onsemi NCP7815TG

Overview

NCP7815TG from onsemi is a fixed-output, 3-pin positive linear voltage regulator delivering 15 V ±4% at up to 1.0 A output current, featuring internal thermal shutdown, short-circuit current limiting, and safe-area compensation. It operates with input voltages from 17.5 V to 35 V and is commonly used in industrial power supplies, embedded control modules, and legacy analog instrumentation requiring stable +15 V bias rails.

For engineers reviewing the NCP7815TG datasheet, pinout, applications, or equivalent options, key selection considerations include dropout voltage (2.0 V at 1.0 A), ripple rejection (54–70 dB at 120 Hz), quiescent current (3.0–8.0 mA), thermal resistance (R_JA = 65 °C/W), and TO-220-3 package compatibility with standard heatsinking.

Technical Context

The NCP7815TG implements a monolithic series-pass transistor architecture with built-in protection circuitry: thermal overload shutdown triggers at ~150 °C junction temperature, and short-circuit current limiting holds peak output current to 0.3 A under fault conditions. Safe-area compensation dynamically reduces short-circuit current as V_IN–V_OUT increases, preventing second breakdown of the pass device.

It requires no external components for basic regulation but benefits from a 0.33 µF input bypass capacitor when located >2 inches from the bulk filter. Output capacitance is not required for stability but improves transient response; values below 0.1 µF may cause instability.

Key Specifications

Pinout & Package

Package: TO-220-3 (Case 221AB), Pb-free, vertical mounting with heatsink surface electrically connected to Pin 2 (GND). Pin 1 is input, Pin 2 is ground, Pin 3 is output - compatible with standard TO-220 clip-on heatsinks.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC7815CT and LM7815CD2T, the NCP7815TG provides the optimal balance of through-hole manufacturability, legacy drop-in compatibility, Pb-free compliance, and enhanced ESD resilience - making it the preferred choice for industrial repair, mid-volume production, and RoHS-compliant upgrades.

Availability

NCP7815TG is available at Aetrix Electronics and suitable for industrial control systems, analog instrumentation, legacy system repairs, and embedded power supply designs requiring stable component supply and long-term lifecycle support.

Supply support for NCP7815TG 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, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The NCP7800 series was designed as a rugged, drop-in replacement for the MC7800 family - targeting cost-sensitive, high-reliability linear regulation in industrial controls, power supplies, and legacy equipment where simplicity, thermal robustness, and proven architecture matter most.

FAQ

What is the minimum input voltage required for stable operation of the NCP7815TG?

The NCP7815TG requires a minimum input voltage of 17.5 V under full-load conditions (1.0 A), per its specified operating range. This ensures the 2.0 V dropout margin is maintained across temperature and load variations. At light loads (<50 mA), input can be reduced to 17.0 V, but design margin should retain ≥17.5 V to guarantee regulation across all conditions. The NCP7815TG datasheet specifies this as Vin(min) = V_OUT + V_DO = 15 V + 2.0 V = 17.0 V, with 17.5 V recommended for safety.

Does the NCP7815TG require an input bypass capacitor?

Yes - an input bypass capacitor is recommended for the NCP7815TG when the regulator is located more than ~2 inches from the main power supply filter or when driving large capacitive loads. A 0.33 µF tantalum or ceramic capacitor placed directly across Pins 1 and 2 minimizes high-frequency instability and improves transient response. The NCP7815TG will function without it in low-noise, short-trace lab setups, but production designs must include it for robustness.

Can the NCP7815TG be used in adjustable-output configurations?

Yes - the NCP7815TG can be adapted for adjustable output using an external op-amp feedback network, as shown in Figure 10 of the NCP7800 datasheet. However, the NCP7815TG itself is a fixed 15 V device; adjustment requires adding components like the MC34072V op-amp and resistive divider. For native adjustability, consider the LM317 or NCP7805 with external resistors - the NCP7815TG's internal feedback is not accessible.

What thermal derating applies to the NCP7815TG at 85 °C ambient temperature?

At 85 °C ambient, the NCP7815TG's maximum continuous output current drops to ~650 mA when mounted on a standard TO-220 heatsink (R_HS = 15 °C/W), based on its R_JA = 65 °C/W and T_J(max) = 150 °C. Without a heatsink, usable current falls below 200 mA. Derating curves in Figure 13 of the NCP7815TG datasheet confirm this - always verify junction temperature using P_D = (V_IN − 15 V) × I_OUT and T_J = T_A + P_D × R_JA.

Is a protection diode necessary when using the NCP7815TG?

A protection diode is recommended across the NCP7815TG's input and output terminals if the input supply can be rapidly shorted to ground (e.g., crowbar circuits or hot-swap events) while the output capacitor remains charged. The NCP7815TG has an internal ~1 Ω reverse path rated for ≤5 A surge, but large output caps (>100 µF) with high input voltage (≥24 V) can exceed this limit. Per Figure 15, a 1N5822 Schottky diode (rated ≥5 A peak) connected anode-to-output, cathode-to-input prevents damage.