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LM340, LM340A, LM7805, LM7812, LM7815

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SNOSBT0K – FEBRUARY 2000 – REVISED JULY 2016

Product Folder Links: LM340 LM340A LM7805 LM7812 LM7815

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9 Power Supply Recommendations

The LM340 is designed to operate from a wide input voltage up to 35 V. Please refer to electrical characteristics

tables for the minimum input voltage required for line/load regulation. If the device is more than six inches from

the input filter capacitors, an input bypass capacitor, 0.1 μF or greater, of any type is needed for stability.

10 Layout

10.1 Layout Guidelines

Some layout guidelines must be followed to ensure proper regulation of the output voltage with minimum noise.

Traces carrying the load current must be wide to reduce the amount of parasitic trace inductance. To improve

PSRR, a bypass capacitor can be placed at the OUTPUT pin and must be placed as close as possible to the IC.

All that is required for the typical fixed output regulator application circuit is the LM340x/LM78xx IC and a 0.22-µF

input capacitor if the regulator is placed far from the power supply filter. A 0.1-µF output capacitor is

recommended to help with transient response. In cases when VIN shorts to ground, an external diode must be

placed from VOUT to VIN to divert the surge current from the output capacitor and protect the IC.

10.2 Layout Example

Figure 27. Layout Example DDPAK