Analog Devices Inc. LTC4008EGN#PBF

Overview

LTC4008EGN#PBF from Analog Devices is a synchronous, constant-current/constant-voltage battery charger controller for Li-ion, Li-polymer, and multi-chemistry batteries. It delivers up to 4A charge current with ±0.8% voltage accuracy, 96% peak efficiency, and supports 6V–28V input / 3V–28V output ranges. Designed for notebook computers and portable instruments, it integrates thermistor-based temperature qualification, AC adapter current limiting, and dual gate drivers for external N/P-MOSFETs.

For engineers reviewing the LTC4008EGN#PBF datasheet, LTC4008EGN#PBF pinout, LTC4008EGN#PBF application, or LTC4008EGN#PBF equivalent, key selection criteria include its ±4% charge current programming accuracy, 98% maximum duty cycle, 300kHz quasi-constant-frequency PWM architecture, thermistor sampling interval control via RT pin, and integrated input FET driver (present in LTC4008 but not LTC4008-1).

Technical Context

The LTC4008EGN#PBF implements a synchronous, current-mode, constant-off-time buck converter architecture with quasi-constant switching frequency (255–345kHz) to avoid audible noise with ceramic capacitors. Its inner loop uses ITH voltage to regulate peak inductor current, while outer loops manage voltage regulation (via VFB/BATMON), input current limiting (CLP/CLN), and thermistor-based safety shutdown (NTC/FAULT).

It features dual gate drivers (TGATE/BGATE) for external high-side PMOS and low-side NMOS switches, plus an integrated INFET driver for input P-MOSFET control - enabling reverse-current protection, AC-present indication (ACP/SHDN), and adaptive input current limiting. The device operates across –40°C to 125°C junction temperature with 90°C/W thermal resistance in its 20-pin narrow SSOP package.

Key Specifications

Pinout & Package

Package: 20-lead narrow plastic SSOP (GN), RoHS-compliant, operating junction temperature range –40°C to 125°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC4008EGN-1#PBF and BQ24725ARHRT, the LTC4008EGN#PBF uniquely combines analog thermistor qualification, integrated input FET control, and standalone operation - making it optimal for cost-sensitive, microcontroller-free, safety-critical portable chargers.

Availability

LTC4008EGN#PBF is available at Aetrix Electronics and suitable for notebook computers, portable instruments, and battery backup systems requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant manufacturing.

Supply support for LTC4008EGN#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 (now part of Analog Devices, Inc. following merger with Linear Technology) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.

The LTC4008EGN#PBF belongs to Linear Technology's precision battery management product line, designed specifically for high-efficiency, multi-chemistry, thermally qualified charging in space- and thermal-constrained portable electronics.

FAQ

What is the function of the RT pin on the LTC4008EGN#PBF?

The RT pin on the LTC4008EGN#PBF sets the thermistor sampling interval via an external 150kΩ resistor. It controls a clock that governs the sample-and-hold timing for NTC measurements: ~6.7ms sampling duration followed by ~26µs hold time. This enables JEITA-compliant temperature qualification without requiring external timing circuitry or firmware intervention. The LTC4008EGN#PBF relies on this pin to suspend charging if battery temperature exceeds safe thresholds.

Does the LTC4008EGN#PBF support LiFePO₄ battery chemistry?

Yes, the LTC4008EGN#PBF supports LiFePO₄ batteries through its wide 3V–28V programmable output voltage range and external resistor-divider-based float voltage setting. Using the internal 1.19V reference and appropriate R8/R9 values (e.g., R8 = 100kΩ, R9 = 30.1kΩ for 5.2V float), users can configure precise termination voltages required by LiFePO₄ cells. Its ±0.8% voltage accuracy ensures safe and repeatable full-charge cutoff, and the thermistor input provides essential temperature qualification during charging.

How does the LTC4008EGN#PBF handle input current limiting?

The LTC4008EGN#PBF implements analog input current limiting using the CLP and CLN pins. A 100mV threshold between CLP and CLN triggers the CL1 amplifier to reduce the ITH voltage, thereby lowering charge current proportionally. The ICL pin asserts low to signal this condition, allowing the host system to adapt its power budget. Unlike digital current limiting, this method operates continuously and autonomously - maximizing charge rate under marginal AC adapters without interrupting the charging cycle. The LTC4008EGN#PBF maintains regulation even during sustained input current limiting.

What is the difference between LTC4008EGN#PBF and LTC4008EGN-1#PBF?

The LTC4008EGN#PBF includes a functional INFET driver (Pin 20) and full ACP/SHDN functionality (Pin 3), enabling automatic reverse-current protection and AC-present detection. The LTC4008EGN-1#PBF disables the INFET driver (Pin 20 = NC) and reduces ACP/SHDN to shutdown-only operation. Both share identical pinout, package, and core charging functions, but only the LTC4008EGN#PBF provides integrated input FET control. This makes the LTC4008EGN#PBF suitable for designs requiring autonomous adapter detection and reverse-current blocking without external drivers.

Can the LTC4008EGN#PBF operate in dropout mode?

Yes, the LTC4008EGN#PBF supports dropout operation with up to 98% maximum duty cycle and a 0.5V dropout voltage specification. When input voltage approaches battery voltage, the controller extends switch-on time to maintain regulation - enabling charging from sources like 12.8V adapters into 12.6V Li-ion packs. Its constant-off-time architecture adapts frequency downward to ~20–25kHz in dropout, and the integrated PWM watchdog prevents audible noise by injecting brief gate pulses if switching stalls. This behavior is confirmed in the LTC4008EGN#PBF's electrical characteristics table and typical performance plots.