecting the TIMER pin to V_CC, which disables the voltage regulation loop and timer - however, external termination (e.g., –ΔV or temperature cutoff) is required since the IC does not provide NiMH-specific termination logic.

What is the minimum recommended R_SENSE value for the LTC1731EMS8-8.2#PBF?

The LTC1731EMS8-8.2#PBF does not specify a minimum R_SENSE value, but practical design limits arise from sense voltage headroom: the SENSE pin must remain within –0.3V to V_CC, and typical designs use 100mV drop at full scale (e.g., 0.2Ω for 500mA). Lower values increase noise sensitivity and reduce accuracy - 0.1Ω is usable but requires careful layout.

How does the LTC1731EMS8-8.2#PBF enter and exit sleep mode?

The LTC1731EMS8-8.2#PBF enters sleep mode automatically when V_CC – V_BAT drops below 54mV (e.g., input supply removed), reducing battery drain to 15µA; it exits sleep mode when V_CC rises above 8.2V UVLO threshold and a valid R_PROG is connected - no reset or pin toggle is needed.

Is the LTC1731EMS8-8.2#PBF pin-compatible with the SO-8 version LTC1731ES8-8.2?

No - although both share identical electrical functionality and pin assignments, the LTC1731EMS8-8.2#PBF uses an 8-lead MSOP package (3.0mm × 3.0mm, 0.65mm pitch), while LTC1731ES8-8.2 uses an 8-lead SOIC-N package (3.9mm × 4.9mm, 1.27mm pitch); PCB layout and thermal design are not interchangeable.