LM27262 National Semiconductor Corporation, LM27262 Datasheet

LM27262

Manufacturer Part Number

LM27262

Description

Intel Cpu Core Voltage Regulator Controller For VRD10 Compatible PCS

Manufacturer

National Semiconductor Corporation

Datasheet

1.LM27262.pdf (22 pages)

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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

The LM27262 is available in a 48-lead TSSOP package and

in a 48-lead LLP package.

Features

n Compatible with “VRD10 Voltage Regulation

n Supports Intel SpeedStep

n Uses external gate drivers (LM2724) for maximum

n Fixed frequency PWM architecture

n Pin selectable internal or external voltage reference

n 0.5% core voltage set-point accuracy when using

n 0.9% accurate internal bandgap reference

n 2-, 3- or 4-phase operation

n Out-of-phase switching reduces input ripple current,

n VID-code programmable output voltage range of

Pentium

Specification” for Intel Pentium 4 and Prescott

Processors

(Geyserville-III

switching of the CPU core voltage and the CPU clock

frequency

layout flexibility and noise immunity

external voltage reference

thereby minimizing input capacitor requirements

0.8375V through 1.6000V

™

is a trademark of Intel Corporation.

™

), which enables real-time dynamic

™

4 and Prescott

™

technology

DS200834

™

processors.

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

n User programmable fault latch that can be used to

n Very fast transient response

n VID-transition masked PWRGOOD output

n True-differential current sensing for each phase ensures

n User programmable cycle-by-cycle current limit

Key Specifications

n Fast transient response to minimize output capacitor

n Shorter design cycles through the use of external gate

n Fully integrated solution. All VRD-10 control functions

n Accurate current balancing eliminates need to over

n Fixed frequency PWM minimizes EMI issues

n Low input capacitor requirements due to multi-phase

n Fault latching allows use of smaller power path

n Only need to buy as many drivers as the design needs

Applications

n Server and desktop computer CPU core power supplies

n Transportable notebook computers using desktop CPUs

n Low cost transportable notebook computers using 2- or

Protection (UVP), and Over Current Protection (OCP) to

defend against potentially catastrophic events

disable the regulator in the event a power system fault

accurate load current sharing

requirements

drivers for reduced power dissipation, ease of PCB

layout and reduced noise sensitivity

provided by a single device

design the power path

interleaving

components and minimizes the chance of damage to

the load in the event of a fault

while keeping only one controller in inventory

requiring a 2, 3- or 4-phase voltage regulator delivering

up to 100A

3-phase designs

November 2003

www.national.com

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