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General Description

The MAX1813 step-down controller is intended for core

CPU DC-DC converters in notebook computers. The

controller features a dynamically adjustable output (5-

bit DAC), ultra-fast transient response, high DC accura-

cy, and high efficiency necessary for leading-edge

CPU core power supplies. Maxim’s proprietary Quick-

PWM™ quick-response, constant-on-time PWM control

scheme handles wide input/output voltage ratios with

ease and provides 100ns “instant-on” response to load

transients while maintaining a relatively constant switch-

ing frequency.

The MAX1813 is designed specifically for CPU core

applications requiring a voltage-positioned supply. The

voltage-positioning input (VPCS), combined with a

high-DC-accuracy control loop, is used to implement a

power supply that modifies its output set point in

response to the load current. This arrangement

decreases full-load power dissipation and reduces the

required number of output capacitors.

The output voltage can be dynamically adjusted

through the 5-bit digital-to-analog converter (DAC)

inputs over a 0.600V to 2V range. The MAX1813

includes an internal multiplexer that selects between

three different DAC code settings. The first two inputs

are controlled by five digital input pins (D0–D4). The

third input is used for the suspend mode and controlled

by two 4-level input pins (S0, S1). Output voltage transi-

tions are accomplished with a proprietary precision

slew-rate control that minimizes surge currents to and

from the battery while guaranteeing “just-in-time” arrival

at the new DAC setting.

The MAX1813’s 28V input range enables single-stage

buck conversion from high-voltage batteries for the

maximum possible efficiency. Alternatively, the con-

troller’s high-frequency capability combined with two-

stage conversion (stepping down the +5V system

supply instead of the battery) allows the smallest possi-

ble physical size.

The MAX1813 is available in a 28-pin QSOP package.

Applications

Notebook Computers

(Intel IMVP–II

™

/Coppermine™)

Docking Stations

CPU Core Supply

Single-Stage (BATT to V

CORE

) Converters

Two-Stage (+5V to V

CORE

) Converters

Features

♦ High-Efficiency Voltage Positioning

♦ Quick-PWM Architecture

♦ ±1% V

OUT

Accuracy Over Line

♦ Adjustable Output Slew Rate

♦ 0.600V to 2V Adjustable Output Range (5-Bit DAC)

♦ 2V to 28V Battery Input Range

♦ 200/300/600/1000kHz Switching Frequency

♦ Output Undervoltage and Overvoltage Protection

♦ Drives Large Synchronous-Rectifier MOSFETs

♦ ±20% Accurate Current-Limit

♦ 10µA Shutdown Supply Current

♦ 2V ±1% Reference Output

♦ Power-Good (PGOOD) Indicator

♦ Small 28-Pin QSOP Package

MAX1813

Dynamically-Adjustable, Synchronous Step-Down

Controller with Integrated Voltage Positioning

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-2010; Rev 0; 4/01

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

PART TEMP. RANGE PIN-PACKAGE

MAX1813EEI -40°C to +85°C 28 QSOP

Quick-PWM is a trademark of Maxim Integrated Products, Inc.

Coppermine and IMVP-

ΙΙ

are trademarks of Intel Corp.

Typical Operating Circuit appears at end of data sheet.

BST

PGND

CODE

ZMODE

SUS

GND

PGOOD

ILIM

REF

TON

TIME

SKP/SDN

VPCS

V+

QSOP

TOP VIEW

MAX1813

Pin Configuration

Summary of content (38 pages)

