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PowerWise buck IC family expands design options

Santa Clara, Calif.—National Semiconductor says its LM20xxx buck switching regulator family is the first in the industry to offer high power density and self-synchronization. The 10 new PowerWise chips provide a broad range of input/output, power sequencing, switching frequency, and clock synchronization options for point-of-load designs suited to communications, data storage, industrial, and automotive applications.

Technical features
The LM201xx and LM202xx regulators include 2-, 3-, 4-, and 5-amp outputs. Each regulator, which integrates two switching MOSFETs, features an externally compensated peak current-mode control loop with nonlinear slope compensation to optimize transient response. Just two external components are required for the compensation loop.

The devices also include tracking and soft-start features. They also provide monotonic start-up into a pre-biased load to minimize latch-up in FPGA and ASIC applications, and circuitry (with power good indicator) that regulates the output voltage within tolerance and can sequence loads that have an enable input

Nine of the regulators are low-voltage devices, operating at 2.95 to 5.5 volts. Both fixed and adjustable switching frequency versions are available.
The low-voltage LM20123, LM20124, and LM20125 buck regulators feature fixed frequency operation at 1.5 MHz at 3 amps, 1 MHz at 4 amps, and 500 kHz at 5 amps, respectively, for smallest solution size.

The LM20143, LM20144, and LM20145 buck regulators feature adjustable frequency for maximum design flexibility. The LM20133 and LM20134 provide for synchronization to an external clock source. In addition, the LM20154 features an out-of-phase clock output for current sharing or out-of-phase operation.

Each buck regulator, in a 16-pin thermally enhanced TSSOP package, maintains internal circuitry that's accurate to 1.5 percent over -40 to 125°C. The devices 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.

The high-voltage LM20242 device, offered in a 20-pin TSSOP package with exposed pad, is rated for an input voltage of 4.5 to 36 volts and delivers up to 2 amps continuous output. The LM20242 features adjustable frequency from 250 kHz to 1 MHz.

Design software
The company also offers a downloadable power supply design tool to aid in design. The tool, in a Microsoft Excel spreadsheet format, calculates component values based on user-specified design parameters, and quickly creates a complete power supply design. The tool allows the design engineer to analyze control loop response and thermal performance.

Availability : Now. The regulators are priced from $2.30 to $3 each in 1k-unit quantities.

National Semiconductor , 1-800-272-9959, www.national.com

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