Analog Devices Inc. LTC1729CMS8-4.1#PBF

Overview

LTC1729CMS8-4.1#PBF 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, temperature qualification via NTC thermistor, and automatic battery/charger presence detection. It integrates with step-down or SEPIC chargers like LT1510 and LT1769 in portable power management.

For engineers reviewing the LTC1729CMS8-4.1#PBF datasheet, LTC1729CMS8-4.1#PBF pinout, LTC1729CMS8-4.1#PBF application, or LTC1729CMS8-4.1#PBF equivalent, key selection criteria include its ±0.2% internal voltage feedback divider accuracy, 0°C–50°C thermal qualification range, 1-hour trickle-charge timer, open-drain VC and STATUS outputs, and MSOP-8 package compatibility with space-constrained handheld devices.

Technical Context

The LTC1729CMS8-4.1#PBF implements a deterministic state machine with six comparators (COMP1–COMP6), an internally trimmed 131kHz oscillator, and 25-bit counter for timing control. Its OVP pin uses a precision 2.465V reference to monitor battery voltage against the 4.1V/cell threshold with ±0.2% accuracy, while the SENSE pin sinks 100µA to set the C/10 current threshold via external sense resistor.

Thermal qualification is enforced via NTC bias current (100µA) and three comparator thresholds: cold hold (>2.79V), hot hold (<0.405V), and reset (<0.2V). The BAT pin sources 12mA during preconditioning and 1.3mA during charging, with internal clamping at 4.5V/cell to prevent overvoltage transients from battery protection circuit disconnection.

Key Specifications

Pinout & Package

Package: 8-lead MSOP (MS8), 3.0mm × 3.0mm × 0.86mm body, 0.65mm pitch, RoHS-compliant, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1729CMS8-4.2#PBF, the LTC1729CMS8-4.1#PBF delivers tighter voltage matching for 4.1V LiFePO₄-compatible cells, while LTC4065L-4.1#TRMPBF trades external charger flexibility for simplified layout and built-in thermal foldback-making it suitable for cost-sensitive, low-current designs.

Availability

LTC1729CMS8-4.1#PBF is available at Aetrix Electronics and suitable for cellular phones, PDAs, cradle chargers, and camcorders requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for LTC1729CMS8-4.1#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 product support, documentation, and manufacturing continuity for all Linear-branded ICs.

The LTC1729 series belongs to Linear's precision battery management portfolio, designed specifically for cost-sensitive, space-constrained portable electronics requiring robust, autonomous Li-ion charge termination without MCU dependency.

FAQ

What is the primary function of the LTC1729CMS8-4.1#PBF in a lithium-ion charging system?

The LTC1729CMS8-4.1#PBF serves as a dedicated charge termination controller that autonomously stops charging after either three hours or when the current drops below C/10-whichever occurs first. It does not regulate voltage or current itself but coordinates with external switching chargers (e.g., LT1510) to enforce precise 4.1V/cell constant-voltage termination, trickle preconditioning, thermal qualification, and battery presence detection-all without host processor involvement.

How does the LTC1729CMS8-4.1#PBF handle deeply discharged batteries?

The LTC1729CMS8-4.1#PBF detects batteries below 2.7V/cell using its V_MIN comparator and automatically initiates a 12mA trickle-charge preconditioning phase with a 1-hour timeout. During this phase, the BAT pin sources 12mA while the STATUS pin remains hard-pulled low. Once V_BAT exceeds 2.7V/cell, the device transitions to full-charge mode, enabling the external charger via the VC pin and beginning the 3-hour main timer.

Can the LTC1729CMS8-4.1#PBF be used with 2-cell battery packs?

No-the LTC1729CMS8-4.1#PBF is strictly configured for single-cell 4.1V Li-ion termination. For 2-cell (8.2V) applications, the correct variant is LTC1729CMS8-8.2#PBF, which features a different internal voltage reference and adjusted comparator thresholds. Using LTC1729CMS8-4.1#PBF with a 2-cell pack would result in premature termination at ~4.1V total, causing severe undercharging and capacity loss.

What is the role of the NTC pin on the LTC1729CMS8-4.1#PBF, and what happens if it's left unconnected?

The NTC pin on the LTC1729CMS8-4.1#PBF accepts a 10kΩ NTC thermistor to enforce 0°C–50°C charging qualification. If left floating, the pin voltage becomes undefined, potentially triggering false Hold or Reset states and disabling charging unpredictably. The datasheet explicitly requires either a thermistor or 10kΩ pull-up/down resistor-never an open circuit-to ensure deterministic thermal safety behavior.

How does the STATUS pin of the LTC1729CMS8-4.1#PBF provide three distinct charge states to a microcontroller?

The STATUS pin of the LTC1729CMS8-4.1#PBF supports three-state signaling via dual pull-up resistors (e.g., 3kΩ and 200kΩ). During active charging (I_BAT > C/10), the internal MOSFET pulls it low regardless of pull-up. At C/10, the MOSFET turns off and a 50µA soft pull-down holds it mid-rail (~1.5V with 3kΩ). After timeout, STATUS goes high-Z, allowing the 200kΩ pull-up to drive it high. This enables a single GPIO to decode charge progress without ADC or additional logic.