The Texas Instruments LM2585S - ADJ is a highly versatile and efficient switching regulator that has found wide - spread use in various power management applications. In this blog post, we will explore its features, specifications, and common applications.
Features
1. Wide Input Voltage Range
The
LM2585S - ADJ can operate with an input voltage ranging from 4 V to 40 V. This wide range makes it suitable for a variety of power sources, such as batteries (e.g., Li - ion batteries with different charge states), regulated power supplies with varying output voltages, and automotive electrical systems which typically have a nominal voltage of 12 V but can experience fluctuations.
2. High Output Current Capability
It is capable of providing an output current of up to 3 A. This makes it sufficient for powering a wide range of electronic devices, from small - to - medium - power integrated circuits to low - power microcontrollers and their associated peripherals.
3. Current - Mode Operation
The device operates in current - mode. This mode offers several advantages, including improved transient response. When there are sudden changes in the load or input voltage, the current - mode control allows the regulator to quickly adjust the output voltage, minimizing voltage spikes and dips. It also provides better line regulation, ensuring that the output voltage remains stable even when the input voltage varies. Additionally, it enables accurate current limiting, protecting the circuit from over - current conditions.
4. Fixed - Frequency Oscillator
The LM2585S - ADJ has an internal fixed - frequency oscillator that operates at 100 kHz (with a switching frequency range of 85 - 115 kHz). This fixed frequency allows for the use of small - sized magnetics components such as inductors and transformers. Smaller magnetics not only save board space but also reduce the overall cost of the power supply circuit.
5. Internal Soft - Start Function
To reduce the in - rush current during start - up, the LM2585S - ADJ incorporates an internal soft - start function. In - rush current can be a significant problem as it can cause damage to components or trigger circuit breakers in some cases. The soft - start function gradually ramps up the output voltage, limiting the initial current draw and protecting the circuit.
6. Multiple Protection Features
- Current Limit: The output transistor is protected by a current - limiting circuit. If the output current exceeds a predefined limit, the regulator will reduce the duty cycle of the switching signal to limit the current, preventing damage to the output transistor and other components in the circuit.
- Under Voltage Lockout (UVLO): This feature ensures that the regulator does not operate when the input voltage is below a certain threshold. If the input voltage drops below the UVLO level, the regulator is disabled, protecting the circuit from abnormal operation due to insufficient power.
- Thermal Shutdown: In case of excessive heat, the LM2585S - ADJ will enter thermal shutdown mode. When the temperature of the device exceeds the specified maximum operating temperature, the regulator shuts down to prevent damage from overheating. Once the device cools down, it will automatically resume normal operation.
7. Adjustable Output Voltage
As the "ADJ" in its part number implies, the output voltage of the LM2585S - ADJ is adjustable. The minimum output voltage is 1.23 V, and it can be adjusted up to 60 V. This flexibility allows designers to customize the output voltage according to the specific requirements of their circuits.
8. Requirement of Few External Components
The LM2585S - ADJ requires only a minimum number of external components to function. This simplifies the circuit design process and reduces the overall cost of the power supply solution. The datasheet provides guidance on selecting the appropriate external components such as diodes, capacitors, and inductors.
Specifications
1. Electrical Specifications
- Input Voltage (Vin): Minimum of 4 V and maximum of 40 V.
- Output Voltage (Vout): Adjustable from 1.23 V to 60 V.
- Output Current (Iout): Maximum of 3 A.
- Switching Frequency: 85 - 115 kHz (nominal 100 kHz).
- Quiescent Current (Iq): Typically 11 mA.
- Line Regulation: Within 100 mV over the input voltage range.
- Load Regulation: Also within 100 mV over the load current range.
- Efficiency: Up to 93%, which means that a high percentage of the input power is converted into useful output power, minimizing power losses and heat generation.
2. Thermal Specifications
- Operating Temperature Range: - 40 °C to 125 °C. This wide temperature range makes the LM2585S - ADJ suitable for use in various environments, from cold outdoor applications to high - temperature industrial settings.
- Thermal Resistance: The thermal resistance between the junction and the ambient (θja) is an important parameter that depends on the PCB layout. A proper PCB layout can help in efficiently dissipating heat generated by the device.
3. Package Specifications
The LM2585S - ADJ comes in a 5 - pin TO - 263 package. The package dimensions are as follows:
The TO - 263 package is a surface - mount package that offers good electrical and thermal performance, and it is easy to assemble on printed circuit boards.
Applications
1. Flyback Regulators
The LM2585S - ADJ is well - suited for flyback regulator applications. In flyback converters, energy is stored in an inductor (or transformer) during the on - time of the switching transistor and then transferred to the output during the off - time. The wide input voltage range, high output current capability, and current - mode operation of the LM2585S - ADJ make it an ideal choice for flyback regulators used in power supplies for electronic devices such as computers, consumer electronics, and industrial equipment.
2. Step - Up (Boost) Converters
As a step - up converter, the LM2585S - ADJ can increase the input voltage to a higher output voltage. This is useful in applications where a higher voltage is required than what is available from the power source. For example, in battery - powered devices, the battery voltage may decrease as it discharges. A boost converter using the LM2585S - ADJ can maintain a constant higher output voltage even as the battery voltage drops. It is also used in LED driver circuits, where a higher voltage is needed to drive multiple LEDs in series.
3. Forward Converters
In forward converter applications, the LM2585S - ADJ can be used to convert an input voltage to a regulated output voltage. Forward converters are commonly used in power supplies for applications that require a well - regulated output voltage, such as in telecommunications equipment, where stable power is crucial for the proper functioning of sensitive electronic components.
4. Multiple - Output Regulators
The LM2585S - ADJ can be used in multiple - output regulator designs. By using additional components such as secondary windings on a transformer or additional rectifier and filter circuits, multiple output voltages can be generated from a single LM2585S - ADJ - based power supply. This is useful in systems that require different voltage levels for different components, such as in a microcontroller - based system where the microcontroller may require 3.3 V, while its peripherals may need 5 V or 12 V.
5. Automotive Applications
Due to its wide input voltage range (which can handle the voltage variations in an automotive electrical system) and high - temperature operation capability, the LM2585S - ADJ is used in various automotive applications. It can be found in power supplies for in - car entertainment systems, automotive sensors, and electronic control units (ECUs). For example, it can be used to regulate the voltage for a car radio, ensuring stable operation even when the engine is starting or when there are electrical load changes in the vehicle.
In conclusion, the Texas Instruments LM2585S - ADJ is a powerful and flexible switching regulator with a range of features and specifications that make it suitable for a wide variety of power management applications. Its ease of use, thanks to the requirement of few external components, and its robust protection features make it a popular choice among designers looking for efficient and reliable power supply solutions.
Posted
Aug 05 2025, 11:42 PM
by
Lisleapex