The LM317MBSTT3G is a specific part number for an adjustable voltage regulator from ON Semiconductor. This part is typically used in power management applications, where the voltage needs to be regulated or adjusted for various components or circuits.
Here's a detailed explanation of its specifications, pin functions, and the circuit principle.
Package Type and Pin Count:
The "LM317MBSTT3G" corresponds to the TO-263 package. The TO-263 package is a surface-mount type with 5 pins.
Pin Function List:
The LM317MBSTT3G has 5 pins, and here is the detailed explanation of each pin:
Pin Number Pin Name Pin Function Description Pin 1 Adj (Adjust) This is the adjustment pin that allows you to set the output voltage using an external resistor divider network. The voltage at this pin is used to control the output voltage. By connecting a resistor divider from the output to this pin, the voltage regulator can adjust the output to the desired value. Pin 2 Vin (Input Voltage) This pin connects to the input power source voltage, typically a DC voltage source that is higher than the desired output voltage. The input voltage is applied here, and it must be higher than the output voltage for proper regulation. Typically, the voltage range for this pin is 3V to 40V for the LM317. Pin 3 Vout (Output Voltage) This pin delivers the regulated output voltage, which is determined by the input voltage and the adjustable resistor network on the adjust pin. The regulated voltage is provided here. You can adjust it using external resistors connected to the Adjust pin, which sets the desired output voltage (typically between 1.25V and 37V). Pin 4 Tab (Heat Sink) The metal tab is used to dissipate heat generated by the regulator, helping to prevent overheating. The tab connects directly to the internal junction of the regulator. It's essential to mount it to a heatsink to allow proper thermal management, as the device can dissipate considerable heat. Pin 5 NC (No Connection) This pin is not internally connected to any functional part of the regulator. It's left unused and does not have any electrical function. This pin serves no purpose electrically and should be left unconnected. It is provided as a mechanical feature or as part of the device's footprint design.Pin Function Description for LM317MBSTT3G:
Pin 1: Adj (Adjust): This pin allows you to set the output voltage through an external resistor network. Typically, a resistor connected between the output pin and the adjust pin (R1), and another resistor between the adjust pin and ground (R2), determines the output voltage using the following formula:
[ V{out} = V{ref} \times \left(1 + \frac{R1}{R2}\right) + I_{Adj} \times R1 ]
Where (V{ref}) is the reference voltage (1.25V), and (I{Adj}) is the current through the adjust pin (which is typically very small).
Pin 2: Vin (Input Voltage): This is where you apply the voltage that needs to be regulated. The LM317 requires the input voltage to be at least 3V higher than the output voltage to regulate properly.
Pin 3: Vout (Output Voltage): This pin provides the regulated voltage. The output voltage depends on the resistor values set at the adjust pin.
Pin 4: Tab (Heat Sink): This is the thermal pin, and it needs to be connected to a heat sink to prevent the voltage regulator from overheating.
Pin 5: NC (No Connection): This pin has no internal connection and can be ignored in most circuits.
Circuit Principle:
The LM317 is an adjustable three-terminal regulator. It works by comparing the voltage between the output and adjust pins and maintains a constant reference voltage (typically 1.25V) across the resistor network connected between the adjust and output pins. By varying the resistance, you can change the output voltage.
When using this regulator, it is important to note the input voltage requirements (higher than the output voltage) and the necessity of good thermal management to prevent overheating.
20 FAQs for LM317MBSTT3G:
Q: What is the minimum input voltage required for LM317MBSTT3G? A: The minimum input voltage should be at least 3V higher than the output voltage.
Q: What is the output voltage range of the LM317MBSTT3G? A: The output voltage can range from 1.25V to 37V, depending on the resistor values used in the adjustment network.
Q: How do I set the output voltage of LM317MBSTT3G? A: The output voltage is set by selecting appropriate resistors for the external voltage divider connected to the Adjust pin.
Q: Can LM317MBSTT3G be used with a 5V input? A: Yes, LM317MBSTT3G can be used with a 5V input, but the output voltage must be less than 5V.
Q: What is the typical current output for LM317MBSTT3G? A: The LM317MBSTT3G can typically supply up to 1.5A of current with proper heat dissipation.
Q: Can LM317MBSTT3G regulate negative voltages? A: No, the LM317MBSTT3G is designed for positive voltage regulation.
Q: What is the reference voltage of LM317MBSTT3G? A: The reference voltage of the LM317MBSTT3G is 1.25V.
Q: Is the LM317MBSTT3G suitable for battery-powered applications? A: Yes, it can be used for battery-powered circuits, as long as the input voltage is higher than the output voltage by at least 3V.
Q: What happens if the input voltage drops below the output voltage? A: The LM317MBSTT3G will stop regulating, and the output voltage will drop to the input voltage level.
Q: What is the maximum input voltage for LM317MBSTT3G? A: The maximum input voltage is typically 40V for the LM317MBSTT3G.
Q: What is the power dissipation of LM317MBSTT3G? A: The power dissipated by the LM317MBSTT3G depends on the input-output voltage difference and the current drawn by the load.
Q: Does LM317MBSTT3G require a heatsink? A: Yes, the LM317MBSTT3G typically requires a heatsink for efficient thermal management, especially at higher output currents.
Q: Can I use LM317MBSTT3G in a 3.3V system? A: Yes, LM317MBSTT3G can be used in a 3.3V system, as long as the input voltage is higher than 3.3V by at least 3V.
Q: What are the common applications of LM317MBSTT3G? A: It is commonly used in power supply circuits, adjustable voltage regulators, and battery charging circuits.
Q: What is the dropout voltage of LM317MBSTT3G? A: The typical dropout voltage is around 3V.
Q: What is the tolerance of the output voltage for LM317MBSTT3G? A: The output voltage tolerance depends on the resistor values used, but typically it is within 1% for well-selected resistors.
Q: Can LM317MBSTT3G be used to supply multiple outputs? A: Yes, but each output must be individually regulated, and additional components may be required for each output.
Q: How do I calculate the resistor values for LM317MBSTT3G? A: You can calculate the resistor values using the voltage divider formula mentioned earlier: (V{out} = V{ref} \times (1 + \frac{R1}{R2})).
Q: Can LM317MBSTT3G regulate high current? A: Yes, LM317MBSTT3G can supply up to 1.5A of current, but it requires adequate heat sinking for high current applications.
Q: What is the typical operating temperature range for LM317MBSTT3G? A: The operating temperature range is typically -40°C to 125°C.
This detailed explanation provides you with a comprehensive understanding of the LM317MBSTT3G adjustable voltage regulator and its pin functions.
