STMicroelectronics LD1117V33 Voltage Regulator Instruction Manual

1. Introduction

This manual provides essential information for the proper use and understanding of the STMicroelectronics LD1117V33 Linear Voltage Regulator. The LD1117V33 is designed to provide a stable 3.3V output from a higher input voltage, suitable for various electronic applications requiring a regulated power supply.

Figure 1: A set of STMicroelectronics LD1117V33 linear voltage regulators. These components are commonly used to convert a higher input voltage to a stable 3.3V output for electronic circuits.

2. Key Features

• Output Voltage: Fixed 3.3V
• Output Current: Up to 950mA (typical)
• Low Dropout Voltage: Ensures efficient operation even with small input-output voltage differences.
• Thermal Overload Protection: Integrated circuitry to prevent damage from excessive temperature.
• Short-Circuit Protection: Safeguards the device against output short circuits.
• Available Packages: Commonly found in SOT-223, DPAK, TO-220, and SO-8 packages.

3. Pin Configuration

Understanding the pinout is crucial for correct installation and operation. The LD1117V33 is available in several packages, each with a specific pin assignment. The most common packages are SOT-223, DPAK, TO-220, and SO-8.

Figure 2: Pin connections for various LD1117 packages. Pin 1 is typically Ground (GND), Pin 2 is Output Voltage (V_OUT), and Pin 3 is Input Voltage (V_IN) for the SOT-223, DPAK, and TO-220 packages. For the SO-8 package, pins are distributed differently, with multiple V_OUT and NC (No Connect) pins.

Note: For TO-220 and DPAK packages, the metal tab is internally connected to V_OUT.

4. Block Diagram

The internal structure of the LD1117 series voltage regulator includes a voltage generator, current generator, thermal compensation, and thermal protection circuits, all working together to provide stable and protected output.

Figure 3: Internal block diagram of the LD1117. This diagram illustrates the main functional blocks, including the voltage reference, error amplifier, pass transistor, and protection circuits, which ensure stable output voltage and device safety.

5. Schematic Application

A typical application circuit for the LD1117V33 requires minimal external components. Input and output capacitors are recommended for stability and improved transient response.

Figure 4: Typical application circuits for the LD1117. The top circuit shows a 1.2V application with a feedback resistor, while the bottom circuit illustrates a fixed output voltage configuration (like 3.3V) using input (C_IN) and output (C_OUT) capacitors. C_IN is typically 100nF and C_OUT is 10µF for stability.

For fixed output voltage versions like the LD1117V33, connect the ADJ/GND pin directly to ground. A 100nF capacitor (C_IN) on the input and a 10µF capacitor (C_OUT) on the output are generally recommended for optimal performance and stability, especially when the regulator is far from the power supply or load.

6. Electrical Characteristics

The following tables detail the electrical characteristics of the LD1117V33 under specified test conditions. These parameters are crucial for designing and verifying circuit performance.

Figure 5: Electrical characteristics table for the LD1117#12 variant. This table provides typical, minimum, and maximum values for parameters such as output voltage, line regulation, load regulation, and operating input voltage under specific test conditions.

Figure 6: Electrical characteristics table for the LD1117#33 variant, specifically detailing parameters for the 3.3V output version. Key parameters include output voltage (V_O) at 3.3V, quiescent current, output current, and supply voltage rejection (SVR).

Key parameters to observe include:

• Output Voltage (V_O): The regulated output voltage, typically 3.3V.
• Line Regulation (ΔV_O): Change in output voltage due to change in input voltage.
• Load Regulation (ΔV_O): Change in output voltage due to change in load current.
• Dropout Voltage (V_d): The minimum input-to-output voltage differential required for the regulator to maintain regulation.
• Output Current (I_O): The maximum continuous current the regulator can supply.

7. Setup and Installation

1. Identify Pins: Refer to the pin configuration diagram (Figure 2) to correctly identify the Input (V_IN), Output (V_OUT), and Ground (GND) pins for your specific package.
2. Connect Input: Connect the unregulated DC input voltage to the V_IN pin. Ensure the input voltage is within the specified operating range (e.g., up to 15V).
3. Connect Output: Connect the V_OUT pin to the circuit requiring 3.3V regulated power.
4. Connect Ground: Connect the GND pin to the common ground of your circuit.
5. Add Capacitors: Place a 100nF ceramic capacitor between V_IN and GND, and a 10µF electrolytic or tantalum capacitor between V_OUT and GND. These capacitors should be placed as close as possible to the regulator pins to ensure stability and filter noise.
6. Thermal Management: For applications drawing significant current (e.g., above 200-300mA, depending on input-output differential), a heatsink may be required to dissipate heat and prevent the regulator from overheating. The TO-220 and DPAK packages are designed for better heat dissipation.

Safety Precaution: Always ensure power is disconnected before making or changing connections. Incorrect wiring can damage the regulator and connected components.

8. Operating Guidelines

• Input Voltage Range: The input voltage (V_IN) must be at least V_OUT + V_dropout (typically 3.3V + 1.1V = 4.4V) and not exceed the maximum specified input voltage (e.g., 15V).
• Output Current: Do not exceed the maximum output current of 950mA. Operating near this limit without adequate thermal management will lead to overheating and thermal shutdown.
• Thermal Considerations: The LD1117V33 includes thermal shutdown protection. If the junction temperature exceeds its limit, the regulator will temporarily shut down to prevent damage. This indicates insufficient heat dissipation.
• Load Stability: Ensure the load connected to V_OUT is stable and does not draw excessive transient currents that could cause voltage dips.

9. Maintenance

The STMicroelectronics LD1117V33 is a solid-state electronic component and generally requires no routine maintenance. However, proper handling and environmental conditions are important:

• Cleanliness: Keep the component and surrounding circuit free from dust, dirt, and moisture.
• Temperature: Operate within the specified ambient temperature range.
• Physical Damage: Avoid physical stress or bending of pins, which can lead to internal damage.

10. Troubleshooting

If the LD1117V33 is not functioning as expected, consider the following troubleshooting steps:

• No Output Voltage:
  • Verify input voltage (V_IN) is present and above the minimum required (V_OUT + V_dropout).
  • Check all pin connections for correct polarity and continuity.
  • Ensure the ground connection is solid.
  • Check for short circuits on the output.
• Incorrect Output Voltage:
  • Confirm the input voltage is stable and within the operating range.
  • Check for excessive load current exceeding the regulator's capacity.
  • Verify the output capacitors are correctly installed and not faulty.
• Overheating:
  • Reduce the load current.
  • Increase the input-output voltage differential if possible (though this increases power dissipation).
  • Install or improve the heatsink.
  • Ensure adequate airflow around the component.
• Oscillation:
  • Ensure input and output capacitors are correctly placed and of appropriate values (100nF ceramic for input, 10µF electrolytic/tantalum for output, placed close to pins).

11. Specifications

Below is a summary of key specifications for the STMicroelectronics LD1117V33. For detailed electrical characteristics, refer to the tables in Section 6.

12. Warranty and Support

STMicroelectronics products are manufactured to high-quality standards. Specific warranty information for the LD1117V33 voltage regulator is typically provided by the distributor or reseller at the point of purchase. For technical support, detailed datasheets, and application notes, please refer to the official STMicroelectronics website or contact their authorized support channels.

It is recommended to retain your purchase receipt for any warranty claims.