SC1486A Datasheet | SEMTECH

Description The SC1486A is a dual output constant on-time synchronous buck PWM controller optimized for cost effective mobile DDR and DDR2 applications. Features include high efficiency, a fast dynamic response with no minimum on time, a REFIN input and a buffered REFOUT pin capable of sourcing 3m A. The excellent transient response means that SC1486A based solutions will require less output capacitance than peting fixed frequency converters. The output voltage of the first controller can be adjusted from 0.5V to VCCA. In DDR applications, this voltage is set to 2.5 volts, and in DDR2, 1.8V. A resistor divider from this supply is used to drive the REFIN pin of the second controller. A unity gain buffer drives the REFOUT pin to the same potential as REFIN. The second controller regulates its output to REFOUT. Two frequency setting resistors set the on-time for each buck controller. The frequency can thus be tailored to minimize crosstalk. The integrated gate drivers feature adaptive shoot-through protection and soft switching, requiring no gate resistors for the top MOSFET. Additional Features include cycleby-cycle current limit, digital soft-start, over-voltage and under-voltage protection, and a Power Good output for each controller. Features ‹ 1% DC accuracy ‹ patible with DDR & DDR2 memory power ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ ‹ requirements Constant on-time for fast dynamic response VIN range = 1.8V - 25V DC current sense using low-side RDS(ON) sensing or sense resistor Integrated reference buffer for VTT Low power S3 state with high-Z VTT Resistor programmable on-time Cycle-by-cycle current limit Digital soft-start PSAVE option for VDDQ Over-voltage/under-voltage fault protection <20µA shutdown current Low quiescent power dissipation Two Power Good indicators Separate enable for each switcher Integrated gate drivers with soft switching - no gate resistors required Efficiency >90% 28 Lead TSSOP (lead free available) Applications ‹ Notebook puters ‹...