Texas Instruments LMH6551QMME/NOPB

Overview

LMH6551QMME/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 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 automotive-grade systems.

For engineers reviewing the LMH6551QMME/NOPB datasheet, LMH6551QMME/NOPB pinout, LMH6551QMME/NOPB application, or LMH6551QMME/NOPB equivalent, key selection criteria include differential output drive capability (±65 mA linear), AEC-Q100 Grade 1 qualification (−40°C to +125°C), VCM-controlled common-mode output setting, and stability with capacitive loads up to 57 pF - critical for ADC interface and high-speed line driver designs.

Technical Context

The LMH6551QMME/NOPB implements a three-channel architecture: two independent differential signal paths (V+ and V−) operating as inverting-mode amplifiers, plus a dedicated common-mode feedback circuit that enforces output balance and sets output common-mode voltage via the VCM pin. This enables true single-ended-to-differential conversion without external transformers.

It operates as a voltage-feedback amplifier with gain set by external 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 define output common-mode level; noise on VCM directly degrades dynamic range and balance error (−70 dB typical at 10 MHz).

Key Specifications

Pinout & Package

LMH6551QMME/NOPB is housed in an 8-pin VSSOP package (Package Code DGK), 3.0 mm × 3.0 mm, 0.65 mm pitch, with exposed thermal pad. Pin 1 is marked by a dot; top view matches TI's standard DGK pinout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561IRGET and ADA4940-1ARZ-R7, LMH6551QMME/NOPB uniquely combines AEC-Q100 Grade 1 qualification, VCM-programmable common-mode output, and 370 MHz bandwidth with <−94 dBc HD2 - making it the only choice for automotive video-over-cable and high-MSPS ADC interfaces requiring guaranteed operation at +125°C.

Availability

LMH6551QMME/NOPB is available at Aetrix Electronics and suitable for automotive camera modules, high-speed data acquisition systems, and RF front-end designs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LMH6551QMME/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 leader specializing in analog and embedded processing technologies, with decades of expertise in high-speed amplifiers and automotive-qualified ICs.

The LMH6551QMME/NOPB belongs to TI's LMH™ high-speed differential amplifier product line, engineered specifically for demanding signal chain applications including ADC driving, video transmission, and IF/RF conditioning in automotive and industrial environments.

FAQ

What is the maximum differential output voltage swing of the LMH6551QMME/NOPB?

The LMH6551QMME/NOPB delivers ±7.8 V peak-to-peak differential output swing under ±5 V supply conditions, corresponding to ±3.9 V single-ended relative to common mode. At 5 V single supply (VCM = 2.5 V), it achieves ±2.8 V peak-to-peak differential swing. These values assume RL = 500 Ω and linear operation within ±65 mA output current limits - exceeding typical requirements for driving 100 Ω differential ADC inputs or CAT-5 cables. The LMH6551QMME/NOPB maintains this swing across its full −40°C to +125°C operating range.

How does the VCM pin function in the LMH6551QMME/NOPB?

The VCM pin on the LMH6551QMME/NOPB sets the output common-mode voltage level by feeding a low-impedance reference into an internal buffer. It must be bypassed with a 0.1 µF ceramic capacitor to ground, placed within 3 mm of the pin. Noise or ripple on VCM directly couples to both outputs, degrading dynamic range and balance error. When left unconnected, the internal 25 kΩ resistive divider defaults output common mode to mid-supply. The LMH6551QMME/NOPB uses this pin to enable flexible level-shifting - critical for interfacing with ADCs requiring specific common-mode input voltages.

Is the LMH6551QMME/NOPB suitable for single-ended-to-differential conversion?

Yes, the LMH6551QMME/NOPB is explicitly designed for high-fidelity single-ended-to-differential conversion using its integrated common-mode feedback circuit. With one input grounded or terminated, the VCM loop actively balances the outputs to maintain symmetry - achieving −70 dB balance error at 10 MHz. This eliminates the need for passive baluns and avoids their inherent bandwidth and phase-matching limitations. The LMH6551QMME/NOPB supports this mode across all supply configurations (±5 V, +5 V, +3.3 V) and maintains distortion performance (−93 dBc HD3 at 5 MHz) comparable to fully differential operation.

What layout practices are critical for optimal LMH6551QMME/NOPB performance?

For optimal LMH6551QMME/NOPB performance, maintain strict symmetry between +IN/−IN and +OUT/−OUT traces - equal length, width, and spacing - to minimize imbalance-induced common-mode error. Place 0.01 µF and 0.1 µF ceramic bypass capacitors ≤3 mm from each supply pin (V+, V−), connecting directly to solid ground plane. Route VCM with short, low-impedance trace and bypass locally. Avoid vias in high-speed paths; use controlled-impedance routing for differential pairs. The LMH6551QMME/NOPB's 8-pin VSSOP package demands tight layout adherence to achieve specified −94 dBc HD2 and <18 ns settling time.

Does the LMH6551QMME/NOPB require external gain-setting resistors?

Yes, the LMH6551QMME/NOPB is a voltage-feedback amplifier requiring external resistors to set closed-loop gain. Typical configurations use matched RF and RG (e.g., 365 Ω each for G = +1) between outputs and inputs. Gain is calculated as AV = RF/RG for differential output. Resistor matching tolerance (≤0.1%) directly impacts CMRR and harmonic distortion - mismatch degrades HD2/HD3 by up to 10 dB. The LMH6551QMME/NOPB does not include internal gain resistors; all gain configuration is external and field-adjustable, supporting flexible system-level calibration.