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Intersil's new VRM10 multiphase PWM controller offers MOSFET RDS-ON- and inductor DCR current sensing.

Intersil Corporation (Nasdaq:ISIL), a leader in the design and manufacture of high performance analog and wireless networking solutions, recently announced the new Endura ISL6561 precision 2- to 4-phase PWM controller IC for new VRM10-based platforms. The ISL6561 IC is the world's first PWM controller to offer designers a choice of either lower MOSFET RDS(ON) or output inductor DCR (DC Resistance) current-sensing topologies. This advanced controller is supplied in the space-saving and thermally efficient 40-pad 6 X 6 mm Quad Flat No-lead (QFN) package. It is targeted for new VRM10 desktop, workstation, and server designs where reliability, and precision performance are critical.

"Combined with our QFN packaged MOSFET drivers, the ISL6561 precision controller provides VRM10 platform designers with everything they need to meet stringent performance, space and cost requirements," said Cindy Drapcho, director of Intersil's Desktop Power Products. "The ISL6561 meets all VRM10 specifications and gives designers the freedom of choice for either of the popular current-sensing techniques."

Today's microprocessors require a tightly regulated output voltage position versus load current (droop). This CPU core voltage pre-positioning enables the DC/DC converter to maintain its regulation during severe load transients without the addition of energy-storing output capacitors. The ISL6561 senses the output current by utilizing patented techniques to measure the voltage across the RDS(ON) of the lower MOSFETs or DCR of the output inductor during their conduction intervals. Current sensing provides the needed signals for precision droop, channel-current balancing and over current protection.

The accuracy of the RDS(ON) current-sensing method is enhanced by the ISL6561's integrated temperature compensation function. Droop accuracy, phase current balance and over-current protection can be affected by temperature related changes in RDS(ON) or DCR. The ISL6561 uses an internal temperature-sensing element to provide programmable temperature compensation. This eliminates the need for an external thermistor. Correctly applied, temperature compensation can completely nullify the effect of RDS(ON) or inductor DCR temperature sensitivity.

A unity gain, differential amplifier is provided for remote voltage sensing. Any potential difference between remote and local grounds can be completely eliminated using the remote-sense amplifier. Eliminating ground differences improves regulation and protection accuracy. The threshold-sensitive enable input is available to accurately coordinate the start-up of the ISL6561 with Intersil's external MOSFET drivers.

Dynamic VID technology allows seamless on-the-fly VID (Voltage Identification number) changes. The offset pin allows accurate voltage offset settings that are independent of the VID setting. The ISL6561 has a built-in shunt regulator to allow 12-V-only bias using a small external limiting resistor. Differential current sensing further enhances current sensing accuracy because any errors introduced by an asymmetrical multiphase layout are offset. The ISL6561 is a precise multiphase PWM controller providing 0.5% system accuracy over load, line and temperature.
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Publication:EDP Weekly's IT Monitor
Geographic Code:1USA
Date:Feb 24, 2003
Words:452
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