Analog Devices Inc. LTC1261LIMS8#TRPBF

Overview

LTC1261LIMS8#TRPBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated negative voltage inverter IC designed to generate a stable –4V output from a single 4.5V–5.25V positive supply. It delivers up to 20mA output current with ±4.5% regulation accuracy, features an open-drain REG flag for power-valid indication, and operates in an industrial temperature range (–40°C to +85°C). It is used in GaAs FET bias generation and battery-powered systems requiring compact, low-quiescent-power negative rails.

For engineers reviewing the LTC1261LIMS8#TRPBF datasheet, LTC1261LIMS8#TRPBF pinout, LTC1261LIMS8#TRPBF application, or LTC1261LIMS8#TRPBF equivalent, key selection criteria include fixed –4V output regulation, shutdown current of 5µA, MSOP-8 package compatibility, REG pin behavior under ±5% output tolerance, and capacitor-based charge-pump topology requiring only three external components.

Technical Context

The LTC1261LIMS8#TRPBF implements a 650kHz internal oscillator-driven inverting charge pump with feedback regulation via an internal 1.23V reference and comparator-controlled duty-cycle truncation. Output voltage is stabilized by monitoring a divided replica of VOUT at the ADJ/COMP pin relative to this reference.

Its REG pin functions as an open-drain indicator that pulls low when |VOUT| is within 5% of the setpoint (e.g., ≥ –3.8V for –4V output), sinking up to 5mA at 5V VCC. Shutdown is asserted by pulling SHDN high, disabling the pump and reducing quiescent current to 5µA typical.

Key Specifications

Pinout & Package

Package: 8-lead plastic MSOP (MS8), 3.0mm × 3.0mm × 0.86mm body, 0.65mm pitch, exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar regulated negative voltage inverter applications.

Compared with MAX680ESA+ and LTC1044CS8#PBF, the LTC1261LIMS8#TRPBF uniquely combines factory-trimmed –4V output, integrated REG flag, and industrial temperature rating - making it optimal for GaAs bias and battery-sensitive instrumentation where accuracy and system awareness are mandatory.

Availability

LTC1261LIMS8#TRPBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, battery-powered instrumentation, and single-supply analog signal chains requiring stable component supply and guaranteed industrial-temperature performance.

Supply support for LTC1261LIMS8#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 maintains full product support, documentation, and manufacturing continuity for legacy Linear parts including the LTC1261L series.

The LTC1261LIMS8#TRPBF belongs to Linear's precision switched-capacitor voltage inverter family, engineered specifically for compact, low-power negative rail generation in RF, portable, and industrial analog systems where inductors are prohibited.

FAQ

What is the guaranteed output voltage accuracy of the LTC1261LIMS8#TRPBF?

The LTC1261LIMS8#TRPBF guarantees ±4.5% output regulation over its full industrial temperature range (–40°C to +85°C), supply voltage (4.35V–5.25V), and load current (0–20mA). This means the actual output remains between –3.82V and –4.18V under all specified conditions - a specification confirmed in the Electrical Characteristics table on page 3 of the official datasheet.

Does the LTC1261LIMS8#TRPBF require external resistors to set its –4V output?

No, the LTC1261LIMS8#TRPBF does not require external resistors. It is the fixed –4V variant (LTC1261L-4) with internal resistor divider connected to the COMP pin. Unlike the adjustable LTC1261L version, no external R1/R2 network is needed - simplifying layout and eliminating resistor tolerance errors that affect output accuracy.

How does the REG pin on the LTC1261LIMS8#TRPBF behave during startup and regulation?

The REG pin on the LTC1261LIMS8#TRPBF is an open-drain output that remains high-impedance until VOUT reaches ≥95% of its nominal value (i.e., ≥ –3.8V for –4V output), then pulls low to indicate regulation. It sinks up to 5mA at 5V VCC and can be pulled up to 6V - enabling direct interfacing with 3.3V or 5V logic without level shifters.

What external capacitors are mandatory for stable operation of the LTC1261LIMS8#TRPBF?

Three mandatory capacitors are required: a 0.1µF ceramic flying capacitor between C1+ and C1–, a ≥1µF ceramic input bypass capacitor from VCC to GND, and a ≥3.3µF low-ESR output capacitor from OUT to GND. An optional 100pF capacitor from COMP to GND further reduces output ripple by stabilizing the regulation loop bandwidth.

Can the LTC1261LIMS8#TRPBF operate below 4.35V supply voltage?

The LTC1261LIMS8#TRPBF may function below 4.35V, but output regulation is not guaranteed per datasheet specifications. The Electrical Characteristics table explicitly defines minimum VCC = 4.35V for the –4V output version; operation at lower voltages risks exceeding ±4.5% regulation error and reduced output current capability - verified in Figure G04 (Output Voltage vs Supply Voltage) on page 4.