Texas Instruments LMH6518SQE/NOPB

Overview

LMH6518SQE/NOPB from Texas Instruments is a digitally controlled variable gain amplifier (DCVGA) with 40 dB gain range in 2 dB steps, −3 dB bandwidth of 900 MHz across all gains, and differential main/auxiliary outputs for oscilloscope trigger and ADC driver applications. It features SPI interface, selectable bandwidth limiting (20–750 MHz), and overvoltage clamps enabling fast recovery in high-speed signal chains.

For engineers reviewing the LMH6518SQE/NOPB datasheet, LMH6518SQE/NOPB pinout, LMH6518SQE/NOPB application, or LMH6518SQE/NOPB equivalent, key selection criteria include its 8.5 mdB combined gain resolution with GSPS ADCs, input-referred noise of 0.98 nV/√Hz at max gain, ±0.1 dB gain matching between main and auxiliary outputs, and dual common-mode control (VCM/VCM_AUX) for precision differential signaling.

Technical Context

The LMH6518SQE/NOPB implements a two-stage architecture: a programmable preamplifier (high-gain/low-gain mode) followed by a 10-step 2 dB ladder attenuator, enabling precise digital gain control. Its fully differential signal path supports dc-coupled operation with independent common-mode voltage control on both main and auxiliary outputs.

Bandwidth limiting is implemented via a shared filter network supporting seven settings (20/100/200/350/650/750 MHz or full BW), and the auxiliary output replicates the main output's amplitude and timing for oscilloscope trigger circuitry while maintaining <100 ps propagation delay variation across gain changes.

Key Specifications

Pinout & Package

The LMH6518SQE/NOPB is housed in a 16-pin WQFN package (RGH), 4 mm × 4 mm, with exposed thermal pad electrically connected to pins 5 and 8 (GND).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digitally controlled VGA applications.

Compared with ADL5330ACPZ-R7 and LMH6514SQE/NOPB, the LMH6518SQE/NOPB uniquely delivers simultaneous differential main/auxiliary outputs with independent common-mode control, SPI programmability, and 900 MHz flat bandwidth-making it the only option suited for high-fidelity oscilloscope front-ends and synchronized ADC+trigger architectures.

Availability

LMH6518SQE/NOPB is available at Aetrix Electronics and suitable for oscilloscope front-ends, GSPS ADC driver circuits, and RF/IF receiver gain control requiring stable component supply, traceable sourcing, and long-term lifecycle support.

Supply support for LMH6518SQE/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, embedded processing, and high-performance signal chain solutions.

The LMH6518SQE/NOPB belongs to TI's high-speed amplifier product line, designed specifically for precision gain control in test equipment, communications infrastructure, and medical imaging systems demanding wide bandwidth, low distortion, and digital configurability.

FAQ

What is the gain control interface used by the LMH6518SQE/NOPB?

The LMH6518SQE/NOPB uses a standard 3-wire SPI interface (CS, SCLK, SDIO) operating up to 10 MHz. Gain is programmed via an 8-bit command and 16-bit data word, allowing full 40 dB range control in 2 dB steps. The interface supports both write-only configuration and read-back of register status, enabling robust system calibration and fault detection in production environments using the LMH6518SQE/NOPB.

Does the LMH6518SQE/NOPB support dc-coupled operation?

Yes, the LMH6518SQE/NOPB supports fully dc-coupled operation on both inputs and outputs. Its differential inputs accept common-mode voltages from 1.9 V to 3.1 V, and main/auxiliary outputs feature independent VCM and VCM_AUX pins to set output common-mode levels from 0.95 V to 1.45 V. This enables seamless integration into baseband and low-frequency signal chains without ac-coupling capacitors, preserving signal integrity down to 0 Hz when using the LMH6518SQE/NOPB.

How does the auxiliary output of the LMH6518SQE/NOPB differ from the main output?

The auxiliary output of the LMH6518SQE/NOPB mirrors the main output's amplitude, phase, and timing with ±0.2 dB gain matching and <100 ps propagation delay variation. It features independent VCM_AUX control and identical bandwidth limiting, but is optimized for low-latency trigger generation rather than high-fidelity signal acquisition. Unlike the main output, the auxiliary path is not intended for high-precision ADC driving-its primary role is synchronous event detection, as defined in the LMH6518SQE/NOPB datasheet.

What bandwidth limiting options are available on the LMH6518SQE/NOPB?

The LMH6518SQE/NOPB offers seven selectable bandwidth limiting settings: 20 MHz, 100 MHz, 200 MHz, 350 MHz, 650 MHz, 750 MHz, or full 900 MHz bandwidth. These are configured via SPI register bits and apply identically to both main and auxiliary outputs. Each setting maintains flat group delay and minimal peaking (<1 dB), making them suitable for anti-aliasing and noise reduction without introducing phase distortion in the LMH6518SQE/NOPB signal path.

What is the power consumption profile of the LMH6518SQE/NOPB under typical operating conditions?

At TA = 25°C with VCC = 5 V and VDD = 3.3 V, the LMH6518SQE/NOPB draws 210 mA from VCC (analog supply) and 350 µA from VDD (digital supply), totaling ~1.1 W. When the auxiliary output is disabled, VCC current drops to 165 mA (~0.75 W). Thermal resistance is RθJA = 40°C/W (RGH package), requiring adequate PCB copper area under the thermal pad (pins 5/8) to maintain junction temperature below 150°C in continuous operation using the LMH6518SQE/NOPB.