Linear Technology Corporation has introduced two new power management devices for automotive applications. They are the LT1936, a current mode PWM step-down dc/dc converter with an internal 1.9 A power switch, and the LT3782, a step-up dc/dc controller with two-phase operation to deliver high output power using only two inductors, thus eliminating the need for power and current sense transformers.
Packaged in a thermally enhanced, eight-lead MSOP package, the LT1936 features a 3.6 V to 36 V input range that suits it for regulating power from a variety of sources, including automotive batteries. It can operate with sub 4 V inputs as required for automotive “cold crank” conditions. Its 500 kHz operating frequency allows the use of small, low-cost inductors and ceramic capacitors, resulting in low, predictable output ripple.
A low VCESAT (410 mV at 1.2 A) internal switch ensures efficiencies as high as 88%, maximizing battery run-time. Cycle-by-cycle current limit provides protection against shorted outputs, and soft-start eliminates input current surge during start up. A low current (<2 uA) shutdown mode provides easy power management in battery-powered systems.
The LT3782 targets automotive and other applications in which a step-up dc/dc converter must deliver high power with low heat dissipation and occupy a small space. Features such as adjustable slope compensation, time delay, undervoltage lockout, synchronous operation and clock synchronization, enable power supply designers to tailor the circuit for optimum performance.
The LT3782 can regulate a 50 V output at 4 A load current with 96% efficiency from an input source ranging from 10 V to 36 V. Its two-phase operation minimizes input and output ripple currents and reduces the value requirements of the input and output capacitors.
With 10 V gate drive and 4 A peak drive current, the LT3782 can drive industrial-grade high-power MOSFETs at high efficiency. The LT3782 uses a constant frequency (150 kHz to 500 kHz) current mode architecture to improve line and load regulation, reduce the size of inductors and capacitors and provide a precision pulse-by-pulse current limit.
