onsemi NCP4681DMX29TCG

Overview

NCP4681DMX29TCG from onsemi is a 150 mA ultra-low-quiescent-current CMOS linear voltage regulator with 2.9 V fixed output, 1 µA typical supply current, and 0.25 V dropout at 150 mA (V_OUT = 2.9 V). It features an enable pin (active-high), integrated soft-start, auto-output discharge, and operates from 1.40 V to 5.25 V input - designed for power management in compact battery-powered sensors and portable microcontroller subsystems.

For engineers reviewing the NCP4681DMX29TCG datasheet, pinout, applications, or equivalent options, this page delivers verified technical context, package-specific pin functions, real-world use cases, and validated alternative options - all grounded in onsemi's official NCP4681/D Rev. 3 documentation.

Technical Context

The NCP4681DMX29TCG implements a CMOS-based low-dropout architecture with a built-in constant-slope soft-start circuit that prevents output overshoot and limits inrush current. Its internal N-channel pass transistor enables ultra-low quiescent current (1 µA) and supports fast output discharge via an integrated V_OUT-to-GND switch during disable.

It operates across −40°C to +85°C ambient, maintains ±1.0% output voltage accuracy over temperature and load, and achieves 25 dB PSRR at 1 kHz. The device is stable with ≥0.1 µF ceramic output capacitors and includes fold-back current limiting and thermal shutdown protection.

Key Specifications

Pinout & Package

XDFN4 0.8 mm × 0.8 mm (Case 711AB), thermally enhanced with exposed GND pad on underside. Pin 1 marked by chamfered corner; tab connected internally to GND - recommended to solder to PCB ground plane for optimal thermal performance (R_JA = 350°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-quiescent-current LDO applications.

Compared with MCP1700T-2902E/TT and XC6206P292MR-G, the NCP4681DMX29TCG uniquely combines 1 µA IQ, 2.9 V fixed output, active-high enable, and integrated auto-discharge - making it optimal for energy-harvested or long-life battery systems requiring controlled power-down behavior.

Availability

NCP4681DMX29TCG is available at Aetrix Electronics and suitable for wearable health monitors, industrial wireless transmitters, smart home sensors, and portable diagnostic equipment requiring stable component supply with guaranteed long-term availability.

Supply support for NCP4681DMX29TCG 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, and sensor solutions for automotive, industrial, and cloud infrastructure markets.

The NCP4681 series belongs to onsemi's ultra-low-I_Q LDO portfolio, engineered specifically for battery-constrained edge devices where nanowatt-level standby power and fast, controlled power sequencing are mandatory.

FAQ

What is the maximum input voltage rating for the NCP4681DMX29TCG?

The absolute maximum input voltage for the NCP4681DMX29TCG is 6.0 V. However, per the datasheet's Electrical Characteristics note, continuous operation above 5.25 V is limited to ≤500 hours total lifetime. For reliable long-term use, the recommended operating input range remains 1.40 V to 5.25 V - and the NCP4681DMX29TCG must be operated within this window in production designs.

Does the NCP4681DMX29TCG require an external pull-up resistor on the CE pin?

No - the NCP4681DMX29TCG includes an internal pull-down current source (0.3 µA typical) on the CE pin. When enable functionality is not used, connecting CE directly to VIN is acceptable and ensures reliable turn-on without external components. An external pull-up is unnecessary and may increase standby current if improperly sized.

How does the auto-discharge function operate in the NCP4681DMX29TCG?

When the CE pin is driven LOW, the NCP4681DMX29TCG activates an internal NMOS transistor between V_OUT and GND. This provides a low-impedance discharge path, collapsing the output voltage to <100 mV within 1 ms (typ.) for a 1 µF output capacitor. This behavior is exclusive to the "D" suffix variants like the NCP4681DMX29TCG and is not present in "H" or "E" versions.

Can the NCP4681DMX29TCG be used with a 0.22 µF ceramic output capacitor?

Yes - the NCP4681DMX29TCG is stable with ceramic capacitors ≥0.1 µF, including 0.22 µF. Larger values improve transient response and reduce output ripple but do not affect stability. Ensure the capacitor has low ESR (<100 mΩ) and is placed within 2 mm of the V_OUT and GND pins to maintain control-loop integrity and avoid oscillation.

What is the thermal resistance (R_JA) of the NCP4681DMX29TCG in its XDFN package?

The NCP4681DMX29TCG in the XDFN4 0.8 mm × 0.8 mm package (Case 711AB) has a junction-to-air thermal resistance (R_JA) of 350°C/W, as specified in the Thermal Characteristics table. This value assumes standard JEDEC test conditions (single-layer copper, no thermal vias); actual R_JA improves significantly with proper PCB layout - e.g., connecting the exposed thermal pad to a ≥100 mm² internal GND plane reduces R_JA to ~120°C/W.