The LM3489 device 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 in output ripple. A
dedicated enable pin provides a shutdown mode drawing only 7 µA. Leaving the enable pin unconnected
defaults to on.
Current limit protection can be implemented by measuring the voltage across the PFETs
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.
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