LM27262MTDX National Semiconductor, LM27262MTDX Datasheet

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LM27262MTDX

Manufacturer Part Number
LM27262MTDX
Description
LM27262MTDXIntel CPU Core Voltage Regulator Controller for VRD10 Compatible PCs
Manufacturer
National Semiconductor
Datasheet
© 2005 National Semiconductor Corporation
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
October 2004
www.national.com

Related parts for LM27262MTDX

LM27262MTDX Summary of contents

Page 1

... VID-code programmable output voltage range of 0.8375V through 1.6000V Pentium ™ trademark of Intel Corporation. © 2005 National Semiconductor Corporation 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) ...

Page 2

Typical Application Circuit FIGURE 1. 2 20083401 ...

Page 3

... Connection Diagrams Top View 48-Lead TSSOP (MTD) Order Number LM27262MTD See NS Package Number MTD48 Ordering Information Order Number LM27262MTD LM27262MTDX LM27262LQ LM27262LQX NS Package Number LQA48B 20083402 Package Drawing MTD48 MTD48 LQA48B LQA48B 3 Top View 48-Lead LLP Order Number LM27262LQ Supplied As 38 Units/Rail ...

Page 4

Pin Description (All pin numbers referred to here correspond to the TSSOP/ LLP package) Pin 1/44, PHASES: tri-level logic input: HIGH logic level switches controller into 2-phase operation mode, phases A and C active. LOW logic level activates 3-phase operation, ...

Page 5

Processor Pins (0 = low high) VID5 VID4 VID3 VID2 VID1 ...

Page 6

... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications PHASES, IREF, VSTDOS, VPROG, SLADJ1, SLADJ2, VREF, REFINT, CLIMADJ, VCORE, COMP, VFB, VILx, VIHx, SOFTCAP, PWRGD, VIDPGD, VID0-VID5, VRON -0. Differential Voltage (VILx – ...

Page 7

Electrical Characteristics Symbol Parameter DAC Voltage Accuracy VID codes from 1.5625V to 1.6000V with Internal VREF VID codes from 0.8375V to 1.1000V VID codes from 1.1125V to 1.5500V DAC Voltage Accuracy VID codes: 1.5500V & 1.6000V with External VREF = ...

Page 8

Electrical Characteristics Symbol Parameter Error Amp Input Offset VDAC = 1.3V Voltage Error Amplifier Open VFB = 1.3V, Comp Pin open loop DC Gain OSCILLATOR Active Mode Switching Frequency Minimum On-Time Maximum Duty Cycle SOFT START AND SOFT STOP (SOFTCAP), ...

Page 9

... The Absolute Maximum power dissipation should be de-rated by 12.5mW per ˚C above 25˚C ambient. The LM27262 actively limits its junction temperature to about 165˚C. Note 3: For detailed information on soldering plastic small-outline packages, refer to the Packaging Databook available from National Semiconductor Corporation. Note 4: For testing purposes, ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5kΩ resistor. ...

Page 10

www.national.com 10 ...

Page 11

Typical Performance Characteristics LM27262 Efficiency vs I Soft-Start Soft-Stop CORE CORE 20083405 20083407 20083409 11 LM27262 CORE CORE 20083406 Soft-Start 20083408 Soft-Stop 30A CORE 20083410 www.national.com ...

Page 12

Typical Performance Characteristics Load Transient 24A to 75A Load Transient 24A to 75A to 24A V vs Temperature DAC External Ref, DAC Trim www.national.com (Continued) 20083413 Over Current Protection Threshold vs Temperature 20083415 @ 1.325V External Ref, DAC Trim 20083417 ...

Page 13

Typical Performance Characteristics External V vs Temperature (LM27201) REF Switching Frequency Percent Change vs Temperature (Continued) V DAC Internal Ref, DAC Trim 20083419 Pin I REF 20083421 13 vs Temperature @ 1.325V 20083420 Voltage vs Temperature 20083422 www.national.com ...

Page 14

... Due to the required precision of the VRD-10 specification, the LM27262 was designed with the ability to use an external precision reference. Since National Semiconductor’s preci- sion 0.2% accurate voltage references have a 1.225V typical output voltage, the LM27262 has a 10mV internal offset switched in when REFINT selects an external reference ...

Page 15

Operation Descriptions be recalculated as 1.4V / 1.74kΩ = 80.46mA. Using a stan- dard 309Ω, 1% value for the offset resistor produces a nominal offset voltage of 24.86mV for an error of 0.14mV. LOAD LINE SLOPE The Load Line Slope ...

Page 16

Operation Descriptions SOFTSTART-RAMP CORE SOFTCAP 0.5V/V VIDPGD SOFTSTART-RAMP TURN-ON VIDPGD CORE SOFTCAP I = 3.2µA and Volt, Amp and Farad units are used. SOFTCAP For example: ...

Page 17

Component Selection Since VRD-10 designs must support large load transients while maintaining very tight output regulation, a good place to start the design is the output capacitors. OUTPUT CAPACITOR SELECTION For designs that will be subjected to large load current ...

Page 18

Component Selection V = 1.526V MAX There will also be an initial step equal to ∆I in our example will be approximately 41mV. The two effects are not entirely additive since the voltage across the ESR is decreasing as the ...

Page 19

Component Selection Since and the capacitor will be charged to 5V, the minimum capacitance required is 0.06µF. A 0.1µF would be a good choice. In some instances, it’s desirable to add small resistors between the ...

Page 20

Layout Considerations www.national.com (Continued) FIGURE 8. Power Path Layout 20 20083428 ...

Page 21

Physical Dimensions inches (millimeters) unless otherwise noted 48-Lead LLP Package Order Number LM27262LQ NS Package Number LQA48B 48-Lead TSSOP Package Order Number LM27262MTD NS Package Number MTD48 21 www.national.com ...

Page 22

... BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. ...

Page 23

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