Texas Instruments LMH6321MR/NOPB

Overview

LMH6321MR/NOPB from Texas Instruments is a high-speed unity-gain buffer IC with 1800 V/μs slew rate, 110 MHz small-signal bandwidth, ±300 mA continuous output current, and adjustable current limit (10–300 mA) set via external resistor on the CL pin. It operates from ±5 V to ±15 V supplies and drives heavy capacitive loads without oscillation - used in sonar transducer drivers and high-current line drivers.

For engineers reviewing the LMH6321MR/NOPB datasheet, LMH6321MR/NOPB pinout, LMH6321MR/NOPB application, or LMH6321MR/NOPB equivalent, key selection criteria include programmable current limiting accuracy (±5 mA ±5%), thermal shutdown flag (EF pin), SO PowerPAD™ package thermal performance, and stability into >1 nF capacitive loads with 50 Ω source impedance.

Technical Context

The LMH6321MR/NOPB uses an open-loop complementary emitter-follower topology optimized for unity-gain operation - not a closed-loop op-amp configuration - delivering minimal propagation delay and phase shift. Its current-limit circuit shares sourcing and sinking paths, with CL pin voltage directly controlling both directions via external reference current.

Thermal shutdown activates at 168°C junction temperature (10°C hysteresis), asserting low-voltage error flag (EF) while reducing supply current to ~3 mA. The EF pin is open-collector, requiring external pull-up; it signals fault condition but does not disable output.

Key Specifications

Pinout & Package

The LMH6321MR/NOPB is packaged in an 8-pin SO PowerPAD™ (SOIC-8 with exposed thermal pad), measuring 4.9 mm × 3.9 mm × 1.75 mm. The exposed pad must be soldered to PCB ground plane for optimal thermal performance (R_θJB = 11.7°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-current buffer applications.

Compared with THS3091D and LMH6321MF/NOPB, the LMH6321MR/NOPB uniquely balances programmable current limiting, thermal fault signaling, and SOIC-8 manufacturability - making it optimal for space-constrained, fault-aware industrial drivers where design reuse and thermal margin are prioritized over peak speed or ultra-low thermal resistance.

Availability

LMH6321MR/NOPB is available at Aetrix Electronics and suitable for sonar transducer drivers, industrial line drivers, and motor phase current monitor circuits requiring stable component supply, long-term lifecycle support, and traceable sourcing for production programs.

Supply support for LMH6321MR/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 designing analog ICs, embedded processors, and connectivity solutions for industrial, automotive, and communications markets.

The LMH6321MR/NOPB belongs to TI's high-speed buffer product line, engineered specifically for applications demanding high output current, fast transient response, and robust protection - including test equipment, medical ultrasound, and precision motion control.

FAQ

What is the purpose of the CL pin on the LMH6321MR/NOPB?

The CL pin on the LMH6321MR/NOPB accepts an external reference current (25 µA to 750 µA) to set the symmetrical sourcing and sinking current limit between 10 mA and 300 mA. This current is converted internally with ±5 mA ±5% accuracy, enabling precise, field-adjustable overcurrent protection without additional components. The LMH6321MR/NOPB uses this pin to define its primary safety boundary during short-circuit or overload conditions.

Does the LMH6321MR/NOPB require external compensation for stability?

No, the LMH6321MR/NOPB is internally compensated for unity-gain stability and remains stable into ≥1 nF capacitive loads when driven from a 50 Ω source - no external compensation components are needed. Its open-loop complementary follower architecture avoids phase-margin tradeoffs typical of op-amps, eliminating the need for feedback network tuning. Layout best practices (e.g., short traces, proper grounding) still apply to maintain RF immunity.

How does the EF (Error Flag) pin function on the LMH6321MR/NOPB?

The EF pin on the LMH6321MR/NOPB is an open-drain output that pulls low during thermal shutdown (at 168°C junction temperature) and remains low until junction temperature drops by 10°C hysteresis. It requires an external pull-up resistor (e.g., 5 kΩ to +5 V) and provides a system-level fault signal - independent of output state - allowing host controllers to log events or initiate safe shutdown. The LMH6321MR/NOPB continues operating unless manually reset or power-cycled.

Can the LMH6321MR/NOPB operate from a single supply?

Yes, the LMH6321MR/NOPB supports single-supply operation from +5 V to +30 V, with V− pin connected to GND. Input common-mode range extends to the negative rail (GND), and output swing reaches within ~1.2 V of GND at 300 mA load. For rail-to-rail input/output, external level-shifting or biasing is required - the LMH6321MR/NOPB itself does not provide true rail-to-rail performance but maintains specified AC performance across the supported single-supply range.

What thermal performance advantages does the SO PowerPAD™ package offer for the LMH6321MR/NOPB?

The SO PowerPAD™ package of the LMH6321MR/NOPB features an exposed copper thermal pad on the bottom surface, soldered directly to the PCB ground plane. This reduces junction-to-board thermal resistance to 11.7°C/W - significantly lower than standard SOIC-8 - enabling higher continuous output current in thermally constrained layouts. Proper pad design (≥4× thermal vias to inner ground planes) is essential to realize the full benefit; the LMH6321MR/NOPB's thermal shutdown threshold remains at 168°C regardless of package variant.