Datasheet

Applications information L78M

24/46 DocID2146 Rev 20

7 Applications information

7.1 Design considerations

The L78M series of fixed voltage regulators are designed with thermal overload protection

that shuts down the circuit when subjected to an excessive power overload condition,

internal short-circuit protection that limits the maximum current the circuit will pass, and

output transistor safe-area compensation that reduces the output short-circuit as the voltage

across the pass transistor is increased. In many low current applications, compensation

capacitors are not required. However, it is recommended that the regulator input be

bypassed with a capacitor if the regulator is connected to the power supply filter with long

wire lengths, or if the output load capacitance is large. An input bypass capacitor should be

selected to provide good high-frequency characteristics to insure stable operation under all

load conditions. A 0.33 µF or larger tantalum, mylar, or other capacitor having low internal

impedance at high frequencies should be chosen. The bypass capacitor should be mounted

with the shortest possible leads directly across the regulators input terminals. Normally good

construction techniques should be used to minimize ground loops and lead resistance drops

since the regulator has no external sense lead.

Note: Although no output capacitor is need for stability, C

improve transient response if present.

is required if regulator is located an appreciable distance from power supply filter.

Figure 17. Fixed output regulator