ON Semiconductor

The CS5231-3 combines a three-terminal linear regulator with circuitry controlling an external PFET transistor thus managing two input supplies. The part provides a 3.3V regulated output either from the main 5V supply or a 3.3V auxiliary that switches on when the 5V supply is not present. This delivers constant, uninterrupted power to the load. The CS5231-3 meets Intel's "Instantly Available" power requirements which follows from the "Advanced Configuration and Power Interface" (ACPI) standards developed by Intel, Microsoft and Toshiba.The CS5231-3 linear regulator provides a fixed 3.3V output at 500mA with an overall accuracy of +/- 2%. The internal NPN-PNP composite pass transistor provides a low dropout voltage and requires less supply current than a straight PNP design. Full protection with both current limit and thermal shutdown is provided.Designed for low reverse current, the IC prevents excessive current from flowing from VOUTto either VINor ground when the regulator input voltage is lower than the output voltage.The CS5231-3 can be used to provide power to an ASIC on a PCI Network Interface Card (NIC). When the system enters a Sleep State and the 5V input drops below 4.4V, the AuxDrv control signal on the CS5231-3 is activated turning on the external PFET. This switches the supply source from the 5V input to the 3.3V input through the PFET, guaranteeing a constant 3.3V output to the ASIC that is "glitch free."The CS5231-3 is available in two package types: the 5-Lead D2PAK (TO263) package and the 8-Lead SOIC 4-Leadfused (DF) package. Other applications include desktop computers, power supplies with multiple input sources and PCMCIA/PCI interface cards.

This new very low dropout linear regulator reduces total power dissipation in the application. To achieve very low dropout, the internal pass transistor is powered separately from the control circuitry. Furthermore, with the control and power inputs tied together, this device can be used in single supply configuration and still offer a better dropout voltage than conventional PNP-NPN based LDO regulators. In this mode the dropout is deter-mined by the minimum control voltage.The CS5253B-8 is offered in a five-terminal D 2 PAK package, which allows for the implementation of a remote-sense pin permitting very accurate regulation of output voltage directly at the load, where it counts, rather than at the regulator. This remote sensing feature virtually eliminates output voltage variations due to load changes and resistive voltage drops. Typical load regulation measured at the sense pin is less than 1mV for an output voltage of 2.5V with a load step of 10mA to 3A.The CS5253B-8 has a very fast transient loop response.Internal protection circuitry provides for "bust-proof" operation, similar to three-terminal regulators. This circuitry, which includes over-current, short circuit, and over-temperature protection will self protect the regulator under all fault conditions.The CS5253B-8 is ideal for generating a 2.5V supply to power graphics controllers used on VGA cards. Its remote sense and low value capacitance requirements make this a low cost high performance solution. The CS5253B-8 is optimized from the CS5253-1 to allow a lower value of output capacitor to be used at the expense of a slower transient response.

The CS5301 is a three-phase step down controller which incorporates all control functions required to power high performance processors and high current power supplies. Proprietary multi-phase architecture guarantees balanced load current distribution and reduces overall solution cost in high current applications. Enhanced V 2 control architecture provides the fastest possible transient response, excellent overall regulation, and ease of use.The CS5301 multi-phase architecture reduces output voltage and input current ripple, allowing for a significant reduction in inductor values and a corresponding increase in inductor current slew rate. This approach allows a considerable reduction in input and output capacitor requirements, as well as reducing overall solution size and cost.