LM7818 IC : PinOut, Features Equivalent, Circuit, Working, Datasheet & Its Applications

Voltage regulators are essential components in electronic systems, designed to protect sensitive devices by maintaining a constant voltage level. The LM7818 is a fixed linear voltage regulator from the popular 78xx series, providing a stable 18V output. The LM7818 IC widely used and easily implemented linear voltage regulator. This article explains the LM7818 IC’s pin-out, features, specifications, circuit design, and practical applications.

What is the LM7818 IC?

The LM7818 is a linear voltage regulator chip from the LM78xx series available in the TO-220 package that regulates voltage to generate a 18V stable output. Engineers commonly use this voltage regulator in various electronic circuits to control voltage variations. Several manufacturers have designed the LM7818, but some produce it with either a 1A or 1.5A output current. Therefore, you should verify the specifications before acquiring it for your specific application.

You must use a heat sink with this IC during operation; otherwise, it will not function correctly. Furthermore, its in-built features will make it stable and also make it the perfect choice to use within commercial equipment.

LM7818 IC Working Principle

The LM7818 linear voltage regulator IC works by maintaining a stable output voltage regardless of input voltage or load conditions. So this voltage regulator is easy to utilize and doesn’t need any outside circuitry. This IC works as a positive voltage regulator that uses a fluctuating input voltage and generates a fixed 18V. It works as a voltage buffer to defend sensitive circuits from power variations by maintaining a constant 18V output.

The LM7818 IC includes thermal shutdown, a safe operating area, and internal current limiting protection. So it provides a regulated output voltage when the input voltage fluctuates, with a 2A output current, and with a heat sink. This IC has a complex resistor and transistor network that forms a feedback loop that checks the output voltage constantly and adjusts the current flowing throughout the inside pass transistor to keep the preferred 18V output.

This IC has a regulation mechanism like a negative feedback loop, where a little part of the output voltage is compared to a reference voltage in the regulator chip. If the output voltage diverges from the fixed point, then automatically feedback loop automatically adjusts the inner circuitry to correct the voltage.

The main component of this LM7818 IC is a high-power transistor that works like a pass element that allows the current supply while changing the voltage level from the input supply to the output supply.

Pin Configuration:

The LM7818 IC pin configuration is shown below. So this IC includes three pins, which are discussed below.

   LM7818 IC Pin Configuration

• Pin-1(Input): It is an input voltage pin of the voltage regulator IC that supplies this IC.
• Pin- 2(GND): It is a ground pin of the voltage regulator IC.
• Pin-3 (Output): It is an output pin of the voltage regulator IC that provides the output voltage.

Features & Specifications:

The features and specifications of the LM7818 IC include the following.

• LM7818 is a voltage regulator IC.
• This IC includes three terminals with a TO-220 Package.
• Its output current ranges from 1A to 1.5A
• This IC has short-circuit shutdown and overheats shutdown functions.
• These are reliable, low-cost, long-life & easily available.
• Its fixed output is 18V.
• Standby current is 8mA only.
• Its input voltage ranges from 20V to 35V DC.
• Its fixed output is 18V.
• Its dropout voltage is 2V.
• Ripple rejection of this IC is 69 dB.
• Its line regulation and load regulation are normally specified as 360 mV. So the output voltage will change by 360 mV maximum voltage, for a change within the input voltage or load current.
• The operating current or IQ is 5mA.
• Its output current is up to 1Amps.
• It has high power dissipation and thermal overload protection internally.
• This IC is Ideal to utilize in commercial equipment.
• Its thermal overload protection feature shuts down the voltage regulator if the temperature goes beyond a certain limit.
• Its output transition SOA protection feature protects the safe operating area of the output transistor.
• This IC needs a heat sink to dissipate extreme heat, particularly at higher current-based loads.
• Its operating temperature ranges from 0 to 150°C.
• Its storage temperature ranges from -65 to 150°C.

