Analog Devices Inc. LTC1682IS8-3.3#PBF

Overview

LTC1682IS8-3.3#PBF 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. It accepts 2.0V–4.4V input, delivers up to 50mA output current, achieves 58µV_RMS output noise (10Hz–100kHz), and operates at 550kHz switching frequency in an 8-pin SO package.

For engineers reviewing the LTC1682IS8-3.3#PBF datasheet, LTC1682IS8-3.3#PBF pinout, LTC1682IS8-3.3#PBF application, or LTC1682IS8-3.3#PBF equivalent, key selection criteria include low-noise VCO supply capability, fixed 3.3V regulation without external feedback, shutdown current <5µA, thermal/short-circuit protection, and compatibility with ceramic capacitors only-no inductors required.

Technical Context

The LTC1682IS8-3.3#PBF integrates a switched-capacitor voltage doubler and a low-dropout linear regulator in series: the charge pump generates ~2×VIN at CPO, and the LDO filters ripple to deliver ultra-low-noise 3.3V output. Its internal 550kHz oscillator drives nonoverlapping clock phases for minimal EMI.

Operation includes Burst Mode for efficiency below 100µA load (slightly higher noise), automatic LDO enable/disable based on CPO voltage thresholds (1.75×VIN enable, 1.45×VIN disable), and internal 1nF reference filtering on the FILT pin-eliminating need for external FB resistors while maintaining 3.3V accuracy of ±2.1% over temperature and load.

Key Specifications

Pinout & Package

Package: 8-lead plastic SO (Small Outline, narrow 0.150"), RoHS-compliant, surface-mountable, θ_JA = 140°C/W.

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 LTC1682IS8-3.3#PBF offers lower cost and standard SO packaging but trades off thermal resistance and board area; versus LT3467EDD-3.3, it delivers superior noise performance at lower current, making it optimal for RF bias where spectral purity outweighs raw power capability.

Availability

LTC1682IS8-3.3#PBF is available at Aetrix Electronics and suitable for cellular phone VCO supplies, wireless PCMCIA cards, portable medical instruments, remote transmitters, and low-power data acquisition systems requiring stable component supply across industrial temperature ranges.

Supply support for LTC1682IS8-3.3#PBF 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 LTC1682 family.

The LTC1682 product line was designed specifically for ultra-low-noise, inductorless power conversion in RF and portable communications systems-targeting VCO, PLL, and mixer biasing where switching noise directly degrades system sensitivity and spectral mask compliance.

FAQ

What is the operating temperature range for the LTC1682IS8-3.3#PBF?

The LTC1682IS8-3.3#PBF is rated for the industrial temperature range of –40°C to +85°C. All electrical specifications-including output voltage accuracy (±2.1%), output noise (58µV_RMS), and dropout voltage (75mV typ.)-are guaranteed across this full range. This makes the LTC1682IS8-3.3#PBF suitable for deployment in automotive infotainment modules, outdoor wireless sensors, and industrial handheld test equipment where ambient conditions exceed commercial-grade limits.

Can the LTC1682IS8-3.3#PBF be used with input voltages below 2.0V?

No-the LTC1682IS8-3.3#PBF has a minimum specified input voltage of 2.0V, as confirmed in the Electrical Characteristics table (VIN Operating Voltage, LTC1682-3.3: 2.0V to 4.4V). Operation below 2.0V may result in failure to enable the LDO (which requires CPO ≥ 1.75×VIN), unstable regulation, or increased output noise. For sub-2.0V applications, consider the adjustable LTC1682IS8 or alternative micropower charge pumps like the LTC1522.

Does the LTC1682IS8-3.3#PBF require an external feedback resistor network?

No-the LTC1682IS8-3.3#PBF is the fixed 3.3V version and uses an internal resistor divider. Pin 3 is labeled FILT (not FB) and must be connected to a 1nF capacitor to ground for optimal noise performance. Unlike the adjustable LTC1682IS8, no external R1/R2 network is needed, simplifying layout and eliminating resistor tolerance errors that affect output accuracy.

How does the LTC1682IS8-3.3#PBF handle short-circuit conditions on VOUT?

The LTC1682IS8-3.3#PBF provides indefinite short-circuit protection on VOUT. Internal current limiting engages to cap output current, preventing damage. If sustained overload causes junction temperature to exceed 150°C, thermal shutdown activates; the device cycles between enabled and shutdown states until the fault is removed and temperature drops below 140°C. This behavior is verified in Absolute Maximum Ratings and Typical Performance Characteristics.

What is the recommended flying capacitor value for the LTC1682IS8-3.3#PBF?

The recommended flying capacitor for the LTC1682IS8-3.3#PBF is 0.22µF ceramic (X7R or better), placed as close as possible between C+ (Pin 7) and C– (Pin 5). This value is specified in all typical application circuits (e.g., Figure TA03) and optimized for 550kHz operation, low ESR, and minimal voltage droop. Larger values (e.g., 0.47µF) may reduce CPO ripple slightly but offer diminishing returns and increase board area unnecessarily.