Texas Instruments LM2651MTCX-3.3/NOPB

Overview

LM2651MTCX-3.3/NOPB from Texas Instruments is a 1.5 A synchronous step-down DC-DC switching regulator in a 16-pin TSSOP package, delivering fixed 3.3 V output from 4–14 V input, achieving up to 97% efficiency and featuring patented current-mode control without external sense resistors. It operates in fixed 300 kHz PWM mode under medium/heavy loads and auto-switches to low-power hysteretic mode below 100 mA, enabling long battery life in portable PDAs and handheld scanners.

For engineers reviewing the LM2651MTCX-3.3/NOPB datasheet, LM2651MTCX-3.3/NOPB pinout, LM2651MTCX-3.3/NOPB application, or LM2651MTCX-3.3/NOPB equivalent, key selection criteria include its 3.3 V fixed output, 1.5 A continuous load capability, 75 mΩ internal high-side MOSFET R_DS(on), 7 µA shutdown current, and integrated soft-start with programmable ramp via external capacitor.

Technical Context

The LM2651MTCX-3.3/NOPB implements current-mode PWM control with cycle-by-cycle current limiting at 2 A and automatic transition to hysteretic sleep mode when load drops below 100 mA. Its patented internal current sensing eliminates external shunt resistors, improving noise immunity and reducing BOM count.

It integrates a 300 kHz oscillator, undervoltage lockout (3.8 V rising threshold with 210 mV hysteresis), thermal shutdown at 165 °C, and bootstrap gate drive for the high-side MOSFET. The feedback pin references a precise 1.238 V internal bandgap, enabling tight 3.3 V regulation (±1.2% over temperature and line/load).

Key Specifications

Pinout & Package

LM2651MTCX-3.3/NOPB is housed in a 16-pin TSSOP package (5.00 mm × 4.40 mm body size) with exposed thermal pad (PGND-connected) for enhanced thermal performance in space-constrained layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS54302DDCR and LM2678SD-3.3/NOPB, LM2651MTCX-3.3/NOPB uniquely balances 1.5 A capability, 97% efficiency, fixed 3.3 V output, and ultra-low 7 µA shutdown - making it optimal for space- and battery-limited portable systems where simplicity and runtime are prioritized over raw current headroom or ultra-wide input range.

Availability

LM2651MTCX-3.3/NOPB is available at Aetrix Electronics and suitable for personal digital assistants, computer peripherals, battery-powered handheld scanners, and high-efficiency 5-V conversion applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LM2651MTCX-3.3/NOPB 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-efficiency DC-DC conversion and industrial-grade reliability.

The LM2651 product line was designed specifically for battery-powered portable electronics demanding high efficiency across wide load ranges - emphasizing ultralow quiescent current, integrated protection, and minimal external component count.

FAQ

What is the output voltage tolerance of the LM2651MTCX-3.3/NOPB over temperature and load?

The LM2651MTCX-3.3/NOPB delivers a fixed 3.3 V output with ±1.2% tolerance across the full operating junction temperature range (−40 °C to 125 °C) and load range (15 mA to 1.5 A). This specification is confirmed in the Electrical Characteristics table of the SNVS032E datasheet, where V_OUT for the LM2651-3.3 variant is specified as 3.265 V (min) to 3.379 V (max) at T_J = 25 °C and I_LOAD = 900 mA, with tighter limits maintained across extremes via internal bandgap and error amplifier design.

Does the LM2651MTCX-3.3/NOPB require an external feedback resistor divider?

No, the LM2651MTCX-3.3/NOPB does not require an external feedback resistor divider because it is the fixed-output 3.3 V version. The internal feedback network is trimmed to reference the 1.238 V bandgap voltage, resulting in a precise 3.3 V output. Only the LM2651-ADJ variant requires external R1/R2 resistors; the -3.3/NOPB variant connects the FB pin directly to the output and omits external components for simplified layout and improved stability.

What is the maximum duty cycle supported by the LM2651MTCX-3.3/NOPB?

The LM2651MTCX-3.3/NOPB supports a maximum duty cycle of 92% (typical) at V_IN = 4 V, as specified in the Electrical Characteristics table under D_MAX. This enables operation down to a minimum input-to-output ratio of ~1.08:1, allowing reliable regulation even as input voltage approaches the 3.3 V output level - critical for maintaining functionality near end-of-battery-life in 4×AA or Li-ion systems.

How does the LM2651MTCX-3.3/NOPB achieve current-mode control without an external sense resistor?

The LM2651MTCX-3.3/NOPB uses a patented internal current sensing technique that monitors the voltage drop across the internal high-side MOSFET's R_DS(on) during conduction, eliminating the need for an external sense resistor. This method preserves efficiency, reduces board area, and improves noise immunity compared to traditional shunt-based current sensing - a feature explicitly documented in Sections 7.3 and 8.1 of the SNVS032E datasheet.

What thermal performance can be expected from the LM2651MTCX-3.3/NOPB in a standard PCB layout?

In a standard 2-layer PCB with 1 oz copper and moderate copper pour on the PGND pins and thermal pad, the LM2651MTCX-3.3/NOPB exhibits a junction-to-ambient thermal resistance (R_θJA) of 97.3 °C/W, as measured per JEDEC JESD51 standards. At 1.5 A load and 10 V input, typical power dissipation is ~0.5 W, resulting in ~49 °C junction-to-ambient rise - well within the 125 °C max rating. Layout guidelines in Section 10 of SNVS032E recommend maximizing PGND copper area to further reduce thermal impedance.