Analog Devices Inc. LTC4425EMSE#PBF

Overview

LTC4425EMSE#PBF from Analog Devices (formerly Linear Technology) is a linear supercapacitor charger with integrated ideal diode, active cell balancing, and voltage clamping for 2-cell series supercap stacks. It delivers up to 2A charge current, features 50mΩ ideal diode on-resistance, programmable 2.45V/2.7V per-cell clamp, and operates from 2.7V–5.5V input to support Li-Ion, USB, or current-limited supplies in backup power systems.

For engineers reviewing the LTC4425EMSE#PBF datasheet, LTC4425EMSE#PBF pinout, LTC4425EMSE#PBF application, or LTC4425EMSE#PBF equivalent, key selection criteria include its dual-mode charging (LDO vs. smart current profile), real-time VIN–VOUT current monitoring via PROG pin, internal leakage balancer eliminating external resistors, thermal regulation at 105°C, and MSOP-12 package compatibility with space-constrained industrial PDAs and portable instrumentation.

Technical Context

The LTC4425EMSE#PBF implements a constant-current/constant-voltage/constant-temperature architecture with two distinct operating modes: LDO mode (FB grounded) for fixed-output voltage regulation, and normal mode (FB tied to VIN) for VIN-following with adaptive current limiting based on VIN–VOUT differential. Its ideal diode controller maintains 15mV forward drop and blocks reverse current.

Internal circuitry includes a precision 1.2V feedback reference, 1000× current-sense ratio between PROG and VOUT paths, dual shunt transistors (PMOS top / NMOS bottom) for cell voltage clamping, and an active VMID balancer that forces midpoint voltage to exactly VOUT/2 with ±1mA sourcing/sinking capability-enabling passive balancing without external components.

Key Specifications

Pinout & Package

The LTC4425EMSE#PBF is housed in a 12-lead plastic MSOP package with exposed GND pad (Pin 13) requiring PCB thermal vias for optimal heat dissipation. Pin functions are validated per Linear Technology's official Datasheet Rev. D (4425fa).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC3225EDE#PBF and BQ24650RGER, the LTC4425EMSE#PBF uniquely integrates ideal diode conduction, per-cell voltage clamping, and active midpoint balancing in a single MSOP-12 package-reducing component count by ≥7 parts and eliminating layout-sensitive external balancing networks.

Availability

LTC4425EMSE#PBF is available at Aetrix Electronics and suitable for industrial portable instruments, USB-powered backup systems, power meter energy storage, and medical monitoring equipment requiring stable component supply across extended temperature ranges (–40°C to 125°C).

Supply support for LTC4425EMSE#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 product support, documentation, and manufacturing continuity for all Linear ICs including the LTC4425 family.

The LTC4425EMSE#PBF belongs to Linear's supercapacitor management product line, designed specifically for high-reliability backup power systems requiring precise cell voltage control, minimal quiescent power, and seamless source transition without external discrete components.

FAQ

What is the maximum supercapacitor stack voltage supported by the LTC4425EMSE#PBF?

The LTC4425EMSE#PBF supports a 2-cell series supercapacitor stack with maximum total voltage of 4.9V (2.45V per cell) or 5.4V (2.7V per cell), selected via the SEL pin. It does not support 3-cell or higher stacks, and exceeding these voltages risks permanent damage to the internal clamp circuitry and supercap cells.

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

The LTC4425EMSE#PBF uses an internal leakage balancing amplifier (LBA) that actively drives the VMID pin to exactly VOUT/2. This circuit sources or sinks up to ±1mA to correct minor voltage mismatches caused by capacitor leakage variance, eliminating the need for power-wasting 100kΩ external balancing resistors typically required in passive designs.

Can the LTC4425EMSE#PBF operate with the input voltage lower than the output voltage?

Yes - when EN is high and VIN falls below VOUT or floats, the LTC4425EMSE#PBF remains partially active, drawing only 20µA from VOUT to sustain monitoring functions (PFO, clamp comparators). However, the VMID balancer disables in this state, and no charging occurs until VIN rises above VOUT minus 250mV.

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

Beyond programming charge current via R_PROG, the PROG pin provides real-time analog monitoring of actual VOUT current: V_PROG = I_CHG × R_PROG / 1000. This enables system microcontrollers to log charge progress, detect faults (e.g., open-circuit stack), and implement adaptive charge algorithms without adding sense resistors or ADC channels.

Does the LTC4425EMSE#PBF require external compensation components for stability?

No external compensation is needed for typical supercapacitor loads ≥0.2F in LDO mode. In constant-current mode, stability relies on minimizing capacitance at the PROG pin - additional C_PROG reduces maximum allowable R_PROG per R_PROG ≤ 1/(2π × 100kHz × C_PROG). Layout best practice is to keep PROG trace short and avoid nearby noisy signals or ground planes.