National Semiconductor expands buck switching regulator portfolio

(Product News, 9 Feb 2007)

National Semiconductor has added six high-frequency buck regulators to its Simple Switcher product family along with a "dial-in" performance enhancement to its WEBENCH design environment. The buck regulators and WEBENCH suite of tools enable power supply designers to "dial-in" their size and efficiency requirements, and results are verified by the tool's online electrical and thermal simulations. The BuildIt custom prototype power supply kit enables 24-48 hour delivery. The new regulators operate with an input voltage range up to 75V and provide up to 3A of continuous output current. The emulated-current-mode technology provides desirable load transient response in low duty cycle applications that are not addressable by traditional current mode control. Operating frequency is adjustable from 50kHz to 1 MHz.

To reduce EMI, a frequency synchronization pin allows multiple ICs from the family to self-synchronize or to synchronize to an external clock. They regulators offer cycle-by-cycle current limit, short-circuit protection and thermal shut-down. Emulated current mode control emulates the buck switch current signal, which is then used for current mode control. The emulated buck switch current signal is the sum of an emulation ramp current and the sampled diode current just before switching occurs. Avoiding direct buck switch current measurement minimizes the effect of switching noise, while maintaining the benefits of current mode control.

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