Document
19-3360; Rev 0; 8/04
Multiphase, Fixed-Frequency Controller for AMD Hammer CPU Core Power Supplies
General Description
The MAX8707 is a multiphase (3-/4-phase), interleaved, fixed-frequency, step-down controller for AMD Hammer CPU core supplies. Interleaved multiphase operation reduces the input ripple current and output voltage ripple while easing component selection and layout placement. The MAX8707 includes active voltage positioning with adjustable gain and offset, reducing power dissipation and bulk output-capacitance requirements. The MAX8707 is intended for two different notebook CPU core applications: stepping down the battery directly or stepping down the +5V system supply to create the core voltage. The single-stage conversion method allows these devices to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, 2-stage conversion (stepping down the +5V system supply instead of the battery) at higher switching frequency provides the minimum possible physical size. The MAX8707 features dedicated differential currentsense inputs for each phase and includes a fifth pair of current-sense inputs to provide an accurate voltagepositioning slope and average current-limit protection using a single current-sense resistor. The MAX8707 also has two dedicated inputs that provide differential remote voltage sensing. The MAX8707 provides an analog input for setting the suspend voltage and a slew-rate controller for transitions between VID codes or the suspend voltage. The controllers reduce the transition slew rate during startup and shutdown, providing soft-start with minimal input surge current and damped soft-shutdown without negative output undershoot. The MAX8707 includes output fault protection—undervoltage, nonlatched overvoltage, and thermal overload—and an independent voltageregulator power-OK (VROK) output. The MAX8707 has a selectable switching frequency, allowing 200kHz, 300kHz, or 600kHz per-phase operation. The MAX8707 is available in the low-profile, 40-pin, 6mm x 6mm thin QFN package. Refer to the MAX8702/ MAX8703 for compatible drivers.
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Features
o 3-/4-Phase Interleaved Fixed-Frequency Controller o ±0.75% VOUT Accuracy Over Line, Load, and Temperature o 5-Bit On-Board Digital-to-Analog Converter (DAC)—0.80V to 1.55V o Adjustable Suspend Voltage Input o Active Voltage Positioning with Adjustable Gain and Offset o Accurate Lossless Current Balance o Accurate Droop and Current Limit o Remote Output and Ground Sense o Output Slew-Rate Control o Power-Good Window Comparator o Selectable 200kHz/300kHz/600kHz Switching Frequency o Output Overvoltage and Undervoltage Protection o Thermal Fault Protection o 2V ±0.7% Reference Output o Soft-Startup and Shutdown
MAX8707
Ordering Information
PART MAX8707ETL TEMP RANGE -40°C to +85°C PIN-PACKAGE 40 Thin QFN 6mm x 6mm
Applications
AMD Hammer Desknote Computers Multiphase CPU Core Supplies Voltage-Positioned Step-Down Converters Notebook/Desktop Computers Servers
Pin Configuration appears at end of data sheet.
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For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Multiphase, Fixed-Frequency Controller for AMD Hammer CPU Core Power Supplies MAX8707
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V D0–D4 to GND..........................................................-0.3V to +6V SKIP, SUS, VROK, ILIM(AVE) to GND......................-0.3V to +6V SUSV, OFS, OSC to GND.........................................-0.3V to +6V CSP_, CSN_, CRSP, CRSN to GND .........................-0.3V to +6V VPS, FBS, CCV, REF to GND .....................-0.3V to (VCC + 0.3V) ILIM(PK), TRC, TIME to GND .....................-0.3V to (VCC + 0.3V) PWM_, DRSKP to PGND ............................-0.3V to (VCC + 0.3V) PGND, GNDS to GND ...........................................-0.3V to +0.3V
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SHDN to GND (Note 1)...........................................-0.3V to +14V REF Short-Circuit Duration .........................................Continuous Continuous Power Dissipation (TA = +70°C) 40-Pin 6mm x 6mm Thin QFN (derate 26.3mW/°C above +70°C) ................................2.105W Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not.