Texas Instruments LM2676T-3.3

Overview

LM2676T-3.3 from Texas Instruments is a monolithic step-down (buck) DC-DC switching regulator delivering up to 3A output current with fixed 3.3V output, 8–40V input range, 260kHz fixed-frequency operation, ±2% output voltage tolerance over line/load/temperature, and 150mΩ internal DMOS switch. It serves as the primary power conversion stage in industrial power supplies requiring stable low-voltage rails.

For engineers reviewing the LM2676T-3.3 datasheet, LM2676T-3.3 pinout, LM2676T-3.3 application, or LM2676T-3.3 equivalent, key selection criteria include its 3A continuous output capability, thermal shutdown and current limiting protection, ON/OFF control interface, 50µA standby quiescent current, and compatibility with standard off-the-shelf inductors and Schottky diodes.

Technical Context

The LM2676T-3.3 implements a fixed-frequency PWM buck controller with an integrated high-side DMOS power switch. Its 260kHz oscillator enables predictable EMI behavior and supports compact external passive sizing. The device operates in continuous conduction mode at full load and transitions to discontinuous mode under light loads.

Internal feedback uses a precision 1.21V reference with dedicated FB pin for fixed-output variants-where FB is shorted directly to VOUT-and includes built-in thermal shutdown, cycle-by-cycle current limiting, and logic-level ON/OFF enable control with 1.4V threshold and 20µA input bias current.

Key Specifications

Pinout & Package

LM2676T-3.3 is supplied in the KTW (TO-263-7) thermally enhanced surface-mount package (10.1mm × 15.24mm), featuring exposed DAP for PCB thermal relief and mechanical anchoring.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2676T-3.3, LM2576T-3.3 trades efficiency and control flexibility for legacy compatibility and lower BOM cost, while LMR14030SDDAR delivers superior integration and thermal performance at the expense of design simplicity and fixed-frequency predictability.

Availability

LM2676T-3.3 is available at Aetrix Electronics and suitable for industrial power supplies, smart metering systems, and embedded communication modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM2676T-3.3 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 LM2676 series belongs to TI's SIMPLE SWITCHER® portfolio - designed specifically for ease-of-use in non-isolated DC-DC buck applications where minimal external components, predictable performance, and rugged industrial operation are prioritized.

FAQ

What is the maximum input voltage rating for LM2676T-3.3?

The absolute maximum input voltage for LM2676T-3.3 is 45V, but the recommended operating range is 8V to 40V DC. Exceeding 40V continuously risks violating safe operating area limits and may trigger internal protection circuits. Designers should maintain at least 1V margin below 40V under worst-case transient conditions. The LM2676T-3.3 datasheet specifies 40V as the upper limit for reliable long-term operation across temperature and process variation.

Does LM2676T-3.3 require an external catch diode?

Yes, LM2676T-3.3 requires an external Schottky diode connected between the SW pin (Pin 1) and GND (Pin 4). The internal DMOS switch is high-side only, so the diode provides the freewheeling path during switch-off periods. TI recommends a 3A-rated Schottky diode with VF < 0.5V and low reverse recovery charge - such as the SS34 or MBR340 - to maintain high efficiency and minimize thermal stress. The LM2676T-3.3 does not integrate a synchronous rectifier.

Can LM2676T-3.3 be used in adjustable-output configurations?

No, LM2676T-3.3 is a fixed-output variant and cannot be reconfigured for adjustable output. Its internal feedback divider is trimmed to deliver precisely 3.3V; the FB pin (Pin 6) must be connected directly to the output capacitor. For adjustable operation, the LM2676-ADJ part number must be used instead, which provides access to the 1.21V reference via the FB pin and requires two external resistors to set VOUT. Attempting to modify LM2676T-3.3 for adjustment will result in incorrect regulation or instability.

What thermal considerations apply to LM2676T-3.3 in TO-263 (KTW) package?

In the KTW (TO-263-7) package, LM2676T-3.3 achieves a junction-to-ambient thermal resistance (RθJA) of 35°C/W with 0.4896 in² copper area and 26°C/W with 1.0064 in² copper area - assuming proper DAP grounding. To sustain 3A output at 125°C ambient, designers must ensure ≥1 in² of 1oz copper connected to the DAP via ≥4 thermal vias. Without adequate copper, thermal shutdown will activate at ~2.2A load. The LM2676T-3.3 thermal shutdown threshold is typically 160°C.

Is LM2676T-3.3 RoHS compliant and lead-free?

Yes, LM2676T-3.3 is RoHS compliant and lead-free per TI's current product definitions. It meets JEDEC J-STD-020 moisture sensitivity level (MSL) 3 and is compatible with standard Pb-free reflow profiles (peak 260°C). TI's official packaging information confirms halogen-free construction and exemption from REACH SVHC substances above threshold. Full compliance documentation, including CoC and test reports, is available through TI's Quality & Environmental page for LM2676T-3.3.