Texas Instruments LMR33630BDDA

Overview

LMR33630BDDA from Texas Instruments is a synchronous step-down DC/DC converter optimized for rugged industrial power conversion, delivering up to 3 A output current across a 3.8 V to 36 V input range with adjustable output (1 V–24 V), 1.4 MHz fixed switching frequency, and peak efficiency exceeding 95% in VQFN layouts - deployed in motor drive inverters, PLC CPU supplies, and HVAC control systems.

For engineers reviewing the LMR33630BDDA datasheet, LMR33630BDDA pinout, LMR33630BDDA application, or LMR33630BDDA equivalent, key selection criteria include its 1.4 MHz operation enabling compact magnetics, integrated compensation eliminating external loop components, precision enable thresholds (1.231 V typical turn-on), and dual thermal/overcurrent protection with hiccup-mode short-circuit response.

Technical Context

The LMR33630BDDA implements peak-current-mode control with automatic PFM/PWM mode transition to maintain high light-load efficiency, supported by internal 5-V VCC LDO and bootstrap circuitry driving integrated 95 mΩ/66 mΩ high-side/low-side MOSFETs. Its architecture enables regulation down to 3.8 V input at 3.3 V output while sustaining 1.4 MHz operation.

It features a precision power-good flag with 105–110% rising threshold and 60–170 µs glitch filter, cycle-by-cycle current limiting (4.5 A typical peak), and thermal shutdown at 165°C with 148°C hysteresis recovery - all within an 8-pin HSOIC package with PowerPAD™ thermal pad.

Key Specifications

Pinout & Package

LMR33630BDDA uses an 8-pin HSOIC package (5.00 mm × 4.00 mm) with exposed thermal pad (PowerPAD™) soldered to PCB ground plane for optimal thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LMR33630BDDA, the ADDA variant trades switching speed for lower EMI and relaxed layout, while the BRNX offers superior thermal performance and smaller footprint at the cost of more complex routing - both retain identical control architecture, protection features, and functional safety documentation support.

Availability

LMR33630BDDA is available at Aetrix Electronics and suitable for motor drive inverters, PLC CPU power supplies, and HVAC control units requiring stable component supply across extended industrial temperature ranges and multi-year production cycles.

Supply support for LMR33630BDDA 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 reliability validation.

The LMR33630 series belongs to TI's SIMPLE SWITCHER® portfolio - engineered specifically for rugged, wide-input industrial DC/DC conversion where ease of design, thermal resilience, and functional safety readiness are mandatory.

FAQ

What is the switching frequency of the LMR33630BDDA and how is it set?

The LMR33630BDDA operates at a fixed 1.4 MHz switching frequency, determined by internal oscillator circuitry and not user-adjustable. This frequency is factory-trimmed and specified as 1.2–1.6 MHz over temperature and process variation. It enables compact magnetic design and places fundamental EMI energy above common noise-sensitive bands. The LMR33630BDDA does not support external frequency synchronization or programming - unlike the "C" version variants which offer 2.1 MHz operation.

Does the LMR33630BDDA require external compensation components?

No, the LMR33630BDDA integrates a complete Type-II compensation network internally, eliminating the need for external resistors or capacitors on the COMP or FB pins. This simplifies layout, reduces BOM count, and guarantees stable operation across the full 1 V–24 V output range and 0–3 A load. External feedback resistors (RFBT/RFBB) remain necessary to set the output voltage, but no loop compensation tuning is required for standard applications.

What package type and thermal characteristics apply to the LMR33630BDDA?

The LMR33630BDDA is supplied exclusively in the 8-pin HSOIC package (5.00 mm × 4.00 mm) with PowerPAD™ thermal pad. Its junction-to-ambient thermal resistance (RθJA) is 42.9°C/W on a 4-layer JEDEC board, and junction-to-board (RθJB) is 13.6°C/W. For reliable 3 A operation at +125°C ambient, the PCB must provide adequate copper area under the thermal pad connected to a solid ground plane - insufficient thermal relief will trigger thermal shutdown at ~165°C junction temperature.

How does the power-good (PG) flag behave during startup and fault conditions for the LMR33630BDDA?

The LMR33630BDDA PG pin is an open-drain output that remains low for ~4 ms after EN assertion, then transitions high only when VOUT reaches 105–110% of the target (e.g., 5.25–5.5 V for 5 V output). It pulls low during undervoltage (VOUT < 90–95%), overcurrent, thermal shutdown, or EN deactivation. A built-in 60–170 µs glitch filter prevents false triggering from transient line/load disturbances. No external timing components are needed - behavior is fully internal and specified across –40°C to +125°C.

Can the LMR33630BDDA be used in functional safety–compliant systems?

Yes, the LMR33630BDDA is functional safety-capable: TI provides documentation including FIT rate data, failure mode analysis (FMEA), and diagnostic coverage guidance to support ISO 26262 ASIL-B or IEC 61508 SIL-2 system development. While the device itself is not certified, its architecture - featuring redundant current limit, thermal shutdown with hysteresis, power-good flag with glitch filtering, and precision enable thresholds - enables safe state transitions in safety-critical subsystems such as elevator controllers or industrial safety PLCs. Full qualification requires system-level integration per applicable standards.