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LM27262 Datasheet(PDF) 1 Page - National Semiconductor (TI) |
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LM27262 Datasheet(HTML) 1 Page - National Semiconductor (TI) |
1 / 22 page LM27262 Intel CPU Core Voltage Regulator Controller for VRD10 Compatible PCs General Description The LM27262 is a versatile synchronous buck voltage regu- lator controller designed according to the Intel VRD10 Speci- fication. It’s a fixed-frequency voltage-mode control PWM with average current modulation of the reference voltage to achieve the desired output impedance. This approach im- parts a pseudo current mode behavior to the control loop. The part provides the control for a voltage regulator consist- ing of either 2-, 3- or 4-phases to provide power to a desktop CPU. Pulse-by-pulse phase current balancing ensures ac- curate current sharing. CPU core currents of over 90A can be supported without requiring significant over design of the power path. The LM27262 contains a precision 6-bit digital- to-analog converter (DAC) that uses a VID-code provided by the CPU to program the desired CPU core voltage. The regulator output voltage can be dynamically adjusted by changing the VID-code “on the fly”. The part is intended to provide all the specified functions laid out in the VRD-10 specification, making it as simple as possible for the user to realize a fully compliant CPU core supply for Intel’s Pentium™4 and Prescott™ processors. The LM27262 is available in a 48-lead TSSOP package and in a 48-lead LLP package. Features n Compatible with “VRD10 Voltage Regulation Specification” for Intel Pentium 4 and Prescott Processors n Supports Intel SpeedStep™ technology (Geyserville-III™), which enables real-time dynamic switching of the CPU core voltage and the CPU clock frequency n Uses external gate drivers (LM2724) for maximum layout flexibility and noise immunity n Fixed frequency PWM architecture n Pin selectable internal or external voltage reference n 0.5% core voltage set-point accuracy when using external voltage reference n 0.9% accurate internal bandgap reference n 2-, 3- or 4-phase operation n Out-of-phase switching reduces input ripple current, thereby minimizing input capacitor requirements n VID-code programmable output voltage range of 0.8375V through 1.6000V n User programmable, low loss, load line slope n User programmable Standard VID offset n User programmable VCORE slew rate n 5V power rail Under Voltage Lock Out (UVLO) n Over Voltage Protection (OVP), Under Voltage Protection (UVP), and Over Current Protection (OCP) to defend against potentially catastrophic events n User programmable fault latch that can be used to disable the regulator in the event a power system fault n Very fast transient response n VID-transition masked PWRGOOD output n True-differential current sensing for each phase ensures accurate load current sharing n User programmable cycle-by-cycle current limit Key Specifications n Fast transient response to minimize output capacitor requirements n Shorter design cycles through the use of external gate drivers for reduced power dissipation, ease of PCB layout and reduced noise sensitivity n Fully integrated solution. All VRD-10 control functions provided by a single device n Accurate current balancing eliminates need to over design the power path n Fixed frequency PWM minimizes EMI issues n Low input capacitor requirements due to multi-phase interleaving n Fault latching allows use of smaller power path components and minimizes the chance of damage to the load in the event of a fault n Only need to buy as many drivers as the design needs while keeping only one controller in inventory Applications n Server and desktop computer CPU core power supplies requiring a 2, 3- or 4-phase voltage regulator delivering up to 100A n Transportable notebook computers using desktop CPUs n Low cost transportable notebook computers using 2- or 3-phase designs Pentium™ is a trademark of Intel Corporation. October 2004 © 2005 National Semiconductor Corporation DS200834 www.national.com |
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