It's not enough to have a good switching-supply controller: an effective design also requires selection and modeling of the requisite MOSFETs. A new series of synchronous buck-regulator controllers from National Semiconductor address this issue by adding online selection guides for MOSFETs from many leading vendors, along with modeling tools to assess performance of the IC plus MOSFET pairings.
Depending on specific LM315x family device, the four new Simple Switcher controllers offer adjustable- or fixed-switching frequencies between 250 kHz and 1 MHz, input voltages from 6 to 42V, fixed (3.3V) or adjustable output voltage down to 0.6V, and output current capability to 12A. The control topology is a constant-on-time (COT) approach, which eliminates the need for an external compensation network and reduces external component count. The emulated ripple-mode technology (patent pending) means that the overall circuit can use smaller, low ESR (equivalent series resistance) output capacitors. Claimed efficiency is 93% at load.
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Along with the controllers, National has added MOSFET selection to their Webench design tool, so users can select, simulate, evaluate, and assess the cost, efficiency, footprint, efficiency, and thermal tradeoffs of the combination of controller plus discrete devices, and optimize for their intended priorities.
The four controllers are available in 14-lead, thermally enhanced packages, priced between $2.22 and $2.30 each, in 1000-piece orders.
For more information, contact National Semiconductor Corp.