7805 Regulator and 7805 Datasheet
The 7805 voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads.
7805 Regulator Description
The 7805 voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads. 7805 is a three-terminal positive voltage regulator.
With adequate heatsinking, it can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation.
7805 regulator comes from the 78xx family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is a very popular choice for many electronic circuits which require a regulated power supply, due to their ease of use and relative cheapness. When specifying individual ICs within this family, the xx is replaced with a two-digit number, which indicates the output voltage the particular device is designed to provide (for example, the 7805 voltage regulator has a 5 volt output, while the 7812 produces 12 volts). The 78xx line are positive voltage regulators, meaning that they are designed to produce a voltage that is positive relative to a common ground. There is a related line of 79xx devices which are complementary negative voltage regulators. 78xx and 79xx ICs can be used in combination to provide both positive and negative supply voltages in the same circuit, if necessary.
7805 ICs have three terminals and are most commonly found in the TO220 form factor, although smaller surface-mount and larger TO3 packages are also available from some manufacturers. These devices typically support an input voltage which can be anywhere from a couple of volts over the intended output voltage, up to a maximum of 35 or 40 volts, and can typically provide up to around 1 or 1.5 amps of current (though smaller or larger packages may have a lower or higher current rating).
The 7805 series has several key advantages over many other voltage regulator circuits which have resulted in its popularity:
- 7805 series ICs do not require any additional components to provide a constant, regulated source of power, making them easy to use, as well as economical, and also efficient uses of circuit board real estate. By contrast, most other voltage regulators require several additional components to set the output voltage level, or to assist in the regulation process. Some other designs (such as a switching power supply) can require not only a large number of components but also substantial engineering expertise to implement correctly as well.
- 7805 series ICs have built-in protection against a circuit drawing too much power. They also have protection against overheating and short-circuits, making them quite robust in most applications. In some cases, the current-limiting features of the 7805 devices can provide protection not only for the 7805 itself, but also for other parts of the circuit it is used in, preventing other components from being damaged as well.
7805 Regulator Circuit
7805 Voltage Regulator Pinout
Cross Reference 7805 vs LM317 Voltage Regulators
For a regulated 5V supply, is there any reason to use a LM317 circuit rather than the 7805 regulator?
- If it's for digital, consider a switching power supply; they're far more efficient.
- If it's for linear, you really need a linear supply.
The 7805 and LM317 ICs have been around for a long time, and they still work. However, they have a minimum Vdrop of about 1.7V across them, which means they consume power and generate heat. "Low dropout voltage" it means that the difference between the input and output voltage is lower than the typical 1.7V. Those regulators use a more efficient scheme to pass current through than traditional linear regulators.
Project: 7805 Regulator in an Uninterruptible Power Supply for a Burglar Alarm
Although this Power Supply was designed for the Modular Burglar Alarm - it has other applications. It provides an output of 12-volts - at a current of up to 1-amp. In the event of a mains failure - the back-up battery takes over immediately. And when mains power is restored - the battery recharges automatically.
The 7805 needs the larger heatsink because it has to dissipate a lot of energy - especially when called upon to recharge a flat battery. Its heatsink is at 9v1 - and must NOT be connected to ground. The 7812 never has to dissipate more than 2-watts - so its heatsink can be smaller.
Many of the components, which are shown lying flat on the board, are actually mounted standing upright. The links are bare copper wire on the component side of the board. The heatsinks are folded strips of aluminium, about 2mm thick. Use a well-insulated panel mounted fuse holder for the mains supply to the transformer - and fit it with a 1-amp fuse.
Use a genuine alarm type back-up battery. They are maintenance-free. Their terminals can be held at 13v8 for many years - with no apparent ill effects. They have a life expectancy of about five years. However, they tend not to recover from a very deep discharge. If you wish - you can use a smaller or larger capacity battery.
7805 Regulator Datasheet and Related Keywords
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