PAGE 1
9-2010; Rev 0; 4/01 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning Applications Notebook Computers (Intel IMVP–II™/Coppermine™) Docking Stations CPU Core Supply Single-Stage (BATT to VCORE) Converters Two-Stage (+5V to VCORE) Converters Typical Operating Circuit appears at end of data sheet. Features ♦ High-Efficiency Voltage Positioning ♦ Quick-PWM Architecture ♦ ±1% VOUT Accuracy Over Line ♦ Adjustable Output Slew Rate ♦ 0.
PAGE 2
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ABSOLUTE MAXIMUM RATINGS V+ to GND ..............................................................-0.3V to +30V VCC, VDD to GND .....................................................-0.3V to +6V PGND to GND.....................................................................±0.3V D0–D4, CODE, ZMODE, SUS, PGOOD to GND ......-0.3V to +6V SKP/SDN to GND (Note 1) .....................................-0.
PAGE 3
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning (Circuit of Figure 1, V+ = +15V, VCC = VDD = 5V, VPCS = ZMODE = GND = PGND, SKP/SDN = CODE = VCC, VOUT set to 1.5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, V+ = +15V, VCC = VDD = 5V, VPCS = ZMODE = GND = PGND, SKP/SDN = CODE = VCC, VOUT set to 1.5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS VBST - VLX forced to 5V 1.2 3.5 Ω High state (pull up) 1.3 3.5 Low state (pull down) 0.4 1.0 IDH DH forced to 2.
PAGE 5
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning (Circuit of Figure 1, V+ = +15V, VCC = VDD = 5V, VPCS = ZMODE = GND = PGND, SKP/SDN = CODE = VCC, VOUT set to 1.5V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 6
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ELECTRICAL CHARACTERISTICS (continued) (Circuit of Figure 1, V+ = +15V, VCC = VDD = 5V, VPCS = ZMODE = GND = PGND, SKP/SDN = CODE = VCC, VOUT set to 1.5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 5) PARAMETER SYMBOL Shutdown Supply Current (V+) Reference Voltage CONDITIONS MIN SKP/SDN = GND, VCC = VDD = 0 or 5V VREF REF Fault Lockout Voltage MAX UNITS 5 µA VCC = 4.5V to 5.
PAGE 7
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning (Circuit of Figure 1, V+ = +15V, VCC = VDD = 5V, VPCS = ZMODE = GND = PGND, SKP/SDN = CODE = VCC, VOUT set to 1.5V, TA = -40°C to +85°C, unless otherwise noted.) (Note 5) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS 4-Level Logic Input High (VCC) TON (200kHz operation), S0, S1 VCC 0.4 4-Level Logic Input UpperMiddle (Float) TON (300kHz operation), S0, S1 2.8 3.
PAGE 8
Typical Operating Characteristics (Circuit from Figure 1, components from Table 2, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. LOAD CURRENT (VOUT = 1.4V) V+ = 4.5V B1: V+ = 7V 100 B1 A1 90 100 MAX1813 toc01 A1: C1 90 B1 A1 D1: V+ = 24V PWM MODE (SKIP = VCC) V+ = 4.5V B2: V+ = 7V C2: V+ = 15V D2: V+ = 24V D1 80 C2 70 D2 60 C2 D2 70 60 0.1 1 10 100 0.1 1 10 90 A1 B1 C1 80 C2 D1 D2 70 1.44 100 PWM MODE SKIP MODE 1.42 1.40 1.38 VBATT = 7V 1.36 1.
PAGE 9
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning SWITCHING FREQUENCY vs. TEMPERATURE 380 ON TIME (ns) IOUT = 5A 280 260 360 IOUT = 5A 340 320 IOUT = 1A IOUT = 10A 300 240 IOUT = 20A 280 260 220 -15 10 35 60 -15 10 35 60 85 TEMPERATURE (°C) TEMPERATURE (°C) CURRENT-LIMIT DEVIATION vs. TEMPERATURE NO-LOAD SUPPLY CURRENT vs. BATTERY INPUT VOLTAGE (SKIP MODE) 1.5 ICC + IDD 1.0 SUPPLY CURRENT (mA) VILIM = 2V 1.0 1.2 MAX1813 toc11 2.0 0.
PAGE 10
