The LT3975 is a 42V step-down switching regulator that can deliver 2.5A of continuous output current and requires only 2.7µA of quiescent current. Similarly, the LT3976 can operate from a 40V input, delivers up to 5A of output current and requires only 3.3µA of quiescent current. Both devices offer a 4.2V to a nominal 40V input voltage range, making them ideal for automotive and industrial applications. Their internal high 75mOhm switches deliver efficiencies as high as 90%. The LT3975's and LT3976's Burst Mode operation offers ultralow quiescent current, a feature that is also well suited for automotive and industrial systems applications that demand always-on operation and optimum battery life. The devices' unique design maintains a minimum dropout voltage of only 500mV when the input voltage drops below the programmed output voltage, a functional necessity in applications subject to automotive cold-crank conditions. Switching frequency is user-programmable from 200kHz to 2MHz, and synchronizable from 250kHz to 2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of their 16-lead thermally enhanced MSOP package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.These devices use a high efficiency 75mOhm switch, with the boost diode, oscillator, control and logic circuitry integrated into a single die. Special design techniques and a new high voltage process deliver high efficiency over a wide input voltage range, and their current-mode topology enables fast transient response and excellent loop stability. The LT3975 and LT3976 are available in E-grade, I-grade and H-grade versions and prices range from $3.10 to $4.38 each in 1,000-piece quantities.
