Synchronous step-down DC-DC converter delivers high efficiency

Linear Technology Corporation has announced the LT8607, a 750mA, 42V input synchronous step-down switching regulator. A unique synchronous rectification topology delivers 93% efficiency while switching at 2MHz, enabling designers to avoid critical noise-sensitive frequency bands, such as AM radio while using a very compact solution footprint. Burst Mode operation keeps quiescent current under 3µA in no-load standby conditions, ideal for always-on systems. The device’s 3.0V to 42V input voltage range is well suited for automotive applications that must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3.0V and load dump transients in excess of 40V. Its internal 1.2A switches deliver up to 750mA of continuous output current. The device maintains a minimum dropout voltage of only 250mV (at 500mA) under all conditions, enabling it to excel in scenarios such as automotive cold-crank. Spread spectrum frequency modulation and special design techniques ensure low EMI operation, enabling it to meet CISPR25, Class 5 EMI limits required by many automotive and industrial applications. Furthermore, a fast minimum on-time of only 45ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output. The device’s eight-lead thermally enhanced 2mm x 2mm DFN or 10-lead MSOP package and high switching frequency, which keeps the external inductor and capacitors small, provide a compact, thermally efficient footprint. The device utilizes internal top and bottom high efficiency power switches with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 10mVP-P. Unique design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the device’s current mode topology enables fast transient response and excellent loop stability. Other features include internal compensation, a power good flag, output soft-start/tracking and thermal protection.