Analog Devices Inc. LTC1729CS8-8.2#PBF

Overview

LTC1729CS8-8.2#PBF from Analog Devices (formerly Linear Technology) is a smart lithium-ion battery charge termination controller for 2-cell (8.2V nominal) applications. It provides C/10 current detection, 3-hour time-out termination, trickle-charge preconditioning below 5.4V, temperature qualification via NTC thermistor, and automatic battery/charger presence detection. It interfaces with external step-down or SEPIC chargers such as LT1512 and LT1513 in portable power systems.

For engineers reviewing the LTC1729CS8-8.2#PBF datasheet, LTC1729CS8-8.2#PBF pinout, LTC1729CS8-8.2#PBF application, or LTC1729CS8-8.2#PBF equivalent, key selection criteria include its 8.2V/cell voltage threshold, 10.4V UVLO lockout, NTC-based thermal qualification (0°C–50°C), integrated 3-hour timer, and compatibility with high-current switch-mode chargers requiring precise end-of-charge signaling.

Technical Context

The LTC1729CS8-8.2#PBF implements a state-machine-driven termination logic with six internal comparators: COMP1 (C/10 detection), COMP2 (VBAT overvoltage clamp at 9.013V), COMP3 (VMIN low-voltage preconditioning at 5.4V), COMP4/COMP5 (NTC cold/hot hold thresholds), and COMP6 (NTC reset). Its oscillator is trimmed to 131kHz, driving a 25-bit counter for timing functions including TIMER1 (1-hour trickle timeout), TIMER2 (3-hour main charge timeout), and digital filters for VMAX and VC/10 detection.

It operates in three primary functional states: Precondition (12mA trickle charge if VBAT < 5.4V), Charger "ON" (enables external charger via open-drain VC pin), and Done (VC pulled low, STATUS high-impedance). Battery presence detection relies on BAT pin voltage ramp-up exceeding 9.013V; thermal hold disables charging when NTC pin voltage falls outside 0.405V–2.79V range, freezing timers and pulling VC low.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (Small Outline, narrow 0.150", S8 package per LTC DWG #05-08-1610), RoHS-compliant, rated for 0°C to 70°C operating temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1729CMS8-8.2#PBF, the SO-8 variant offers better thermal performance in high-power cradle chargers but occupies more PCB area; versus BQ24075RGTR, it delivers scalable, high-current, multi-topology support essential for professional 2-cell Li-ion systems - neither alternative matches its combination of precision dual-cell termination, thermal hold, and external charger interoperability.

Availability

LTC1729CS8-8.2#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 RoHS-compliant sourcing.

Supply support for LTC1729CS8-8.2#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 the LTC portfolio.

The LTC1729CS8-8.2#PBF belongs to Linear's precision battery management IC family, designed specifically for autonomous, high-reliability termination in multi-cell Li-ion charging systems where external charger control, thermal safety, and deep-discharge recovery are mandatory.

FAQ

What is the exact V_MAX threshold voltage for LTC1729CS8-8.2#PBF?

The LTC1729CS8-8.2#PBF has a typical V_MAX high-going threshold of 9.013V, with min/max limits of 8.5V and 9.5V respectively. This value is factory-trimmed and applies across the full operating temperature range (0°C to 70°C). It defines both the battery overvoltage clamp point and the battery-present detection threshold, ensuring reliable operation with 2-cell Li-ion packs rated at 8.2V nominal.

How does LTC1729CS8-8.2#PBF handle deeply discharged batteries?

The LTC1729CS8-8.2#PBF initiates trickle-charge preconditioning when VBAT drops below 5.4V (V_MIN threshold), sourcing 12mA from the BAT pin to safely raise cell voltage. This state lasts up to 1 hour (TIMER1) before transitioning to full-charge mode. The IC continuously monitors VBAT and will re-enter preconditioning if voltage falls below V_MIN during charging, ensuring robust recovery of abused 2-cell Li-ion batteries.

Can LTC1729CS8-8.2#PBF be used with SEPIC topology chargers?

Yes, the LTC1729CS8-8.2#PBF is explicitly validated for use with SEPIC topology chargers including the LT1512 (2A switch) and LT1513 (3A switch). Its VC pin directly controls the charger's enable function, and its six-pin interface (OVP, BAT, SENSE, NTC, STATUS, VC) integrates seamlessly without modification. Application Note 1729 TA01 demonstrates a working 1A SEPIC design using LTC1729CS8-8.2#PBF with LT1512.

What is the purpose of the NTC pin on LTC1729CS8-8.2#PBF?

The NTC pin on LTC1729CS8-8.2#PBF accepts a 10kΩ negative-temperature-coefficient thermistor to enforce temperature-qualified charging between 0°C and 50°C. It sources 100µA to generate voltage thresholds: <0.405V (hot hold), >2.79V (cold hold), and <0.2V (reset). During hold, the state machine freezes and VC pulls low - disabling the charger without resetting timers - ensuring compliance with UN38.3 and IEC 62133 thermal safety standards.

Does LTC1729CS8-8.2#PBF require external passive components for basic operation?

Yes, the LTC1729CS8-8.2#PBF requires four minimum external components for functional operation: a 10kΩ NTC thermistor (or resistor) on NTC pin, a current-sense resistor on SENSE pin to set C/10 threshold, a pull-up resistor on STATUS pin for LED/microcontroller interface, and a voltage-divider network on OVP pin if not using the internal 2.465V reference directly. No external timing components are needed due to its integrated oscillator and counters.