The L78 series of three-terminal positive regulators is available in several packages, including TO-220, TO-220FP, D2PAK, and DPAK, as well as a variety of fixed output voltages, making it appropriate for a wide range of applications. Local on-card control is possible with these regulators, which removes the distribution concerns that single-point regulation brings. Internal current limiting, thermal shut-down, and safe area protection are all integrated into each kind, making it almost indestructible. If adequate heat sinking is provided, they can deliver over 1 A output current. Although these devices are often intended as fixed voltage regulators, they may be used in combination with external components to produce variable voltage and current.
L78 Series Features & Benefits
• Up to 1.5 A output current ability
• Adjustable voltage output of 5, 6, 8, 8.5, 9, 12, 15, 18, 24 V
• Thermal protection & short-circuit protection
• Safe operating area protection for high-reliable performance
• A version is capable of a tight 2% output voltage tolerance
• A version is promised in the drawn-out temperature range
L78 Pin Connection of Different Packages
L78 Block Diagram
Where to Use L78 Series
The L78 series voltage regulator is commonly found in op-amplifiers, motor drivers, and other circuits to protect them against excessive power surges (e.g. short circuits).
(L78 Typical Application Circuit)
How to Use L78
A short circuit sensing resistor, RSC, and an extra PNP transistor can be added to the circuit in Figure 1 to offer supply safety against a short circuit. Because the current detecting PNP must be able to manage the three-terminal regulator's short circuit current, a four-ampere plastic power transistor is specified.
(Figure 1. 0.5V to 10V regulator)
An external diode is required in applications with large capacitance loads and output voltages of more than 6 volts to prevent the device from input short circuit (see Figure 2. Reducing power dissipation using a dropping resistor). In this situation, the input voltage drops quickly while the output voltage drops gradually. The capacitance of the regulator is discharged via the base-emitter junction of the series pass transistor. The L78 series voltage regulator is used to protect circuits from excessive power rush (e.g. short circuit) and is usually seen in op-amplifiers, motor drivers, and more. The transistor may be damaged if the energy is high enough. The current from the IC is bypassed by the external diode, which sends it to the ground.
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