Analog Devices Inc. LT1505CG#PBF

Overview

LT1505CG#PBF from Analog Devices (formerly Linear Technology) is a synchronous current-mode PWM battery charger controller for Li-Ion, NiMH, and NiCd chemistries. It delivers up to 4A charging current with 0.5% voltage accuracy at preset outputs (12.3V, 12.6V, 16.4V, 16.8V), 5% current accuracy, and 0.5V dropout - enabling high-efficiency fast charging in notebook computers and portable instruments.

For engineers reviewing the LT1505CG#PBF datasheet, LT1505CG#PBF pinout, LT1505CG#PBF application, or LT1505CG#PBF equivalent, key selection criteria include its 200kHz switching frequency, input current limiting capability (LT1505 variant only), 28-pin SSOP package, and dual-loop constant-current/constant-voltage control architecture optimized for adapter-powered multi-chemistry battery systems.

Technical Context

The LT1505CG#PBF implements a synchronous buck topology with integrated gate drivers for external N-channel MOSFETs (TGATE/BGATE), supporting duty cycles >99.5% via cycle-skipping at low V_IN–V_BAT. Its three independent control loops manage battery charge current (via PROG/VC/CA1/CA2), battery voltage regulation (via VFB/VA/2.465V reference), and AC adapter input current limit (via CLP/CLN/CL1).

It features adaptive low-dropout operation using BOOSTC for CA1 biasing, undervoltage lockout (6.7V UV threshold), open-collector FLAG output signaling Li-Ion charge completion at 20% of programmed current, and micropower shutdown (<10µA battery drain) with automatic sleep mode on adapter removal.

Key Specifications

Pinout & Package

LT1505CG#PBF is housed in a 28-lead plastic SSOP (G package), 0.025" pitch, with exposed thermal pad (not electrically connected). Pin assignments are validated per Linear Technology's official 1505fc datasheet Rev. G.

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, the LT1505CG#PBF uniquely combines integrated adapter current limiting, factory-trimmed multi-chemistry voltage presets, and external FET control - making it optimal for industrial and professional equipment requiring both flexibility and robustness.

Availability

LT1505CG#PBF is available at Aetrix Electronics and suitable for notebook computers, portable medical instruments, multi-chemistry industrial chargers, and lead-acid backup systems requiring stable component supply and long-term design continuity.

Supply support for LT1505CG#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 legacy Linear products including the LT1505 family.

The LT1505 product line was designed specifically for high-efficiency, multi-chemistry battery charging in portable computing and instrumentation - emphasizing precision voltage/current regulation, adapter-aware power management, and robust thermal performance in SSOP packaging.

FAQ

What battery chemistries does the LT1505CG#PBF support?

The LT1505CG#PBF supports lithium-ion (Li-Ion), nickel-metal hydride (NiMH), and nickel-cadmium (NiCd) battery chemistries through configurable constant-current and constant-voltage charging profiles. Its 0.5% voltage accuracy and 5% current accuracy ensure safe, efficient charging across all three types. The LT1505CG#PBF achieves this using internal preset resistor networks for common Li-Ion voltages (12.3V, 12.6V, 16.4V, 16.8V) and flexible PROG pin programming for NiMH/NiCd current levels.

Does the LT1505CG#PBF include input current limiting functionality?

Yes, the LT1505CG#PBF includes dedicated input current limiting via CLP and CLN pins with a 92mV threshold - a feature absent in the LT1505CG-1 variant. This allows the LT1505CG#PBF to dynamically reduce battery charge current when total adapter load (system + charging) approaches its rated limit, preventing adapter overload and enabling simultaneous device operation and fast charging. The LT1505CG#PBF implements true analog closed-loop control for this function.

How is charge completion signaled on the LT1505CG#PBF?

The LT1505CG#PBF signals charge completion via the open-collector FLAG pin, which pulls low when battery charging current drops to 20% of the programmed maximum value - a standard criterion for Li-Ion full-charge detection. This signal is generated by comparator E6 monitoring the filtered current sense signal at the CAP pin. A pull-up resistor is required on FLAG, and the pin can sink ≥1mA. This direct hardware indication eliminates the need for external microcontroller current sampling.

What is the purpose of the BOOSTC pin on the LT1505CG#PBF?

The BOOSTC pin on the LT1505CG#PBF supplies boosted bias voltage to the current sense amplifier (CA1), enabling operation when input voltage (VCC) is as low as 0.4V above battery voltage - extending low-dropout capability beyond standard buck limitations. It requires an external diode and capacitor to generate the elevated rail. If VCC remains ≥3V above VBAT, BOOSTC may be tied to VCC or left floating. Forcing BOOSTC below VCC is prohibited.

What package type and thermal characteristics does the LT1505CG#PBF have?

The LT1505CG#PBF is packaged in a 28-lead plastic SSOP (G package) with θ_JA = 100°C/W and T_JMAX = 125°C. Its exposed thermal pad (though not electrically connected) enhances heat dissipation in high-current applications. The SSOP footprint supports automated assembly and provides adequate creepage for 24V-rated systems. Layout guidelines emphasize separate AGND and PGND planes, minimized SW node area, and localized high-frequency bypassing at VCC and GBIAS pins.