Analog Devices Inc. LT1505CG-1#PBF

Overview

LT1505CG-1#PBF from Analog Devices (formerly Linear Technology) is a synchronous PWM battery charger controller for Li-Ion, NiMH, and NiCd chemistries. It delivers up to 4A charging current with 0.5% voltage accuracy, 5% current accuracy, and 0.5V dropout-enabling high-efficiency fast charging in notebook computers and portable instruments.

For engineers reviewing the LT1505CG-1#PBF datasheet, LT1505CG-1#PBF pinout, LT1505CG-1#PBF application, or LT1505CG-1#PBF equivalent, key selection criteria include preset 12.3V/12.6V/16.4V/16.8V battery voltage support, resistor- or DAC-programmable charge current, 200kHz switching frequency, and absence of input current limiting (per datasheet note).

Technical Context

The LT1505CG-1#PBF implements a synchronous current-mode buck topology with dual control loops: constant-current/constant-voltage regulation for battery charging and internal 9.1V GBIAS regulator for gate drivers. Its VC pin controls inner-loop current programming, while VFB, 4.1V, 4.2V, and 3CELL pins configure preset battery voltages via internal resistor networks.

Unlike the standard LT1505, the LT1505CG-1#PBF omits CLP/CLN/COMP1 functionality-no input current limiting-and requires COMP1 tied to GND. It retains full 28-pin SSOP package compatibility, 0.5V dropout operation, and 10µA shutdown quiescent current, but disables the adapter current limit loop per datasheet specification.

Key Specifications

Pinout & Package

LT1505CG-1#PBF is housed in a 28-lead plastic SSOP (G package) with 0.635mm pitch. Thermal resistance θJA = 100°C/W; maximum junction temperature TJMAX = 125°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery charger controller applications.

Compared with LTC4000-1 and MP2617, LT1505CG-1#PBF provides the highest voltage accuracy (0.5%) and simplest preset-based configuration for fixed-output Li-Ion chargers, while omitting input current limiting to reduce complexity and cost in applications where adapter overload protection is managed externally.

Availability

LT1505CG-1#PBF is available at Aetrix Electronics and suitable for notebook computers, portable medical monitors, and industrial handheld scanners requiring stable component supply, long-lifecycle availability, and commercial-temperature-grade reliability.

Supply support for LT1505CG-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 its legacy precision analog and power management product lines with full datasheet, simulation model, and application support.

The LT1505 family was designed as a high-efficiency, synchronous PWM battery charger controller targeting portable computing and instrumentation-emphasizing low dropout, preset voltage flexibility, and minimal external component count.

FAQ

What is the key functional difference between LT1505CG-1#PBF and the standard LT1505?

The LT1505CG-1#PBF omits the input current limiting function: CLP, CLN, and COMP1 pins are not connected internally and must be tied to GND (COMP1) per datasheet. This removes adapter current limiting capability while retaining all battery charging control, preset voltage selection, and 0.5V dropout features of the base LT1505. The LT1505CG-1#PBF is intended for applications where adapter overload protection is handled externally or not required.

How do I configure LT1505CG-1#PBF for a 12.6V (3-cell Li-Ion) battery pack?

To configure LT1505CG-1#PBF for 12.6V output, short pins 4.2V (15), VFB (17), and 3CELL (16) together. Connect BAT2 (20) to the battery positive terminal. This activates the internal 3×4.2V resistor divider, setting the constant-voltage regulation point to 12.6V with ±0.5% accuracy. Ensure PROG (19) is connected to RPROG to set desired charging current, and VC (18) has a 0.33µF soft-start capacitor.

Does LT1505CG-1#PBF support NiMH or NiCd battery chemistries?

Yes, LT1505CG-1#PBF supports NiMH and NiCd batteries via its constant-current charging mode and overvoltage protection using the VA amplifier. Unlike Li-Ion, NiMH/NiCd require only CC charging with voltage cutoff; the LT1505CG-1#PBF's 0.5V dropout and 4A capability enable fast charging, while the FLAG pin can indicate approximate full-charge via dV/dt or -ΔV detection when interfaced with external circuitry.

What is the purpose of the INFET pin on LT1505CG-1#PBF, and how is it used?

The INFET pin (8) on LT1505CG-1#PBF drives an external P-channel MOSFET placed between the AC adapter and VCC. When VCC drops near VBAT, the INFET driver pulls the PFET gate low to maintain VCC regulation-enabling operation with VCC as low as VBAT + 0.4V. This achieves ultra-low dropout, critical for charging from marginal or aging adapters. A typical implementation uses a Si2301 or similar logic-level PFET with gate tied to INFET and source to adapter input.

Can LT1505CG-1#PBF be synchronized to an external clock, and what are the requirements?

Yes, LT1505CG-1#PBF supports external synchronization via the SYNC pin (4). It accepts TTL/CMOS-compatible pulses with 10%–95% duty cycle and frequency range 240–280kHz. The internal one-shot triggered on the rising edge makes it insensitive to sync pulse duty cycle. For reliable locking, apply a clean 3.3V or 5V square wave; floating SYNC disables synchronization and reverts to internal 200kHz oscillator.