onsemi NCP4681DSQ25T1G

Overview

NCP4681DSQ25T1G from onsemi is a 2.5 V, 150 mA CMOS low-dropout linear regulator with ultra-low quiescent current (1 µA typ.), integrated soft-start, and enable control. It operates from 1.40 V to 5.25 V input, delivers ±1.0% output voltage accuracy, and features 0.28 V dropout at 150 mA - optimized for battery-powered portable electronics requiring stable, low-noise power rails.

For engineers reviewing the NCP4681DSQ25T1G datasheet, pinout, applications, or equivalent options, this device is selected for ultra-low-power active/standby operation in space-constrained SC-70 designs where supply current, startup behavior, and ceramic capacitor compatibility are critical selection criteria.

Technical Context

The NCP4681DSQ25T1G implements a CMOS-based LDO architecture with an internal N-channel pass transistor, constant-slope soft-start circuitry, and fold-back current limiting. Its enable pin (CE) supports active-high logic control and reduces standby current to 0.1 µA, while the built-in discharge transistor rapidly discharges the output capacitor during shutdown.

This variant is the SC-70 packaged, 2.5 V fixed-output version of the NCP4681 family with auto-discharge functionality. It is stable with ≥0.1 µF ceramic output capacitors and exhibits 25 dB PSRR at 1 kHz under 30 mA load - enabling clean power delivery in noise-sensitive analog and RF subsystems.

Key Specifications

Pinout & Package

Package: SC-70 (Case 419A−02), 5-pin, Pb-free, 1.80 mm × 1.35 mm footprint. Thermal pad not present; GND pin (Pin 2) serves as primary thermal path.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-2502E/MB and TNIV2525002RA, the NCP4681DSQ25T1G uniquely integrates enable control, auto-discharge, and ultra-low 1 µA quiescent current in the same SC-70 footprint - making it the only option among the three that satisfies simultaneous requirements for low-power sequencing, fast reset, and minimal board area in portable medical and wireless edge devices.

Availability

NCP4681DSQ25T1G is available at Aetrix Electronics and suitable for wearable health monitors, smart home sensors, and industrial wireless transmitters requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for NCP4681DSQ25T1G 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The NCP4681DSQ25T1G belongs to onsemi's ultra-low-power LDO family designed specifically for battery-operated portable electronics where extended runtime, small form factor, and reliable power sequencing are essential.

FAQ

What is the maximum input voltage rating for the NCP4681DSQ25T1G?

The absolute maximum input voltage for the NCP4681DSQ25T1G is 6.0 V. However, the recommended operating input voltage range is 1.40 V to 5.25 V per the datasheet's Electrical Characteristics table. Operation above 5.25 V is only permitted for ≤500 hours total lifetime and must not exceed 5.50 V - sustained use beyond 5.25 V risks reliability degradation. The NCP4681DSQ25T1G is intended for single-cell battery and low-voltage rail applications.

Does the NCP4681DSQ25T1G require an external pull-up resistor on the CE pin?

No, the NCP4681DSQ25T1G does not require an external pull-up resistor on the CE pin. It includes an internal pull-down current source (0.3 µA typical) that holds the CE pin low when unconnected. To enable the regulator, apply a logic-high voltage ≥1.0 V to CE; to disable it, drive CE ≤0.4 V or leave it floating (which defaults to disable via internal pull-down). External pull-up is unnecessary and may increase standby current.

Can the NCP4681DSQ25T1G operate stably with a 0.047 µF ceramic output capacitor?

No - the NCP4681DSQ25T1G requires a minimum output capacitance of 0.1 µF (100 nF) ceramic for guaranteed stability, as specified in the datasheet's "Stable with Ceramic Capacitors" feature and Application Information section. Using 0.047 µF may cause oscillation or poor transient response due to insufficient phase margin. Always use ≥0.1 µF X5R or X7R ceramic capacitors placed within 2 mm of the VOUT and GND pins.

What is the thermal resistance (R_JA) of the NCP4681DSQ25T1G in its SC-70 package?

The junction-to-air thermal resistance (R_JA) for the NCP4681DSQ25T1G in the SC-70 package is 263°C/W, as documented in the Thermal Characteristics table on page 3 of the datasheet. This value assumes standard JEDEC High-K test board conditions. Actual R_JA in end equipment depends on PCB copper area, layer count, and airflow; adding thermal vias under the GND pad can reduce effective R_JA by up to 30%.

How does the auto-discharge function behave during CE deactivation in the NCP4681DSQ25T1G?

When the CE pin is driven low (<0.4 V), the NCP4681DSQ25T1G disables regulation and activates an internal N-channel transistor between VOUT and GND. This discharges the output capacitor rapidly - typically collapsing VOUT from 2.5 V to <0.1 V within 1–2 ms depending on capacitor size and ESR. This behavior is confirmed in Figures 38–40 (Shutdown waveforms) and explicitly described in the "Output Discharger" subsection on page 15 of the datasheet.