Analog Devices Inc. LTC1729CS8-8.2#TRPBF

Overview

LTC1729CS8-8.2#TRPBF 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 (0°C–50°C), and automatic battery/charger presence detection. It interfaces with external step-down or SEPIC chargers such as LT1512 and LT1505 in portable power systems.

For engineers reviewing the LTC1729CS8-8.2#TRPBF datasheet, LTC1729CS8-8.2#TRPBF pinout, LTC1729CS8-8.2#TRPBF application, or LTC1729CS8-8.2#TRPBF equivalent, key selection criteria include its 8.2V battery voltage threshold, VCC UVLO at 9.6V (typ), NTC-based thermal safety lockout, integrated 100µA bias for thermistor sensing, and compatibility with high-current (>2A) charger ICs requiring precise CV termination control.

Technical Context

The LTC1729CS8-8.2#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 internal resistor divider trimmed to ±0.2% to generate 2.465V reference for 8.2V/cell configuration.

It supports dual termination triggers: (1) C/10 current detection via 100µA SENSE pin sink and 3-second digital filter, and (2) 3-hour elapsed time after entering Charger "ON" state. Battery voltage monitoring includes VMAX = 9.013V (high-going) and VMIN = 5.2V (low-going) thresholds, with clamping at 9.0V to protect against overvoltage transients during CC-to-CV transition.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (S8), narrow body, 0.150-inch width. RoHS-compliant, Pb-free, surface-mountable. Thermal resistance θ_JA = 200°C/W.

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, the LTC1729CS8-8.2#TRPBF offers identical termination logic but in a more manufacturable SO-8 package; versus LTC4060EDD-8.2#TRPBF, it retains full flexibility with external high-current chargers but requires separate VC-level translation and layout coordination.

Availability

LTC1729CS8-8.2#TRPBF is available at Aetrix Electronics and suitable for cellular phones, PDAs, and cradle chargers requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing for production programs.

Supply support for LTC1729CS8-8.2#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for the LTC product line, including precision analog and power management ICs.

The LTC1729CS8-8.2#TRPBF belongs to Linear's battery management controller family, designed specifically for safe, autonomous termination of multi-cell Li-ion charging cycles in portable consumer electronics.

FAQ

What is the exact battery voltage configuration supported by the LTC1729CS8-8.2#TRPBF?

The LTC1729CS8-8.2#TRPBF is factory-configured for 2-cell lithium-ion batteries with a nominal 8.2V output (4.1V per cell). Its internal resistor divider is trimmed to produce a precise 2.465V reference at the OVP pin, enabling accurate 8.2V/cell regulation. This differs from the -4.2 variant (4.2V/cell) and -8.4 variant (4.2V × 2), and cannot be reconfigured in-circuit.

How does the LTC1729CS8-8.2#TRPBF handle battery removal during charging?

The LTC1729CS8-8.2#TRPBF detects battery removal via rising voltage on the BAT pin. When V_BAT exceeds 9.013V for >1 second, it transitions to Pause mode, pulls VC low to disable the charger, and holds timers frozen. If voltage remains above threshold, it proceeds to No Bat state. Reinsertion is detected when V_BAT stays <9.013V for 1 second, triggering automatic restart in Precondition mode - no manual reset required.

Can the LTC1729CS8-8.2#TRPBF operate without an NTC thermistor?

No - the NTC pin must never be left open. The LTC1729CS8-8.2#TRPBF requires either a 10kΩ NTC thermistor (e.g., Vishay NTHS1206N02) or a 10kΩ fixed resistor connected to the NTC pin. Omitting this component disables thermal qualification and may cause unsafe charging outside 0°C–50°C. The 100µA internal bias current is mandatory for proper comparator operation (COMP4–COMP6).

What is the function of the STATUS pin in the LTC1729CS8-8.2#TRPBF during different charge states?

The STATUS pin of the LTC1729CS8-8.2#TRPBF operates in three distinct modes: (1) Hard pull-down (N-channel MOSFET) during Precondition and Charger "ON" while I_CHG > C/10; (2) Soft 50µA pull-down after C/10 is sustained for 3 seconds; (3) High-impedance after 3-hour timer expiry or input removal. This enables microprocessor interface using dual pull-up resistors (e.g., 3kΩ + 200kΩ) to distinguish all three states.

Which external charger ICs are explicitly validated with the LTC1729CS8-8.2#TRPBF?

The LTC1729CS8-8.2#TRPBF is explicitly validated with LT1505 (>4A step-down), LT1512 (2A SEPIC), LT1513 (3A SEPIC), and LT1769 (2A step-down) for 2-cell 8.2V applications. These pairings require only six interconnect pins (VC, STATUS, VCC, BAT, SENSE, NTC) and are documented in Figures 1, 12, and 13 of the official datasheet. Compatibility with newer Analog Devices chargers (e.g., LTC4162) requires independent validation.