Texas Instruments LMR33640DDDAR

Overview

LMR33640DDDAR from Texas Instruments is a synchronous step-down DC/DC converter delivering up to 4 A output current across 3.8 V to 36 V input, supporting 1 V to 24 V adjustable output with peak efficiency >95% and integrated compensation. It operates in peak-current mode control with 400 kHz or 1 MHz switching frequency options, features power-good flag and precision enable, and targets rugged industrial power rails for motor drives and automation systems.

For engineers reviewing the LMR33640DDDAR datasheet, LMR33640DDDAR pinout, LMR33640DDDAR application, or LMR33640DDDAR equivalent, key selection considerations include its HSOIC-8 package thermal performance (R_θJB = 13.6°C/W), 24 µA operating quiescent current, –40°C to +125°C junction temperature range, and pin compatibility with LMR33610/LMR33620/LMR33630 for scalable power design.

Technical Context

The LMR33640DDDAR implements peak-current-mode control with automatic PFM/PWM mode transition to maintain high light-load efficiency. Its internal 5-V LDO powers control circuitry via VCC pin and supplies logic for the open-drain PG flag, while BOOT-SW bootstrap capacitor enables high-side MOSFET drive.

Protection architecture includes cycle-by-cycle current limit (ISC = 4.8–6.2 A), hiccup-mode short-circuit response (t_HC = 94 ms), thermal shutdown at 165°C, and input UVLO tied to VCC regulation. The device uses internal loop compensation and zero-current detection (IZC = –0.106 A) to support diode emulation in discontinuous conduction mode.

Key Specifications

Pinout & Package

LMR33640DDDAR is housed in an 8-pin HSOIC (DDA) package with exposed thermal pad (5.00 mm × 4.00 mm), requiring soldering of the bottom thermal pad to a PCB ground plane for optimal electrical integrity and thermal performance (R_θJB = 13.6°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR33630DDDAR and LMR36520ADDAR, the LMR33640DDDAR uniquely balances 4-A capability, 36-V input rating, and drop-in scalability within the SIMPLE SWITCHER family-enabling single-layout support for 1–4 A variants while maintaining thermal headroom for demanding industrial loads.

Availability

LMR33640DDDAR is available at Aetrix Electronics and suitable for motor drive systems, PLC/HMI platforms, and HVAC control boards requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LMR33640DDDAR 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 industrial-grade product validation and broad distribution infrastructure.

The LMR33640DDDAR belongs to TI's SIMPLE SWITCHER® synchronous buck regulator family, engineered specifically for rugged industrial power conversion-emphasizing ease-of-use, thermal robustness, and pin-compatible scalability across voltage and current ratings.

FAQ

What is the maximum input voltage the LMR33640DDDAR can withstand?

The LMR33640DDDAR has an absolute maximum input voltage rating of 38 V, but its recommended operating input voltage range is 3.8 V to 36 V. Operation beyond 36 V may compromise long-term reliability and is not guaranteed per specifications. Transient spikes up to 38 V are tolerated briefly per absolute maximum ratings, but sustained operation above 36 V requires derating and thermal verification. Always reference the latest TI datasheet revision for updated stress limits.

Does the LMR33640DDDAR require external compensation components?

No, the LMR33640DDDAR integrates full Type-II compensation circuitry internally, eliminating the need for external compensation capacitors or resistors. This simplifies design, reduces solution size, and improves consistency across production units. The internal compensation is optimized for standard output voltages (1–24 V) and common inductor values; no external tuning is required unless using non-standard configurations outside the validated design space.

How does the power-good (PG) flag behave during startup and fault conditions?

The LMR33640DDDAR PG pin is an open-drain output that remains low for ~4 ms after EN assertion, then transitions high when output voltage reaches 95% of target. It pulls low during undervoltage (below 90% V_FB), overvoltage (above 110% V_FB), thermal shutdown, or current-limit hiccup events. A 60–170 µs glitch filter prevents false triggering from brief transients. The PG signal is valid even when EN is low, provided VIN ≥ 2 V.

Can the LMR33640DDDAR operate efficiently at very light loads?

Yes, the LMR33640DDDAR automatically enters diode-emulation PFM mode below ~200 mA (load-dependent), reducing switching frequency and quiescent current to 24 µA typical. This maintains >90% efficiency at 1 mA output and avoids forced CCM losses. Efficiency curves show >85% at 10 mA with 12 V input and 5 V output, making it suitable for always-on industrial sensors and standby circuits.

What thermal performance can be expected from the LMR33640DDDAR in a standard 4-layer PCB layout?

In a JEDEC-standard 4-layer board with 2 oz copper and thermal pad soldered to internal ground plane, the LMR33640DDDAR achieves R_θJB = 13.6°C/W. At 4 A output and 12 V input, typical power dissipation is ~1.2 W, resulting in ~16°C rise above board temperature. Full 4-A operation at 125°C ambient requires ≥250 mm² of 2 oz copper connected to the thermal pad; thermal simulation or IR imaging is recommended for enclosure-limited designs.