Analog Devices Inc. LTC4425EMSE#TRPBF

Overview

LTC4425EMSE#TRPBF from Analog Devices (formerly Linear Technology) is a linear supercapacitor charger with integrated ideal diode, active cell balancer, and V/I monitoring-designed to charge 2-cell series supercap stacks from Li-Ion, USB, or 2.7V–5.5V current-limited sources. It delivers 50mΩ ideal diode conduction, programmable 0.2A–2A charge current, and dual-mode operation (LDO/normal), enabling high peak-power backup in portable instrumentation and power meters.

For engineers reviewing the LTC4425EMSE#TRPBF datasheet, LTC4425EMSE#TRPBF pinout, LTC4425EMSE#TRPBF application, or LTC4425EMSE#TRPBF equivalent, key selection criteria include its 2.45V/2.7V per-cell clamp voltage selection via SEL pin, VMID-based leakage balancing without external resistors, PROG-pin current monitoring (1000× scaling), thermal regulation at 105°C, and compatibility with 12-lead MSOP packaging for space-constrained industrial designs.

Technical Context

The LTC4425EMSE#TRPBF implements a three-loop control architecture: constant-current, constant-voltage, and constant-temperature regulation. Its ideal diode controller maintains 15mV forward drop by dynamically adjusting the gate of the internal PMOS pass device, while the charge current profile mode linearly scales output current from 10% to 100% as VIN–VOUT decreases from 750mV to 250mV.

Internal circuitry includes a precision 1.2V feedback reference, 2.45V/2.7V selectable cell voltage clamps with 50mV hysteresis, bidirectional shunt transistors (PMOS top / NMOS bottom), and an active VMID balancer that forces midpoint voltage to exactly VOUT/2 with ±1mA sourcing/sinking capability-eliminating need for external balancing resistors.

Key Specifications

Pinout & Package

Package: 12-lead plastic MSOP (3mm × 4.9mm, 0.65mm pitch), exposed pad (Pin 13) connected to GND for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX17222ETA+T and BQ24650RGER, the LTC4425EMSE#TRPBF uniquely integrates ideal diode conduction, active cell balancing, and dual-mode charging in a single 12-lead MSOP-reducing component count by ≥7 parts while enabling precise per-cell voltage control essential for supercap longevity.

Availability

LTC4425EMSE#TRPBF is available at Aetrix Electronics and suitable for industrial power meters, portable medical monitors, smart grid modules, and USB-powered test equipment requiring stable component supply with guaranteed long-term availability.

Supply support for LTC4425EMSE#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 and continues to manufacture, qualify, and support all Linear ICs-including the LTC4425 family-with full documentation, reliability data, and application engineering resources.

The LTC4425 product line was designed specifically for high-reliability supercapacitor backup systems in industrial and portable instrumentation, emphasizing low quiescent current, precise cell voltage control, and integrated fault protection without external passive components.

FAQ

What is the function of the SEL pin on the LTC4425EMSE#TRPBF?

The SEL pin on the LTC4425EMSE#TRPBF selects the per-cell voltage clamp threshold: logic low sets 2.45V, logic high sets 2.7V. This directly controls the maximum voltage applied to each supercapacitor in the 2-cell stack, preventing overvoltage stress and electrolyte breakdown. The LTC4425EMSE#TRPBF uses internal comparators and shunt transistors to enforce this limit with 50mV hysteresis, and the pin must not be left floating to ensure predictable protection behavior.

How does the LTC4425EMSE#TRPBF implement active cell balancing without external resistors?

The LTC4425EMSE#TRPBF uses an internal leakage balancing amplifier (LBA) that drives the VMID pin to exactly VOUT/2, maintaining equal voltage across both supercapacitors. It sources or sinks up to ±1mA to correct minor mismatches caused by capacitor leakage variance. This eliminates the need for external 100kΩ balancing resistors, reducing BOM cost and board area while improving long-term reliability. The LTC4425EMSE#TRPBF's LBA operates only when VIN is present and is disabled during VOUT-only operation.

Can the LTC4425EMSE#TRPBF operate with VIN lower than VOUT?

Yes-the LTC4425EMSE#TRPBF supports VOUT > VIN operation when EN is high and VIN is absent or below VOUT. In this mode, it draws only 20µA from the supercap stack to maintain VMID monitoring and clamp circuitry, but disables the leakage balancer. The ideal diode remains off, preventing reverse current flow. This enables maintenance of backup voltage integrity during primary source removal, a critical capability for the LTC4425EMSE#TRPBF in fail-safe power architectures.

What is the purpose of the PROG pin beyond setting charge current?

Beyond programming charge current via RPROG-to-GND, the PROG pin on the LTC4425EMSE#TRPBF provides continuous real-time current monitoring: VPROG = ICHG / 1000, so measuring voltage at PROG yields exact charge current without external sense resistors. During soft-start, it ramps from 0V to 1V over ~1.5ms; during thermal regulation or clamp activation, it drops proportionally to reduced current-making the LTC4425EMSE#TRPBF's PROG pin a unified interface for programming, monitoring, and fault diagnostics.

How does the LTC4425EMSE#TRPBF handle thermal overload?

The LTC4425EMSE#TRPBF employs dual thermal protection: a constant-temperature regulator reduces charge current to hold junction temperature at ~105°C, and a hard thermal shutdown cuts all functions at 160°C with automatic recovery at ~146°C. During regulation, the PROG pin continues to reflect actual current, enabling closed-loop thermal management. This allows designers to size heatsinking based on typical ambient conditions while relying on the LTC4425EMSE#TRPBF to self-limit under worst-case scenarios-critical for sealed industrial enclosures.