Analog Devices Inc. LTC3559EUD-1#TRPBF

Overview

LTC3559EUD-1#TRPBF from Analog Devices (formerly Linear Technology) is a highly integrated linear USB battery charger with dual monolithic synchronous buck regulators, designed for single-cell Li-Ion/Polymer handheld systems. It delivers up to 950mA charge current (programmable via PROG pin), provides two independent 400mA buck outputs (1.2V and 2.5V typical), and includes NTC-based temperature-qualified charging, internal timer termination, and bad-battery detection - enabling compact, thermally robust power management in portable medical monitors and low-power IoT edge nodes.

For engineers reviewing the LTC3559EUD-1#TRPBF datasheet, LTC3559EUD-1#TRPBF pinout, LTC3559EUD-1#TRPBF application, or LTC3559EUD-1#TRPBF equivalent, key selection criteria include its 4.100V float voltage (LTC3559-1 variant), 2.25MHz fixed-frequency buck operation, Burst Mode®/pulse-skip mode flexibility via MODE pin, thermal regulation at ~105°C, and compatibility with USB 2.0 power profiles (100mA/500mA via HPWR control).

Technical Context

The LTC3559EUD-1#TRPBF integrates a linear battery charger with dual independent buck regulators sharing a common PVIN input tied to BAT. Its charger employs constant-current/constant-voltage algorithm with programmable 4.100V ±15mV float voltage (LTC3559-1 spec), 4-hour safety timer, and automatic recharge triggered below VRECHRG = VFLOAT –100mV. Trickle charge activates below 2.9V with 36–56mA current and latches bad-battery state after 0.5 hours.

Each buck regulator operates at 2.25MHz (±14%), supports 3V–4.2V PVIN input, delivers up to 400mA output, and features selectable operating modes: low-noise pulse-skip (MODE = 0) or high-efficiency Burst Mode® (MODE = 1). Feedback reference is 800mV (±20mV), with <0.05μA FB input bias and <500mΩ PMOS R_DS(ON) at 150mA.

Key Specifications

Pinout & Package

Package: 16-lead (3mm × 3mm) QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad for rated thermal performance (θ_JA = 68°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar battery charger + dual buck regulator applications.

Compared with MAX14744EWA+T and BQ24195RGER, the LTC3559EUD-1#TRPBF uniquely combines NTC-based thermal safety, dual independent bucks, and USB-compliant current scaling in a 3mm × 3mm QFN - making it optimal for compact, safety-certified portable medical and industrial devices where reliability trumps raw efficiency or configurability.

Availability

LTC3559EUD-1#TRPBF is available at Aetrix Electronics and suitable for portable medical monitors, wearable health sensors, industrial handheld terminals, and smart asset tags requiring stable component supply across multi-year production cycles.

Supply support for LTC3559EUD-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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial automation, and healthcare markets.

The LTC3559EUD-1#TRPBF belongs to Linear's Power Management product line, engineered specifically for space-constrained, battery-powered portable electronics requiring integrated charging, dual regulated rails, and robust thermal/safety compliance.

FAQ

What is the exact float voltage specification for the LTC3559EUD-1#TRPBF?

The LTC3559EUD-1#TRPBF has a nominal float voltage of 4.100V, with guaranteed min/max values of 4.065V and 4.135V across the –40°C to 85°C operating temperature range. This 4.1V setting distinguishes it from the standard LTC3559 (4.2V float) and is optimized for Li-Ion cells requiring lower termination voltage to extend cycle life.

How does the HPWR pin affect charge current in the LTC3559EUD-1#TRPBF?

In the LTC3559EUD-1#TRPBF, the HPWR pin selects between two charge current levels: when pulled above 1.2V, it enables 100% of the current set by the PROG resistor (e.g., 500mA with 1.74kΩ); when pulled below 0.4V, it reduces current to 20% (e.g., 100mA). This allows seamless compliance with USB 2.0 low-power (100mA) and high-power (500mA) port specifications.

Can the LTC3559EUD-1#TRPBF operate with only one buck regulator enabled?

Yes, the LTC3559EUD-1#TRPBF supports independent control of each buck regulator via EN1 and EN2 pins. Either regulator can be disabled while the other remains active - for example, enabling only the 1.2V rail for MCU core power while disabling the 2.5V rail until peripheral initialization - reducing system quiescent current by up to 35μA.

What happens to the LTC3559EUD-1#TRPBF during thermal overload?

When the LTC3559EUD-1#TRPBF die temperature reaches approximately 105°C, its internal thermal regulation loop activates and progressively reduces the battery charge current to maintain safe junction temperature. This occurs without interrupting buck regulator operation or requiring external circuitry, preserving system functionality while preventing thermal damage.

How does the CHRG pin indicate a bad battery condition on the LTC3559EUD-1#TRPBF?

The LTC3559EUD-1#TRPBF drives the CHRG pin with a 35kHz square wave modulated at 6.1Hz (duty cycle alternating between 12.5% and 87.5%) to signal a bad battery - distinct from the 1.5Hz NTC fault pattern. This unique blink signature allows both human operators (via LED) and host microcontrollers to reliably distinguish unresponsive battery events from temperature faults.