LM3489

LM3489/LM3489Q Hysteretic PFET Buck Controller with Enable Pin June 23, 2008 LM3489/LM3489Q Hysteretic PFET Buck Controller with Enable Pin General Description The LM3489 is a high efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, cost effective, switching buck regulator for a wide range of applications. The hysteretic control architecture provides for simple design without any control loop stability concerns using a wide variety of external components. The PFET architecture also allows for low component count as well as ultra-low dropout, 100% duty cycle operation. Another benefit is high efficiency operation at light loads without an increase www.DataSheet4U.com in output ripple. A dedicated Enable Pin provides a shutdown mode drawing only 7µA. Leaving the Enable Pin unconnected defaults to on. Current limit protection can be implemented by measuring the voltage across the PFET’s RDS(ON), thus eliminating the need for a sense resistor. A sense resistor may be used to improve current limit accuracy if desired. The cycle-by-cycle current limit can be adjusted with a single resistor, ensuring safe operation over a range of output currents. ■ ■ ■ ■ ■ ■ ■ ■ ■ High efficiency 93% ±1.3% (±2% over temp) internal reference 100% duty cycle operation Maximum operation frequency > 1MHz Current limit protection Dedicated enable pin (on if unconnected) Shutdown mode draws only 7µA supply current MSOP-8 LM3489 is AEC-Q100 Grade 1 qu...