Texas Instruments LMR66420R5RXBR

Overview

LMR66420R5RXBR from Texas Instruments is a 36-V, 2-A synchronous step-down DC/DC converter in an enhanced HotRod™ QFN package (RXB, 14-pin, 2.6 mm × 2.6 mm), featuring fixed 5-V output, adjustable switching frequency (200 kHz–2.2 MHz via RT pin), 1.5 µA quiescent current at no load, and input transient protection up to 42 V. It serves as a primary power supply for industrial PLCs and test equipment requiring high reliability under –40°C to +150°C junction temperature.

For engineers reviewing the LMR66420R5RXBR datasheet, LMR66420R5RXBR pinout, LMR66420R5RXBR application, or LMR66420R5RXBR equivalent, key selection considerations include its ultra-low IQ operation in auto mode, dual-random spread spectrum for EMI reduction, 5-V fixed output with ±1% accuracy, thermal shutdown at 168°C, and compatibility with minimal external components including internal compensation.

Technical Context

The LMR66420R5RXBR uses peak-current-mode control with frequency foldback in auto mode, enabling seamless PWM-to-PFM transition and maintaining >85% efficiency at 1 mA. Its architecture integrates internal loop compensation and supports light-load diode emulation to prevent reverse inductor current.

It implements dual-random spread spectrum (DRSS) to suppress peak EMI emissions and leverages the enhanced HotRod™ QFN package-bond-wire-free, with wettable flanks and NC pins between high-voltage nodes-to minimize switch-node ringing and improve FMEA robustness in industrial environments.

Key Specifications

Pinout & Package

LMR66420R5RXBR is housed in a 14-pin enhanced HotRod™ VQFN-FCRLF package (RXB), 2.6 mm × 2.6 mm, with wettable flanks and exposed thermal pad (GND/DAP) requiring solder connection to PCB ground for thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous step-down converter applications.

Compared with LMR66420R5RXBR, the LMR66430R5RXBR offers higher current capacity in identical form factor for scalability, while the TPS54202HDDCR trades industrial ruggedness for lower cost and simpler integration in benign environments - neither is pin-compatible beyond shared QFN-14 footprint, and only the LMR66430R5RXBR maintains full electrical and thermal equivalence.

Availability

LMR66420R5RXBR is available at Aetrix Electronics and suitable for factory automation, test and measurement, and medical device applications requiring stable component supply, long-lifecycle assurance, and guaranteed traceability for industrial-grade production.

Supply support for LMR66420R5RXBR 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 power management technologies, with decades of leadership in high-reliability industrial power solutions.

The LMR664x0 product line was designed specifically for demanding industrial applications - emphasizing ultra-low IQ, wide temperature operation, EMI robustness, and functional safety readiness across PLCs, instrumentation, and safety-critical subsystems.

FAQ

What is the maximum input voltage the LMR66420R5RXBR can withstand without damage?

The LMR66420R5RXBR has an absolute maximum input voltage rating of 42 V, meaning it can survive short-duration transients up to this level without latch-up or permanent damage. Its recommended operating input range is 2.7 V (falling threshold) to 36 V after start-up. This 42-V rating is critical for industrial applications subject to load-dump events or inductive switching spikes, and is verified per TI's absolute maximum ratings table in SNVSCJ3.

Does the LMR66420R5RXBR require external compensation components?

No, the LMR66420R5RXBR features fully internal loop compensation optimized for minimal output capacitance, eliminating the need for external compensation networks such as RC filters or type-II/III compensators. This simplifies design, reduces BOM count, and improves layout robustness - confirmed in Section 7.1 and Table 6-5 of the official datasheet SNVSCJ3.

What is the purpose of the NC pins on the LMR66420R5RXBR package?

The NC (no-connect) pins on the LMR66420R5RXBR - specifically pins 2, 4, 5, 9, and 12 - are intentionally unconnected silicon nodes placed between critical high-voltage pins (e.g., VIN, SW, BOOT) to improve pin-level failure mode and effects analysis (FMEA). As documented in Section 1 and Table 5-1, this layout strategy mitigates risks from contamination, dendritic growth, or creepage failure in harsh industrial environments.

Can the LMR66420R5RXBR operate with zero load current?

Yes, the LMR66420R5RXBR supports true zero-load operation in auto mode, drawing only 1.5 µA typical input current at VIN = 13.5 V with no output load. Its frequency foldback and diode emulation ensure stable regulation and no reverse inductor current, making it ideal for always-on systems like remote sensors or watchdog circuits - validated in Section 6.6 (IQVIN) and Figure 6-1 of SNVSCJ3.

Is the LMR66420R5RXBR pin-compatible with other members of the LMR664x0 family?

Yes, the LMR66420R5RXBR shares identical pin configuration, package (RXB, 14-pin VQFN), and footprint with LMR66410R5RXBR and LMR66430R5RXBR. All three variants use the same EN, VIN, VOUT/FB, RT, PG, SW, BOOT, and GND/DAP pin assignments - enabling drop-in current-scaling upgrades without PCB revision, as confirmed in Figure 5-1 and Table 5-1 of SNVSCJ3.