Part Number: LM317DCYR

Manufacturer: Texas Instruments

Description: Linear Voltage Regulators 3 Term Adj. Pos.

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Technical Specifications of LM317DCYR

Datasheet  LM317DCYR datasheet
Category Integrated Circuits (ICs)
Family PMIC – Voltage Regulators – Linear
Manufacturer Texas Instruments
Packaging Tape & Reel (TR)
Part Status Active
Regulator Topology Positive Adjustable
Voltage – Output 1.25 V ~ 37 V
Current – Output 1.5A
Voltage – Dropout (Typical)
Number of Regulators 1
Voltage – Input 4.2 V ~ 40 V
Current – Limit (Min)
Operating Temperature 0°C ~ 125°C
Mounting Type Surface Mount
Package / Case TO-261-4, TO-261AA
Supplier Device Package SOT-223-4

LM317DCYR Description

The LM317 is an adjustable positive-voltage regulator with three terminals that can supply more than 1.5 A throughout an output-voltage range of 1.25 V to 37 V. Its output voltage may also be adjusted. The output voltage may be easily adjusted with two external resistors thanks to its very simple operation and setup. In addition, line regulation and load control are superior to the performance of typically fixed regulators. This device has a higher performance than fixed regulators and offers on-chip current limiting, thermal overload prevention, and safe operating-area protection, in addition to its other protection features. The overload protection will operate normally if the ADJUST terminal is unplugged.

Thanks to its adaptability, the LM317 may be used for various applications, including programmable output regulation and local on-card regulation. Connecting a fixed resistor to the LM317’s ADJUST and OUTPUT connections converts it into a precision current regulator. An output capacitor is not required to improve the transient response further but can be added if desired. Bypassing the ADJUST terminal allows one to get very high ripple-rejection ratios, which are difficult to achieve with regular three-terminal regulators due to the limited number of adjustment points available.

LM317DCYR Features

  • Protection against thermal overloads up to 37 volts
  • Output Safe-Area Compensation.
  • Current Output That Is Greater Than 1.5 A.
  • Internal protection against current surges caused by short circuits

What Is A Linear Voltage Regulator?

A linear voltage regulator is a type of regulator that, as its name suggests, is used to maintain a constant output voltage regardless of the input voltage or the current demand that is imposed on the system. This is the purpose of the linear voltage regulator. As a consequence of this, a linear voltage regulator is utilized to accomplish this goal. In this configuration, an active pass device such as a BJT or MOSFET is controlled by an amplifier with a high gain. The changing conductivity of the active pass element, which is responsible for the flow of current, helps to keep the output voltage stable. A linear voltage regulator can also function as a voltage divider to create the required output voltage. This voltage is the output that the linear regulator of the voltage has produced.

A linear voltage regulator is a type of voltage regulator that sets the desired output voltage by means of a linear component, such as a resistive load. This type of voltage regulator is also a linear component voltage regulator. A transistor can remain in one of three states when it is being used to control voltage. Depending on the conditions, these are the active state, the ohmic state, or the linear state.

Users can stabilize the output voltage by altering the component’s internal resistance value. If the amplifier’s feedback loop possesses the capability to regulate a transistor, then the amplifier can be supplied with various resistances.

Because the output voltage is always lower than the input value, a linear voltage regulator is sometimes referred to as a step-down converter. This is because the input value is always higher than the output voltage. This is because the input voltage is almost invariably higher than the output voltage. It can accomplish this by turning some of the power into heat, allowing the output voltage to remain constant. You are going to have to give up something of this nature.

How Does a Linear Voltage Regulator Work?

Linear voltage regulators, with a low dropout voltage (LDOs), use a transistor regulated by a negative-feedback circuit to maintain a constant output voltage independent of load current and input voltage variations. This allows linear voltage regulators to maintain a constant output voltage over a wide range of load currents and input voltages. There is more than one linear voltage regulator, and one of those types is the low-dropout linear regulator.

A fundamental linear regulator that maintains a constant output voltage has three terminals. You can modify the output voltage of some linear regulators using an external resistor if the regulator is of the linear kind. On certain models, the capability to do so is already integrated.

Voltage linear regulator disadvantages

The low-efficiency linear regulators typically exhibit in various contexts is a significant drawback of using these regulators. Because the transistor inside the regulator operates like a variable series resistance and is connected between the input and output terminals, huge input-to-output voltage differentials paired with high load currents result in significant amounts of power dissipated by the regulator. The total power dissipated is also affected by the current flowing through the regulator’s internal circuitry for it to work properly. This current is denoted in the diagram by the label IGND.

The failure mode of a linear regulator circuit is likely to be thermal concerns, as opposed to solely electrical considerations, which are likely to be accountable for it. This failure mode is likely to be the most likely of the conceivable failure modes. The component’s temperature will increase due to the power lost by the regulator integrated circuit (IC). Suppose insufficient pathways enable heat to flow away from the regulator. In that case, the temperature may ultimately reach a point where it is high enough to impair performance or cause a thermal shutdown substantially. Suppose insufficient pathways allow heat to move away from the regulator. In that case, the temperature may eventually reach a point where it is high enough to cause a thermal shutdown. An essay written by the AAC on thermal design for linear regulators devotes a considerable portion of its content to a discussion of this important topic.

Linear Voltage Regulator Applications

Linear regulators are still commonly employed even though, on average, switching regulators are more efficient than linear regulators. This is the case for several reasons. The three major advantages are ease of usage, minimal output noise, and low cost. The only external components required by the vast majority of linear regulators are input and output capacitors. The capacitance requirements are adjustable enough to make designing the regulator relatively simple.


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