Analog Devices Inc. LTC4085EDE-1#TRPBF

Overview

LTC4085EDE-1#TRPBF from Analog Devices (formerly Linear Technology) is a USB power manager and linear Li-ion battery charger IC with integrated ideal diode control, designed for portable USB-powered devices. It delivers 4.1V float voltage charging, supports up to 500mA input current limit (100% mode) or 100mA (20% mode), and provides seamless power-path management between USB, wall adapter, and single-cell Li-ion battery. It is used in MP3 players, digital cameras, and PDAs requiring thermal-safe battery charging above 60°C.

For engineers reviewing the LTC4085EDE-1#TRPBF datasheet, LTC4085EDE-1#TRPBF pinout, LTC4085EDE-1#TRPBF application, or LTC4085EDE-1#TRPBF equivalent, key selection considerations include its 4.1V fixed float voltage for high-temperature battery longevity, load-dependent charge current reduction to maintain USB compliance, internal 215mΩ ideal diode, NTC thermistor interface, and 14-lead 4mm × 3mm DFN package with exposed pad thermal grounding.

Technical Context

The LTC4085EDE-1#TRPBF implements a dual-loop PowerPath™ architecture: one loop regulates input current via CLPROG/HPWR to enforce USB-compliant limits (e.g., 100mA/500mA), while the other manages constant-current/constant-voltage (CC/CV) charging at 4.1V with ±0.8% accuracy. Its internal ideal diode enables sub-20mV forward drop activation and automatic BAT-to-OUT power switchover when IN is absent or overloaded.

Thermal regulation operates at 105°C junction temperature, and battery safety is enforced via NTC monitoring (cold/hot fault thresholds), C/10 termination detection, and programmable timer-based charge timeout. The device supports wall adapter detection (WALL pin), suspend mode (SUSP), and external PFET gate drive (GATE) for lower conduction loss.

Key Specifications

Pinout & Package

Package: 14-lead (4mm × 3mm) plastic DFN with exposed pad (Pin 15 = GND). Thermal pad must be soldered to PCB ground plane for proper thermal performance and electrical reference.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar USB power management and Li-ion charging applications.

Compared with MAX1555 and BQ24075, the LTC4085EDE-1#TRPBF uniquely combines 4.1V precision float voltage, integrated NTC monitoring, and wall adapter arbitration in a thermally optimized DFN - making it the only option qualified for long-life, high-temperature Li-ion applications with dual-input power sources.

Availability

LTC4085EDE-1#TRPBF is available at Aetrix Electronics and suitable for portable USB cameras, medical handheld monitors, and industrial PDAs requiring stable component supply, long-term lifecycle support, and guaranteed high-temperature battery safety compliance.

Supply support for LTC4085EDE-1#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and healthcare markets.

The LTC4085EDE-1#TRPBF belongs to Linear's PowerPath™ family of battery charging and power management ICs, engineered specifically for USB-powered portable devices needing intelligent dual-input arbitration, thermal-safe Li-ion charging, and minimal external component count.

FAQ

What is the purpose of the 4.1V float voltage in the LTC4085EDE-1#TRPBF?

The 4.1V float voltage in the LTC4085EDE-1#TRPBF is a factory-preset, precision-regulated battery termination voltage with ±0.8% accuracy. It is specifically selected to improve long-term capacity retention and mechanical stability of Li-ion cells operated or stored above ~60°C - reducing electrolyte decomposition, minimizing swelling in prismatic and polymer cells, and preventing pressure-triggered CID activation in cylindrical cells. This trade-off sacrifices ~5% initial capacity for significantly extended battery service life under thermal stress.

How does the LTC4085EDE-1#TRPBF ensure USB compliance during variable load conditions?

The LTC4085EDE-1#TRPBF ensures USB compliance by dynamically adjusting battery charge current (I_BAT) in real time so that total input current (I_IN = I_LOAD + I_BAT) never exceeds the programmed limit - whether set to 100% (e.g., 500mA) or 20% (e.g., 100mA) via the HPWR pin. The CLPROG pin provides continuous current monitoring (I_IN = V_CLPROG/R_CLPROG × 1000), enabling closed-loop enforcement without host software intervention.

Can the LTC4085EDE-1#TRPBF charge a battery while powering a load from a wall adapter?

Yes, the LTC4085EDE-1#TRPBF can simultaneously charge the battery and power the load from a wall adapter. When a voltage >4.25V is applied to the WALL pin, the device disconnects the IN-to-OUT path and enables charging from the OUT pin (powered by the wall adapter) to the BAT pin. This is confirmed by the ACPR pin going low and the internal charge controller remaining active - allowing true "wall-powered charging" without requiring separate charger circuitry.

What is the role of the GATE pin on the LTC4085EDE-1#TRPBF?

The GATE pin on the LTC4085EDE-1#TRPBF drives the gate of an optional external P-channel MOSFET connected between BAT and OUT. It functions as an ideal diode controller to reduce conduction loss beyond the internal 215mΩ diode - enabling lower forward voltage drop and higher efficiency during battery backup. When unused, the GATE pin must be left floating; it is not internally terminated and must maintain high impedance to avoid leakage-induced misoperation.

Does the LTC4085EDE-1#TRPBF support battery temperature monitoring, and how is it implemented?

Yes, the LTC4085EDE-1#TRPBF supports battery temperature monitoring via dedicated NTC and VNTC pins. A precision bias voltage (4.4–4.85V) on VNTC feeds a resistor–thermistor divider connected to NTC. Internal comparators detect cold (0.738×V_{VNTC) and hot (0.326×VVNTC) thresholds with hysteresis, automatically pausing charging outside the safe range. No external op-amps, ADCs, or microcontroller firmware are required - the function is fully autonomous and hardware-based.}