Texas Instruments LMH6554LEX/NOPB

Overview

LMH6554LEX/NOPB from Texas Instruments is a 2.8-GHz fully differential current-feedback amplifier optimized as a high-fidelity ADC driver for 8- to 16-bit data acquisition systems. It delivers 1.8 GHz large-signal bandwidth (2 V_PP), −96 dBc HD2/−97 dBc HD3 at 75 MHz, 0.9 nV/√Hz input voltage noise, and operates on ±2.5 V or single 5-V supplies in a 2.5 mm × 2.5 mm UQFN-14 package.

For engineers reviewing the LMH6554LEX/NOPB datasheet, LMH6554LEX/NOPB pinout, LMH6554LEX/NOPB application, or LMH6554LEX/NOPB equivalent, key selection criteria include differential output drive capability into 200 Ω loads, VCM-controlled common-mode output setting, enable/disable functionality via VEN, and stability with capacitive loads up to 68 pF when isolated with series resistors.

Technical Context

The LMH6554LEX/NOPB implements a proprietary differential current-mode input stage enabling gain-bandwidth independence: small-signal bandwidth remains 2.8 GHz at unity gain and sustains 1.6 GHz at AV = 4 without sacrificing flatness or distortion. Its integrated common-mode feedback loop forces matched +OUT/−OUT amplitude and phase inversion even during single-ended input operation, while decoupling output common-mode voltage (set via VCM pin) from input common-mode conditions.

As a current-feedback amplifier (CFA), it uses external RF/RG resistor networks to define closed-loop gain and input impedance; optimal performance requires ≤0.1% tolerance matching to preserve CMRR (>82 dB), DC offset (<±10 µA IBI), and output balance error (<−64 dB). Internal compensation ensures stable operation with RF = 200 Ω across PCB layouts and 200 Ω load conditions.

Key Specifications

Pinout & Package

LMH6554LEX/NOPB is housed in a 2.5 mm × 2.5 mm, 14-pin UQFN (NHJ) package with wettable flanks and thermal pad. The package supports high-density PCB layouts and efficient heat dissipation (R_θJA = 60 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with THS4561IRGT and ADA4961ACPZ-R7, LMH6554LEX/NOPB uniquely combines 2.8 GHz bandwidth, integrated VCM control, and 15 ns enable/disable timing in a 2.5 mm × 2.5 mm footprint - making it optimal for compact, high-performance, power-aware ADC interface designs demanding DC-coupled single-ended conversion.

Availability

LMH6554LEX/NOPB is available at Aetrix Electronics and suitable for high-speed data acquisition, RF instrumentation, and automotive safety sensor signal conditioning requiring stable component supply and long-term production continuity.

Supply support for LMH6554LEX/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 over 90 years of innovation in high-performance signal chain solutions.

LMH6554LEX/NOPB belongs to TI's high-speed differential amplifier product line, engineered specifically for ultra-linear, wideband signal conditioning in precision data converter interfaces and RF infrastructure applications.

FAQ

What supply configurations does the LMH6554LEX/NOPB support?

The LMH6554LEX/NOPB operates on either split supplies (±2.5 V) or a single 5-V supply with V− tied to ground. Split-supply operation enables unrestricted AC/DC coupling and optimal distortion performance; single-supply use requires attention to input common-mode range and may necessitate AC coupling depending on gain configuration. Both modes maintain full 2.8 GHz bandwidth and 1.8 GHz large-signal response.

How does the VCM pin function in the LMH6554LEX/NOPB?

The VCM pin on the LMH6554LEX/NOPB sets the output common-mode voltage with a fixed 1 V/V gain. It must be driven by a low-impedance reference (e.g., ADC reference voltage) and bypassed to ground with a 0.1-µF ceramic capacitor. Any noise or signal coupled into VCM appears directly at the outputs, degrading balance and distortion - so clean, well-decoupled routing is essential for LMH6554LEX/NOPB performance.

Can the LMH6554LEX/NOPB drive capacitive loads like ADC inputs?

Yes, the LMH6554LEX/NOPB can drive capacitive loads up to 68 pF when isolated with series resistors (e.g., 5 Ω for 68 pF), as documented in Figure 7-5 of the datasheet. This isolation prevents peaking and instability while preserving pulse fidelity. Direct connection to capacitive loads without series resistance risks ringing and bandwidth reduction - always apply the recommended RO values per measured CL in LMH6554LEX/NOPB applications.

What is the role of the +FB and −FB pins on the LMH6554LEX/NOPB?

The +FB and −FB pins on the LMH6554LEX/NOPB are dedicated feedback terminals that connect directly to +OUT and −OUT to close the differential loop. They define closed-loop gain via external RF/RG resistor ratios and must be matched precisely (≤0.1% tolerance) to maintain CMRR, output balance (<−64 dB), and low harmonic distortion. Unlike voltage-feedback amplifiers, these pins do not accept direct input signals - their sole function is feedback path establishment for the current-feedback core.

Does the LMH6554LEX/NOPB support single-ended input operation?

Yes, the LMH6554LEX/NOPB supports robust single-ended-to-differential conversion without transformers. When only +IN is driven (−IN terminated), its internal common-mode feedback forces −OUT to mirror +OUT with opposite polarity, achieving balanced outputs. Performance depends critically on resistor matching: Table 7-1 specifies RF/RG/RT values for 0 dB, 6 dB, and 12 dB gains in 50-Ω systems - using these ensures <−96 dBc HD2 at 75 MHz in LMH6554LEX/NOPB implementations.