Texas Instruments LMR51420YDDCR

Overview

LMR51420YDDCR from Texas Instruments is a synchronous buck DC-DC converter optimized for rugged industrial power supplies, delivering up to 2-A continuous output current from a 4.5-V to 36-V input. It operates at a fixed 1.1-MHz switching frequency in PFM mode, features ±1.5% reference voltage accuracy, 70-ns minimum on-time, and integrated high- and low-side MOSFETs in a 6-pin SOT-23 package - ideal for space-constrained motor drive auxiliary rails.

For engineers reviewing the LMR51420YDDCR datasheet, LMR51420YDDCR pinout, LMR51420YDDCR application, or LMR51420YDDCR equivalent, key selection considerations include its 1.1-MHz PFM operation for light-load efficiency, prebias start-up capability, precision enable with adjustable UVLO, hiccup-mode short-circuit protection, and thermal shutdown at 163°C junction temperature.

Technical Context

The LMR51420YDDCR employs fixed-frequency peak-current mode control with internal compensation, eliminating external loop components. Its 1.1-MHz PFM operation dynamically reduces switching frequency under light load to maintain >90% efficiency at 1-mA output while preserving regulation.

It integrates 120-mΩ high-side and 70-mΩ low-side NMOS FETs, supports 98% maximum duty cycle with frequency foldback down to ~133 kHz, and implements cycle-by-cycle current limiting with valley detection to prevent inductor runaway during sustained short circuits.

Key Specifications

Pinout & Package

LMR51420YDDCR is housed in a thermally enhanced 6-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, with exposed pad for improved PCB heat dissipation (R_θJB = 23.3°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck converter applications.

Compared with LMR51420XDDCR, the LMR51420YDDCR delivers superior power density and light-load efficiency due to its 1.1-MHz PFM operation, while versus TPS54202DDCR it adds critical industrial features including wider input range, hiccup protection, and prebias start-up - making it the preferred choice for new ruggedized designs.

Availability

LMR51420YDDCR is available at Aetrix Electronics and suitable for industrial motor drives, building automation controllers, appliance control boards, and general-purpose wide-VIN power supplies requiring stable component supply, long-term manufacturability, and automotive-grade thermal resilience.

Supply support for LMR51420YDDCR 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 expertise in high-reliability power conversion ICs.

The LMR51420YDDCR belongs to TI's SIMPLE SWITCHER® family - engineered specifically for ease-of-use, ruggedness, and minimal external component count in industrial and automotive power supply designs.

FAQ

What is the switching frequency of the LMR51420YDDCR and how does it affect design?

The LMR51420YDDCR operates at a nominal 1.1 MHz in PFM mode. This high frequency enables use of smaller inductors (1.0–2.2 µH) and output capacitors, reducing solution size by up to 40% versus 500-kHz alternatives. It also shifts EMI fundamentals above 30 MHz, easing compliance with CISPR-22 Class B limits. Frequency foldback extends regulation range down to ~133 kHz under extreme duty-cycle conditions without sacrificing stability.

Does the LMR51420YDDCR support prebiased output startup?

Yes, the LMR51420YDDCR supports prebias start-up, allowing safe turn-on when the output capacitor is already charged to a non-zero voltage. This feature prevents reverse current flow through internal FETs and avoids output voltage undershoot or latch-up - critical in hot-swap, redundant power, and multi-rail sequencing applications. No external components are required to enable this behavior.

What protection features are built into the LMR51420YDDCR?

The LMR51420YDDCR includes cycle-by-cycle overcurrent limiting on both high- and low-side FETs, hiccup-mode short-circuit protection (135-ms off-time), thermal shutdown at 163°C with 22°C hysteresis, input undervoltage lockout (UVLO rising threshold 4.5 V), and internal soft-start. These features collectively protect against overload, output shorts, overtemperature, input brownouts, and inrush transients - eliminating need for external protection circuitry.

Can the LMR51420YDDCR be used with an adjustable output voltage?

Yes, the LMR51420YDDCR has an adjustable output voltage set via a resistor divider from VOUT to the FB pin. Using the internal 0.6-V reference, outputs from 0.6 V up to 95% of VIN can be configured. TI recommends 1% tolerance resistors with R_FBB = 10 kΩ and R_FBT between 10 kΩ and 100 kΩ for optimal noise immunity and regulation accuracy. The LMR51420YDDCR maintains ±1.5% reference tolerance across –40°C to +150°C.

What is the thermal performance of the LMR51420YDDCR in a standard PCB layout?

In a typical 4-layer JEDEC board layout, the LMR51420YDDCR exhibits a junction-to-board thermal resistance (R_θJB) of 23.3°C/W. With proper copper pour under the exposed pad and 2 oz. inner layers, it sustains 2-A continuous output at ambient temperatures up to +85°C without forced airflow. Derating begins above 100°C ambient, and full 2-A operation is guaranteed up to +150°C junction temperature per datasheet specifications.