Texas Instruments LM2651MTC-3.3

Overview

LM2651MTC-3.3 from Texas Instruments is a 1.5 A synchronous step-down DC-DC switching regulator in a 16-pin TSSOP package, delivering a fixed 3.3 V output from a 4–14 V input. It achieves up to 97% efficiency via internal MOSFETs (R_DS(on) = 75 mΩ), operates at 300 kHz fixed frequency, and enters hysteretic sleep mode below 100 mA load to maintain >80% efficiency at 15 mA - ideal for battery-powered PDAs and handheld scanners.

For engineers reviewing the LM2651MTC-3.3 datasheet, LM2651MTC-3.3 pinout, LM2651MTC-3.3 application, or LM2651MTC-3.3 equivalent, key selection considerations include its integrated current-mode control without external sense resistor, 7 µA shutdown current, 60 mV sleep-mode output hysteresis, and thermal shutdown at 165°C with 25°C hysteresis.

Technical Context

The LM2651MTC-3.3 uses constant-frequency (300 kHz) current-mode PWM control under moderate-to-heavy loads (>100 mA), then automatically transitions to low-frequency hysteretic mode at light loads to sustain high efficiency. Its patented internal current sensing eliminates the need for an external sense resistor, reducing BOM cost and noise susceptibility.

It integrates dual N-channel MOSFETs (high-side and low-side), a bootstrap regulator (6.7 V typical), undervoltage lockout (3.8 V rising threshold with 210 mV hysteresis), and adjustable soft-start via external capacitor on the SD(SS) pin. Thermal shutdown activates at 165°C with 25°C hysteresis, and cycle-by-cycle current limiting trips at 2 A.

Key Specifications

Pinout & Package

LM2651MTC-3.3 is housed in a 16-pin TSSOP package (5.00 mm × 4.40 mm, 0.65 mm pitch), optimized for thermal performance with separate analog (AGND) and power (PGND) ground pins and dedicated bootstrap (VCB) and switch-node (SW) terminals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2651MTC-3.3, TPS54331DR offers higher current headroom at the expense of layout complexity and lower light-load efficiency, while MP2315GJ-Z reduces solution size but sacrifices the precise 60-mV hysteresis and 7-µA shutdown critical for long-life battery systems.

Availability

LM2651MTC-3.3 is available at Aetrix Electronics and suitable for battery-powered devices, handheld scanners, and computer peripherals requiring stable component supply with consistent parametric performance across production lots.

Supply support for LM2651MTC-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 and embedded processing technologies, with over 90 years of innovation in power management ICs.

The LM2651 product line delivers highly integrated synchronous buck regulators targeting portable and battery-critical applications where efficiency, small solution size, and reliability are paramount.

FAQ

What is the maximum recommended input voltage for LM2651MTC-3.3?

The absolute maximum input voltage for LM2651MTC-3.3 is 15 V, but the recommended operating range is 4 V to 14 V per the datasheet. Exceeding 14 V risks triggering the undervoltage lockout hysteresis or accelerating degradation; sustained operation above 14 V voids warranty and may cause premature failure. LM2651MTC-3.3 includes internal protection, but design margins should respect the 14-V upper limit for reliable long-term use.

Does LM2651MTC-3.3 require an external Schottky diode?

Yes, TI recommends an external Schottky diode (D1) placed between SW and PGND to prevent conduction through the intrinsic body diode of the low-side MOSFET during dead time. Without it, reverse-recovery losses degrade efficiency by 1–2%, especially at high input voltages and loads. LM2651MTC-3.3 does not integrate this diode, and omitting D1 increases thermal stress and EMI. The diode's breakdown voltage should exceed 1.25 × max VIN.

How is the output voltage set for LM2651MTC-3.3?

LM2651MTC-3.3 features a factory-trimmed, fixed 3.3 V output - no external feedback resistors are required. The internal reference is 1.238 V, and the FB pin is internally connected to generate precisely 3.3 V (3.265–3.379 V over temperature). This differs from the LM2651-ADJ variant, which requires R1/R2 divider. Using LM2651MTC-3.3 simplifies layout and eliminates resistor tolerance errors affecting regulation accuracy.

What thermal metrics apply to LM2651MTC-3.3 in its TSSOP package?

LM2651MTC-3.3 in the 16-pin TSSOP (PW) package has a junction-to-ambient thermal resistance (R_θJA) of 97.3°C/W with standard JEDEC 2-layer board, junction-to-board (R_θJB) of 43.1°C/W, and thermal shutdown at 165°C with 25°C hysteresis. To sustain 1.5 A continuously, minimum 2 oz copper with 4+ thermal vias under PGND pads is recommended. Derating begins above 25°C ambient at 7.14 mW/°C.

Can LM2651MTC-3.3 operate with a 3.6-V lithium-ion battery input?

No - LM2651MTC-3.3 has a minimum input voltage of 4 V per its recommended operating conditions. A fully charged 3.6-V Li-ion cell (4.2 V) meets the lower bound only briefly; as voltage drops to 3.7 V or below, the device will cease regulation due to undervoltage lockout (VINUV = 3.8 V rising threshold). For single-cell Li-ion, use LM2651MTC-ADJ with external resistors or a dedicated low-VIN buck like TPS62130.