Analog Devices Inc. LTC1729CMS8-4.2#PBF

Overview

LTC1729CMS8-4.2#PBF from Analog Devices (formerly Linear Technology) is a precision lithium-ion battery charge termination controller for 1-cell or 2-cell systems with 4.2 V/cell nominal voltage. It provides C/10 current detection, 3-hour time-out termination, temperature qualification (0°C to 50°C), trickle-charge preconditioning below 2.7 V/cell, and automatic battery/charger presence detection. It is designed for integration with step-down or SEPIC chargers such as LT1510, LT1769, and LT1512 in portable power management.

For engineers reviewing the LTC1729CMS8-4.2#PBF datasheet, LTC1729CMS8-4.2#PBF pinout, LTC1729CMS8-4.2#PBF application, or LTC1729CMS8-4.2#PBF equivalent, key selection criteria include its ±0.2% internal voltage feedback divider accuracy, NTC-based thermal qualification, open-drain VC and STATUS outputs, MSOP-8 package compatibility, and support for both 1-cell (4.2 V) and 2-cell (8.4 V) configurations via variant selection.

Technical Context

The LTC1729CMS8-4.2#PBF implements a state-machine-driven charge control architecture with six internal comparators (COMP1–COMP6), an internally trimmed 131 kHz oscillator, and digital timers for preconditioning (1 hr), main charging (3 hr), and filtering (0.859 sec VMAX, 3.5 sec C/10). Its logic block enforces strict sequencing: trickle charge → full charge → C/10 detection or timeout → Done/No Bat transitions.

It interfaces directly with external chargers via six pins: VC (charger enable/disable), STATUS (C/10 and charge status), SENSE (C/10 threshold setting), BAT (battery voltage monitoring and clamp), NTC (thermistor bias and thermal qualification), and OVP (precision 2.465 V reference input). All analog inputs feature defined absolute max ratings and temperature-compensated thresholds.

Key Specifications

Pinout & Package

Package: 8-lead plastic MSOP (MS8), 3 mm × 3 mm body, 0.65 mm lead pitch, θ_JA = 200°C/W, T_JMAX = 150°C.

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 4.1V variant offers identical functionality at reduced cell voltage, while LTC4066EMS8#PBF trades flexibility (no SEPIC support, fixed current) for integration density - making it suitable only for simpler, lower-power use cases.

Availability

LTC1729CMS8-4.2#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 for production programs.

Supply support for LTC1729CMS8-4.2#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 technical and manufacturing continuity for the LTC portfolio, including precision analog and power management ICs.

The LTC1729 series belongs to Linear's dedicated battery management product line, engineered specifically for autonomous, safety-critical Li-ion charge termination in portable consumer electronics - emphasizing accuracy, thermal robustness, and minimal external component count.

FAQ

What is the primary function of the LTC1729CMS8-4.2#PBF?

The primary function of the LTC1729CMS8-4.2#PBF is to provide autonomous, hardware-based termination of lithium-ion battery charging. It stops the external charger after three hours of constant-voltage/constant-current operation or when the charge current drops below C/10 - ensuring safety and longevity without host processor involvement. The LTC1729CMS8-4.2#PBF achieves this using internal comparators, timers, and precision references calibrated for 4.2 V/cell systems.

How does the LTC1729CMS8-4.2#PBF handle deeply discharged batteries?

The LTC1729CMS8-4.2#PBF initiates trickle charge preconditioning when the battery voltage falls below 2.7 V/cell, sourcing a regulated 12 mA current to safely raise the cell voltage before full charging begins. This 1-hour preconditioning phase prevents damage to over-discharged Li-ion cells and is automatically disabled once V_BAT exceeds the V_MIN threshold. The LTC1729CMS8-4.2#PBF enforces this behavior through COMP3 and the state machine - no external circuitry is needed.

Can the LTC1729CMS8-4.2#PBF be used with 2-cell Li-ion batteries?

Yes - the LTC1729CMS8-4.2#PBF is specified for both 1-cell (4.2 V) and 2-cell (8.4 V) configurations. When used in 2-cell mode, it operates with the same 4.2 V/cell reference, meaning total battery voltage is monitored at 8.4 V. The IC's BAT pin clamp (4.5 V/cell), OVP threshold (2.465 V), and thermal qualification remain valid per cell. External charger selection (e.g., LT1512 or LT1505) must support the higher voltage and current requirements of 2-cell systems.

What is the role of the NTC pin on the LTC1729CMS8-4.2#PBF?

The NTC pin on the LTC1729CMS8-4.2#PBF supplies a 100 µA bias current to a 10 kΩ NTC thermistor and monitors its voltage to enforce temperature-based charging qualification. Voltages above 2.79 V (indicating <0°C) or below 0.405 V (indicating >50°C) trigger Hold mode - freezing timers and disabling the charger via the VC pin. A voltage below 0.2 V forces Reset mode. The LTC1729CMS8-4.2#PBF requires either an NTC thermistor or 10 kΩ resistor on this pin; leaving it open is not permitted.

How does the STATUS pin indicate different charge states on the LTC1729CMS8-4.2#PBF?

The STATUS pin on the LTC1729CMS8-4.2#PBF provides three distinct states: hard pull-down (0.9 V max at 3 mA) during active charging; 50 µA soft pull-down (enabling ~2 V with 3 kΩ pull-up) when C/10 is detected; and high-impedance (allowing full pull-up voltage) after 3-hour timeout or adapter removal. This enables microprocessor detection of "charging", "nearly full", and "complete" states using a single GPIO pin and two resistors - a capability confirmed in Figure 7 of the official datasheet for the LTC1729CMS8-4.2#PBF.