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Regulators debut with self-synchronization

Posted: 19 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:synchronous buck regulators? self-synchronization feature?

LM201xx, LM202xx

National Semiconductor Corp. has introduced a line of buck switching regulators that are said to be the first in the industry to feature high power density and self-synchronization.

The 10 synchronous buck regulators provide high-efficiency DC/DC power conversion for point-of-load power supply designs in communication, data storage, industrial and automotive applications. Part of National's PowerWise energy-efficient product family, the highly integrated regulators feature a variety of input voltages and output currents, and offer a combination of power sequencing, adjustable switching frequency and clock synchronization options.

The LM201xx and LM202xx synchronous buck regulators includes 2A, 3A, 4A and 5A output current devices. Each regulator integrates two switching MOSFETs and uses an externally compensated peak current-mode control loop, providing superior load transient response in low duty cycle applications. The external compensation allows the performance to be optimized for the output capacitor and inductor. With current-mode control, just two external components are needed for compensation. The ability of the 3A and 4A clock synchronization devices to self-synchronize when in out-of-phase operation reduces input capacitance and voltage ripple in power supply designs.

National offers a downloadable power supply design tool for the new low voltage synchronous buck regulators that eliminates the need for tedious hand calculations. The tool calculates component values based on user-specified design parameters to quickly create a complete power supply design. The design tool allows the design engineer to quickly analyze the control loop response, thermal performance and efficiency of the design.

Technical features
Offered in a 16-pin thermally enhanced TSSOP package, the nine low-voltage buck regulators operate with from 2.95V to 5.5V and deliver up to 5A of continuous output current.

Each buck regulator has a precise internal voltage of 1.5 percent accuracy from -40C to 125C while providing line and load regulation. They include a precision enable pin that allows accurate setting of the turn-on threshold and sequencing of the turn-on of multiple devices, eliminating the need for an external voltage supervisor chip. Also included is a power good indicator that regulates the output voltage within tolerance.

A tracking and soft-start feature allows the design engineer to set the output to accurately track an external supply, as well as provide a controlled voltage ramp to protect loads against in-rush current that could cause latch-up. The monotonic start-up into pre-biased load feature prevents the possibility of latch-up in FPGA and ASIC applications.

The buck regulators enhance system reliability by using an accurate current limit to provide robust protection for long-term hard shorts while minimizing the inductor size. Over-voltage and under-voltage events are monitored at the output voltage.

The devices are available today.

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