Analog Devices Inc. LTC1550LCMS8-2.5#TRPBF

Overview

LTC1550LCMS8-2.5#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output, low-noise switched-capacitor voltage inverter with integrated linear post-regulator, delivering –2.5V at up to 20mA load current with ±2.5% output regulation over line, load, and temperature. It operates from a single 3.05V–5.25V supply, features 900kHz charge pump frequency, <1mV_P-P output ripple, and TTL-compatible active-low shutdown. It is optimized for GaAs FET bias generation in portable RF transmitters.

For engineers reviewing the LTC1550LCMS8-2.5#TRPBF datasheet, LTC1550LCMS8-2.5#TRPBF pinout, LTC1550LCMS8-2.5#TRPBF application, or LTC1550LCMS8-2.5#TRPBF equivalent, key selection criteria include guaranteed –2.5V output regulation across 3.05V–5.25V input range, 0.2µA shutdown current, MSOP-8 package compatibility, and minimal external component count (four capacitors only).

Technical Context

The LTC1550LCMS8-2.5#TRPBF integrates a 900kHz inverting charge pump stage followed by a negative linear regulator using an N-channel MOSFET pass device and internal 1.225V reference. Its feedback loop is optimized for fast transient response to suppress switching artifacts from CPOUT, enabling stable regulation under dynamic loads up to 20mA.

It employs star-ground layout requirements for VCC bypass, CPOUT, and VOUT capacitors to minimize noise coupling. The REG pin provides open-drain power-valid indication when output is within ±5% of nominal –2.5V, sinking up to 4mA at 5V supply.

Key Specifications

Pinout & Package

Package: 8-lead MSOP (MS8), 3.0mm × 3.0mm × 0.85mm body, exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1550LCS8-2.5#PBF, the LTC1550LCMS8-2.5#TRPBF saves 58% PCB area in compact RF modules; compared with LTC1551LCMS8-2.5#TRPBF, it eliminates need for level-shifting on the shutdown line in microcontroller-based designs with open-drain outputs.

Availability

LTC1550LCMS8-2.5#TRPBF is available at Aetrix Electronics and suitable for portable RF transmitters, GaAs FET bias generators, and single-supply instrumentation requiring stable component supply, guaranteed long-term availability, and traceable sourcing.

Supply support for LTC1550LCMS8-2.5#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.

The LTC1550L/LTC1551L product line was designed specifically for low-noise, space-efficient negative voltage generation in battery-powered RF and portable communications equipment.

FAQ

What is the minimum input voltage required for the LTC1550LCMS8-2.5#TRPBF to maintain regulation at full 20mA load?

The LTC1550LCMS8-2.5#TRPBF requires a minimum VCC of 4.1V to deliver –2.5V at 20mA while maintaining ±2.5% regulation, as specified in the Electrical Characteristics table under "VOUT Output Regulation" for 4.1V ≤ VCC ≤ 5.25V, 0 ≤ IOUT ≤ 20mA. Below 4.1V, output current capability degrades progressively.

Can the LTC1550LCMS8-2.5#TRPBF be used with ceramic output capacitors only, or is a tantalum capacitor required?

The LTC1550LCMS8-2.5#TRPBF requires a moderate-ESR output capacitor for loop stability - a pure low-ESR ceramic capacitor alone may cause oscillation. The datasheet recommends ≥10µF tantalum (or aluminum polymer) in parallel with 0.1µF ceramic to achieve both stability and <1mV_P-P ripple. Using only ceramic violates the ESR zero requirement in the regulator feedback loop.

Does the REG pin on the LTC1550LCMS8-2.5#TRPBF require an external pull-up resistor, and what voltage can it tolerate?

Yes, the REG pin on the LTC1550LCMS8-2.5#TRPBF is open-drain and requires an external pull-up resistor to function. It can be pulled up to 6V above ground without damage, making it compatible with 3.3V, 5V, or mixed-voltage system rails. The pin sinks up to 4mA when active low, indicating valid –2.5V output regulation.

How does the LTC1550LCMS8-2.5#TRPBF achieve <1mV_P-P output ripple without inductors or complex filtering?

The LTC1550LCMS8-2.5#TRPBF achieves <1mV_P-P ripple through its two-stage architecture: a 900kHz charge pump minimizes flying capacitor size and noise energy, followed by a fast-response linear regulator that actively filters residual switching artifacts. Combined with proper 10µF + 0.1µF output capacitance and star-ground layout, this eliminates need for external LC filters.

Is the LTC1550LCMS8-2.5#TRPBF pin-compatible with other members of the LTC1550L/LTC1551L family in the MSOP-8 package?

Yes, all LTC1550L and LTC1551L variants in the MS8 package share identical pinout and footprint, including LTC1550LCMS8-2.5#TRPBF, LTC1550LCMS8-4.1#TRPBF, and LTC1551LCMS8-2.5#TRPBF. The only functional difference is SHDN polarity (active-low for LTC1550L, active-high for LTC1551L), which must be accounted for in system design.