LM317SSLASHNOPB datasheet(16/51 Pages) TI

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LM317-N

LM117, LM317-N

SNVS774Q – MAY 2004 – REVISED JUNE 2020

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9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers must

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The LM117 and LM317-N are versatile, high performance, linear regulators with high accuracy and a wide

temperature range. An output capacitor can be added to further improve transient response, and the ADJ pin can

be bypassed to achieve very high ripple-rejection ratios. Its functionality can be utilized in many different

applications that require high performance regulation, such as battery chargers, constant current regulators, and

microprocessor supplies.

9.2 Typical Applications

9.2.1 1.25-V to 25-V Adjustable Regulator

The LM117 can be used as a simple, low-dropout regulator to enable a variety of output voltages needed for

demanding applications. By using an adjustable R2 resistor, a variety of output voltages can be made possible

as shown in Figure 18.

NOTE: Full output current not available at high input-output voltages

*Needed if device is more than 6 inches from filter capacitors.

†Optional—improves transient response. Output capacitors in the range of 1 μF to 1000 μF of aluminum or tantalum

electrolytic are commonly used to provide improved output impedance and rejection of transients.

Figure 18. 1.25-V to 25-V Adjustable Regulator

9.2.1.1 Design Requirements

The device component count is very minimal, employing two resistors as part of a voltage divider circuit and an

output capacitor for load regulation. An input capacitor is needed if the device is more than 6 inches from filter

capacitors. An optional bypass capacitor across R2 can also be used to improve PSRR.

9.2.1.2 Detailed Design Procedure

The output voltage is set based on the selection of the two resistors, R1 and R2, as shown in Figure 18. For

details on capacitor selection, refer to External Capacitors.

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