onsemi NCP121AMX165TCG

Overview

NCP121AMX165TCG from onsemi is a fixed-output, high-accuracy, very low dropout (VLDO) linear voltage regulator with NMOS pass transistor and separate bias rail (VBIAS). It delivers 150 mA at 1.65 V output with ±1.0% accuracy over line/load/temperature, 75 mV max dropout at full load, and operates from 0.8 V to 5.5 V input while requiring 2.4–5.5 V bias supply. It is used in space-constrained, noise-sensitive portable electronics such as smartphone core logic rails.

For engineers reviewing the NCP121AMX165TCG datasheet, pinout, applications, or equivalent options, key selection criteria include ultra-low dropout under 150 mA load, dual-rail operation (VIN + VBIAS), active output discharge capability, stability with 1 µF ceramic output capacitor, and thermal shutdown protection at 160°C junction temperature.

Technical Context

The NCP121AMX165TCG implements a dual-rail NMOS-based VLDO architecture where VIN supplies the pass element and VBIAS powers internal control circuitry-including reference, error amplifier, and EN logic-enabling stable regulation even when VIN approaches VOUT. Its bias-supplied topology decouples control-loop power from the main rail, improving PSRR (80 dB from VBIAS) and reducing sensitivity to VIN ripple.

It features monotonic startup with controlled slew rate, internal current limiting (200–600 mA), thermal shutdown with hysteresis (160°C trip / 140°C recovery), and an enable pin with 0.9 V high-threshold and 0.4 V low-threshold. The NCP121AMX165TCG variant includes active output discharge (R_DISCH = 150 Ω) activated during shutdown.

Key Specifications

Pinout & Package

The NCP121AMX165TCG is housed in a Pb-free, halogen-free XDFN6 package (Case 711AT), measuring 1.2 mm × 1.2 mm × 0.4 mm with an exposed thermal pad. This ultra-compact footprint minimizes PCB area and enhances thermal performance when soldered to ground plane.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout, fixed-output regulator applications.

Compared with TPS7A05165PDBVR and MCP1826T-16502E/DB, the NCP121AMX165TCG uniquely supports dual-rail operation for superior noise rejection and delivers lowest dropout (75 mV) with integrated active discharge - critical for compact, battery-constrained systems requiring fast, clean power sequencing.

Availability

NCP121AMX165TCG is available at Aetrix Electronics and suitable for smartphone core rails, tablet I/O domains, digital camera sensor biasing, and STB peripheral power management requiring stable component supply, tight output accuracy, and ultra-low dropout performance.

Supply support for NCP121AMX165TCG 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 focused on energy-efficient electronics, delivering silicon solutions for automotive, industrial, cloud, and intelligent edge applications.

The NCP121 series belongs to onsemi's high-precision, ultra-low-noise LDO portfolio designed specifically for battery-powered portable devices demanding minimal dropout, sub-1% accuracy, and compact packaging.

FAQ

What is the guaranteed output voltage tolerance for NCP121AMX165TCG across temperature and load?

The NCP121AMX165TCG guarantees ±1.0% output voltage accuracy over −40°C to +85°C junction temperature, full line (V_IN = V_OUT(NOM) + 0.3 V to 5.0 V), and load (1 mA to 150 mA), with tighter ±0.2% accuracy at 25°C. This is confirmed in the Electrical Characteristics table of the official datasheet (Rev. 1, October 2019), ensuring reliable core voltage delivery without external trimming.

Does NCP121AMX165TCG require an external bias supply, and what happens if VBIAS is out of spec?

Yes, NCP121AMX165TCG requires a separate VBIAS supply between 2.4 V and 5.5 V to power its internal control circuitry. If VBIAS falls below the UVLO threshold (typically 1.6 V rising, with 0.2 V hysteresis), the device disables regardless of EN state. Operation outside the specified VBIAS range risks loss of regulation, increased noise, or complete shutdown - per Absolute Maximum Ratings and Electrical Characteristics sections.

Can NCP121AMX165TCG operate with only VIN connected and VBIAS tied to VIN?

No - while VBIAS may be tied to VIN in some configurations, the datasheet specifies distinct minimum VBIAS requirements (≥2.4 V or V_OUT + 1.35 V, whichever is greater). For NCP121AMX165TCG (1.65 V output), VBIAS must be ≥2.4 V. Tying VBIAS to a low VIN (e.g., 1.8 V) violates this condition and triggers UVLO, disabling regulation. A dedicated ≥2.4 V bias source is required.

What is the purpose of the N/C pin (Pin 2) on NCP121AMX165TCG, and how should it be handled on the PCB?

Pin 2 of NCP121AMX165TCG is Not Connected (N/C) - it has no internal bond wire or circuit connection. Per the Pin Function Description table (page 2), it must remain electrically unconnected. On the PCB, this pad should not be routed, plated, or tied to any net (including ground or power); leaving it floating avoids parasitic coupling or unintended current paths that could affect noise or thermal behavior.

How does the active output discharge feature work in NCP121AMX165TCG, and when is it engaged?

The active output discharge in NCP121AMX165TCG engages automatically when the EN pin is driven low (<0.4 V), pulling the OUT pin to GND through an internal 150 Ω resistor. This rapidly discharges external output capacitance, preventing residual voltage from causing latch-up or false wake-up in downstream logic. It is present only in "A" suffix variants like NCP121AMX165TCG - confirmed in Figure 2 block diagram footnote and Ordering Information table.