L78M12AB STMicroelectronics, L78M12AB Datasheet - Page 17

• Manufacturer Part Number: L78M12AB
• Description: Precision 500 mA regulators
• Manufacturer: STMicroelectronics

L78MxxAB, L78MxxAC
7
7.1
Figure 17. Current regulator
Figure 18. Adjustable output regulator
V
V
O
I
- V
= 7.0 V to 20 V
O
I
O
≥ 2.0 V
= V
Applications information
Design considerations
The L78MxxA 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.
XX
/R
1
+I
d
Doc ID 2147 Rev 12
Applications information
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