The LM series of adjustable 3-terminal positive voltage ative complement, see LM series data sheet. LM/LMA/LM Package Options. Part. Datasheets, LM/N Datasheet. Design Resources, Development Tool Selector. Featured Product, LMSeries, Adjustable, Three-Pin Positive Voltage. LMH Datasheet, LM National Semiconductor 3-Terminal Adjustable Voltage Regulator Datasheet.

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The LM is a popular adjustable positive linear voltage regulator.

LMH/NOPB from Texas Instruments

The LM negative complement to the LM regulates voltages below, rather than above, the reference. It was designed by Robert “Bob” Pease. Linear regulators inherently waste power, the power dissipated is the current passed multiplied by the voltage difference between input and output.

In use an LM commonly requires a heat sink to prevent the operating temperature datzsheet too high. For large voltage differences, the energy lost as heat can ultimately be greater than that provided to the circuit.

This is the trade-off for using linear regulators which are a simple way to provide a stable voltage with few additional components. The alternative is to use a switching voltage regulator which is usually more efficient but has a larger footprint and requires a larger number of associated components.


National Semiconductor

In packages with a heat-dissipating mounting tab, such as TOthe tab is connected internally to the output pin which may make it necessary to electrically isolate the tab or the heat sink from other parts of the application circuit. Failure to do this may cause the circuit to short. The LM has three pins: How the adjustment pin is connected determines the output voltage as follows.

If the adjustment pin is connected to ground the output pin delivers a regulated voltage of 1. Higher regulated voltages are obtained by connecting the adjustment pin to a resistive voltage divider between the output and ground. Because some quiescent current flows from the adjustment pin of the device, an error term is added:.

The device can be configured to regulate the current to a load, rather than the voltage, by replacing the low-side resistor of the divider with the load itself.

The output current is that resulting from dropping the reference voltage across the resistor. The LM is an adjustable analogue to the popular 78xx fixed regulators.

Like the LM, each of the 78xx regulators is designed to adjust the output voltage until it is some fixed voltage above the adjustment pin which in this case is labelled ” ground “. The mechanism used is similar enough that a voltage divider can be used in the same way as with the LM and the output follows the same formula, using the regulator’s fixed datawheet for Dataheet ref e.


However, the 78xx device’s quiescent current is substantially higher and less stable. Because of this, the error term in the formula cannot be ignored and the value of the low-side resistor becomes more critical.

National Semiconductor – datasheet pdf

The LM is designed to compensate for these fluctuations internally, making such measures unnecessary. The LM relates in the same way to the fixed 79xx regulators.

From Wikipedia, the free encyclopedia. Archived from the original on 17 December Accidenti come scotta questo transistor.

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