onsemi NCP121AMX170TCG

Overview

NCP121AMX170TCG 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 1.70 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 NCP121AMX170TCG 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 performance in the XDFN6 1.2 mm × 1.2 mm package.

Technical Context

The NCP121AMX170TCG employs an NMOS pass transistor architecture powered by independent VIN and VBIAS supplies-enabling ultra-low dropout (37 mV typ. at 150 mA) and reduced sensitivity to output capacitor ESR. Its internal reference and error amplifier maintain ±1.0% output accuracy across −40°C to +85°C with 0.2% typical accuracy at 25°C.

It integrates EN-controlled ON/OFF functionality with hysteresis, thermal shutdown (160°C trip), current limiting (200–600 mA), and - uniquely for the "A" variant - active output discharge via internal pull-down (R_DISCH = 150 Ω). Bias current is only 80 µA typ. in active mode and drops to 0.5 µA in shutdown.

Key Specifications

Pinout & Package

The NCP121AMX170TCG is housed in an XDFN6 package (Case 711AT), 1.2 mm × 1.2 mm × 0.4 mm, with exposed thermal pad soldered to ground plane for thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout, dual-rail voltage regulator applications.

Compared with the NCP121AMX170TCG, the XC6217B172MR-G offers smaller footprint but sacrifices bias-rail noise immunity and current capability, while the RT9080AL-17PUF trades dual-rail operation and active discharge for higher output current - making the NCP121AMX170TCG optimal for thermally constrained, noise-critical 150 mA applications requiring precise sequencing and fast discharge.

Availability

NCP121AMX170TCG is available at Aetrix Electronics and suitable for smartphone processor rails, tablet memory I/O, wearable camera sensors, and portable DVR ISPs requiring stable component supply with guaranteed long-term availability and RoHS-compliant packaging.

Supply support for NCP121AMX170TCG 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, offering power management, analog, sensing, and connectivity solutions for automotive, industrial, and consumer markets.

The NCP121AMX170TCG belongs to onsemi's high-accuracy VLDO regulator product line, designed specifically for battery-powered portable devices demanding ultra-low dropout, low noise, and dual-rail flexibility in sub-2 mm² packages.

FAQ

What is the exact output voltage of the NCP121AMX170TCG?

The NCP121AMX170TCG provides a factory-trimmed fixed output voltage of 1.70 V. This value is guaranteed within ±1.0% tolerance over full operating conditions (−40°C to +85°C, line and load variations), and exhibits ±0.2% typical accuracy at 25°C per the datasheet specifications.

Does the NCP121AMX170TCG require an external bias supply, and what voltage range is acceptable?

Yes, the NCP121AMX170TCG requires a separate bias supply connected to the BIAS pin. The acceptable range is 2.4 V to 5.5 V - and must be at least (V_OUT + 1.35 V) per datasheet, i.e., ≥3.05 V for the 1.70 V output. This rail powers internal control circuitry independently of the main input (IN).

What does the "A" suffix in NCP121AMX170TCG indicate, and why does it matter?

The "A" suffix identifies the NCP121AMX170TCG as part of the active-discharge variant family. Only NCP121A devices integrate an internal 150 Ω pull-down transistor on the OUT pin that activates during shutdown, ensuring rapid discharge of load capacitance - essential for power sequencing and avoiding floating nodes in modern portable systems.

Can the NCP121AMX170TCG operate with only 1 µF output capacitance, and is it stable?

Yes - the NCP121AMX170TCG is explicitly characterized and guaranteed stable with a minimum 1 µF ceramic output capacitor (effective capacitance, accounting for DC bias and temperature effects). No additional ESR or parallel capacitors are required, simplifying layout and reducing bill-of-materials cost.

What thermal considerations apply to the NCP121AMX170TCG in continuous 150 mA operation?

The NCP121AMX170TCG has a junction-to-air thermal resistance (R_JA) of 170 °C/W in its XDFN6 package. At 150 mA and 75 mV dropout, power dissipation is ~11.25 mW; however, PCB layout - especially soldering the exposed thermal pad to a solid ground plane - is mandatory to maintain safe junction temperature and avoid thermal shutdown activation.