LM1085 IC : PinOut, Features, Specifications, Circuit, Working, Datasheet & Its Applications

A low dropout regulator or LDO regulator is a simple and inexpensive linear regulator IC that provides a regulated o/p voltage even when the voltage drop in between the input & output is tiny often < 0.2Volts. This voltage regulator operates at extremely low potential variation between the input & output voltages. Since these regulators operate at a lower potential difference between the input & output voltage, then this regulator helps to control the increase in heat and allows efficient utilization of energy. This article discusses an overview of LDO regulators like LM1085 IC, pinout, features, specifications, and applications.

What is the LM1085 IC?

The LM1085 is an LDO (low dropout) positive voltage regulator IC that is utilized to regulate the voltage: This regulator’s maximum dropout voltage at 3 A load current is 1.5 V. This IC is available with a current limiting, thermal shutdown, and zener trimmed bandgap reference. This voltage regulator IC is available in fixed and adjustable output voltage versions. Its fixed voltage versions are; 3.3 V, 5.0 V, & 12.0 V and its adjustable output voltage versions need two resistors to set the o/p voltage.

Working

The LM1085 voltage regulator IC works by creating a stable current supply throughout resistors to set the o/p voltage. This IC creates a 1.25Volts reference voltage between the output & adjust terminals of the IC. A resistor can be arranged in between the output and adjust pins of the IC to create a stable current flow that has a 10mA minimum load current. To set the output voltage, the voltage drop across the resistor integrates with the reference voltage. The adjustable o/p voltage version of this IC needs two resistors to set the o/p voltage.

LM1085 IC Pin Configuration:

The pin configuration of LM1085 IC is shown below. This LDO voltage regulator IC includes three pins which are discussed below.

         LM1085 IC Pin Configuration

• Pin-1 (ADJ/GND): It is an adjustable pin or GND pin where the ADJ pin adjusts the output version while GND is used for fixed version type.
• Pin-2 (Output): It is an output voltage pin of the LDO voltage regulator IC.
• Pin-3 (Input): It is an input voltage pin.

Features and Specifications:

The features and specifications of LM1085 IC include the following.

• The LM1085 IC is a series of LDO positive voltage regulators.
• It includes three pins.
• This IC is available in TO-220, DDPAK, and TO-263 packages.
• Its maximum dropout voltage at 3A load current is 1.5V.
• This IC has a similar pin configuration to the LM317 IC from National Semiconductor’s industry.
• It is accessible in an adjustable version that sets the output voltage with two external resistors only.
• This IC is available in 3.3V, 5.0V, 12Volts & customizable versions.
• Its output current is 3 amps.
• Maximum input voltage is typically 25V.
• Its typical line regulation is 0.015% and load regulation is 0.1%.
• This IC has thermal protection and current limiting.
• The maximum output voltage is 27.5V.
• The minimum output voltage is 1.25V.
• Thermal resistance θJA is 23 °C/W.
• Its noise is 38 uVrms.
• Its PSRR at 100 KHz is 30 dB.
• Accuracy is 4%.
• Its typical dropout voltage or Vdo is 1300 mV.
• The operating temperature ranges from -40 to 125.

Equivalents & Alternatives

Equivalent LM1085 ICs are LM1084 and LM1086. Alternative LM1085 ICs are; LM1117, LM7805, LM2940, LM29152 LM1117, LM317, LM2940, LM29152, etc.

Please refer to this link for Voltage Regulators MCQs.

1.2Volts to 15Volts Adjustable RPS with LM1085 IC

DC-to-DC adjustable converter power supplies are significant parts of most electronic devices. They fulfill a wide range of requirements within academic and industrial settings like load matching and test bench supply applications for mainly variable DC drives. So these DC supplies are used by hobbyists or electronics enthusiasts. Thus, we are going to make 1.2V To 15V simple and adjustable RPS with LM1085 IC.

