Analog Devices Inc. LTC1261CS8#TRPBF

Overview

LTC1261CS8#TRPBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated voltage inverter IC that generates a stable negative output from a single 3V–8V positive supply. It delivers up to 12mA output current with ±5% regulation, 5mV typical output ripple, and features an open-drain REG pin indicating regulation status. Designed for space-constrained systems requiring clean negative bias, it supports fixed or adjustable outputs (e.g., –4V, –4.5V, –5V) using only three external capacitors.

For engineers reviewing the LTC1261CS8#TRPBF datasheet, LTC1261CS8#TRPBF pinout, LTC1261CS8#TRPBF application, or LTC1261CS8#TRPBF equivalent, key selection considerations include its SO-8 package compatibility, 550kHz internal oscillator, shutdown current of 5µA, adjustable output via ADJ/COMP pin, and guaranteed regulation across 0°C to 70°C.

Technical Context

The LTC1261CS8#TRPBF operates exclusively in doubler mode-generating V_OUT = –V_CC-with no tripler-mode capability due to its 8-pin SO package and absence of C2+ and C2– pins. Its charge pump core uses an internal 550kHz oscillator and precision 1.24V reference to regulate output by dynamically adjusting duty cycle via comparator feedback at the ADJ/COMP pin.

Regulation is enforced through a dual-comparator architecture: COMP1 compares the divided output against 1.24V to control charge transfer, while COMP2 references 1.18V (5% below V_REF) to drive the open-drain REG output. The IC requires only one 0.1µF flying capacitor (C1+ to C1–), plus input and output bypass capacitors, with optional 100pF compensation at ADJ/COMP to suppress ripple.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (SO-8), 0°C to 70°C operating temperature range, JEDEC MS-012AC compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX680ESA+ and ICL7660SIPAZ, the LTC1261CS8#TRPBF uniquely combines SO-8 packaging, 550kHz switching for low EMI, on-chip regulation with status indication, and flexible fixed/adjustable output-all while maintaining 600µA operating current and 5µA shutdown draw.

Availability

LTC1261CS8#TRPBF is available at Aetrix Electronics and suitable for GaAs FET bias generation, portable instrumentation power rails, op-amp dual-supply synthesis, and sensor signal conditioning requiring stable component supply and lead-free compliance.

Supply support for LTC1261CS8#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 its legacy of high-performance analog ICs, emphasizing precision, reliability, and application-specific integration for industrial, automotive, and communications markets.

The LTC1261 family was designed specifically for compact, efficient generation of regulated negative voltages in single-supply systems-targeting applications where transformerless, low-noise, and low-quiescent-power bias is critical.

FAQ

What output voltage options are supported by the LTC1261CS8#TRPBF?

The LTC1261CS8#TRPBF supports both adjustable and factory-configured fixed outputs. Adjustable range spans –1.25V to –8V via external resistor divider at the ADJ/COMP pin. Fixed versions include –4V (LTC1261CS8-4#TRPBF), –4.5V (LTC1261CS8-4.5#TRPBF), and –5V (LTC1261CS8-5#TRPBF), each requiring zero external components for regulation. Output accuracy is guaranteed within ±5% under load.

Can the LTC1261CS8#TRPBF operate in tripler mode like the 14-lead LTC1261CS?

No, the LTC1261CS8#TRPBF cannot operate in tripler mode. Its 8-pin SO package lacks C2+ and C2– pins required for tripler configuration. It is strictly a doubler-mode device, generating V_OUT ≈ –V_CC. Tripler functionality (e.g., –5V from 3.3V) is exclusive to the 14-lead LTC1261CS variant, which provides separate flying capacitor terminals.

How does the REG pin function on the LTC1261CS8#TRPBF?

The REG pin on the LTC1261CS8#TRPBF is an open-drain output that pulls low when the magnitude of the output voltage is within ±5% of the programmed setpoint (e.g., –4.75V to –5.25V for a –5V target). It sinks up to 8mA with a 5V V_CC and requires an external pull-up resistor. This signal serves as a hardware power-valid flag for system sequencers or fault monitors.

What is the minimum output capacitor required for specified ripple performance with the LTC1261CS8#TRPBF?

To achieve the datasheet-specified 5mV typical output ripple at 5mA load, the LTC1261CS8#TRPBF requires a minimum 3.3µF output capacitor. Ceramic types are preferred for low ESR; if using tantalum or aluminum electrolytic, a parallel 0.1µF ceramic capacitor is mandatory to prevent ESR-induced regulation errors and ripple amplification.

Does the LTC1261CS8#TRPBF require external resistors for fixed-output configurations?

No, the LTC1261CS8#TRPBF does not require external resistors for fixed-output versions. Models like LTC1261CS8-4#TRPBF integrate an on-chip resistor string connected internally to the ADJ/COMP pin, enabling –4V, –4.5V, or –5V operation with no external components. Only adjustable versions need a resistor divider between OUT and ADJ/COMP to set custom voltages.