Analog Devices Inc. LTC1682CS8-3.3#TRPBF

Overview

LTC1682CS8-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a fixed-output 3.3V doubler charge pump with integrated low-noise LDO regulator, designed for powering noise-sensitive RF circuitry such as VCOs in wireless transceivers. It operates from 2.0V to 4.4V input, delivers up to 50mA output current, achieves 58µV_RMS output noise (10Hz–100kHz), and uses only ceramic capacitors-no inductors required.

For engineers reviewing the LTC1682CS8-3.3#TRPBF datasheet, LTC1682CS8-3.3#TRPBF pinout, LTC1682CS8-3.3#TRPBF application, or LTC1682CS8-3.3#TRPBF equivalent, key selection considerations include its 3.3V fixed regulated output, 550kHz switching frequency, 1µA shutdown current, thermal/short-circuit protection, and compatibility with compact SO-8 layout in portable RF systems.

Technical Context

The LTC1682CS8-3.3#TRPBF integrates a switched-capacitor voltage doubler and a low-dropout linear regulator in a single die. The charge pump generates ~2×VIN at CPO, which feeds the LDO stage that filters ripple and regulates precisely to 3.3V with ±70mV total output variation over temperature and load.

It employs burst-mode operation below 100µA load to reduce quiescent current to 150µA while maintaining regulation, and features internal power-on reset, thermal shutdown at 150°C, and current limiting. Pin 3 functions as FILT (not FB), requiring a 1nF capacitor to ground for optimal reference filtering and noise performance.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (narrow, 0.150") - RoHS-compliant, surface-mount, compatible with standard reflow profiles and automated assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise charge-pump regulator applications.

Compared with LTC1682IMS8-3.3, the LTC1682CS8-3.3#TRPBF offers identical noise and regulation performance in a larger, more manufacturable SO-8 package but with narrower 0°C to 70°C rating; versus LT3467ES6-3.3, it trades ~10% efficiency for >3× lower output noise - decisive for VCO biasing.

Availability

LTC1682CS8-3.3#TRPBF is available at Aetrix Electronics and suitable for cellular phone VCO supplies, wireless PCMCIA card power, and portable medical instrument sensor bias requiring stable component supply across production lifecycles.

Supply support for LTC1682CS8-3.3#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 technical and manufacturing continuity for all Linear legacy products including the LTC1682 family.

The LTC1682 series was designed specifically to replace inductor-based DC-DC converters in RF power supply applications where low noise, small size, and simplicity are mandatory - targeting cellular infrastructure, portable wireless, and precision analog systems.

FAQ

What is the maximum output current capability of the LTC1682CS8-3.3#TRPBF?

The LTC1682CS8-3.3#TRPBF delivers up to 50mA of continuous regulated 3.3V output current under typical conditions (VIN = 3.3V, TA = 25°C). At higher ambient temperatures or lower input voltages, derating applies due to thermal limits and LDO dropout constraints - full 50mA is guaranteed only when junction temperature remains ≤125°C and VIN ≥ 2.7V.

Does the LTC1682CS8-3.3#TRPBF require an external resistor divider to set the output voltage?

No. The LTC1682CS8-3.3#TRPBF is the fixed 3.3V version of the LTC1682 family and contains an internal resistor network to set VOUT. Pin 3 is labeled FILT (not FB) and must be bypassed with a 1nF capacitor to ground - no external resistors are needed or used for voltage programming.

Can the LTC1682CS8-3.3#TRPBF operate from a 1.8V input supply?

No. The LTC1682CS8-3.3#TRPBF has a minimum input voltage of 2.0V, as specified in its Electrical Characteristics table. While the adjustable LTC1682 variant supports 1.8V–4.4V, the -3.3 fixed version is optimized for 2.0V–4.4V operation to ensure stable 3.3V regulation across its full temperature range.

What capacitor values are required for stable operation of the LTC1682CS8-3.3#TRPBF?

Four capacitors are required: 0.22µF ceramic flying capacitor (C1) between C+ and C–; 1nF ceramic on FILT-to-ground; and ≥2µF low-ESR ceramic on both VIN and VOUT (C2/C3). A fourth ≥2µF capacitor (C4) is recommended on VIN for improved input ripple suppression - all must be X5R/X7R ceramics placed as close as possible to respective pins.

How does the LTC1682CS8-3.3#TRPBF achieve its low output noise specification?

The LTC1682CS8-3.3#TRPBF achieves 58µV_RMS noise through dual-stage noise reduction: first, a carefully slew-controlled 550kHz charge pump minimizes switching spike energy; second, an integrated LDO with high PSRR filters residual CPO ripple. The 1nF FILT capacitor further stabilizes the internal 1.235V reference, suppressing low-frequency noise contributions.