onsemi NCP1117DT12G: Datasheet, Pinout, and Typical Application Circuits
The onsemi NCP1117DT12G is a ubiquitous and highly reliable low-dropout (LDO) linear voltage regulator, part of a famous family of devices designed to provide a fixed 1.2V output at currents up to 1A. Housed in the robust DPAK surface-mount package, it is engineered for a wide range of applications, from consumer electronics to industrial systems, where stable and efficient voltage regulation is paramount.
This component is prized for its balance of performance, cost-effectiveness, and ease of use, making it a go-to choice for engineers for both new designs and legacy products.
Datasheet Overview and Key Specifications
The NCP1117DT12G datasheet details its critical electrical and mechanical characteristics. Key specifications that define its performance include:
Output Voltage: Fixed at 1.2V (The DT12 suffix denotes this fixed voltage; other variants provide 1.5V, 1.8V, 2.5V, 3.3V, and 5.0V).
Output Current: Up to 1A.
Dropout Voltage: Typically 1.2V at 1A load current. This is the minimum voltage difference required between the input (VIN) and output (VOUT) for the device to regulate properly.
Line Regulation: 0.2% (Typ.)
Load Regulation: 0.4% (Typ.)
Package: DPAK (TO-252), which offers an excellent thermal performance-to-footprint ratio, allowing it to dissipate heat effectively when used with a sufficient copper pour on the PCB.
Protection Features: The device includes internal current limiting and thermal shutdown protection, safeguarding both the regulator and the load from damage during fault conditions.
Pinout Configuration
The NCP1117DT12G in the DPAK package has three pins/pads:
1. Pin 1 (Input): This is the input voltage pin. The unregulated input supply voltage, which must be higher than VOUT + VDROP, is applied to this pin. A input capacitor (typically 10µF) should be placed close to this pin for stability.
2. Pin 2 (Ground / Adjust): For the fixed-voltage version (NCP1117DT12G), this pin is the ground (GND) reference for the internal voltage divider and error amplifier.
3. Pin 3 (Output): This pin provides the regulated 1.2V output. An output capacitor is required between this pin and ground to ensure loop stability and improve transient response. A value of 10µF to 22µF tantalum or aluminum electrolytic is recommended.
The tab of the DPAK package is internally connected to Pin 3 (Output) and must be soldered to the PCB's copper area to act as a heatsink.
Typical Application Circuits
The primary application for the NCP1117DT12G is as a fixed-voltage regulator. The basic circuit is straightforward, requiring only two external components.
1. Basic Fixed 1.2V Regulator Circuit:
This is the most common application. The input voltage (VIN) must be at least 1.2V + 1.2V (dropout) = 2.4V or higher. For example, it can efficiently regulate a 3.3V or 5V rail down to a stable 1.2V for low-voltage logic or core voltages.
CIN (10µF): An input capacitor placed near the regulator to filter incoming noise and ensure stable operation. While a tantalum capacitor is often specified, a low-ESR ceramic capacitor can also be used.
COUT (10µF): An output capacitor critical for maintaining stability. The regulator is designed to be stable with low-ESR tantalum or aluminum electrolytic capacitors. Using ceramic capacitors may require careful evaluation and possibly the addition of a small series resistor to ensure stability.
2. Circuit with Enhanced Filtering:
For applications sensitive to power supply ripple, such as analog or RF circuits, additional filtering can be added. A small ferrite bead can be placed in series with the input path, followed by a secondary bypass capacitor to ground. Similarly, a smaller value ceramic capacitor (e.g., 100nF) can be placed parallel to the main output capacitor to filter high-frequency noise.
ICGOODFIND Summary
The onsemi NCP1117DT12G stands as a testament to simple, effective, and robust power management. Its key strengths lie in its 1A output capability, low dropout voltage, and comprehensive internal protection. The fixed 1.2V output makes it an ideal solution for powering low-voltage digital ICs, microcontroller cores, and other subsystems requiring a clean, stable voltage rail from a higher input source. Its simple two-component typical application circuit allows for rapid implementation, reducing design time and complexity. When designing with this LDO, paying close attention to thermal management via PCB copper heatsinking and proper capacitor selection is crucial for achieving optimal, reliable performance.
Keywords: LDO Voltage Regulator, 1.2V Output, 1A Output Current, DPAK Package, Thermal Shutdown