Equivalents & Alternatives

LM7818 IC equivalents are; LM7809 IC, LM317 IC, LM2596ADJ IC, etc. Alternative LM7818 ICs are; L7805CV IC, LM7824 IC, KA7818, LM2940T-10, KA7818ETU, UA7818CKC, UA7810CKCS, L78S18CV, TS7818CZ, BA17818T, etc.

How to Long Run LM7818 IC Safely in a Circuit?

For the long-term performance of the LM7818 IC in a circuit, these points must be followed.

• Avoid drawing current above 1.5 amps.
• Use a proper heat sink to avoid thermal shutdown.
  Keep the input voltage between 20V and 30V for efficiency.
• Ensure operating temperature remains between 0 degrees centigrade to +125 degrees centigrade.
• Do not exceed storage temperature beyond -65 degrees C to +150 degrees C.

18 Volts DC Power Supply Circuit with LM7818 IC

The 18V DC power supply circuit with LM7818 IC is shown below. This power supply circuit works precisely where you require a stable 18 volts DC supply and provides up to 1.5A current. This IC has many features like short circuit protection, internal current limiting, safe area protection, thermal shutdown, etc.

The required components to make this circuit mainly include LM7818 IC, 1000uF 35V and 100uF 35V electrolytic capacitors, and 1000V 1A 1N4007 silicon diode. Connect this circuit as per the circuit below.

18Volts DC Power Supply Circuit with LM7818 IC

Working

The AC input voltage is the transformer’s AC input voltage that ranges from 18 volts to 22 volts. Here 18VAC 1A transformer is used, which provides 1A output current. The input AC voltage is stepped down using a transformer (18VAC 1A). A full-wave bridge rectifier converts it into pulsating DC, which is then filtered using electrolytic capacitors before being regulated to 18V DC using the LM7818 IC.

Finally, we have a stable 18V DC power supply that can be used for different applications. Here, a suitable heat sink must be used with this IC while it works with the maximum current, because a high current may damage the IC.

Comparison Table

The comparison table of LM7818 IC, LM317 IC and LM7805 IC is shown below.

Advantages & Disadvantages

The advantages of the LM7818 IC include the following.

• The LM7818 IC changes the output voltage to a stable value whenever the input voltage or load changes.
• If the LM7818 IC gets too much power, then the circuit will be shut down.
• This IC has built-in short-circuit protection.
• It is low-cost, simple to use, reliable, versatile, and perfect for commercial equipment.
• This voltage regulator IC doesn’t need any external components or circuitry for voltage regulation.

The disadvantages of the LM7818 IC include the following.

• This IC needs a heat sink during operation, otherwise, it will not work correctly and damage the IC.
• The loss is huge, and the efficiency is poor whenever there is a huge variation between the I/O voltages.
• Its voltage gain is < 1 & the power gain is less; thus, it amplifies the current below what we require.

Applications

The applications of the LM7818 IC include the following.

• The LM7818 linear voltage regulator IC generates a stable 18-volt output voltage in powering electronic circuits & devices.
• LM7818 IC can power electronic circuits & devices with reasonable power requirements.
• This IC provides a stable output voltage instead of changes within the input voltage (or) connected load.
• This IC can be utilized with external components to get an adjustable voltage.
• It is used in power supplies, voltage converter applications, solar-related circuits, microcontroller circuits, battery management systems, battery charger applications, computer & telecommunication-based circuits, etc.
• This fixed voltage regulator is used in commercial equipment.

Please refer to this link for the LM7818 IC Datasheet.

Thus, this is an overview of the LM7818 IC, pinout, features, specifications, and applications. This is a linear voltage regulator IC that generates an 18V regulated output voltage. So it is a simple and popular IC that is simple to utilize and doesn’t need external components. This IC will make the circuit safer by simply controlling voltage changes within the input. So this can power a variety of electronic circuits & devices with modest power requirements. Here is a question for you: What is the LM317 IC?