onsemi NCP112PG

Overview

NCP112PG from onsemi is a supervisory IC designed for desktop ATX power supply monitoring, providing simultaneous overvoltage and undervoltage protection for 3.3 V, 5.0 V, and 12 V outputs with 40–130 mV hysteresis, programmable blanking and delay timing via external 100 nF capacitors, and a precision 2.5 V reference output sourcing up to 20 mA - deployed in multi-output switch-mode PSUs to enable system controller fault reporting and power sequencing.

For engineers reviewing the NCP112PG datasheet, pinout, applications, or equivalent options, key selection considerations include its triple-rail voltage monitoring capability, remote on/off control with adjustable delay, fault latching behavior, and compatibility with standard ATX power-good signaling requirements.

Technical Context

The NCP112PG integrates independent UV/OV comparators for three fixed rails (3.3 V, 5 V, 12 V), each with internal 1.28 V threshold references and user-adjustable hysteresis; it also includes a fourth adjustable OVP input (ADJ) logically ORed into the fault path with 100 µs delay filtering. All sense inputs feature built-in hysteresis to prevent chatter during threshold crossings.

Its timing architecture relies on internal current sources charging external capacitors (CTUV, CTPG, CTREMOTE) to generate programmable delays: undervoltage blanking at power-up (100–500 ms), power-good assertion (100–500 ms), and remote on/off response (35–60 ms). The FAULT output latches after 100 µs of detected overvoltage, while PGO remains active-high only when all monitored rails and PGI are valid.

Key Specifications

Pinout & Package

Package: PDIP-14 (Case 646, Pb-free), 18.16 mm × 6.10 mm × 3.69 mm body, through-hole mounting compatible with legacy ATX PSU designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar supervisory IC applications.

Compared with TL3127CDR and MAX6816EPA+, the NCP112PG uniquely delivers ATX-specific triple-rail supervision with integrated timing capacitor interfaces, latched fault signaling, and a 2.5 V reference - making it irreplaceable in desktop and server PSU designs requiring strict compliance and minimal external components.

Availability

NCP112PG is available at Aetrix Electronics and suitable for ATX desktop power supplies, industrial multi-output PSUs, and embedded computing platforms requiring stable component supply, long-term lifecycle support, and Pb-free compliance.

Supply support for NCP112PG 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 manufacturer specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The NCP112PG belongs to onsemi's power supply supervision product line, engineered specifically for ATX-compliant desktop and server power supplies requiring precise, multi-rail voltage monitoring and fault coordination.

FAQ

What is the function of the ADJ pin on the NCP112PG?

The ADJ pin on the NCP112PG serves as an additional overvoltage protection input with a fixed 1.28 V threshold. When the voltage at this pin falls below 1.28 V, it triggers the FAULT output, and its signal is logically ORed with the main rail OV detectors. This allows monitoring of auxiliary conditions such as fan failure or temperature sensor output, extending supervision beyond the three primary rails. The NCP112PG uses the same 100 µs fault delay on ADJ as on VS33/VS5/VS12.

How does the NCP112PG handle undervoltage detection during power-up?

The NCP112PG avoids false undervoltage assertions during startup using the CTUV capacitor on Pin 6, which sets a programmable blanking delay of 100–500 ms. During this interval, the UV comparators are disabled, allowing the 3.3 V, 5 V, and 12 V rails to stabilize before supervision begins. This behavior is confirmed in the Electrical Characteristics table (TUV parameter) and functional description section of the NCP112PG datasheet.

Can the NCP112PG be used in place of the TSM112?

Yes - the NCP112PG is explicitly documented as an enhanced replacement for the TSM112, offering identical pinout, improved hysteresis performance, Pb-free packaging, and optimized timing capacitor compatibility. It maintains full functional and electrical compatibility while adding tighter voltage reference accuracy (±1.6% vs. ±2%) and extended operating temperature range (−40°C to +125°C ambient).

What is the maximum sink current capability of the FAULT output on the NCP112PG?

The FAULT output on the NCP112PG is rated for 20 mA sink current at VCC = 5 V, with a saturation voltage of ≤0.4 V at that load. This allows direct interfacing with standard PWM controller enable/disable inputs without external buffering. The datasheet specifies IFAULT = 20 mA (min) and VFAULTsat ≤ 0.4 V (max) under 20 mA load, confirming robust drive strength for industrial-grade controllers.

Does the NCP112PG require external components to operate?

The NCP112PG requires three external 100 nF timing capacitors (CTUV, CTPG, CTREMOTE) to set undervoltage blanking, power-good delay, and remote on/off timing - all optimized for low-cost ceramic types. No external resistors or precision references are needed. The VREF output is self-stabilized and requires no bypass capacitor, and the internal pull-up on REMOTE eliminates the need for an external resistor.