LT1085CT Datasheet, Features, Pinout, and Applications

The LT1085CT is a low-dropout (LDO) linear voltage regulator designed by Analog Devices (formerly Linear Technology). This high-performance voltage regulator provides up to 3 A of output current with a fixed or adjustable output voltage. It is widely used in applications requiring precise voltage regulation, such as embedded systems, power supplies, and industrial control systems. The LT1085CT offers superior regulation with a low dropout voltage, making it ideal for power-sensitive applications.

The LT1085CT is packaged in a TO-220-3 (3-pin through-hole) package, allowing for efficient heat dissipation and easy integration into various designs.

Overview of the LT1085CT

The LT1085CT is a high-efficiency linear voltage regulator designed to deliver up to 3 A of output current while maintaining a low dropout voltage. The device can operate with an input-to-output differential as low as 1.2V, which minimizes heat generation and power loss, making it suitable for applications where power efficiency is critical. The LT1085CT comes in both fixed output voltage versions (3.3V, 5V) and an adjustable output version, allowing designers to set the output voltage using an external resistor divider.

This LDO voltage regulator offers thermal overload protection, current limiting, and safe area protection, ensuring reliable operation even in challenging environments.

Specifications and Features

LT1085CT Specifications

• Output Current: Up to 3 A
• Dropout Voltage: Typically 1.2V at 3 A load
• Output Voltage:
  • Fixed versions: 3.3V, 5V
  • Adjustable version: 1.25V to 30V (via external resistor)
• Input Voltage Range: 3.3V to 30V (depending on the output version)
• Line Regulation: 0.015% (typical)
• Load Regulation: 0.1% (typical)
• Thermal Regulation: 0.01%/W
• Protection Features: Current limiting, thermal shutdown, and safe area protection
• Package Type: TO-220-3 (3-pin through-hole)
• Operating Temperature Range: -40°C to +125°C

LT1085CT Features

• Low Dropout Voltage: Ensures efficient regulation with minimal input-to-output voltage differential.
• High Output Current: Capable of delivering up to 3 A of current, making it suitable for power-hungry applications.
• Adjustable and Fixed Output Voltage Versions: Offers flexibility with both fixed (3.3V and 5V) and adjustable (1.25V to 30V) output voltage options.
• Thermal Overload Protection: Automatically shuts down the device if it exceeds safe operating temperatures, protecting against overheating.
• Current Limiting: Protects the device from overcurrent conditions, preventing damage due to short circuits or excessive load.
• TO-220-3 Package: Provides efficient heat dissipation with a through-hole design, making it easy to mount on PCBs with heatsinks for thermal management.

LT1085CT Pinout

Pin Configuration and Numbering

The LT1085CT is housed in a TO-220-3 package with three pins for power input, output, and ground or adjustment. The TO-220 package allows for easy thermal management with the option to attach a heatsink for additional heat dissipation.

Pin Configuration

Functions of Each Pin

• Input (Pin 1): This pin is connected to the unregulated input voltage, which should be higher than the desired output voltage by at least the dropout voltage (typically 1.2V). The input voltage can range from 3.3V to 30V, depending on the output configuration.
• Output (Pin 2): This pin provides the regulated output voltage. In the fixed version, it outputs a preset voltage (3.3V or 5V), while in the adjustable version, the output voltage can be set by connecting a resistor divider between the Adjust pin and ground.
• Ground/Adjust (Pin 3): In the fixed-output version, this pin serves as the ground connection for the device. In the adjustable version, this pin is used to adjust the output voltage by connecting it to a resistor divider network.

LT1085CT Applications

Power Supply for Embedded Systems

The LT1085CT is widely used in embedded systems to provide a stable and efficient power supply to microcontrollers, processors, and peripherals. Its low dropout voltage and high current output make it ideal for powering low-voltage devices while minimizing power loss.

Industrial Control Systems

In industrial control systems, the LT1085CT ensures that sensors, actuators, and control circuits receive a regulated supply voltage, even in environments with fluctuating input voltages. Its high output current capability allows it to drive power-hungry loads commonly found in industrial applications.

Battery-Powered Devices

The LT1085CT is used in battery-powered devices such as portable instruments and communication devices where efficiency and reliability are critical. Its low dropout voltage helps extend battery life by minimizing the input-to-output voltage difference, allowing more energy to be utilized from the battery.

Consumer Electronics

In consumer electronics, such as TVs, audio systems, and gaming consoles, the LT1085CT provides reliable power regulation for sensitive components. Its ability to regulate voltage with high accuracy ensures stable performance across different operating conditions.