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning Typical Operating Characteristics (continued) (Circuit from Figure 1, components from Table 2, TA = +25°C, unless otherwise noted.) LOAD TRANSIENT (PWM MODE) LOAD TRANSIENT (VOLTAGE POSITIONING DISABLED) LOAD TRANSIENT (SKIP MODE) MAX1813 toc15 MAX1813 toc17 MAX1813 toc16 20A 20A 20A 10A A 0 1.41V B 10A A 0 0 1.41V 1.46V 1.36V 1.36V 1.31V 1.31V 20µs/div A. IOUT = 0.
PAGE 11
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning STARTUP WAVEFORM (HEAVY LOAD) STARTUP WAVEFORM (NO LOAD, PWM MODE) MAX1813 toc21 MAX1813 toc22 1.6V 1.6V A 0 5V A 0 5V B 0 1.4V C B 0 1.4V C 0 0 20A 10A D 0 D 0 200µs/div A. VSKP/SDN = 0 TO 1.6V, 2V/div B. PGOOD, 5V/div C. VOUT = 1.4V, ROUT = 63mΩ, 1V/div D. INDUCTOR CURRENT, 20A/div 200µs/div A. VSKP/SDN = 0 TO 1.6V, 2V/div B. PGOOD, 5V/div C. VOUT = 1.4V, NO LOAD, 1V/div D.
PAGE 12
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning MAX1813 Pin Description PIN NAME 1 V+ 2 VPCS FUNCTION Battery Voltage Sense Connection. Connect V+ to the input power source. V+ is used only for PWM one-shot timing. DH on-time is inversely proportional to the input voltage over a 2V to 28V range. Current-Sense Input. Connect a current-sense resistor (RSENSE) between VPCS and PGND.
PAGE 13
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning PIN NAME 11 REF +2.0V Reference Voltage Output. Bypass to GND with a 0.22µF or greater capacitor. The reference can sink and source ±40µA (min) for external loads. Loading REF degrades FB accuracy according to the REF load regulation error. ILIM Current-Limit Adjustment. The PGND - VPCS current-limit threshold defaults to 50mV if ILIM is tied to VCC.
PAGE 14
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning +5V INPUT BIAS SUPPLY C1 1µF BATTERY (VBATT) 7V TO 24V C2 1µF R1 20Ω CIN VDD VCC RGATE 100kΩ ILIM POWER-GOOD INDICATOR V+ BST PGOOD TIME DH CCOMP RTIME 47pF 120kΩ CC MAX1813 CREF 0.22µF L1 0.68µH 1.4V OUTPUT UP TO 22A COUT LX DL REF QL RVPCS 100Ω D2 VPCS CVPCS 1nF RSENSE SUS OPEN S0 OPEN S1 CODE D0 PGND GND ZMODE FB D1 TO VCC QH CBST 0.
PAGE 15
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning CIRCUIT 1 (FIGURE 1) COMPONENT Table 2. Component Suppliers MANUFACTURER PHONE [COUNTRY CODE] WEBSITE Output Voltage 0.6V to 1.75V MOSFETs Input Voltage Range 7V to 24V Maximum Load Current 22A Fairchild Semiconductor [1] 888522-5372 www.fairchildsemi.com Inductor 0.68µH Sumida CDEP134H-0R6 or Panasonic ETQP6F0R6BFA International Rectifier [1] 310322-3331 www.irf.
PAGE 16
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning VBATT 5V TO 24V REF ILIM V+ TON 5V BIAS VCC 5V BIAS SUPPLY FROM DAC TON COMPUTE BST MAX1813 DH CHIP SUPPLY Q TOFF ONE-SHOT 9R TRIG R LX GND REF S 2V REF TON TRIG ONE-SHOT SET SOFT-START Q R CLR Q Q VPCS ZERO CROSSING VDD CC DL VPCS S Gm 2V REF SKP/SDN REF -12% REF +10% SET Q PGND R CLR Q OVP/UVP DETECT FB SUS PGOOD 5-BIT R-2R DAC S0 DECODER (SEE FIGURE 6) AND SLEW-RAT
PAGE 17
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning K(VOUT + 75mV) VIN where K is set by the TON pin-strap connection, and 75mV is an approximation to accommodate for the expected drop across the low-side MOSFET switch and current-sense resistor (Table 3). The on-time one-shot has good accuracy at the operating points specified in the Electrical Characteristics table. On-times at operating points far removed from the conditions specified can vary over a wide range.
PAGE 18
