ADI LT1111

LT1111 General Description

Overall, the LT1111 is a versatile and efficient DC/DC converter that offers fixed output voltage options, wide input voltage ranges, and various features to adapt to different power conversion needs in electronic circuits.

The LT1111 is a flexible DC/DC converter that can operate in step-up, step-down, or inverting modes. This versatility makes it suitable for a wide range of applications.

The device can provide a fixed output voltage of either 5V or 12V. This is accomplished with the use of only three external components, making it simple to configure.

The LT1111 can accept input voltages ranging from 2V to 12V when operating in step-up mode, and up to 30V when operating in step-down mode. This wide input voltage range enhances its applicability in various scenarios.

The internal oscillator of the LT1111 operates at 72kHz. This frequency is optimized for use with off-the-shelf surface mount inductors, making component selection and integration more straightforward.

The switch current limit of the LT1111 can be set using a single external resistor. This feature allows for customization of the device's current limiting behavior to suit the application.

The LT1111 includes an auxiliary open-collector gain block that can be configured for various purposes, such as a low-battery detector, linear post regulator, undervoltage lock-out circuit, or error amplifier. This adds flexibility to the device's functionality.

The device is suggested for input sources of less than 2V, with the note to use the LT1110 for such cases. This indicates that the LT1110 is better suited for very low input voltage scenarios.

Block Diagram

Manufacturer

Linear Technology, often referred to as Linear, was a well-known semiconductor company specializing in high-performance analog integrated circuits. The company's products found applications in various industries, including industrial, automotive, communications, and computing. Linear Technology was recognized for its emphasis on high-quality and reliable analog ICs, covering a broad spectrum of functions.

Linear Technology was founded in 1981 and had its headquarters in Milpitas, California. In 2017, Linear Technology was acquired by Analog Devices, Inc., another prominent semiconductor manufacturer. This acquisition combined the strengths and expertise of both companies to offer an even broader range of analog and mixed-signal solutions to customers. 

Linear Technology's product portfolio included amplifiers, voltage regulators, data converters, power management ICs, and interface products. These components played vital roles in enabling a wide range of electronic systems and devices to function effectively. The company's analog ICs were employed in diverse applications, including automotive systems, industrial automation, energy management, telecommunications, and more. Their products were critical components in various electronic devices and equipment.

Pinout

Pin function:

ILIM (Pin 1): Connect this pin to VIN for normal operation. To limit the switch current to a lower value, connect a resistor between ILIM and VIN. For example, a 220Ω resistor will limit the switch current to approximately 400mA.

VIN (Pin 2): This is the input supply voltage pin. It is where you connect the input power source that you want to convert.

SW1 (Pin 3): This pin is the collector of the power transistor. Depending on the desired mode of operation:

For step-up mode, connect it to the inductor and diode.
For step-down mode, connect it to VIN.
SW2 (Pin 4): This pin is the emitter of the power transistor. Its connection depends on the mode of operation:

For step-up mode, connect it to ground.
For step-down mode, connect it to the inductor and diode. Ensure that it does not go more than a Schottky diode drop below ground.
GND (Pin 5): This is the ground or common reference pin for the device.

A0 (Pin 6): This is the output of the auxiliary gain block (GB) and is open collector, capable of sinking 300µA.

SET (Pin 7): This is the input to the GB. The GB is an operational amplifier (op-amp) with its positive input connected to the SET pin and its negative input connected to a 1.25V reference. This pin allows for adjusting the converter's operation.

FB/SENSE (Pin 8): The function of this pin depends on the specific variant of the LT1111:

On the LT1111 (adjustable version), this pin goes to the comparator input.
On the LT1111-5 and LT1111-12, this pin connects to the internal application resistor that sets the output voltage. This pin is used to configure the output voltage in these fixed voltage versions.

Features

Wide Supply Voltage Range: It can operate over a supply voltage range from 2V to 30V, making it suitable for a variety of input voltage scenarios.

Compatibility with Surface Mount Inductors: The LT1111 is designed to work efficiently with off-the-shelf surface mount inductors, simplifying component selection and integration.

72kHz Oscillator: The internal oscillator in the LT1111 operates at 72kHz, optimized for use with readily available inductors, helping to streamline design and component choices.

Minimal External Components: Only three external components are required to configure the device, which simplifies circuit design and reduces component count.

Step-Up or Step-Down Mode: The LT1111 is capable of functioning in both step-up and step-down modes, allowing for versatility in power conversion applications.

On-Chip Low-Battery Detector Comparator: The device features an on-chip low-battery detector comparator, which can be configured for applications that require monitoring of the input voltage level.

User-Adjustable Current Limit: The LT1111 allows users to adjust the current limit with a single external resistor, providing flexibility in current-limiting settings.

Internal 1A Power Switch: The device is equipped with an internal 1A power switch, which simplifies the design and reduces the need for external switching components.

Fixed or Adjustable Output Voltage Versions: The LT1111 is available in fixed and adjustable output voltage versions, catering to a variety of application requirements.

Space-Saving Packages: The device is available in space-saving 8-Pin MiniDIP or SO-8 packages, making it suitable for applications with limited board space.

Application

3V to 5V, 5V to 12V Converters: The LT1111 can be employed to convert lower voltage sources to higher ones for various electronic devices and components.

9V to 5V, 12V to 5V Converters: It can also work in the reverse direction, stepping down higher voltages to lower ones, which is useful for powering devices with lower voltage requirements.

Remote Controls: The LT1111 can be used in remote controls and other battery-operated devices to efficiently manage power supplies.

Peripherals and Add-On Cards: It's suitable for powering peripherals and expansion cards in computers and other electronic systems.

Battery Backup Supplies: In applications where a battery backup is needed to ensure continuous power, the LT1111 can be used to maintain a stable power source.

Uninterruptible Supplies: It can contribute to uninterruptible power supplies (UPS) systems by efficiently managing power conversion during power interruptions.

Laptop and Palmtop Computers: The LT1111 can be used in portable computing devices to optimize power management and extend battery life.

Cellular Telephones: It can be employed in cellular phones and other mobile devices for efficient voltage conversion and power management.

Portable Instruments: Portable test and measurement instruments can benefit from the LT1111's ability to efficiently manage power supplies.

Flash Memory VPP Generators: The device can be used to generate programming voltages (VPP) for flash memory devices, ensuring accurate and stable programming.

Typical Application

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Absolute Maxium Rating

Typical Application