Analog Devices Inc. LTC1550LCMS8-2#TRPBF

Overview

LTC1550LCMS8-2#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output, low-noise switched-capacitor voltage inverter with integrated linear post-regulator, delivering –2.0V ±2.5% at up to 20mA load current from a 2.7V–5.25V single supply. It features 900kHz charge pump frequency, <1mV_P-P output ripple, and active-low TTL-compatible shutdown (SHDN). It is optimized for GaAs FET bias generation in portable RF transmitters.

For engineers reviewing the LTC1550LCMS8-2#TRPBF datasheet, LTC1550LCMS8-2#TRPBF pinout, LTC1550LCMS8-2#TRPBF application, or LTC1550LCMS8-2#TRPBF equivalent, key selection criteria include guaranteed –2.0V regulation over line/load/temperature, minimal external component count (four capacitors), MSOP-8 package compatibility, and sub-1µA shutdown current.

Technical Context

The LTC1550LCMS8-2#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.

It operates with only four external components: 0.1µF C1+–C1– flying capacitor, 0.1µF CPOUT storage capacitor, 2.2µF input bypass capacitor (CIN), and ≥10µF output filter capacitor (COUT) - with mandatory 0.1µF ceramic in parallel to suppress high-frequency spikes.

Key Specifications

Pinout & Package

Package: 8-lead MSOP (MS8), 3.0mm × 3.0mm × 0.85mm body, exposed pad not connected. Pin pitch: 0.65mm. RoHS-compliant, lead-free, tape-and-reel (#TRPBF).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1550LCS8-2 and LTC1261LCS8-2, the LTC1550LCMS8-2#TRPBF delivers superior ripple performance and higher output current in the smallest footprint, making it optimal for high-density RF biasing where regulation integrity and space are critical.

Availability

LTC1550LCMS8-2#TRPBF is available at Aetrix Electronics and suitable for GaAs FET biasing, portable RF transmitter supplies, and low-noise dual-rail op-amp applications requiring stable component supply and long-term lifecycle support.

Supply support for LTC1550LCMS8-2#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 continuity, technical documentation, and manufacturing for legacy Linear parts including the LTC series.

The LTC1550L family was designed specifically for low-noise, capacitor-based negative voltage generation in portable RF systems - prioritizing ripple suppression, small solution size, and GaAs FET bias accuracy over raw efficiency or high current.

FAQ

What is the guaranteed output voltage tolerance for LTC1550LCMS8-2#TRPBF over temperature and load?

The LTC1550LCMS8-2#TRPBF guarantees –2.0V output with ±2.5% regulation over the full operating temperature range (–40°C to +85°C), line (VCC = 2.7V–5.25V), and load (0–20mA), as specified in the Electrical Characteristics table. This tolerance applies to all conditions simultaneously - not separately - ensuring robust GaAs FET biasing across battery discharge and ambient extremes.

Can LTC1550LCMS8-2#TRPBF operate from a 2.7V supply while delivering –2.0V at 20mA?

No. The LTC1550LCMS8-2#TRPBF requires VCC ≥ 3.75V to deliver –2.0V at 20mA, per the "Minimum Required VCC vs VOUT and IOUT" graph (Figure G04). At 2.7V input, maximum load is ~5mA. For 20mA at low input voltage, consider the LTC1550LCMS8-2.5 or LTC1550LCMS8-4.1 variants with higher VCC minimums matched to their outputs.

Why does LTC1550LCMS8-2#TRPBF require a 0.1µF ceramic capacitor in parallel with the main output capacitor?

The 0.1µF ceramic capacitor suppresses high-frequency switching spikes (~900kHz harmonics) that remain after linear regulation. These spikes - though low energy - can exceed 1mV_P-P if only a bulk tantalum or electrolytic capacitor is used. The ceramic's low impedance at MHz frequencies shunts these artifacts, ensuring the <1mV_P-P ripple specification is met for the LTC1550LCMS8-2#TRPBF.

Is the REG pin on LTC1550LCMS8-2#TRPBF functional, and what is its purpose?

Yes. The REG pin on LTC1550LCMS8-2#TRPBF is an open-drain output that pulls low when VOUT is within ±5% of –2.0V. It sinks up to 4mA and requires an external pull-up (to ≤6V) to indicate valid regulation. This enables power sequencing and fault detection in systems where confirmed bias voltage presence is critical before RF transmission.

Does LTC1550LCMS8-2#TRPBF support synchronization to an external clock?

No. The LTC1550LCMS8-2#TRPBF uses a fixed 900kHz internal oscillator and has no external clock input or synchronization capability. For synchronized operation, consider the LTC1429 - a related Linear/Analog Devices part offering clock-sync up to 2MHz - though it lacks the integrated linear post-regulator and <1mV_P-P ripple performance of the LTC1550LCMS8-2#TRPBF.