LX1681/1682 is a monolithic, PWM controller integrated circuit. They are designed to implement flexible, low-cost step-down (step-down) regulators for power supply with minimal external components. The LX1681 is an asynchronous controller; the LX1682 has a synchronous driver for higher efficiency. The output voltage is adjustable by a resistor divider to set the voltage between 1.25V and 4.5V. Short-circuit current limiting is available with inexpensive current-sense resistors. MOSFETs with RDS(ON) of voltage drop for current sensing - measure delay time of 1µs to eliminate MOSFET ringing errors. Hiccup mode fault protection reduces the average power of the power element during short circuit conditions. The switching frequency is fixed at 200kHz for optimal cost and space. Undervoltage lockout and soft-start for optimum start-up performance. The LX1681/82 can be disabled by pulling the soft-start pin to ground. Small 8-pin SOIC package reduces board space. Optimized for 5V to 3.3V or 5V to 2.5V conversion, the LX1681/82 can also be used for 12V to 5V, 3.3V or other high voltages with high efficiency, eliminating the need for bulky heat sinks.

main feature
* Fixed 200kHz switching frequency
* Constant frequency voltage mode control without external compensation
* Hiccup mode over current protection
* high efficiency
* The output voltage is divided by the resistor divider
* Under voltage lockout
* Soft start and enable
* Synchronous rectification (LX1682)
* Asynchronous rectification (LX1681)
* Small, 8-pin surface mount package

application
* 5V to 3.3V or lower buck regulator
* FPGA power supply
* Microprocessor chip supplies (eg Camino, Whitney, etc.)
*Rambus® RIMMTM Supplies
* Hard disk drive
* Computer add card