Description: 78L05 Voltage Regulator
This is the basic L7805 voltage regulator, a three-terminal positive regulator with a 5V fixed output voltage. This fixed regulator provides a local regulation, internal current limiting, thermal shut-down control, and safe area protection for your project. Each one of these voltage regulators can output a max current of 1.5A. The LM78LXX series of three terminal positive regulators is available with several fixed output voltages making them useful in a wide range of applications. When used as a zener diode/resistor combination replacement, the LM78LXX usually
results in an effective output impedance improvement of two orders of magnitude, and lower quiescent current. These regulators can provide local on card regulation, eliminating the distribution problems associated with single point regulation.The voltages available allow the LM78LXX to be used in logic systems, instrumentation, HiFi, and other solid state electronic equipment.The LM78LXX is available in the plastic TO-92 (Z) package,
the plastic SO-8 (M) package and a chip sized package (8-Bump micro SMD) using National’s micro SMD package
technology. With adequate heat sinking the regulator can deliver 100 mA output current. Current limiting is included to limit the peak output current to a safe value. Safe area protection for the output transistors is provided to limit internal power dissipation. If internal power dissipation becomes too high for the heat sinking provided, the thermal shutdown circuit takes over preventing the IC from overheating.
|Pin No.||Pin Name||Description|
|1||Output (Vo)||Outputs Regulated +5V|
|2||Ground (Gnd)||Connected to Ground|
|3||Input (V+)||Unregulated Input Voltage|
- 5V Positive Voltage Regulator
- Output Current upto 100mA
- Maximum Input Voltage is 30V
- Operating current(IQ) is 5mA
- Internal Thermal Overload and Short circuit current limiting protection is available.
- Available in TO-92,SO-8 and SOT-89 package
Complete Technical Details can be found at the 78L05 datasheet given at the end of this page.
Alternative Regulator for 78L05:
LM7806, LM7809, LM7812, LM317, LM7905, LM7912, LM117V33, XC6206P332MR.
78L05 Equivalent Voltage Regulators:
Where to use 78L05:
Voltage regulators are very common in electronic circuits. They provide a constant output voltage for a varied input voltage. In our case the 78L05 IC is an iconic regulator IC that finds its application in most of the projects. The name 78L05 signifies two meaning, “78” means that it is a positive voltage regulator and “05” means that it provides 5V as output. So our 7805 will provide a +5V output voltage.
The output current of this IC can go up to 100mA. But, the IC suffers from heavy heat loss hence a Heat sink is recommended for projects that consume more current. For example if the input voltage is 12V and you are consuming 50mA, then (12-5) * (50*10^-3) = 0.35W. This 0.35 Watts will be dissipated as heat.
Another popular voltage regulator is 7805 which is bulkier in size but has high current rating of about 1A. So, if you are looking for a smaller package of voltage regulator that has small current rating in TO-92 package then this IC might be the right choice.
How to use 78L05:
The 78L05 is a three terminal voltage regulator. The three terminals are Input, Output and ground as shown in the 78L05 pinout diagram. It is very easy and straight forward to use this IC, just connect the input in to the input voltage which has to be regulated and the ground pin to system ground. The regulated 5V can be obtained from the output pin if the IC.
In the circuit below a input voltage of 12V is regulated to 5V using the 78L05. You use the 5V to power any small loads like LED which is rated for less than 100mA. Because the maximum current that this IC could supply is only upto 100mA.
Also note the Capacitors C1 and C2 are used at both the Input and output end. These capacitors are used to filter any noise that’s coupled with the Input voltage. It’s not mandatory to use the exact value of capacitor but a value of 10uF for C1 and 1uF for C2 would be an ideal choice.
These regulators also have the ability to limit current and protect when the temperature exceeds beyond junction temperature. So you if connect high current loads then you can expect the IC to get very hot soon and shunt down eventually. In that using a high current regulator like 7805 would be an ideal choice.
Apart from using it as a voltage regulator it can also be used as a current regulator, short-circuit protector, booster circuit and even a variable voltage regulator. The circuits for all these applications can be found at page 27/45 in the 78L05 datasheet given below.
- Constant +5V output regulator to power small loads of less than 100mA
- Adjustable Output Regulator
- Current Limiter for certain applications
- Output Polarity-Reversal-Protection Circuit
- Output booster circuit
- 1 x 78L05 Voltage Regulator