Texas Instruments LMH6551MAX

Overview

LMH6551MAX 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 supply), 2400 V/µs slew rate, 18 ns settling time to 0.05%, and −94/−96 dBc HD2/HD3 at 5 MHz - enabling precision video-over-twisted-pair and IF/RF signal conditioning in communications infrastructure.

For engineers reviewing the LMH6551MAX datasheet, LMH6551MAX pinout, LMH6551MAX application, or LMH6551MAX equivalent, this page provides verified technical context, real-world design meaning of key specs, validated SOIC-8 package mapping, confirmed pin functions, and two rigorously cross-referenced alternative parts for differential ADC driver and single-ended-to-differential conversion use cases.

Technical Context

The LMH6551MAX implements a three-channel architecture: two high-gain, inverting-mode differential signal paths (V+ and V−) plus an independent common-mode feedback loop that senses output average voltage and compares it to the VCM pin reference. This enables precise control of output common-mode level and maintains amplitude/phase balance even with single-ended input drive.

It operates as a voltage-feedback amplifier requiring external gain-setting resistors (e.g., RF = RG = 365 Ω for G = +1). The VCM pin accepts a low-impedance reference (bypassed with 0.1 µF ceramic) to set output common-mode voltage; floating it defaults to midsupply via internal 50-kΩ resistors. No internal power-down pin is present - functionality relies on external biasing and resistor network configuration.

Key Specifications

Pinout & Package

LMH6551MAX is packaged in an 8-pin SOIC (4.90 mm × 3.91 mm body) with standard JEDEC MS-012AC footprint and 1.27 mm pitch. Thermal resistance θJA = 150 °C/W on 2-layer board.

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561DR and ADA4940-1ARZ, the LMH6551MAX uniquely balances 370 MHz bandwidth, −96 dBc HD3 at 5 MHz, and ±65 mA drive in a cost-effective SOIC-8 package - making it the most widely deployed solution for mid-bandwidth, high-fidelity differential signal conditioning in telecom and test equipment.

Availability

LMH6551MAX 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 lifecycle support, and consistent parametric performance across production batches.

Supply support for LMH6551MAX 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 leader specializing in analog, embedded processing, and connectivity technologies, with decades of expertise in high-speed amplifier design and manufacturing.

The LMH6551MAX belongs to TI's LMH™ high-speed amplifier family, engineered specifically for demanding signal-chain applications including ADC driving, communications infrastructure, and precision instrumentation where bandwidth, linearity, and noise performance are critical.

FAQ

What is the maximum small-signal bandwidth of the LMH6551MAX under ±5-V supply conditions?

The LMH6551MAX achieves a 370 MHz −3-dB small-signal bandwidth when operated at ±5 V supply with 0.5 VPP differential output. This specification is measured with RF = RG = 365 Ω, RL = 500 Ω, and TA = 25°C. Bandwidth decreases to 350 MHz at +5 V supply and 320 MHz at +3.3 V supply, reflecting supply-dependent transconductance limitations in the LMH6551MAX core amplifier.

Can the LMH6551MAX be used with single-ended input signals?

Yes, the LMH6551MAX supports single-ended-to-differential conversion via its VCM feedback architecture. When only IN+ or IN− is driven (with the other input terminated to VCM), the internal common-mode error amplifier forces the outputs to maintain equal magnitude and opposite phase. Verified application circuits in the LMH6551MAX datasheet confirm <−70 dB balance error at 10 MHz, making it suitable for DAC output buffering and legacy SE source interfacing.

What is the recommended bypassing strategy for the VCM pin on the LMH6551MAX?

The VCM pin on the LMH6551MAX must be bypassed to ground with a 0.1 µF ceramic capacitor placed within 2 mm of the pin. This prevents noise coupling into the common-mode feedback loop, which would degrade output balance and dynamic range. If VCM is driven externally, the source impedance must be <100 Ω; floating VCM defaults to midsupply via internal 50-kΩ resistors, but bypassing remains mandatory for stability.

Does the LMH6551MAX have a power-down feature?

No, the LMH6551MAX does not include an integrated power-down (PD) pin or shutdown function. Its quiescent current (11–14.5 mA) is fixed per supply condition and cannot be externally disabled. For low-power standby modes, system-level supply gating or series FETs on V+ and V− rails are required. This distinguishes the LMH6551MAX from later-generation FDAs like THS4561, which integrate active shutdown control.

What is the output voltage swing capability of the LMH6551MAX at ±5-V supply?

At ±5-V supply, the LMH6551MAX delivers ±7.8 V peak-to-peak differential output swing into high-impedance loads, corresponding to ±3.9 V single-ended swing per output. Under 500-Ω differential load, the guaranteed minimum is ±7.38 VPP. Output swing compresses with increasing load current - e.g., ±7.18 VPP at temperature extremes - and is limited by internal output stage headroom and thermal dissipation in the LMH6551MAX SOIC package.