The required components to make this .2V – 15V adjustable RPS mainly include; LM1085 voltage regulator IC, 17V to 29V at 3A DC supply, 5K Ohms potentiometer, 10uF and 100uF electrolytic capacitor, 120 Ohm resistor, heat sink, breadboard and connecting wires. Connect this circuit as per the circuit diagram shown below.

                      1.2Volts to 15Volts Adjustable RPS with LM1085 IC

Working

The LM1085 IC in this adjustable RPS circuit is a significant component. It is a low dropout positive voltage regulator including a low voltage drop at a higher current value. So the maximum voltage drop with this voltage regulator is 1.5Volts at 3Amps of load current. This IC can also have features like current limiting and overheating protection.

This circuit’s working is very simple, so a DC signal from 17V to 29V range serves as the input for this circuit. After that, the DC signal is supplied through a 10uF smoothing capacitor to remove any remaining noise from the DC source. Here, the input DC signal is sent to the Vin pin of the IC.

The LM1085 IC voltage regulator steps down the input DC signal by maintaining the o/p current at 3 amps. Here, a 5K potentiometer is connected to the ADJ pin of the regulator to tune the o/p voltage to a required range. After that, the regulated DC signal is supplied through a 100uF smoothing capacitor before moving on to the output.

Thus, DC supplies generally power small electronic devices like test bench supplies and portable DC lamps for small electronic projects.

Comparison of LM1085, Lm1084, Lm1086 and Lm317

The comparison between LM1085, LM1084, LM1086, and LM317 voltage regulators includes the following.

Advantages & Disadvantages

The advantages of the LM1085 LDO regulator IC include the following.

• The LM1085 LDO voltage regulator IC is highly efficient and provides 3Amps of current.
• It has a 1.5V maximum dropout voltage at 3 amps of load current.
• Its quick transient response will make this IC to use in low-voltage microprocessor-based applications.
• This IC has thermal & current limiting internally to defend it from overload conditions.
• It is available in both fixed and adjustable versions where its adjustable version is set with two external resistors and its fixed version is set by adjusting integrated resistors.
• Its pin-out is similar to the industry standard LM317 IC.
• This IC is available in TO-263 and TO-220 packages.

The disadvantages of LM1085 LDO regulator IC include the following.

• Whenever there is a huge variation between the input & the output voltage then there will be huge loss and poor efficiency.
• This regulator IC heats up while in operation,
• LDO regulators have a high ground-pin current as compared to quasi-LDOs or standard regulators.
• These ICs may have a lower max input voltage specification as compared to standard regulators.
• Some low drop-out voltage regulators may need specially selected external capacitors to maintain their strength.
• It has a ripple and higher output noise than other voltage regulators.
• This IC has a slower transient response.
• These ICs can dissipate huge amounts of power, thus harming the regulator IC or causing thermal shutdown.

LM1085 IC Applications

The applications of LM1085 IC include the following.

• LM1085 voltage regulator can be utilized as a battery charger and a constant current regulator.
• This IC can be utilized for post-regulation mainly for switching supplies.
• This IC can be used as a microprocessor supply and high-efficiency linear regulator.
• The LM1085 IC is versatile in programmable output regulation & local on-card regulation.
• This IC functions as a precision current regulator when a fixed resistor is connected between the ADJ & o/p terminals.
• These ICs are ideal in low-voltage microprocessor-based applications due to fast transient response and low dropout voltage.
• It is perfect for power supply circuits due to wide input voltage range & precise voltage regulation.

Please refer to this link for the LM1085 IC Datasheet.

Thus, this is an overview of LM1085 IC, pin-out, features, specifications, circuit, working, pros, cons, and its applications. The LM1084 IC is a low dropout voltage positive voltage regulator, available in TO-220 & TO-263 packages. So, its maximum voltage drop is 1.5V at 5 amps of load current. This regulator IC is available with an adjustable version to set the regulated output voltage with two external resistors. It can also be available in 3.3V, 5.0V & 12.0V three fixed voltages. Thus, the ML1084 IC circuit comes with a Zener trimmed bandgap reference mainly for thermal shutdown and current limiting purposes. Here is a question for you, what is LM1086 IC?