Analog Devices Inc. LTC1550CS8-4.1#TRPBF

Overview

LTC1550CS8-4.1#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output, switched-capacitor voltage inverter IC with integrated linear post-regulator, generating a regulated –4.1V output from a single 4.5V–6.5V positive supply. It delivers up to 10mA load current, maintains ±5% output regulation, achieves <1mV_P-P output ripple, and operates at a 900kHz charge pump frequency-optimized for GaAs FET biasing in portable RF transmitters.

For engineers reviewing the LTC1550CS8-4.1#TRPBF datasheet, LTC1550CS8-4.1#TRPBF pinout, LTC1550CS8-4.1#TRPBF application, or LTC1550CS8-4.1#TRPBF equivalent, key selection criteria include its SO-8 package, active-low shutdown (SHDN), 0.2µA shutdown current, requirement of only four external 0.1µF/4.7µF/10µF capacitors, and guaranteed performance across 0°C to 70°C.

Technical Context

The LTC1550CS8-4.1#TRPBF integrates a 900kHz switched-capacitor charge pump followed by a negative linear regulator using an N-channel MOSFET pass device and internal 1.24V reference. Its feedback loop monitors VOUT via the SENSE pin to maintain regulation, enabling fast transient response and suppression of switching artifacts.

It employs a two-phase clock driving external flying capacitor C1 (0.1µF) between C1+ and C1–, transferring charge to CPOUT, which feeds the linear regulator. The fixed –4.1V output is set by internal resistor dividers; no external adjustment components are required-unlike the adjustable LTC1550CGN variant.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (SO-8, narrow 0.150"), JEDEC MS-012, thermal resistance θ_JA = 150°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar switched-capacitor inverter applications.

Compared with LTC1551CS8-4.1#TRPBF, the LTC1550CS8-4.1#TRPBF offers identical regulation and ripple but requires active-low shutdown control; versus LTC1261CS8-4.1#TRPBF, it delivers superior noise performance and simpler design due to integrated regulation-justifying its use in RF-critical applications.

Availability

LTC1550CS8-4.1#TRPBF is available at Aetrix Electronics and suitable for GaAs FET biasing, portable RF power amplifiers, and single-supply instrumentation requiring stable component supply, low-noise negative voltage generation, and commercial-grade temperature operation.

Supply support for LTC1550CS8-4.1#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, datasheet documentation, and long-term manufacturing commitment for legacy Linear parts.

The LTC1550 family was designed specifically for low-noise, low-component-count negative voltage generation in portable RF and battery-powered systems-emphasizing integration, regulation accuracy, and ease of use over raw efficiency.

FAQ

What is the output voltage tolerance of the LTC1550CS8-4.1#TRPBF under full load?

The LTC1550CS8-4.1#TRPBF guarantees ±5% output regulation over 4.5V–6.5V input voltage and 0–10mA load current at 25°C. At VCC = 4.75V and IOUT = 10mA, the output remains within –4.3V to –3.9V. This tolerance is maintained across the commercial temperature range (0°C to 70°C) and reflects total error including line, load, and temperature effects-not just initial accuracy.

Can the LTC1550CS8-4.1#TRPBF operate from a 3.3V supply?

No-the LTC1550CS8-4.1#TRPBF requires a minimum 4.5V supply per its Absolute Maximum Ratings and Electrical Characteristics table. Attempting operation below 4.5V may result in failure to regulate, excessive ripple, or undefined behavior. For 3.3V-input applications, consider the LTC1550CGN (adjustable version) or alternative inverters like the LTC3260.

How does the SENSE pin improve regulation accuracy in the LTC1550CS8-4.1#TRPBF?

The SENSE pin on the LTC1550CS8-4.1#TRPBF provides remote sensing of the VOUT node directly at the load, compensating for voltage drop across PCB traces and connectors. When routed close to the load, it enables the internal feedback loop to maintain ±5% regulation at the point of use-critical for precision biasing where even 50mV error degrades RF PA linearity.

What is the recommended capacitor configuration for achieving <1mVP-P ripple with the LTC1550CS8-4.1#TRPBF?

To achieve <1mV_P-P output ripple, the LTC1550CS8-4.1#TRPBF requires a 10µF tantalum (or low-ESR polymer) capacitor in parallel with a 0.1µF X7R ceramic capacitor at VOUT, plus a 4.7µF input bypass capacitor at VCC and two 0.1µF ceramic flying capacitors (C1+, C1–). Adding a ferrite bead in series with VOUT further suppresses high-frequency spikes.

Is the LTC1550CS8-4.1#TRPBF pin-compatible with the LTC1551CS8-4.1#TRPBF?

Yes-the LTC1550CS8-4.1#TRPBF and LTC1551CS8-4.1#TRPBF share identical SO-8 pinouts, electrical specifications, and thermal characteristics. The sole functional difference is SHDN pin polarity: active-low for LTC1550CS8-4.1#TRPBF and active-high for LTC1551CS8-4.1#TRPBF. No PCB changes are required for substitution-only control logic must be inverted.