Texas Instruments LMH6551MMX/NOPB

Overview

LMH6551MMX/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 (V_OUT = 0.5 V_PP), 2400 V/µs slew rate, and −94/−96 dBc HD2/HD3 at 5 MHz under ±5 V supply - enabling precision differential signaling in video-over-twisted-pair and IF/RF receiver front-ends.

For engineers reviewing the LMH6551MMX/NOPB datasheet, LMH6551MMX/NOPB pinout, LMH6551MMX/NOPB application, or LMH6551MMX/NOPB equivalent, this device supports single-ended-to-differential conversion, wide common-mode input range (±4.7 V), programmable output common-mode voltage via VCM pin, and stable operation with external gain-setting resistors - critical for high-fidelity data acquisition and communications signal conditioning.

Technical Context

The LMH6551MMX/NOPB implements a three-channel architecture: two high-gain differential signal paths (IN+→+OUT, IN−→−OUT) operating in inverting mode, plus 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 precise common-mode control and true single-ended-to-differential conversion without external feedback networks.

Its voltage-feedback topology uses external RF/RG resistors for gain setting (e.g., G = +1 with RF = RG = 365 Ω), while internal 50-kΩ resistive dividers provide midsupply default on VCM when left floating. The amplifier maintains >70 dB CMRR up to 10 MHz and exhibits <18 ns settling time to 0.05% under ±5 V supply - confirming suitability for time-critical sampling systems.

Key Specifications

Pinout & Package

The LMH6551MMX/NOPB is housed in an 8-pin VSSOP package (3.00 mm × 3.00 mm body size), optimized for high-density PCB layouts and high-frequency performance with minimized parasitic inductance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561IRGET and ADA4940-1ARZ, the LMH6551MMX/NOPB uniquely combines 370-MHz bandwidth, programmable VCM, and proven −96-dBc HD3 at 5 MHz - making it the preferred choice for high-speed ADC drivers and broadband communication IF stages requiring flexible common-mode control.

Availability

LMH6551MMX/NOPB is available at Aetrix Electronics and suitable for differential ADC driver, video-over-twisted-pair, and IF amplifier applications requiring stable component supply, consistent parametric performance across temperature, and long-term industrial lifecycle support.

Supply support for LMH6551MMX/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 delivering analog and embedded processing solutions, with deep expertise in high-speed signal chain design and automotive-grade reliability validation.

The LMH6551MMX/NOPB belongs to TI's LMH™ high-speed amplifier family, engineered specifically for demanding differential signal conditioning in communications infrastructure, test equipment, and high-fidelity data acquisition systems.

FAQ

What is the recommended supply configuration for LMH6551MMX/NOPB in a single-ended-to-differential application?

For single-ended-to-differential conversion, LMH6551MMX/NOPB operates optimally with split supplies (e.g., ±5 V) and the VCM pin biased to the target output common-mode voltage - typically 0 V for bipolar ADCs. A 0.1 µF ceramic capacitor must bypass VCM to ground to suppress noise coupling. The IN+ pin receives the single-ended signal while IN− is terminated to VCM, leveraging the internal common-mode feedback loop to generate balanced outputs.

How does the VCM pin function in LMH6551MMX/NOPB, and what happens if left unconnected?

The VCM pin in LMH6551MMX/NOPB sets the average DC voltage of the +OUT and −OUT terminals. When left unconnected, internal 50-kΩ resistors divide the total supply to produce a midsupply reference (e.g., 0 V with ±5 V supplies). However, TI recommends actively driving VCM with a low-impedance source and bypassing it to ground with 0.1 µF to prevent noise injection and ensure stable common-mode control - critical for ADC interface integrity.

Can LMH6551MMX/NOPB drive 50-Ω differential loads directly, and what external components are required?

Yes, LMH6551MMX/NOPB can drive 50-Ω differential loads (e.g., 100-Ω total) directly, but requires external gain-setting resistors (RG and RF) to establish closed-loop gain and stabilize operation. For unity gain (G = +1), TI specifies RG = RF = 365 Ω with 500-Ω load. Series termination resistors (e.g., 50 Ω per output) may be added near the load to damp reflections in high-frequency transmission lines like CAT-5.

What is the maximum output current capability of LMH6551MMX/NOPB, and how does it vary with supply voltage?

LMH6551MMX/NOPB delivers ±65 mA linear output current under ±5 V supply (measured at V_OUT = 0 V), decreasing to ±40 mA at +3.3 V single supply. Short-circuit current reaches 140 mA (±5 V) or 230 mA (+5 V). These values are limited by thermal dissipation - designers must verify junction temperature using R_θJA = 235 °C/W (VSSOP) and ambient conditions to avoid exceeding 150 °C T_JMAX.

Does LMH6551MMX/NOPB support shutdown functionality, and how is it implemented?

LMH6551MMX/NOPB does not include a dedicated shutdown (PD) pin - unlike some newer TI FDAs. Power-down is achieved only by removing supply voltages. Quiescent current remains ~12.5 mA (±5 V) in normal operation. For low-power standby, system-level supply switching is required; no internal enable/disable control is available on the LMH6551MMX/NOPB die.