Analog Devices Inc. DC1945A

Overview

LTC6409 from Analog Devices is a 10 GHz gain-bandwidth, fully differential amplifier optimized as an ADC driver for high-speed data acquisition systems. It features 1.1 nV/√Hz input noise density, 88 dB SFDR at 100 MHz (2 V_P-P), and supports DC-coupled ground-referenced single-ended inputs - enabling precise level-shifting and conversion to differential outputs for driving pipeline ADCs like the LTC2262-14.

For engineers reviewing the LTC6409 datasheet, LTC6409 pinout, LTC6409 application, or LTC6409 equivalent, key selection considerations include its 3300 V/µs slew rate, external gain-setting resistor flexibility (gain ≥1 V/V), –40°C to 125°C operating range, and hardware shutdown capability reducing supply current to 100 µA.

Technical Context

The LTC6409 employs a fully differential architecture with independent common-mode feedback via the VOCM pin, allowing precise output common-mode voltage control (0.5 V to 3.5 V) regardless of input common-mode level. Its input stage includes ground-referenced common-mode range (0 V to 1.5 V at 3 V supply), enabling direct DC coupling of single-ended signals without AC coupling or level-shifting circuitry.

Stability is guaranteed at unity differential gain (AV = 1), supporting low-noise, zero-gain buffering applications. External RI/RF networks define closed-loop gain and frequency response; 0.1% resistor matching is recommended to maintain >54 dB CMRR and minimize common-mode-to-differential conversion artifacts in high-linearity signal chains.

Key Specifications

Pinout & Package

The LTC6409 is housed in a compact 10-pin 3 mm × 2 mm × 0.75 mm leadless QFN package (UDB) with exposed thermal pad connected to V–. Pin 11 (exposed pad) must be soldered to V– for optimal thermal performance and EMI suppression.

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561IDR and ADA4940-1ARZ, the LTC6409 delivers uniquely high GBW (10 GHz) and ultra-low noise (1.1 nV/√Hz) in a VOCM-controlled package - making it the only option capable of driving 14-bit ADCs at 150 MSPS while maintaining >80 dB SFDR through 100 MHz.

Availability

LTC6409 is available at Aetrix Electronics and suitable for high-speed data acquisition cards, communications receiver front-ends, and time-domain reflectometry systems requiring stable component supply with full industrial temperature support.

Supply support for LTC6409 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.

The LTC6409 belongs to Analog Devices' high-speed amplifier product line, engineered specifically for ultra-wideband, low-noise ADC driving in demanding instrumentation and wireless infrastructure applications.

FAQ

What is the minimum recommended gain setting for the LTC6409?

The LTC6409 is stable at differential gain = 1 V/V, which is its minimum configured gain. This configuration delivers lowest output noise and is commonly used for unity-gain buffering of high-fidelity signals before ADC sampling. External resistors RI and RF must be selected to achieve this gain, with RI = RF for AV = 1. The LTC6409 datasheet confirms stability and specified performance down to AV = 1 across the full –40°C to 125°C range.

Can the LTC6409 drive the LTC2262-14 ADC directly?

Yes, the LTC6409 is explicitly characterized driving the LTC2262-14 ADC in its typical application circuit (TA01). It delivers 1.8 V_P-P differential output at 150 MSPS with 71.1 dB SNR and 81.6 dB SFDR - meeting the ADC's dynamic performance requirements. The LTC6409's adjustable VOCM pin allows direct connection to the LTC2262-14's common-mode reference, ensuring optimal input alignment without external biasing.

How does the SHDN pin function on the LTC6409?

The SHDN pin on the LTC6409 is a CMOS logic input with a 150 kΩ internal pull-up resistor. When pulled to V– (ground), the device enters shutdown mode, drawing only 100 µA supply current. When left floating or tied to V+, it operates normally at 52 mA. Turn-on and turn-off times are typically 160 ns and 80 ns respectively - enabling rapid power cycling in burst-mode acquisition systems using the LTC6409.

What is the maximum allowable input common mode voltage for the LTC6409 at 5 V supply?

At a 5 V supply (VS = 5 V), the LTC6409 supports an input common mode voltage range (VICMR) of 0 V to 3.5 V, as specified in the Electrical Characteristics table. This wide range enables compatibility with ground-referenced sources and rail-to-rail input signals. The device maintains specified distortion and offset performance across this full range, verified per Note 7 in the LTC6409 datasheet.

Does the LTC6409 require external compensation components?

No, the LTC6409 is internally compensated and does not require external compensation capacitors. Its stability is guaranteed for differential gains ≥1 V/V with standard RI/RF feedback networks. However, external RC networks may be added to tailor frequency response - for example, adding a capacitor across RF creates a dominant pole for no-overshoot step response in time-domain applications, as described in the Applications Information section of the LTC6409 datasheet.