MC78L00 Datasheet, PDF (7/8 Pages) Motorola, Inc – Three-Terminal Low Current Positive Voltage Regulators

MC78L00, A Series
APPLICATIONS INFORMATION
Design Considerations
The MC78L00 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 limits the
maximum current the circuit will pass.
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. The 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. Good construction techniques
should be used to minimize ground loops and lead resistance
drops since the regulator has no external sense lead.
Bypassing the output is also recommended.
Figure 7. Current Regulator
Input
0.33µF
MC78L05
R
Constant
Current to
IO ^{Grounded Load}
The MC78L00 regulators can also be used as a current source
when connected as above. In order to minimize dissipation the
MC78L05C is chosen in this application. Resistor R determines
the current as follows:
IO =
5.0 V
R
+
IB
IIB = 3.8 mA over line and load changes
For example, a 100 mA current source would require R to be a
50 Ω, 1/2 W resistor and the output voltage compliance would be
the input voltage less 7 V.
Figure 8. ± 15 V Tracking Voltage Regulator
+20V
0.33µF
0.33µF
20V
MC78L15
7 _–2
6
MC1741
+3
4
6.5
MPS U55
MPS A70
+VO
10k
10k
–VO
Figure 9. Positive and Negative Regulator
+VI
0.33µF
MC78LXX
+VO
0.1µF
–VI
0.33µF
MC79LXX
0.1µF
–VO
MOTOROLA ANALOG IC DEVICE DATA
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