Analog Devices Inc. LTC1729CMS8-4.2#TRPBF

Overview

LTC1729CMS8-4.2#TRPBF from Analog Devices (formerly Linear Technology) is a lithium-ion battery charge termination controller IC designed to manage constant-voltage/constant-current charging cycles for single-cell 4.2V Li-ion batteries. It provides C/10 current detection, 3-hour time-out termination, trickle-charge preconditioning below 2.7V, temperature qualification via NTC thermistor (0°C–50°C), and automatic battery/charger presence detection. It interfaces directly with step-down or SEPIC chargers such as LT1510 and LT1769 in portable power systems.

For engineers reviewing the LTC1729CMS8-4.2#TRPBF datasheet, LTC1729CMS8-4.2#TRPBF pinout, LTC1729CMS8-4.2#TRPBF application, or LTC1729CMS8-4.2#TRPBF equivalent, key selection considerations include its 8-pin MSOP package, ±0.2% internal voltage feedback divider accuracy, integrated 12mA trickle-charge source, NTC-based thermal safety lockout, and compatibility with external 0.2Ω sense resistors for C/10 threshold programming.

Technical Context

The LTC1729CMS8-4.2#TRPBF implements a state-machine-driven termination logic with six internal comparators (COMP1–COMP6), a 131kHz trimmed oscillator, and timer-based transitions between Reset, Precondition, Charger "ON", Pause, Done, and Hold modes. Its OVP pin uses a precision 2.465V reference with ±0.2% trimming to monitor 4.2V/cell battery voltage via an internal 55kΩ resistor divider.

It integrates dual current sources (12mA for trickle charge, 1.3mA for main charge) on the BAT pin, a 100µA bias current on NTC for thermistor interfacing, and open-drain VC/STATUS outputs with hard pull-down (for charge indication) and soft 50µA pull-down (for C/10 status). The SENSE pin sinks 100µA to set C/10 threshold via external resistor, with a 3-second digital filter before latching.

Key Specifications

Pinout & Package

Package: 8-lead plastic MSOP (MS8), 3.0mm × 3.0mm body, 0.65mm pitch, exposed pad not electrically connected.

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 delivers tighter alignment with modern 4.2V Li-ion cells, while LTC4066EMS8#TRPBF trades external charger flexibility for integration - making LTC1729CMS8-4.2#TRPBF the preferred choice for scalable, high-efficiency portable power designs.

Availability

LTC1729CMS8-4.2#TRPBF 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 authenticity for production builds.

Supply support for LTC1729CMS8-4.2#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LTC1729CMS8-4.2#TRPBF belongs to Linear's legacy battery management portfolio, engineered specifically for cost-sensitive, space-constrained portable electronics requiring robust, hardware-based charge termination without microcontroller dependency.

FAQ

What is the primary function of the LTC1729CMS8-4.2#TRPBF in a Li-ion charging system?

The LTC1729CMS8-4.2#TRPBF serves as a dedicated hardware charge termination controller. Its core function is to stop external switch-mode chargers (e.g., LT1510) after three hours of constant-voltage charging or when the charge current drops below C/10 - providing dual-layer safety against overcharge. It also enables trickle preconditioning for deeply discharged cells and enforces thermal limits via NTC monitoring, all without firmware.

How does the LTC1729CMS8-4.2#TRPBF interface with an external charger IC like the LT1510?

The LTC1729CMS8-4.2#TRPBF interfaces with the LT1510 using six pins: VC controls charger enable/disable (open = on, pulled low = off), STATUS signals charge state, OVP connects to the LT1510's feedback node for voltage regulation, BAT monitors battery voltage, SENSE sets C/10 threshold, and NTC provides thermal qualification. No communication protocol is needed - operation is fully analog and state-machine driven.

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

No - the LTC1729CMS8-4.2#TRPBF is strictly configured for single-cell 4.2V operation. For 2-cell (8.4V) applications, the correct variant is LTC1729CMS8-8.4#TRPBF, which features scaled voltage thresholds (V_MAX = 9.013V), adjusted UVLO (10.4V), and compatible internal reference. Using LTC1729CMS8-4.2#TRPBF on 2-cell packs will result in premature termination and undercharging.

What happens if the NTC thermistor is omitted from the LTC1729CMS8-4.2#TRPBF circuit?

The NTC pin must never be left floating. If thermal qualification is not required, a 10kΩ pull-up resistor to V_CC must be installed per datasheet Note. Omitting the NTC or resistor causes undefined behavior: the state machine may lock in Hold mode (halting charge) or fail to initialize, as COMP4/COMP5/COMP6 rely on defined voltage boundaries (0.2V–2.79V) for cold/hot/reset detection.

Does the LTC1729CMS8-4.2#TRPBF require external passive components to operate?

Yes - minimal external components are mandatory: a 10kΩ NTC thermistor (or 10kΩ resistor), a 0.2Ω current-sense resistor for C/10 setting, and pull-up resistors on STATUS and VC for open-drain interfacing. Additionally, decoupling capacitors (e.g., 0.1µF on V_CC) are recommended. No external clock, programming, or configuration ICs are needed - all timing and thresholds are internal.