Analog Devices Inc. LTC1261LCS8#TRPBF

Overview

LTC1261LCS8#TRPBF from Analog Devices (formerly Linear Technology) is a switched-capacitor regulated voltage inverter IC that generates a stable negative output from a single positive supply. It operates from 2.7V to 5.25V, delivers up to 20mA output current, maintains ±4.5% output regulation, and features an open-drain REG pin indicating regulation status - used in GaAs FET bias generation and portable battery-powered systems.

For engineers reviewing the LTC1261LCS8#TRPBF datasheet, LTC1261LCS8#TRPBF pinout, LTC1261LCS8#TRPBF application, or LTC1261LCS8#TRPBF equivalent, key selection criteria include input voltage range (2.7–5.25V), adjustable output (–1.23V to –5V), shutdown quiescent current (5µA), 650kHz internal oscillator, and SO-8 package compatibility with standard PCB layouts.

Technical Context

The LTC1261LCS8#TRPBF implements a charge-pump topology with internal 650kHz oscillator driving complementary MOSFET switches to invert and regulate output voltage. Regulation is achieved via feedback of a resistor-divided output signal to the ADJ pin, compared against a 1.23V internal reference relative to VOUT.

Its REG pin uses a second comparator referenced to 1.17V (5% below VREF) to assert low when output magnitude is within 5% of setpoint. Shutdown mode disables the charge pump, collapsing output to 0V and reducing supply current to 5µA typical.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic SO (SO-8, narrow 0.150-inch body), RoHS-compliant, commercial temperature range (0°C to 70°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX680ESA+ and ICL7660SIPAZ, the LTC1261LCS8#TRPBF uniquely combines adjustable output, ±4.5% regulation, REG status signaling, and SO-8 compatibility - making it optimal for GaAs bias and portable instrumentation where both flexibility and reliability are required.

Availability

LTC1261LCS8#TRPBF is available at Aetrix Electronics and suitable for GaAs FET bias generators, portable instrumentation power supplies, and single-supply signal conditioning circuits requiring stable component supply and full commercial-temperature support.

Supply support for LTC1261LCS8#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 precision analog portfolio, emphasizing high-performance power management and signal conditioning ICs.

The LTC1261LCS8#TRPBF belongs to Linear's switched-capacitor voltage converter family, designed specifically for compact, inductorless negative rail generation in battery-powered and space-constrained analog systems.

FAQ

What is the minimum input voltage required for LTC1261LCS8#TRPBF to regulate at –4V output?

The LTC1261LCS8#TRPBF requires a minimum supply voltage of 4.35V to guarantee ±4.5% regulation at –4V output across temperature and load. Below this, regulation may degrade - confirmed in Electrical Characteristics Table under "Output Regulation (LTC1261L/LTC1261L-4)" with VCC ≥ 4.35V condition for 0mA–5mA loads. The LTC1261LCS8#TRPBF datasheet specifies this threshold explicitly for fixed-output operation.

Can LTC1261LCS8#TRPBF generate –1.23V output, and what resistor values are needed?

Yes, the LTC1261LCS8#TRPBF can generate –1.23V output using the ADJ pin with a resistor divider. Since VREF = 1.23V is referenced to VOUT, the divider must satisfy VOUT × [R2/(R1+R2)] = 1.23V. For –1.23V output, R1 = 0Ω (short) and R2 open yields direct connection - but practical implementation uses R1 = 0Ω and no R2, grounding ADJ. The LTC1261LCS8#TRPBF application note confirms this configuration achieves nominal –1.23V.

Does LTC1261LCS8#TRPBF require an external compensation capacitor, and where is it connected?

An optional 100pF capacitor can be connected from ADJ (Pin 5) to GND to reduce output ripple by stabilizing the regulation loop bandwidth - especially beneficial for fixed-output variants like LTC1261L-4. This is not mandatory but recommended when ripple <5mV is required. The LTC1261LCS8#TRPBF datasheet Figure 2 and Applications Information section confirm placement and value for SO-8 packaged units.

What is the maximum continuous output current capability of LTC1261LCS8#TRPBF at 5V input?

The LTC1261LCS8#TRPBF delivers up to 20mA continuous output current when VCC ≥ 3.25V and VOUT = –4V, as verified in the Electrical Characteristics table under "Output Regulation" conditions for 0mA–20mA loads. At VCC = 5V, this rating holds across 0°C to 70°C; derating applies below 3.25V input per the "Minimum Required VCC vs VOUT and IOUT" graph (Figure G02).

How does the REG pin on LTC1261LCS8#TRPBF behave when the output is over-regulated (e.g., –4.3V instead of –4V)?

The REG pin on LTC1261LCS8#TRPBF remains low only when |VOUT| is *within* 5% of the setpoint (e.g., –3.8V to –4.2V for a –4V target). If VOUT is over-regulated (e.g., –4.3V), |VOUT| exceeds the upper bound, so the internal 1.17V comparator does not trip - REG stays high (open-drain, pulled up externally). The LTC1261LCS8#TRPBF Applications Information explicitly states REG indicates "magnitude below setpoint by ≤5%", not deviation in either direction.