Communications Equipment

In telecommunications systems, the LT1085CT is used to provide stable power to networking devices, radios, and other communication systems. The device’s current-limiting feature helps protect the equipment from short circuits or overloads, enhancing reliability.

LT1085CT Advantages and Disadvantages

Advantages:

• Low Dropout Voltage: The LT1085CT can regulate voltage even when the input voltage is only slightly higher than the output, making it more efficient than traditional linear regulators.
• High Current Capability: It can deliver up to 3 A of output current, making it suitable for powering larger loads or multiple devices.
• Thermal and Current Protection: Built-in thermal shutdown and current limiting features ensure the device is protected against overloading and overheating, enhancing overall reliability.
• Adjustable Output: The adjustable version of the LT1085CT allows for a wide range of output voltages (1.25V to 30V), providing flexibility for different applications.

Disadvantages:

• Heat Generation: As with all linear regulators, the LT1085CT can generate significant heat, especially when the input-to-output voltage difference is large, necessitating the use of a heatsink in high-power applications.
• Not Suitable for High Efficiency: Linear regulators, including the LT1085CT, are less efficient than switching regulators when the input-to-output voltage difference is large, as they dissipate excess energy as heat.

LT1085CT Package

The LT1085CT is housed in a TO-220-3 package, which is designed for through-hole mounting and provides efficient heat dissipation. The package’s metal tab allows for easy attachment of a heatsink, which helps manage heat generated by the device during high-power operation.

Key Characteristics of the TO-220-3 Package:

• Efficient Heat Dissipation: The TO-220 package is designed to handle heat dissipation effectively, especially when combined with a heatsink.
• Through-Hole Design: Allows for robust mounting on PCBs, making it suitable for both industrial and consumer applications.
• Compact Size: Despite its power handling capability, the TO-220 package is relatively compact, making it suitable for designs where space is limited.

LT1085CT Manufacturer

The LT1085CT is manufactured by Analog Devices, a global leader in the design and production of high-performance analog, mixed-signal, and digital signal processing integrated circuits. Analog Devices is known for its wide range of power management solutions, including linear regulators, switching regulators, and other power control ICs.

LT1085CT Datasheet

The LT1085CT datasheet provides comprehensive details on electrical characteristics, pin configurations, thermal performance, and application guidelines. Designers should consult the datasheet to ensure proper integration into their systems and to optimize the device's performance for specific applications.

LT1085CT vs. LM317

Comparison of Features and Specifications

• LT1085CT:

  • Output Current: 3 A
  • Dropout Voltage: 1.2V (typical)
  • Package: TO-220-3
  • Fixed and Adjustable versions available

• LM317:

  • Output Current: 1.5 A
  • Dropout Voltage: 3V (typical)
  • Package: TO-220-3
  • Adjustable version only

Differences in Performance and Functionality

The LT1085CT offers higher current output (3 A vs. 1.5 A) and a lower dropout voltage (1.2V vs. 3V) compared to the LM317. This makes the LT1085CT more efficient in low-dropout applications and better suited for higher current loads.

Suitability for Different Applications

The LT1085CT is ideal for applications that require higher current and lower dropout voltage, while the LM317 is a more general-purpose adjustable regulator for applications with lower current requirements.

Conclusion

The LT1085CT is a high-performance low-dropout linear regulator that provides precise voltage regulation for applications requiring up to 3 A of output current. Its low dropout voltage, thermal and current protection features, and flexible output options make it suitable for a wide range of applications, including embedded systems, industrial control, and consumer electronics. With its robust TO-220-3 package, the LT1085CT ensures reliable operation even in challenging environments.

FAQs

What Are the Main Features of the LT1085CT?
The LT1085CT offers up to 3 A of output current, low dropout voltage (1.2V), thermal overload protection, and both fixed and adjustable output voltage versions. It is housed in a TO-220-3 package for efficient heat dissipation.

How Does the LT1085CT Compare to the LM317?
The LT1085CT provides higher current output (3 A vs. 1.5 A) and a lower dropout voltage (1.2V vs. 3V) than the LM317, making it more suitable for high-current and low-dropout applications.

What Applications Are Suitable for the LT1085CT?
The LT1085CT is suitable for embedded systems, industrial control systems, battery-powered devices, consumer electronics, and communications equipment where reliable and efficient voltage regulation is required.

Can the LT1085CT Be Used in Place of Other Low-Dropout Regulators?
Yes, the LT1085CT can be used in place of other LDO regulators, provided the system’s voltage and current requirements are compatible. Its low dropout voltage and high current capability make it an excellent replacement in many applications.