Analog Devices Inc. LTC1731EMS8-4.1#PBF

Overview

LTC1731EMS8-4.1#PBF from Analog Devices (formerly Linear Technology) is a single-cell lithium-ion linear battery charger controller with fixed 4.1V float voltage, ±1% output voltage accuracy, 5% charge current programming accuracy via external R_PROG/R_SENSE, and automatic trickle/constant-current/constant-voltage charging sequence. It drives an external P-channel MOSFET or PNP transistor and supports C/10 end-of-charge detection for portable medical monitors.

For engineers reviewing the LTC1731EMS8-4.1#PBF datasheet, LTC1731EMS8-4.1#PBF pinout, LTC1731EMS8-4.1#PBF application, or LTC1731EMS8-4.1#PBF equivalent, key selection criteria include its 4.1V fixed float voltage (vs. 4.2V variants), 7µA sleep-mode battery drain, programmable timer termination, and MSOP-8 package compatibility with space-constrained handheld diagnostics devices.

Technical Context

The LTC1731EMS8-4.1#PBF implements a dual-loop linear control architecture: a current amplifier servoing the DRV pin to regulate IBAT via R_SENSE, and a voltage amplifier comparing BAT against an internal 2.457V reference scaled by a precision resistor divider to enforce 4.1V float regulation. Trickle charge activates below 2.457V BAT and delivers 10% of programmed current until threshold crossing.

Charge termination uses either C/10 current detection (with 320ms debounce) or a capacitor-programmable timer (t_TIMER = CTIMER × 3h / 0.1µF); both functions disable when TIMER pin is tied to VCC, enabling constant-current-only mode for NiMH/NiCd. Sleep mode engages when VCC drops ≤4.1V or (VCC – VBAT) ≤54mV, reducing ICC to 7µA.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (3mm × 3mm, 0.65mm pitch), moisture sensitivity level 1, RoHS-compliant, with exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1731EMS8-4.1#PBF, the -4.2 variant offers identical functionality but targets mainstream Li-ion cells, while MAX1555ETA+ trades flexibility and precision for integration and lower component count - making LTC1731EMS8-4.1#PBF the sole choice for regulated 4.1V medical or industrial applications requiring programmable current and external pass-device control.

Availability

LTC1731EMS8-4.1#PBF is available at Aetrix Electronics and suitable for portable medical monitors, handheld ultrasound probes, wearable vital sign sensors, point-of-care blood analyzers, and battery-backed data loggers requiring stable component supply across extended production lifecycles.

Supply support for LTC1731EMS8-4.1#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 technical support, manufacturing, and documentation for all Linear-branded products including the LTC series.

The LTC1731EMS8-4.1#PBF belongs to Linear's precision battery management IC family, engineered specifically for space-constrained, safety-critical portable instrumentation requiring accurate, low-noise, and thermally robust linear charging solutions.

FAQ

What is the exact float voltage tolerance of the LTC1731EMS8-4.1#PBF?

The LTC1731EMS8-4.1#PBF guarantees a regulated float voltage of 4.1V with ±1% accuracy over the full –40°C to +85°C operating temperature range. This corresponds to a minimum of 4.059V and maximum of 4.141V under specified conditions (5V ≤ VCC ≤ 12V), directly traceable to the internal 2.457V reference and precision resistor divider network.

Can the LTC1731EMS8-4.1#PBF be used to charge NiMH batteries?

Yes, the LTC1731EMS8-4.1#PBF can charge NiMH batteries by connecting the TIMER pin to VCC to disable constant-voltage regulation and timer functions, configuring it as a pure constant-current source. External termination (e.g., –ΔV or temperature cutoff) remains required, as the C/10 detection and trickle charge features are optimized for Li-ion chemistry.

What is the maximum allowable input voltage for the LTC1731EMS8-4.1#PBF?

The absolute maximum input supply voltage (VCC) for the LTC1731EMS8-4.1#PBF is 13.2V. However, the recommended operating range is 4.5V to 12V per the Electrical Characteristics table; operation above 12V risks exceeding internal clamp limits on the DRV pin and may degrade long-term reliability even if within absolute ratings.

How does the LTC1731EMS8-4.1#PBF enter sleep mode and what is its impact on battery life?

The LTC1731EMS8-4.1#PBF enters sleep mode automatically when either the VCC supply drops below 4.1V or the differential (VCC – VBAT) falls to ≤54mV, reducing battery drain current to 7µA typical. This extends usable shelf life of battery-backed devices by up to 3× compared to controllers with >100µA quiescent drain, critical for infrequently used medical field equipment.

Is the LTC1731EMS8-4.1#PBF pin-compatible with the LTC1731ES8-4.1 version?

No, the LTC1731EMS8-4.1#PBF (MSOP-8) and LTC1731ES8-4.1 (SO-8) share identical electrical functionality and pin assignments but differ in physical package dimensions, thermal resistance (θJA = 200°C/W vs. 125°C/W), and mounting requirements. PCB layouts are not interchangeable without redesign due to distinct land patterns and solder reflow profiles.