onsemi NCP5661MN25T2G

Overview

NCP5661MN25T2G from onsemi is a fixed-output, 2.5 V, 1.0 A ultra-fast transient response low dropout (LDO) linear regulator in a thermally robust DFN6 3×3.3 mm package. It features 1.0 V typical dropout at 1.0 A load, 26 µV_rms output noise without bypass capacitor, and integrated Enable control - designed for post-regulation in high-current server and networking power supplies.

For engineers reviewing the NCP5661MN25T2G datasheet, pinout, applications, or equivalent options, key selection criteria include its 2.5 V fixed output accuracy (±1% at 25°C), error flag functionality, thermal shutdown at 160°C, and compatibility with low-ESR ceramic output capacitors ≥10 µF.

Technical Context

The NCP5661MN25T2G implements a precision 0.9 V internal reference with adjustable feedback architecture repurposed for fixed 2.5 V output via internal resistor divider. Its ultra-fast transient response (1–3 µs settling time) stems from a high-gain error amplifier and optimized internal compensation, enabling stable operation with 10–150 µF ceramic output capacitors and ESR as low as 10 mΩ.

It integrates independent enable logic with 1.3 V rising-edge threshold and 0.3 V falling-edge threshold, plus an open-drain Error Flag (Pin 5) that asserts low when output falls below 88% of nominal (2.2 V at 2.5 V output), requiring only a 100 kΩ pull-up to Vin. Thermal protection activates at 160°C with automatic recovery.

Key Specifications

Pinout & Package

Package: DFN6 (3.0 × 3.3 mm, 0.95 mm pitch, exposed thermal pad). Thermally enhanced layout with 18 °C/W junction-to-lead resistance supports 1.0 A operation without heatsink under 1 in² copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A4700RGWR and MCP1826-2502E/DB, the NCP5661MN25T2G uniquely combines integrated Error Flag, 26 µV_rms noise without bypass cap, and DFN6 thermal performance - making it optimal for space-constrained, fault-aware digital power rails.

Availability

NCP5661MN25T2G is available at Aetrix Electronics and suitable for server VRMs, ASIC power supplies, and networking equipment requiring stable component supply, automotive-grade traceability (via NCV variant), and long-term production continuity.

Supply support for NCP5661MN25T2G 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, sensors, and connectivity solutions for automotive, industrial, computing, and consumer markets.

The NCP5661 series belongs to onsemi's high-current LDO portfolio, engineered specifically for post-regulation in high-performance computing and communications infrastructure where ultra-fast transient response and diagnostic capability are mandatory.

FAQ

What is the maximum input voltage rating for the NCP5661MN25T2G?

The NCP5661MN25T2G has an absolute maximum input voltage (Vin) rating of 18 V. However, for reliable operation within specifications, the recommended input range is 2.0 V to 9.0 V - ensuring proper dropout margin and thermal stability at 1.0 A output. Exceeding 9.0 V may increase power dissipation beyond safe limits in the DFN6 package.

Does the NCP5661MN25T2G require an external bypass capacitor to achieve its specified 26 µV_rms noise performance?

No, the NCP5661MN25T2G achieves 26 µV_rms output noise (10 Hz–100 kHz) without any external bypass capacitor - a key differentiator confirmed in the Electrical Characteristics table on page 3 of the datasheet. This eliminates BOM cost and layout complexity while maintaining low-noise operation across its full 10 mA–1.0 A load range.

How does the Error Flag pin on the NCP5661MN25T2G behave during startup and fault conditions?

The Error Flag (Pin 5) on the NCP5661MN25T2G is an open-drain output that remains high-impedance until VOUT reaches regulation. Once active, it pulls low when output drops below 88% of nominal (2.2 V), with 50 µs blanking to ignore startup undershoot. During sustained fault, it holds low until VOUT recovers above threshold - enabling direct connection to MCU interrupt pins for real-time monitoring.

Can the NCP5661MN25T2G be used with ceramic output capacitors smaller than 150 µF?

Yes - the NCP5661MN25T2G is guaranteed stable with output capacitance as low as 10 µF, provided ESR is <300 mΩ. The datasheet confirms stability down to 10 µF in Figure 13 and 14, and recommends multilayer ceramic capacitors placed close to the VOUT pin to preserve its ultra-fast transient response. Larger values (e.g., 100–150 µF) improve low-frequency ripple rejection.

What thermal derating applies to the NCP5661MN25T2G in a standard 1 in² copper layout?

In a standard 1 in² 1 oz copper layout, the NCP5661MN25T2G exhibits R_θJA = 82 °C/W (DFN6, Note 2). At 1.0 A load with 3.5 V input (1.0 V dropout), power dissipation is ~1.0 W - resulting in ~82°C junction rise above ambient. With 70°C ambient, junction temperature reaches ~152°C, near the 150°C max operating limit; thus, derating to ≤0.85 A is recommended for continuous operation at 70°C ambient.