The LTC3810 high efficiency input limiter protects its load from excessive input voltage. At normal input voltages (<60V), it operates open loop at a very high duty cycle (>95%) to pass the input to the output at up to 5A with minimal voltage drop. When the input rises to an undesirable point (up to 75V), the loop is closed and the buck regulator maintains the output at 57V. Efficiency at normal input voltages is typically 98.7%.
The LTC3810 is a synchronous step-down switching regulator controller that can directly step-down voltages from up to 100V, making it ideal for telecom and automotive applications. The LTC3810 uses a constant on-time valley current control architecture to deliver very low duty cycles with accurate cycle-by-cycle current limit, without requiring a sense resistor.
A precise internal reference provides 0.5% DC accuracy. A high bandwidth (25MHz) error amplifier provides very fast line and load transient response. Large 1Ω gate drivers allow the LTC3810 to drive multiple MOSFETs for higher current applications. The operating frequency is selected by an external resistor and is compensated for variations in VIN and can also be synchronized to an external clock for switching-noise sensitive applications. A shutdown pin allows the LTC3810 to be turned off, reducing the supply current to 240μA.
Integrated bias control generates gate drive power from the input supply during start-up and when an output short-circuit occurs, with the addition of a small external SOT23 MOSFET. When in regulation, power is derived from the output for higher efficiency.