POWER AND LINEAR IC SOLUTIONS

Regulators Deliver Full Functionality of Higher Voltage Parts

National Semiconductor has expanded its family of step-down switching regulators with 42V-rated parts that offer the same levels of integrated functionality commonly found on parts rated to 75V and above. The new parts are ideal for automotive and other applications where designers are looking for efficient, cost-effective and low component count DC/DC conversion solutions.

Devices in National Semiconductor’s new LM25xxx series of step-down switching regulators are functionally equivalent to the products in the company’s popular LM5000 range but are specifically designed to meet the price points demanded by lower voltage applications.

The new ICs provide 42V output currents up to 2.5A and feature all of the functions necessary to implement an efficient regulator using the minimum of external components. Included in the range is the LM25010, which, with a very low input voltage of just 6V, will be particularly attractive for automotive suppliers. All of the devices offer thermal shutdown, alongside other comprehensive protection features including (depending on the device) Vcc undervoltage lockout, gate drive undervoltage lockout, maximum duty cycle limiter, and external shutdown input.

LM25005 42V, 2.5A Regulator

The LM25005 includes a 42V, 160mΩ N-channel MOSFET with an output current capability of 2.5A. Regulator control method is based on current mode control, which provides inherent line voltage feed-forward, cycle-by-cycle current limiting and ease of loop compensation. Key features include:

• Ultra wide input range: 7V to 42V
• Internal bias regulator
• Adjustable output voltage from 1.225V
• 1.5% feedback reference accuracy
• Single resistor oscillator frequency setting
• Programmable soft start
• Wide bandwidth error amplifier
• Package options: LLP-10 (4mm x 4mm) and TSSOP-14EP

LM25007 42V, 0.5A Regulator

The LM25007 is capable of driving a 0.5A load over a 9V to 42V input range and offers ultra-fast transient response through the use of a constant on-time architecture with Vin feed forward. This feature provides an almost constant operating frequency over load and input variations. Key features include:

• Frequency adjustable to 800kHz using a single resistor
• 2% accurate 2.5V feedback from -40°C to +125°C
• Intelligent current limit protection
• Package options: MSOP-8 and LLP-8 (4mm x 4mm)

Typical Application Circuit and Block Diagram

LM25010 42V, 1.0A Regulator

The LM25010 regulator can accommodate input voltages from just 6.0V to 42V, and has a valley current limit detection feature set at 1.25A. The device offers a constant on-time regulation scheme for fast load transient response and simplified circuit implementation. Other key features include:

• Programmable switching frequency to 1MHz
• Integrated high-voltage bias regulator
• Adjustable output voltage
• Programmable soft-start
• Package options: LLP-10 (4mm x 4mm)
• TSSOP-14EP

LM25115 Secondary Side Post Regulator Controller

The LM25115 operates from AC or DC inputs up to 42V and contains all of the features necessary to implement multiple output power converters using the Secondary Side Post Regulation (SSPR) technique. This technique develops a highly efficient and well regulated auxiliary output from the secondary side switching waveform of an isolated power converter.


Typical Application Circuit

Regulation of the auxiliary output voltage is achieved by leading edge PWM of the main channel duty cycle, which is compatible with either current mode or voltage mode control of the main output. Key features include:

• LDO bias regulator
• Current sense amplifier for overload protection
• Wide 4.5V to 30V bias supply voltage
• Wide 0.75V to 13.5V output
• Adaptive gate driver dead-time control
• Wide bandwidth error amplifier (4MHz)
• Package options: TSSOP-16 and LLP-16

LM25xxx Family – Potential Applications

• 12VDC and 24VDC distributed rail systems
• 24VAC systems
• Automotive body electronics and telematics
• Industrial systems
• HB-LED constant current source
• Non-isolated telecommunications regulator

For further information, including a copy of the LM25xxx Datasheets and information on how to obtain Product Samples, please click here