Analog Devices Inc. LTC1261CS8-4.5#PBF

Overview

LTC1261CS8-4.5#PBF from Analog Devices (formerly Linear Technology) is a fixed-output switched-capacitor voltage inverter IC that generates a regulated –4.5V negative supply from a single 3V–8V positive input. It delivers up to 12mA output current with ±5% regulation, features an open-drain REG pin indicating regulation status, and operates with only one external 0.1µF flying capacitor in SO-8 package. It is used in battery-powered systems requiring compact, low-noise dual-rail supplies.

For engineers reviewing the LTC1261CS8-4.5#PBF datasheet, LTC1261CS8-4.5#PBF pinout, LTC1261CS8-4.5#PBF application, or LTC1261CS8-4.5#PBF equivalent, key selection criteria include fixed –4.5V output, 550kHz internal oscillator, shutdown mode (5µA quiescent), REG flag functionality, and SO-8 thermal performance (θ_JA = 150°C/W).

Technical Context

The LTC1261CS8-4.5#PBF implements a doubler-mode charge pump topology with internal 550kHz oscillator and precision 1.24V bandgap reference. Regulation is achieved via cycle-by-cycle duty-cycle control of the charge transfer switch, where COMP1 compares a divided output against V_REF to modulate pumping activity.

Its fixed –4.5V output is set by an on-die resistor string connected internally to the ADJ/COMP pin; no external resistors are required. The REG pin functions as an open-drain indicator sinking up to 8mA when |V_OUT| is within 5% of –4.5V, and supports pull-up voltages up to 12V.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (SO-8), 150°C/W junction-to-ambient thermal resistance, commercial temperature range (0°C to 70°C).

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 LTC1261CS8-4.5#PBF offers tighter regulation (±5% vs ±10%), lower ripple (5mV vs >20mV), integrated REG signaling, and smaller external component count-making it optimal for compact, precision analog systems needing verified –4.5V rails.

Availability

LTC1261CS8-4.5#PBF is available at Aetrix Electronics and suitable for portable medical sensors, industrial data acquisition modules, automotive infotainment audio subsystems, and test & measurement equipment requiring stable component supply and guaranteed commercial-temperature performance.

Supply support for LTC1261CS8-4.5#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, acquired Linear Technology in 2017 to expand its power management portfolio.

The LTC1261 product line was designed specifically for compact, low-noise, capacitor-based negative voltage generation in space- and power-sensitive applications-targeting portable instrumentation, sensor interfaces, and precision analog signal chains.

FAQ

What is the output voltage tolerance of the LTC1261CS8-4.5#PBF over temperature and load?

The LTC1261CS8-4.5#PBF guarantees ±5% output regulation over the full commercial temperature range (0°C to 70°C) and for output currents from 0mA to 10mA. At 5mA load and 25°C, typical deviation is <±1%. This specification is confirmed in the Electrical Characteristics table under "Output Regulation" for the –4.5V variant, with test conditions explicitly referencing 0 ≤ I_OUT ≤ 6mA and –4.5V ≥ V_OUT ≥ –5V.

Can the LTC1261CS8-4.5#PBF operate from a 3.3V input supply?

Yes, the LTC1261CS8-4.5#PBF operates from 3V to 8V input. At 3.3V input, it delivers –4.5V output with full regulation up to 6mA load (per Electrical Characteristics). Performance remains within ±5% regulation, though maximum output current decreases versus 5V operation. The device's doubler architecture ensures stable inversion even at minimum supply.

How does the REG pin on the LTC1261CS8-4.5#PBF function, and what pull-up voltage can it tolerate?

The REG pin on the LTC1261CS8-4.5#PBF is an open-drain output that pulls low when |V_OUT| is within 5% of –4.5V (i.e., between –4.275V and –4.725V). It sinks up to 8mA with a 5V V_CC. The pin is rated for pull-up voltages up to 12V above ground-enabling direct interfacing with 3.3V, 5V, or 12V logic systems without level-shifting.

What external capacitors are mandatory for basic operation of the LTC1261CS8-4.5#PBF?

Three capacitors are mandatory: (1) 0.1µF ceramic flying capacitor between C1+ and C1–, (2) ≥0.1µF ceramic bypass capacitor from VCC to GND, and (3) ≥3.3µF low-ESR output capacitor from OUT to GND. A 100pF capacitor from COMP to GND is optional but recommended to minimize output ripple under dynamic loads.

Is the LTC1261CS8-4.5#PBF pin-compatible with other variants in the LTC1261 family, such as the LTC1261CS8-4#PBF?

Yes-the LTC1261CS8-4.5#PBF shares identical SO-8 pinout, electrical interface, and functional behavior with other LTC1261CS8-x variants (e.g., -4#PBF, -5#PBF). Only the internal resistor string differs to set the fixed output voltage; all other pins (SHDN, REG, COMP, etc.) retain identical roles and timing characteristics.