Analog Devices Inc. LTC1550LIGN#TRPBF

Overview

LTC1550LIGN#TRPBF from Analog Devices (formerly Linear Technology) is a low-noise, switched-capacitor regulated negative voltage inverter with integrated linear post-regulator, delivering –4.1V output at up to 20mA load current with <1mV_P-P ripple. It operates from a single 4.5V–5.25V supply, features active-low TTL-compatible shutdown (SHDN), and is optimized for GaAs FET bias generation in portable RF transmitters.

For engineers reviewing the LTC1550LIGN#TRPBF datasheet, LTC1550LIGN#TRPBF pinout, LTC1550LIGN#TRPBF application, or LTC1550LIGN#TRPBF equivalent, key selection criteria include guaranteed ±2.5% output regulation over line/load/temperature, 900kHz charge pump frequency enabling compact 0.1µF external capacitors, shutdown quiescent current <1µA, and compatibility with 16-lead SSOP layout for noise-sensitive biasing circuits.

Technical Context

The LTC1550LIGN#TRPBF integrates an inverting charge pump stage (900kHz oscillator, C1+/C1–/CPOUT pins) followed by a negative linear regulator (VOUT, REG, ADJ pins) that actively filters switching artifacts. Its internal N-channel pass device enables low dropout operation down to VCC = 4.5V for –4.1V output while maintaining regulation.

Regulation relies on a 1.225V internal reference compared against the ADJ node via an external resistor divider; the REG pin provides open-drain power-good signaling when |VOUT| is within 5% of target. The 16-pin SSOP package separates analog ground (AGND) and power ground (PGND) to preserve loop stability under dynamic load conditions.

Key Specifications

Pinout & Package

Package: 16-lead narrow SSOP (GN), 0.150" width, exposed pad not present. Pin functions validated per Linear Technology LTC1550L/LTC1551L datasheet Rev. D.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1550LCGN#TRPBF, LTC1550LIGN#TRPBF adds extended temperature qualification and ground separation for lower noise; versus LTC1550LCS8#TRPBF, it provides REG monitoring and superior PSRR via dedicated AGND/PGND routing-critical for RF bias integrity.

Availability

LTC1550LIGN#TRPBF is available at Aetrix Electronics and suitable for portable RF transmitters, GaAs FET bias generators, and battery-powered instrumentation requiring stable component supply with guaranteed industrial temperature operation.

Supply support for LTC1550LIGN#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 full product support, datasheets, and application engineering for legacy Linear parts including the LTC1550L series.

The LTC1550L family was designed specifically for low-noise negative voltage generation in portable RF systems, emphasizing minimal external components, sub-1mV ripple, and robust operation across battery voltage ranges.

FAQ

What is the minimum input voltage required for LTC1550LIGN#TRPBF to deliver its rated –4.1V output?

The LTC1550LIGN#TRPBF requires a minimum VCC of 4.5V to guarantee –4.1V output regulation at up to 5mA load, and 4.75V for full 20mA capability. Below 4.5V, output voltage collapses; this is specified in the Electrical Characteristics table under "VOUT Output Regulation" for LTC1550L-4.1. Operating outside this range risks loss of regulation and increased ripple.

Does LTC1550LIGN#TRPBF require external resistors to set its output voltage?

No, LTC1550LIGN#TRPBF is a fixed –4.1V version and does not require external resistors. Its output is set by internal divider resistors. External resistors are only needed for adjustable versions (e.g., LTC1550LIGN#TRPBF is not adjustable; LTC1550L-ADJ variants use ADJ and external R1/R2). The ADJ pin on LTC1550LIGN#TRPBF is functional but internally tied-no external connection is needed or recommended.

How does the REG pin on LTC1550LIGN#TRPBF function, and what external circuitry is required?

The REG pin on LTC1550LIGN#TRPBF is an open-drain output that pulls low when |VOUT| is within 5% of –4.1V. It sinks up to 4mA but requires an external pull-up resistor (typically 10kΩ to VCC or another logic rail) to assert HIGH. Without pull-up, REG remains floating and cannot signal valid output. This pin enables system-level power sequencing and fault detection in designs using LTC1550LIGN#TRPBF.

Can LTC1550LIGN#TRPBF be used with ceramic output capacitors only, or is a tantalum + ceramic parallel combination mandatory?

LTC1550LIGN#TRPBF can use ceramic-only output capacitance, but must meet two conditions: total capacitance ≥10µF and moderate ESR (20–100mΩ). Very low-ESR ceramics (<5mΩ) risk regulator loop instability and oscillation. Linear Technology recommends 10µF tantalum + 0.1µF ceramic as optimal, but a single 22µF X5R ceramic with ~50mΩ ESR is acceptable if layout minimizes trace inductance. Always verify stability with load transients when substituting.

What is the thermal performance difference between the 16-lead SSOP (LTC1550LIGN#TRPBF) and 8-lead MSOP packages of the LTC1550L family?

LTC1550LIGN#TRPBF in 16-lead SSOP has θ_JA = 200°C/W, while the 8-lead MSOP variant (e.g., LTC1550LCMS8-4.1) has θ_JA = 135°C/W. The SSOP's higher thermal resistance means greater junction temperature rise under identical load-up to 13°C higher at 20mA. This is offset in LTC1550LIGN#TRPBF by PGND/AGND separation improving noise margin, making it preferred for RF bias despite thermal penalty.