onsemi NCP3135MNTXG

Overview

NCP3135MNTXG from onsemi is a fully integrated synchronous buck converter delivering up to 5 A continuous DC output current and 6 A instantaneous load current for 3.3 V and 5 V step-down power rails. It operates across a 2.9 V to 5.5 V input range, supports voltage-mode control with 1.1 MHz switching frequency in FCCM mode, and integrates dual N-MOSFETs in a thermally enhanced 3 mm × 3 mm QFN-16 package - used in compact point-of-load (POL) converters for FPGA, ASIC, and microprocessor core supplies.

For engineers reviewing the NCP3135MNTXG datasheet, pinout, applications, or equivalent options, key selection criteria include its automatic CCM/DCM light-load efficiency mode, pre-bias startup capability, internal 600 mV ±1% reference, power-good indicator with 400 µs delay, and dual over-current protection thresholds (7.2 A high-side, 8.1 A low-side).

Technical Context

The NCP3135MNTXG implements voltage-mode PWM control with an internal 600 mV reference and 14 MHz unity-gain bandwidth error amplifier. Its adaptive architecture enables seamless transition between forced continuous conduction mode (FCCM) and automatic CCM/DCM via the PS pin, where zero-crossing detection terminates low-side conduction at light loads to reduce switching losses.

Protection logic includes latched over-current shutdown (high-side OCP triggers after 4 consecutive cycles; low-side OCP is immediate), ±17% output voltage window monitoring for PGD assertion, 130 mV VIN UVLO hysteresis, and thermal shutdown at 135°C with 40°C hysteresis. Soft-start ramps reference voltage linearly over 1.0 ms, while soft-stop discharges output via an internal 20 Ω switch at EN deassertion.

Key Specifications

Pinout & Package

Package: 3 mm × 3 mm, 0.5 mm pitch QFN-16 with exposed thermal pad (Case 485DA). Thermal resistance: 45°C/W junction-to-ambient, 3.1°C/W junction-to-board.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and TPS54332DR, the NCP3135MNTXG delivers higher continuous current (5 A vs. 4 A/3 A), integrated MOSFETs reducing PCB area by ~35%, and unique automatic CCM/DCM mode that improves light-load efficiency by up to 12 percentage points - critical for always-on subsystems.

Availability

NCP3135MNTXG is available at Aetrix Electronics and suitable for industrial PLC I/O modules, FPGA core power supplies, USB-C powered peripherals, and automotive infotainment SoC rails requiring stable component supply, long-term lifecycle support, and traceable Pb-free sourcing.

Supply support for NCP3135MNTXG 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The NCP3135MNTXG belongs to onsemi's high-efficiency integrated DC-DC converter product line, designed specifically for compact, high-current point-of-load applications in space- and thermal-constrained systems.

FAQ

What is the maximum continuous output current supported by the NCP3135MNTXG?

The NCP3135MNTXG supports up to 5 A continuous DC output current and 6 A instantaneous load current under specified thermal conditions (TA ≤ 85°C, proper PCB copper and thermal vias). This rating assumes operation within the recommended input voltage range (2.9 V to 5.5 V) and use of the 3 mm × 3 mm QFN-16 package with its exposed thermal pad properly soldered to a multi-layer ground plane.

Does the NCP3135MNTXG support pre-bias startup, and how does it function?

Yes, the NCP3135MNTXG supports pre-bias startup. When the output capacitor is pre-charged (e.g., to 0.5 V), the device holds the low-side MOSFET off until the internal soft-start ramp reaches the existing FB voltage - preventing reverse current flow and potential damage to downstream loads. This behavior is confirmed in the datasheet's Detailed Description section and validated in Figure 14 (pre-bias startup waveform).

How does the PS pin configure operation mode in the NCP3135MNTXG?

The PS pin selects between two modes: pulling PS ≤174 kΩ to GND enables automatic CCM/DCM for high light-load efficiency, while leaving PS floating or tied to VDD forces FCCM for constant 1.1 MHz switching. The mode selection is implemented via internal comparators and directly affects zero-crossing detection, frequency modulation, and transient response - as detailed in Table 6 and the Operation Mode section of the datasheet.

What protections are integrated into the NCP3135MNTXG, and which are latched?

The NCP3135MNTXG integrates UVLO (on VIN/VDD), OVP, UVP, thermal shutdown, and dual OCP (high-side cycle-by-cycle, low-side immediate). Low-side OCP, OVP, UVP, and thermal shutdown are latched - requiring power cycle or EN toggle to reset. High-side OCP resets automatically after four consecutive faults cease. All protections are verified in the PROTECTIONS section (pages 11–12) and Electrical Characteristics tables.

Can the NCP3135MNTXG operate with only MLCC output capacitors, and why?

Yes, the NCP3135MNTXG is explicitly designed to support MLCC-only output filtering due to its voltage-mode control architecture, stable phase margin with low-ESR capacitors, and internal compensation optimized for ceramic capacitance. The datasheet states "Support MLCC Output Capacitor" as a key feature and demonstrates stable operation in Figures 4–7 using MLCCs - eliminating need for bulk electrolytic or tantalum capacitors.