Texas Instruments LMR51430XFDDCR

Overview

LMR51430XFDDCR from Texas Instruments is a synchronous buck DC-DC converter IC designed for industrial power conditioning, delivering up to 3 A continuous output current with 4.5 V to 36 V input range, fixed 500-kHz switching frequency, forced PWM (FPWM) operation, and ±1.5% reference voltage accuracy in a 6-pin SOT-23 package.

For engineers reviewing the LMR51430XFDDCR datasheet, LMR51430XFDDCR pinout, LMR51430XFDDCR application, or LMR51430XFDDCR equivalent, this page provides verified functional context, validated pin roles, confirmed FPWM-specific timing behavior, thermal protection thresholds, and real-world design implications of its 70-ns minimum on-time and internal compensation.

Technical Context

The LMR51430XFDDCR implements fixed-frequency peak-current mode control with internal slope compensation and fully integrated high-side/low-side NMOS power stages. Its FPWM mode enforces constant 500-kHz switching across all load conditions, eliminating frequency variation to minimize EMI and ensure predictable output ripple.

It features precision enable with 1.1–1.36 V rising threshold, internal soft-start (4.0 ms typical), and hiccup-mode short-circuit protection triggered at FB ≤ 0.24 V. Thermal shutdown activates at 163°C with 22°C hysteresis, and cycle-by-cycle current limiting uses both high-side peak (4.76 A typ) and low-side valley (3.5 A typ) sensing.

Key Specifications

Pinout & Package

Package: 6-pin SOT-23 (DBV), body size 2.90 mm × 1.60 mm, exposed pad not present, surface-mount compatible with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR51430XDDCR, the LMR51430XFDDCR trades light-load efficiency for deterministic EMI and tighter output regulation; compared with TPS54202DRCT, it delivers higher current, superior thermal robustness in SOT-23, and integrated hiccup protection-making it optimal for rugged 3-A industrial loads.

Availability

LMR51430XFDDCR 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 lifecycle assurance, and traceable sourcing.

Supply support for LMR51430XFDDCR 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 over 90 years of innovation in industrial, automotive, and communications markets.

The LMR51430XFDDCR belongs to TI's SIMPLE SWITCHER® power converter family, engineered specifically for rugged, easy-to-deploy DC-DC solutions in space- and reliability-constrained industrial applications.

FAQ

What distinguishes LMR51430XFDDCR from other variants in the LMR51430 family?

The LMR51430XFDDCR is the 500-kHz FPWM version of the LMR51430 family, meaning it maintains constant switching frequency across all load conditions-unlike the PFM variants (e.g., LMR51430XDDCR) that reduce frequency at light loads. This ensures predictable EMI behavior and stable output ripple, critical for noise-sensitive analog circuits. Its FPWM operation also guarantees tight output voltage regulation and eliminates audible switching artifacts, making it ideal for industrial control applications where deterministic timing is essential. The LMR51430XFDDCR retains all core protections-including hiccup-mode short-circuit response and thermal shutdown-and shares identical pinout and package with other LMR51430 variants.

Can LMR51430XFDDCR operate with an input voltage below 4.5 V?

No, the LMR51430XFDDCR has a specified minimum input voltage of 4.5 V per its Recommended Operating Conditions. Attempting to operate below this threshold risks UVLO activation (VINUVLO falling threshold is 3.35–3.58 V), causing uncontrolled shutdown or erratic regulation. While absolute maximum ratings allow down to –0.3 V, functional operation is not guaranteed below 4.5 V. For sub-4.5 V inputs, consider alternative regulators such as the TPS62864 or LMR36520, which are explicitly rated for lower VIN ranges. The LMR51430XFDDCR's 70-ns minimum on-time and 98% max duty cycle do not override its 4.5 V operational floor.

How does the FB pin function in LMR51430XFDDCR, and what resistor values are recommended?

The FB pin on the LMR51430XFDDCR senses output voltage via an external resistor divider and compares it to an internal 0.6 V ±1.5% reference. To set VOUT, use RFBT (top) and RFBB (bottom) resistors per VOUT = 0.6 × (1 + RFBT/RFBB). TI recommends 1% tolerance, low-TCR resistors with RFBT between 10 kΩ and 100 kΩ; values below 10 kΩ increase power loss, while above 1 MΩ raise noise susceptibility. For a 5 V output, a common choice is RFBT = 73.2 kΩ and RFBB = 10 kΩ. Never short FB to ground during operation, as this triggers hiccup-mode protection. The LMR51430XFDDCR's precision reference ensures stable regulation even across –40°C to +150°C.

Does LMR51430XFDDCR support prebiased output start-up, and how is it implemented?

Yes, the LMR51430XFDDCR supports start-up with a prebiased output-a key feature for hot-swap and redundant power systems. During start-up, the device detects existing VOUT voltage and disables the high-side FET until the internal soft-start ramp reaches that level, preventing reverse current flow into the output capacitor. This behavior is inherent to the control architecture and requires no external components or configuration. It applies equally to FPWM and PFM variants. For reliable prebias operation, ensure EN is asserted only after VIN is stable and the output rail is already charged; the LMR51430XFDDCR will then ramp VOUT smoothly from the prebiased level without overshoot or current surge.

What thermal derating guidance applies to LMR51430XFDDCR at elevated ambient temperatures?

The LMR51430XFDDCR's maximum continuous output current decreases with rising ambient temperature due to thermal limits. At 25°C ambient on a standard 4-layer JEDEC board, it delivers full 3 A. Above 60°C, derating begins: at 85°C ambient, output current drops to ~2.2 A; at 105°C, it falls to ~1.6 A. These values assume proper PCB copper area (≥250 mm² per side under the package) and airflow <1 m/s. The device's thermal shutdown triggers at 163°C junction temperature with 22°C hysteresis, allowing automatic recovery once cooled. For high-temperature deployments, use the LMR51430XFDDCR's 150°C max junction rating and monitor board-level thermal performance using its internal thermal metrics (RθJA = 107.8°C/W, RθJB = 23.3°C/W).