Analog Devices Inc. LTC1729CMS8-4.1#TRPBF

Overview

LTC1729CMS8-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a precision lithium-ion battery charge termination controller for single-cell 4.1V systems. It provides C/10 current detection, 3-hour time-out termination, trickle-charge preconditioning below 2.7V/cell, automatic battery and charger presence detection, and NTC-based temperature qualification (0°C to 50°C). It interfaces with step-down or SEPIC chargers like LT1510 and LT1769 in portable power management circuits.

For engineers reviewing the LTC1729CMS8-4.1#TRPBF datasheet, LTC1729CMS8-4.1#TRPBF pinout, LTC1729CMS8-4.1#TRPBF application, or LTC1729CMS8-4.1#TRPBF equivalent, key selection criteria include its ±0.2% internal voltage feedback divider accuracy, 100µA SENSE pin sink for programmable C/10 threshold, integrated 3-hour timer, thermistor bias current source, and compatibility with external 1.5A–4A switching chargers.

Technical Context

The LTC1729CMS8-4.1#TRPBF implements a state-machine-driven charge control architecture with six comparators (COMP1–COMP6), an internally trimmed 131kHz oscillator, and digital timers for preconditioning (1 hr), main charging (3 hr), and filtering (0.86 sec to 4.17 sec). Its logic block enforces strict sequencing: trickle charge initiates only when VBAT < 2.7V, full charge begins after VBAT > 2.7V, and termination occurs at either C/10 current drop (with 3-second digital filter) or 3-hour timeout.

It integrates precision analog monitoring: OVP pin references a laser-trimmed 0.2% resistor divider to detect 4.1V/cell (2.465V nominal), NTC pin uses 100µA bias for cold/hot hold thresholds (2.79V/0.405V), and BAT pin sources 12mA during preconditioning and 1.3mA during constant-voltage charge - all clamped to 4.5V/cell via internal pull-down.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (MS8), 3.0mm × 3.0mm × 0.85mm body, 0.65mm pitch, RoHS-compliant, tape-and-reel (#TRPBF).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar lithium-ion charge termination applications.

Compared with LTC1729CMS8-4.1#TRPBF, the LTC1729CMS8-4.2#TRPBF offers identical functionality but targets 4.2V/cell chemistry, while the LTC4065L-4.1#TRMPBF integrates charging power delivery but sacrifices scalability beyond 500mA and external charger flexibility.

Availability

LTC1729CMS8-4.1#TRPBF is available at Aetrix Electronics and suitable for cellular phones, PDAs, cradle chargers, and camcorders requiring stable component supply and long-term production continuity.

Supply support for LTC1729CMS8-4.1#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 for legacy Linear parts including the LTC series.

The LTC1729CMS8-4.1#TRPBF belongs to Linear's precision battery management controller family, designed specifically for autonomous, safety-critical Li-ion charge termination in space-constrained portable electronics.

FAQ

What is the primary function of the LTC1729CMS8-4.1#TRPBF in a battery charging system?

The LTC1729CMS8-4.1#TRPBF serves as a dedicated charge termination controller that autonomously stops charging after three hours or when the current drops below C/10 - without requiring microcontroller supervision. It works alongside external switching chargers (e.g., LT1510) and manages safety functions including trickle preconditioning, battery presence detection, and NTC-based thermal qualification. Its core value lies in offloading timing and analog threshold decisions from the host system.

How does the LTC1729CMS8-4.1#TRPBF ensure accurate 4.1V/cell voltage regulation?

The LTC1729CMS8-4.1#TRPBF uses a laser-trimmed internal resistor divider that delivers a precise 2.465V reference to the OVP pin - corresponding to exactly 4.1V per cell. This ±0.2% accuracy eliminates the need for external calibration components and ensures consistent overvoltage protection across temperature and unit-to-unit variation. The OVP pin connects directly to the charger's feedback node, allowing real-time monitoring of regulated battery voltage.

Can the LTC1729CMS8-4.1#TRPBF be used with a 2-cell battery configuration?

No - the LTC1729CMS8-4.1#TRPBF is strictly configured for single-cell 4.1V operation. For 2-cell (8.2V) applications, the correct variant is LTC1729CMS8-8.2#TRPBF, which features a different internal voltage divider calibrated to 8.2V total (4.1V/cell × 2). Using the -4.1 version with two cells would result in premature overvoltage shutdown and failure to reach full charge.

What happens to the STATUS pin during different charge states of the LTC1729CMS8-4.1#TRPBF?

During active charging, the STATUS pin is hard pulled low by an internal MOSFET. When charge current falls below C/10 for ≥3 seconds, the hard pull-down disables and a 50µA soft pull-down remains active. After the 3-hour timer expires or input power is removed, STATUS transitions to high-impedance (open-drain). This three-state behavior allows simple LED or microprocessor interfacing to distinguish charging, C/10 reached, and charge complete conditions - all within the LTC1729CMS8-4.1#TRPBF's native logic.

Why does the LTC1729CMS8-4.1#TRPBF require a 10kΩ NTC thermistor on the NTC pin?

The LTC1729CMS8-4.1#TRPBF sources a precise 100µA current into the NTC pin; with a 10kΩ thermistor, this generates 1V at 25°C, 2.79V at 0°C, and 0.405V at 50°C - matching its internal comparator thresholds for cold/hot hold modes. Substituting a different resistance invalidates thermal qualification. If temperature monitoring is unused, a fixed 10kΩ resistor (not open circuit) must be installed to maintain proper bias and avoid undefined behavior - the NTC pin must never float.