Texas Instruments LMH6551MAX/NOPB

Overview

LMH6551MAX/NOPB from Texas Instruments is a high-speed, fully differential voltage-feedback amplifier optimized for driving high-performance ADCs and balanced transmission lines. It delivers 370 MHz −3-dB bandwidth (±5 V, 0.5 VPP), 2400 V/µs slew rate, and −94/−96 dBc HD2/HD3 at 5 MHz - enabling precision differential signaling in IF/RF and video-over-twisted-pair systems.

For engineers reviewing the LMH6551MAX/NOPB datasheet, LMH6551MAX/NOPB pinout, LMH6551MAX/NOPB application, or LMH6551MAX/NOPB equivalent, this device supports single-ended-to-differential conversion, wide supply range (3–12 V), precise output common-mode control via VCM pin, and operation across −40°C to +125°C industrial temperature range.

Technical Context

The LMH6551MAX/NOPB implements a three-channel architecture: two high-gain differential signal paths (IN+→+OUT, IN−→−OUT) and an independent VCM error amplifier that senses output common-mode voltage and forces it to match the voltage applied to the VCM pin. This enables accurate single-ended input operation without external level-shifting circuitry.

It uses external gain-setting resistors (RF/RG) for flexible gain configuration and requires no internal compensation. The VCM pin accepts a low-impedance reference (bypassed with 0.1 µF ceramic capacitor) and directly controls output DC offset - critical for interfacing with ADCs requiring specific input common-mode voltage levels.

Key Specifications

Pinout & Package

LMH6551MAX/NOPB is packaged in an 8-pin SOIC (D package), 4.90 mm × 3.91 mm body size, with exposed pad not present. Pin functions are validated per TI SNOSAK7D Rev D datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561IRGET and ADA4940-1ARZ, LMH6551MAX/NOPB offers the widest bandwidth among the three (370 MHz), unique VCM pin flexibility for custom common-mode biasing, and extended +125°C operation - making it optimal for high-frequency, thermally demanding, or mixed-supply ADC interface designs.

Availability

LMH6551MAX/NOPB is available at Aetrix Electronics and suitable for differential ADC driver, video-over-twisted-pair, and IF/RF amplifier applications requiring stable component supply, long-term industrial lifecycle support, and traceable sourcing.

Supply support for LMH6551MAX/NOPB 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in high-speed amplifiers, data converters, and power management ICs.

The LMH6551MAX/NOPB belongs to TI's LMH™ high-speed amplifier product line, designed specifically for precision differential signal conditioning in communications, test equipment, and high-fidelity data acquisition systems.

FAQ

What is the recommended power supply configuration for LMH6551MAX/NOPB in ADC driver applications?

For optimal distortion performance in ADC driver applications, LMH6551MAX/NOPB should be operated with ±5 V supplies (10 V total). This configuration delivers the full 370 MHz −3-dB bandwidth, 2400 V/µs slew rate, and −96 dBc HD3 at 5 MHz. Single-supply operation (e.g., 5 V with VCM = 2.5 V) reduces bandwidth to 350 MHz and slew rate to 1800 V/µs but remains viable for lower-frequency systems. Local 0.1 µF ceramic decoupling at each supply pin is mandatory.

How does the VCM pin function in LMH6551MAX/NOPB, and what happens if left unconnected?

The VCM pin on LMH6551MAX/NOPB sets the average DC voltage of the +OUT and −OUT outputs. When left unconnected (floating), internal 50-kΩ resistors divide the supply to generate a mid-rail reference (e.g., 0 V for ±5 V supplies). However, TI strongly recommends driving VCM with a low-impedance source (e.g., precision voltage reference) and bypassing it to ground with a 0.1 µF ceramic capacitor - otherwise, noise coupling degrades dynamic range and common-mode rejection.

Can LMH6551MAX/NOPB be used with single-ended input signals, and how is gain set?

Yes, LMH6551MAX/NOPB supports single-ended input operation using only IN+ or IN− while the other input is grounded or terminated. Gain is set externally by resistor pairs: AV = 1 + RF/RG for differential input, or AV = RF/RG for single-ended input (with one input grounded). For example, RF = 730 Ω and RG = 365 Ω yields AV = 2. Matching tolerance of RF/RG resistors to ≤0.1% is critical to maintain balance and minimize even-order distortion.

What thermal considerations apply to LMH6551MAX/NOPB in continuous high-output-current operation?

LMH6551MAX/NOPB has a junction-to-ambient thermal resistance (RθJA) of 150°C/W in SOIC-8. At ±5 V supply and 65 mA linear output current per output, power dissipation reaches ~130 mW. With TA = +85°C, junction temperature rises to ~105°C - within the 150°C absolute max. To ensure reliability, use minimum 2-layer PCB with thermal vias under the package, avoid enclosing the device, and limit sustained output current to ≤50 mA unless heatsinking is added.

Is LMH6551MAX/NOPB compatible with high-impedance SAW filters, and what input characteristics support this?

Yes, LMH6551MAX/NOPB is well-suited for SAW filter buffering due to its 5 MΩ differential input resistance and only 1 pF differential input capacitance. These values prevent Q-factor degradation and resonance frequency shifts in narrowband SAW devices (e.g., 140–160 MHz GPS or LTE filters). Its low input bias current (±4 µA max) further minimizes DC offset errors when interfacing with high-Z passive components in RF front-ends.