Analog Devices Inc. LTC1261LIS8#PBF

Overview

LTC1261LIS8#PBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated negative voltage inverter IC designed to generate a stable, adjustable or fixed negative output from a single 2.7V–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 with only three external capacitors. It is commonly used in GaAs FET bias generation and battery-powered systems requiring compact, low-quiescent-power negative rails.

For engineers reviewing the LTC1261LIS8#PBF datasheet, LTC1261LIS8#PBF pinout, LTC1261LIS8#PBF application, or LTC1261LIS8#PBF equivalent, key selection criteria include output voltage adjustability (–1.23V to –5V), industrial temperature range (–40°C to +85°C), SO-8 package compatibility, shutdown current (5µA), and guaranteed regulation under load across VCC and IOUT operating conditions.

Technical Context

The LTC1261LIS8#PBF implements a 650kHz internal oscillator-driven inverting charge pump topology with feedback regulation via an internal 1.23V reference. Output voltage is set either by internal resistor dividers (for fixed-output variants like –4V/–4.5V) or externally via the ADJ pin (for adjustable versions), where the divided output voltage is compared against the reference to control duty cycle of the charge transfer switches.

Regulation is enforced through dual comparators: COMP1 maintains output accuracy by truncating clock pulses when the divided output reaches 1.23V relative to OUT; COMP2 asserts the open-drain REG signal when the output enters ±5% of the set value. The device supports indefinite output short-circuit protection and includes internal pull-down on SHDN for default-enable operation.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic SO (Narrow, 0.150-inch width), RoHS-compliant lead-free finish (PBF), 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 regulated negative voltage inverter applications.

Compared with MAX680ESA+ and ICL7660AIPAZ, the LTC1261LIS8#PBF uniquely combines adjustable/fixed output capability, ±4.5% guaranteed regulation, integrated REG flag, and 5µA shutdown - making it optimal for industrial and RF-bias applications demanding verified rail integrity and thermal robustness.

Availability

LTC1261LIS8#PBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, battery-powered instrumentation, and single-supply signal conditioning requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for LTC1261LIS8#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 technical and manufacturing continuity for legacy Linear products including the LTC1261L series.

The LTC1261L product line was designed specifically for compact, low-power regulated negative voltage generation in space- and efficiency-constrained analog and RF systems - emphasizing minimal external components, industrial temperature operation, and reliable power-good signaling.

FAQ

What is the maximum output current supported by the LTC1261LIS8#PBF?

The LTC1261LIS8#PBF delivers up to 20mA output current while maintaining ±4.5% regulation accuracy across its full operating temperature range (–40°C to +85°C) and supply voltage range (2.7V to 5.25V). This rating applies under worst-case conditions including minimum VCC and maximum ambient temperature, as verified in the manufacturer's Electrical Characteristics table.

Does the LTC1261LIS8#PBF require an external resistor divider for all configurations?

No - the LTC1261LIS8#PBF is the industrial-grade SO-8 version of the base LTC1261L, which is an adjustable-output variant. It requires an external resistor divider between OUT and ADJ pins to set the desired output voltage (e.g., –2V, –3V, –4V). Fixed-output versions (e.g., LTC1261LIS8-4#PBF) have internal dividers and do not require external resistors.

How does the REG pin on the LTC1261LIS8#PBF function, and what external components are needed?

The REG pin on the LTC1261LIS8#PBF is an open-drain output that pulls low when the magnitude of VOUT is within 5% of the set value. It requires an external pull-up resistor (typically 10kΩ to 5V or VCC) to assert a logic-high state. The pin can be safely pulled up to 6V and sinks up to 5mA at 5V VCC - enabling direct interfacing with microcontroller GPIO or supervisor ICs.

What is the purpose of the capacitor on the ADJ/COMP pin of the LTC1261LIS8#PBF?

The capacitor on the ADJ/COMP pin (typically 100pF for fixed-output variants, value dependent on R-divider for adjustable LTC1261LIS8#PBF) compensates the regulation loop to prevent comparator hunting and reduce output voltage ripple. It stabilizes feedback response to rapid output transients caused by the 650kHz charge pump switching, especially under heavy load or with high-ESR output capacitors.

Can the LTC1261LIS8#PBF operate from a 3.3V supply, and what output voltages are achievable?

Yes - the LTC1261LIS8#PBF operates from 2.7V to 5.25V, so a 3.3V supply is fully supported. With appropriate external resistor values on the ADJ pin, it can generate any regulated negative output from –1.23V to –5V. For example, at VCC = 3.3V, it reliably delivers –2V at 10mA with ±4.5% regulation, as confirmed in the Typical Performance Characteristics graphs (Figures G01–G04).