AMS1117 3.3V
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The AMS1117-3.3 is one of the most common voltage regulators used in 5V-based electronic projects (like those running off USB or Arduino) when a stable 3.3V supply is required for peripheral components, such as microcontrollers, Wi-Fi modules (like the ESP8266), or sensors.
Here is a quick overview of its key specifications and how it's used:
The AMS1117-3.3 is a Low Dropout (LDO) Linear Voltage Regulator.
Input (V_IN): It takes an unregulated DC voltage (typically 4.5V to 15V).
Output (V_OUT): It outputs a fixed, regulated voltage of 3.3V.
Low Dropout: It can maintain the 3.3V output even when the input voltage is only slightly higher (e.g., 4.5V), requiring a minimum voltage difference (dropout voltage) of about 1.2V.
| Specification | Value | Note |
| Fixed Output Voltage | 3.3V | Requires no external resistors for voltage setting. |
| Maximum Output Current | 800mA | Typically rated for 1A peak, but usually 800mA continuous. |
| Dropout Voltage | 1.2V (at 800mA) | Input must be at least 4.5V (3.3V + 1.2V) for regulation. |
| Typical Packages | SOT-223, TO-220 | SOT-223 is the most common surface-mount package. |
| Power Dissipation | Critical! | The excess power (P = (V_IN - 3.3V) times I_OUT) is dissipated as heat. High input voltage or high current requires a large heat sink (especially the SOT-223 uses the PCB copper for heat sinking). |
3. Pinout (SOT-223 Package)
The SOT-223 package is the most common for the AMS1117 series and has three main pins plus a thermal pad.
| Pin | Name | Description |
| 1 | GND | Ground connection. |
| 2 | Vout | The regulated 3.3V output (also connected to the large thermal pad on the bottom). |
| 3 | Vin | The unregulated input voltage (e.g., 5V from a USB source). |
4. Typical Application Circuit [Circuit diagram showing AMS1117 with input/output caps]
The AMS1117 is generally very easy to use and typically only requires two external capacitors for stability:
Input Capacitor (C_N): A capacitor (usually 1muF or 10muF) placed between V_IN and GND. This smooths out any ripple on the input power.
Output Capacitor (C_OUT): A capacitor (usually 10muF or greater, often Tantalum or low-ESR ceramic) placed between V_OUT and GND. This is critical for maintaining the stability of the 3.3V output.
In summary, the AMS1117-3.3V is a robust and essential component for stepping down a higher supply voltage to a clean, stable 3.3V power rail in many modern electronics projects.