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Features
Compatible with “VRD10 Voltage Regulation Specification” for Intel Pentium 4 and Prescott Processors
Supports Intel SpeedStep
™ technology (Geyserville-III
™), which enables real-time dynamic switching of the CPU core voltage and the CPU clock frequency
Uses external gate drivers (LM2724) for maximum layout flexibility and noise immunity
Fixed frequency PWM architecture
Pin selectable internal or external voltage reference
0.5% core voltage set-point accuracy when using external voltage reference
0.9% accurate internal bandgap reference
2-, 3- or 4-phase operation
Out-of-phase switching reduces input ripple current, thereby minimizing input capacitor requirements
VID-code programmable output voltage range of 0.8375V through 1.6000V
User programmable, low loss, load line slope
User programmable Standard VID offset
User programmable VCORE slew rate
5V power rail Under Voltage Lock Out (UVLO)
Over Voltage Protection (OVP), Under Voltage Protection (UVP), and Over Current Protection (OCP) to defend against potentially
catastrophic events
User programmable fault latch that can be used to disable the regulator in the event a power system fault
Very fast transient response
VID-transition masked PWRGOOD output
True-differential current sensing for each phase ensures accurate load current sharing
User programmable cycle-by-cycle current limit
Description The LM27262 is a versatile synchronous buck voltage regulator controller designed according to the Intel VRD10 Specification.
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 imparts a pseudo current mode behavior to the control loop. The part provides the control
for a voltage regulator consisting of either 2-, 3- or 4-phases to provide power to a desktop CPU. Pulse-by-pulse phase current
balancing ensures accurate 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 Pentium4 and Prescott
™ processors.
The LM27262 is available in a 48-lead TSSOP package and in a 48-lead LLP package.
Key Specification
Fast transient response to minimize output capacitor requirements
Shorter design cycles through the use of external gate drivers for reduced power dissipation, ease of PCB layout and reduced
noise sensitivity
Fully integrated solution. All VRD-10 control functions provided by a single device
Accurate current balancing eliminates need to over design the power path
Fixed frequency PWM minimizes EMI issues
Low input capacitor requirements due to multi-phase interleaving
Fault latching allows use of smaller power path components and minimizes the chance of damage to the load in the event of
a fault
Only need to buy as many drivers as the design needs while keeping only one controller in inventory
Applications
Server and desktop computer CPU core power supplies requiring a 2, 3- or 4-phase voltage regulator delivering up to 100A
Transportable notebook computers using desktop CPUs
Low cost transportable notebook computers using 2- or 3-phase designs
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Also Recommended
| LM5642X▲ | 200-500 KHz Osc Switch Frequencies |
| LM27212 | Two-Phase Current-Mode Hysteretic Buck |
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