Buck regulators target automotive designs, but their attributes can take them further

Milpitas, Calif.—There's more to automotive-targeted designs than serving the needs of big-battery hybrid and all-electric vehicles (HEV/EV). Even mainstream gas/diesel cars need to handle higher-voltage rails than are found in portable, battery-powered products; must  avoid potential interference with in-dash AM radio (yes, those still are in use); and have "off" current drain below the manufacturer's quiescent allocation (which is a very miserly 15 to 20 mA).

The LT8610 from Linear Technology  Corp. focuses on the have special requirements of automotive regulators but, of course, is not restricted to that application:

•it takes input voltages spanning single digits to 40V. The IC operates from 3.9 to 42V (it can function at "cold-crank" battery voltages), with efficiency up to 96% with 12V input/5V output, and up to 94% with 3.3V output, delivering up to 2.5A via internal switches.

•it switches at frequencies from 200kHz up to 2MHz, even at very low duty cycles (a result of the 50ns minimum on time); this means it can operate beyond the 550 to 1600kHz AM band, thus removing it as in-band interference source.

•finally, the IC's no-load quiescent current (I_Q) is below 2.5μA, making it a very small burden on the vehicle's quiescent budget.

The LT8610 and LT8611 synchronous buck regulators from Linear Technology support the higher voltages needed in automotive designs, along with switching beyond the AM-radio band and ultra-low quiescent current.

In addition, careful control of the switching edge rates (slew rate) contributes to low overall EMI. Output ripple is also very low for a switcher, below 10mV_p-p. Dropout is 200mV at 1A load. It also includes now-standard features such as output soft-start and tracking, internal compensation, undervoltage lockout, and a thermally enhanced package.

The otherwise-similar LT8611 adds an uncommitted op amp with monitor and control pins. You can use this as a rail-to-rail current-sense amplifier, to implement input or output current regulation and limiting.

Packaging, price, and availability: both ICs are available in volume now. The -40⁰C to +125⁰C LT8610 is housed a 16-lead MSOP package, and priced at $3.55 each (1000 pieces); the more auto-compatible version for -40⁰C to +150⁰C operation is $4.16. The LT8611 is in a 3×5 mm QFN-24 package, priced at $3.80 (1000 pieces) for the more-modest range version.

For more information: go the http://www.linear.com/product/LT8610 and http://www.linear.com/product/LT8611.