78L05 Voltage Regulator: Circuit, Equivalent, and 78L05 vs 7805

The LM78L05 is a 5 V-fixed three-terminal positive voltage regulator that employs internal current limiting and thermal shutdown, making it essentially indestructible. The 78L05 can provide local, on-card regulation, eliminating distribution problems associated with single-point regulation. 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 is too high for the heat sinking provided, the thermal shutdown circuit prevents the IC from overheating.

When used as a Zener diode/resistor combination replacement, the 78L05 offers effective output impedance improvement of two orders of magnitude along with lower quiescent current and lower noise. The 78L05 can also be used with power-pass elements to make high-current voltage regulators. The LM78L05 is also a low-current substitute (max 0.1 A) for LM7805.

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Footprint

3D Model

• Type of IC: 5 V-Fixed 3-Terminal Positive Voltage Regulator

• Package: SOT-89 (also available in TO-92 and SO-8 package)

• Output Configuration: Positive

• Fixed Output Voltage: 5 V

• Max Output Current: 150 mA

• Max Input Voltage: 35 V

• Power Dissipation: 0.5 W

• Operating Temperature: -40 to +85 °C 

Note: Different manufacturers may have different ratings

• Output voltage tolerances of ±5% over the temperature range

• Thermal overload protection

• Short-circuit protection

• Output transistor safe area protection

• Full military temperature range

• No external components are required

• Available in either ±4% (A) or ±8% (C) selection

L4931-5.0, LM2931-5.0, NTE977, LP2950 5.0, LM7805, AMS7111, LM7806, LM7809, LM7812, LM317, LM7905, LM7912, LM117V33, XC6206P332MR

Please check the pin configuration and parameters before replacing them in your circuit.

79L05

The 78L05 is a three-terminal integrated voltage regulator with excellent internal current limit and thermal shutdown characteristics. The 78L05 is suitable for many commercial and educational applications. It can be combined with other power transfer devices to form a high-current regulated power supply, such as a voltage regulator that can drive an output current of up to 100 mA. But, the 78L05 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) = 0.35 W. This 0.35 Watts will be dissipated as heat.

The 78L05 also has a wide input supply range that is from 7V to 35V DC. The input voltage should not be less than 7V because the 78L05 requires a minimum of two volts above its output voltage to provide stable 5V output.

The 78L05 is a three-terminal voltage regulator. The three terminals are input, output, and ground. The 78L05 is fairly easy to use, you only have to connect the input pin to the input voltage that has to be regulated and the ground pin to the system ground. The regulated 5V can be obtained from the output pin.

In the circuit below an input voltage of 12V is regulated to 5V using the 78L05.

Also, note the capacitors C1 and C2 are used at both the input and output ends. 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 the circuit when the temperature exceeds junction temperature. The 78L05 can be used to power small loads like LED which is rated for less than 100mA. But if you connect high current loads, the 78L05 will get very hot and will shut down eventually. In that case, a high current regulator like 7805 would be an ideal replacement.

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.

• Introduction

The LM7805 is a voltage regulator that outputs +5 volts and 1 A. Like most other regulators in the market, it is a three-pin IC: input pin for accepting incoming DC voltage, ground pin for establishing the ground for the regulator, and output pin that supplies the positive 5 volts.

The LM78L05 is an IC of the LM78Lxx series of positive voltage regulators that provides a fixed output of 5 V and 100 mA DC.

• Part Numbers

The 7805 is the original manufacturer part number, 78 means positive voltage, whereas 79 means negative voltage, and 05 means positive 5 V output.

The letter between “78” and “05” stands for its current. “78L05” means low current which is 0.1 A, “78M05” means medium current which is 0.5 A, “78S05” means high current which is 2 A, and “78T05” with a higher current which can be as high as 3 A, while the “7805” has a typical current of 1A.

The last two digits stand for different output voltages. For example, 7805 means 5 V output, 7806 means 6 V output, 7808 means 8 V output, etc.

• Substitution

In most cases, the 78L05 can be replaced by 7805, but they also have their differences. Their functions are the same, but their pins are reversed, for 7805 its pin 1, 2, 3 stand for input, ground, and output; while for 78L05 its pin 1, 2, 3 stands for output, ground, and input. And they often come in different packages. The 7805 often comes in the TO-220 package and the 78L05 often comes in a TO-92 package. Their output voltage is the same, but their output current is different where the 78L05 is 0.1 A and the 7805 is 1 A. The 78L05 is physically smaller than 7805 and can dissipate less power, and may be rated for less current.

• Adjustable output regulator

• Power small loads under 100 mA

• LED lighting

• Output polarity-reversal-protection circuit

• Output booster circuit

• Current limiter

• Voltage step down circuits

• Power supply circuits

• Battery charger circuits

• Microcontroller related applications

• Portable instrumentation

78L05 High Output Current Short-Circuit Protected

78L05 Output Boost Circuit

78L05 Current Regulator

78L05 Adjustable Output Regulator

78L05 ±15-V, 100-mA Dual Power Supply Circuit

78L05 Variable Output Regulator Circuit (0.5 V to 18 V)

78L05 Package Outline

78L05 Mechanical Data

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