Analog Devices Inc. LTC1261LCS8-4.5#TRPBF

Overview

LTC1261LCS8-4.5#TRPBF from Analog Devices (acquired Linear Technology) is a fixed-output switched-capacitor voltage inverter IC that generates –4.5V from a single 4.75V–5.25V supply, delivers up to 20mA output current, maintains ±4.5% output regulation, and features an open-drain REG pin indicating regulation status within 5% of setpoint - used in GaAs FET bias generation and battery-powered negative supply systems.

For engineers reviewing the LTC1261LCS8-4.5#TRPBF datasheet, LTC1261LCS8-4.5#TRPBF pinout, LTC1261LCS8-4.5#TRPBF application, or LTC1261LCS8-4.5#TRPBF equivalent, key selection considerations include input voltage range (4.75–5.25V), guaranteed –4.5V output at 5mA load, shutdown quiescent current (5µA), REG pin logic behavior, and MSOP/SO-8 package compatibility with 3 external capacitors.

Technical Context

The LTC1261LCS8-4.5#TRPBF implements a 650kHz internal oscillator-driven inverting charge pump topology with feedback regulation referenced to the output rail (not ground). Its control loop compares a divided replica of VOUT at the ADJ/COMP pin against an internal 1.23V reference to modulate charge transfer duty cycle.

Regulation accuracy relies on internal resistor division for fixed –4.5V output, while the REG pin uses a separate 1.17V comparator threshold (5% below 1.23V) to assert low when |VOUT| ≥ 95% of nominal. Shutdown disables the pump and collapses VOUT to 0V, reducing ICC to 5µA.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (S8), 0.150-inch narrow body, JEDEC MS-012AC compliant, thermal resistance θ_JA = 135°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX680ESA+ and LTC1983ES6-5#TRMPBF, the LTC1261LCS8-4.5#TRPBF uniquely combines guaranteed ±4.5% regulation across temperature and load with a dedicated REG pin - making it optimal for applications requiring verified rail readiness, such as GaAs FET biasing and precision analog subsystems.

Availability

LTC1261LCS8-4.5#TRPBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, battery-powered instrumentation, and industrial sensor signal conditioning requiring stable component supply, lead-free compliance, and commercial temperature grade (0°C to 70°C).

Supply support for LTC1261LCS8-4.5#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.

The LTC1261L series belongs to ADI's precision switched-capacitor power management portfolio, designed specifically for low-noise, low-component-count negative voltage generation in RF, portable, and industrial analog systems.

FAQ

What is the minimum input voltage required for stable operation of the LTC1261LCS8-4.5#TRPBF?

The LTC1261LCS8-4.5#TRPBF requires a minimum supply voltage of 4.75V to guarantee ±4.5% output regulation at full load, as specified in the Electrical Characteristics table. Operation below 4.75V is possible but not characterized for regulation performance - the LTC1261LCS8-4.5#TRPBF may deliver unregulated or out-of-spec output under those conditions.

Can the LTC1261LCS8-4.5#TRPBF be used with a 3.3V input supply?

No - the LTC1261LCS8-4.5#TRPBF is not rated for 3.3V operation. Its specified input range is strictly 4.75V to 5.25V. Attempting to power the LTC1261LCS8-4.5#TRPBF from 3.3V will result in failure to regulate the –4.5V output and potential instability. For 3.3V input, consider the adjustable LTC1261LCS8 or other low-VIN inverter ICs.

How does the REG pin on the LTC1261LCS8-4.5#TRPBF function, and what external components are needed?

The REG pin on the LTC1261LCS8-4.5#TRPBF is an open-drain output that pulls low when |VOUT| ≥ 95% of –4.5V (i.e., VOUT ≥ –4.275V). It requires an external pull-up resistor to VCC or another logic rail (up to 6V). The LTC1261LCS8-4.5#TRPBF sinks ≥5mA at 5V, so a 10kΩ pull-up yields ~2.5V logic-high under load - confirming rail readiness to host controllers.

What external capacitors are mandatory for basic operation of the LTC1261LCS8-4.5#TRPBF?

Three capacitors are mandatory: a 0.1µF ceramic flying capacitor between C1+ and C1–, a ≥1µF ceramic input bypass capacitor from VCC to GND, and a ≥3.3µF ceramic output capacitor from OUT to GND. An optional 100pF capacitor from ADJ/COMP to GND further reduces output ripple - all values confirmed in the Typical Applications section of the LTC1261LCS8-4.5#TRPBF datasheet.

Is the LTC1261LCS8-4.5#TRPBF pin-compatible with the LTC1261LCS8-4#TRPBF?

Yes - the LTC1261LCS8-4.5#TRPBF and LTC1261LCS8-4#TRPBF share identical SO-8 pinout, electrical interface, and package dimensions. They differ only in internal feedback resistor ratio, resulting in fixed –4.5V vs –4V output. No PCB change is required when substituting between these two variants, provided the input voltage meets each part's minimum specification (4.75V for –4.5V, 4.35V for –4V).