Analog Devices Inc. LTC6400IUD-8#PBF

Overview

LTC6400IUD-8#PBF from Analog Devices (formerly Linear Technology) is a high-speed, low-noise, low-distortion differential ADC driver amplifier optimized for DC–300MHz signal conditioning in precision data acquisition systems. It features fixed 8dB (2.5V/V) gain, 2.2GHz –3dB bandwidth, –99dBc IMD3 at 70MHz, 1nV/√Hz input-referred voltage noise, and 400Ω differential input impedance. It drives 12-/14-/16-bit ADCs such as the LTC2208 in direct-coupled, transformerless configurations.

For engineers reviewing the LTC6400IUD-8#PBF datasheet, LTC6400IUD-8#PBF pinout, LTC6400IUD-8#PBF application, or LTC6400IUD-8#PBF equivalent, key selection criteria include output common-mode adjustability (1V–1.6V), differential I/O capability, shutdown control via ENABLE pin, 3mm × 3mm QFN package constraints, and verified OIP3 performance across 70–300MHz bands.

Technical Context

The LTC6400IUD-8#PBF implements a fully differential op amp architecture with on-chip feedback network (200Ω/500Ω resistors) setting fixed 2.5V/V gain and 400Ω differential input impedance. Its internal common-mode feedback loop operates at ~400MHz, enabling fast rejection of output common-mode disturbances while VOCM pin control bandwidth remains at 14MHz for noise suppression.

It supports both AC- and DC-coupled operation with independent VOCM biasing, eliminating need for transformers or coupling capacitors in many ADC interface designs. Output stage includes unfiltered (+OUT/–OUT, 12.5Ω series) and filtered (+OUTF/–OUTF, 50Ω + 2.7pF) terminals, enabling flexible external filtering or 50Ω single-ended matching without layout redesign.

Key Specifications

Pinout & Package

Package: 16-lead 3mm × 3mm × 0.75mm plastic QFN (UD package) with exposed V– pad (Pin 17) requiring PCB soldering for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar differential ADC driver applications.

Compared with LTC6401IUD-8#PBF and THS4561IRGET, the LTC6400IUD-8#PBF delivers superior high-frequency linearity and integrated VOCM control-critical for transformerless, DC-coupled 16-bit ADC interfaces-while accepting higher quiescent power as a trade-off for guaranteed –99dBc IMD3 at 70MHz and 2.2GHz bandwidth.

Availability

LTC6400IUD-8#PBF is available at Aetrix Electronics and suitable for high-resolution data acquisition, IF sampling receivers, single-ended-to-differential conversion, and SAW filter interfacing requiring stable component supply across industrial temperature ranges.

Supply support for LTC6400IUD-8#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors.

The LTC6400 family was designed specifically as ultra-low-noise, low-distortion differential ADC drivers for high-speed, high-resolution data converters-targeting applications demanding DC-coupled, transformerless signal chains with guaranteed industrial temperature operation.

FAQ

What is the operating temperature range specified for the LTC6400IUD-8#PBF?

The LTC6400IUD-8#PBF is rated for operation from –40°C to +85°C and is fully specified and tested across this industrial temperature range. Unlike the C-grade variant (LTC6400CUD-8#PBF), the 'I' grade guarantees performance compliance-including gain flatness, noise figure, and IMD3-at all temperatures within this span, making it suitable for embedded systems deployed in uncontrolled thermal environments.

Does the LTC6400IUD-8#PBF require external gain-setting resistors?

No, the LTC6400IUD-8#PBF does not require external gain-setting resistors. It features internally fixed gain of 8dB (2.5V/V), achieved via precision on-chip 200Ω/500Ω feedback resistors. This eliminates gain drift, layout sensitivity, and component count associated with external networks-ensuring repeatable performance across production units and temperature.

How is output common-mode voltage controlled on the LTC6400IUD-8#PBF?

The LTC6400IUD-8#PBF uses the VOCM pin (Pin 2) to set output common-mode voltage between 1V and 1.6V. This high-impedance input accepts a DC bias voltage (e.g., 1.25V from an ADC's VCM pin) and tracks it with <15mV offset. A 0.1μF bypass capacitor is required at VOCM to suppress noise, and its 14MHz control bandwidth prevents high-frequency common-mode injection into the output stage.

Can the LTC6400IUD-8#PBF drive ADCs without transformers or AC-coupling capacitors?

Yes, the LTC6400IUD-8#PBF is explicitly designed for transformerless, DC-coupled ADC interfacing. Its independently adjustable VOCM pin aligns output common-mode voltage to match ADC requirements (e.g., 1.25V for LTC2208), while differential inputs accept DC or AC signals. This eliminates baluns, coupling caps, and associated phase imbalance or low-frequency roll-off-verified in Figure 7 of the datasheet with LTC2208.

What is the difference between the +OUT/–OUT and +OUTF/–OUTF pins on the LTC6400IUD-8#PBF?

The +OUT/–OUT pins (Pins 5, 8) provide unfiltered differential outputs with 12.5Ω series resistance for stability and flexibility in custom filter design. The +OUTF/–OUTF pins (Pins 6, 7) integrate 50Ω series resistors and 2.7pF shunt capacitance, forming a 590MHz low-pass filter ideal for 50Ω single-ended matching or noise reduction-enabling immediate use without external components in wideband applications.