The LM1117DTX-3.3 is a Low Dropout Regulator (LDO) manufactured by Texas Instruments. This specific model is a 3.3V output version of the LM1117 family, which is widely used for voltage regulation applications.
Pin Function Specifications
The LM1117DTX-3.3 is housed in the SOT-223 package, which has 5 pins in total. Below is a detailed explanation of the pin functions for this component:
Pinout and Pin Functions Pin Number Pin Name Pin Function 1 IN Input: This is the input pin where the unregulated voltage is applied. It typically ranges from 4.5V to 15V, depending on the dropout voltage and the load. It should be decoupled using a capacitor close to the pin for stable operation. 2 GND Ground: This is the ground pin, which should be connected to the system's ground to complete the circuit. 3 OUT Output: This is the output pin where the regulated 3.3V output voltage is provided. The output voltage is a stable 3.3V with respect to the ground. 4 Adj Adjust: This pin is used for adjusting the output voltage in adjustable versions of the LM1117 series. In this fixed version (LM1117DTX-3.3), this pin is typically not used, and it is internally connected to a reference voltage. 5 NC No Connection: This pin is not connected to any internal circuitry and does not have any function. It is typically left floating in designs that use this pinout. Detailed Pin DescriptionsPin 1 (IN): The input voltage should be at least 1.1V higher than the desired output voltage (4.4V for a 3.3V output) to ensure proper operation, considering the dropout voltage of the regulator. The input pin should be bypassed with a capacitor (usually 10µF or greater) for stable performance.
Pin 2 (GND): It serves as the reference ground for the regulator and should be connected to the system's common ground. A proper ground plane is essential to minimize voltage fluctuations and noise.
Pin 3 (OUT): This pin provides the regulated output voltage. For the LM1117DTX-3.3, it outputs 3.3V under nominal load conditions. A capacitor should be placed at the output for stability, typically a 10µF ceramic capacitor.
Pin 4 (Adj): Although it is used for adjusting output voltage in adjustable versions, in the LM1117DTX-3.3, this pin is internally connected to the regulator's reference voltage and does not require external components or connections.
Pin 5 (NC): This is not connected internally. Some versions of the LM1117 series use this pin for additional functions, but for the LM1117DTX-3.3, it is unused.
Package Information
Package Type: SOT-223 Number of Pins: 5 Mounting Type: Surface Mount Thermal Resistance Junction-to-Case: 55°C/W Operating Temperature: -40°C to +125°CApplication Circuit
In typical applications, the LM1117DTX-3.3 is used to regulate the voltage from a higher input (such as 5V or 12V) to a stable 3.3V output. The typical circuit would involve connecting a suitable input capacitor (10µF) at the input pin and a suitable output capacitor (10µF) at the output pin for stability. Proper grounding and layout are crucial for minimizing noise and ensuring reliable operation.
FAQ: 20 Common Questions and Answers about the LM1117DTX-3.3
What is the output voltage of the LM1117DTX-3.3? The output voltage is 3.3V, which is regulated and stable under normal load conditions.
What is the dropout voltage of the LM1117DTX-3.3? The typical dropout voltage is around 1.1V, meaning the input voltage must be at least 4.4V for proper regulation.
Can the LM1117DTX-3.3 handle a 12V input? Yes, the LM1117DTX-3.3 can handle input voltages up to 15V, but the dropout voltage must be considered to maintain proper 3.3V output.
How much current can the LM1117DTX-3.3 supply? The LM1117DTX-3.3 can supply up to 800mA of output current, depending on thermal and Power dissipation constraints.
What type of capacitors should be used for the input and output? It is recommended to use a 10µF ceramic capacitor at both the input and output for stable operation.
Does the LM1117DTX-3.3 require a heatsink? A heatsink is not typically required for the LM1117DTX-3.3 unless the power dissipation is high, such as when the input voltage is significantly higher than 3.3V and the load current is large.
Can the LM1117DTX-3.3 be used in battery-powered applications? Yes, it can be used in battery-powered circuits, but the input voltage must be sufficient to account for the dropout voltage.
Is the LM1117DTX-3.3 short-circuit protected? Yes, the LM1117DTX-3.3 has built-in short-circuit protection to prevent damage in the event of a short circuit at the output.
What is the maximum input voltage for the LM1117DTX-3.3? The maximum input voltage is 15V. Exceeding this voltage could damage the regulator.
What is the typical output current for the LM1117DTX-3.3? Under normal conditions, the LM1117DTX-3.3 can supply a maximum of 800mA. The exact current depends on the thermal conditions.
Can the LM1117DTX-3.3 be used for powering microcontrollers? Yes, the LM1117DTX-3.3 is often used to power microcontrollers and other low-power devices requiring a stable 3.3V supply.
What are the thermal limitations of the LM1117DTX-3.3? The LM1117DTX-3.3 can operate with a thermal resistance of 55°C/W junction-to-case. Power dissipation should be kept within limits to prevent overheating.
What is the quiescent current of the LM1117DTX-3.3? The typical quiescent current is around 5mA, which is important to consider for low-power applications.
How do I adjust the output voltage? The LM1117DTX-3.3 is a fixed voltage version, so the output is not adjustable. For adjustable versions, you would use external resistors to set the output voltage.
Is the LM1117DTX-3.3 suitable for high-frequency applications? The LM1117DTX-3.3 is designed for low-frequency and general-purpose regulation. For high-frequency applications, other regulators with higher switching speeds may be more suitable.
Can the LM1117DTX-3.3 be used in automotive applications? Yes, as long as the input voltage remains within specified limits (typically 15V), the LM1117DTX-3.3 can be used in automotive power supplies.
How should the ground pin be connected? The ground pin should be connected directly to the system ground with low impedance. A ground plane is recommended for low-noise performance.
What is the thermal shutdown temperature of the LM1117DTX-3.3? The thermal shutdown is typically set around 150°C to protect the device from overheating.
Can I use the LM1117DTX-3.3 for 5V input? Yes, the LM1117DTX-3.3 can regulate a 5V input down to 3.3V, given the dropout voltage of approximately 1.1V.
What is the recommended PCB layout for the LM1117DTX-3.3? The input and output capacitors should be placed as close as possible to the input and output pins for stability. Proper grounding and thermal management are key to ensuring efficient operation.