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning Table 4. Operating Mode Truth Table SKP/SDN DL MODE COMMENTS GND High Shutdown Micropower shutdown state (ICC = 2µA typ). VCC Switching Normal Operation Automatic switchover from PWM mode to pulse-skipping PFM mode at light loads. Prevents inductor current from recirculating into the input.
PAGE 19
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning Current-Limit Circuit (ILIM) The current-limit circuit employs a unique “valley” current-sensing algorithm. If the current-sense signal is above the current-limit threshold, the MAX1813 will not initiate a new cycle (Figure 4). The actual peak current is greater than the current-limit threshold by an amount equal to the inductor ripple current.
PAGE 20
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning to select the new 0.600V to 1.750V DAC codes, which are compatible with the IMVP-II specifications. CODE also determines the polarity of ZMODE (Table 7). +5V VBATT BST 5Ω TYP DH LX MAX1813 Figure 5. Reducing the Switching-Node Rise Time Suspend-Mode Operation (S0, S1) When the CPU clock stops, the processor enters suspend mode and requires a lower supply voltage to minimize power consumption.
PAGE 21
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning MAX1813 Table 5. Output Voltage vs. DAC Codes D4 D3 D2 D1 D0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OUTPUT VOLTAGE (V) CODE = 0 CODE = 1 0 2.000 1.750 0 1 1.950 1.700 1 0 1.900 1.650 0 1 1 1.850 1.600 0 1 0 0 1.800 1.550 0 1 0 1 1.750 1.500 0 0 1 1 0 1.700 1.450 0 0 1 1 1 1.650 1.400 0 1 0 0 0 1.600 1.350 0 1 0 0 1 1.550 1.300 0 1 0 1 0 1.500 1.
PAGE 22
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ZMODE MUX D0 D1 D2 D3 D4 D0-D4 DECODER 01 OR 10 OUT IMPEDANCE DECODER IN SUS MUX 0 OUT 00 OR 11 CODE OUT OUT SEL0 SEL1 (FIGURE 7) ZMODE CODE DAC S0/S1 DECODER S0 S1 IN 1 OUT SUS MAX1813 SUS Figure 6. Internal Multiplexers Block Diagram an internal 40kΩ pullup for about 4µs to see if the pin voltage can be forced high (Figure 7).
PAGE 23
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning VCC MAX1813 3.0V TO 5.5V 26kΩ 26kΩ 26kΩ 26kΩ 26kΩ D4 100kΩ 100kΩ D3 B-DATA LATCH D2 where ƒSLEW = 150kHz x 120kΩ/RTIME, VOLD is the original output voltage, and VNEW is the new output voltage. See TIME Frequency Accuracy in Electrical Characteristics for ƒSLEW accuracy. The practical range of RTIME is 47kΩ to 470kΩ, corresponding to 2.6µs to 26µs per 25mV step.
PAGE 24
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning Output Overvoltage Protection The overvoltage protection circuit is designed to protect the CPU against a shorted high-side MOSFET by drawing high current and activating the battery’s protection circuit. The output voltage is continuously monitored for overvoltage. If the output exceeds the overvoltage threshold, the fault protection is triggered and the circuit shuts down.
PAGE 25
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning VSAG =  V  K L(ILOAD1 -ILOAD2 )2  OUT  + t OFF(MIN)   VIN    (V - V  )K  2COUT VOUT  IN OUT  - t OFF(MIN)  V    IN   where tOFF(MIN) is the minimum off-time (see Electrical Characteristics), and K is from Table 3.
PAGE 26
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ƒ ƒ ESR = SW π where: ƒ ESR = 1 2πRESR COUT For a standard 300kHz application, the ESR zero frequency must be well below 95kHz, preferably below 50kHz. Tantalum, Sanyo POSCAP, and Panasonic SP capacitors in wide-spread use at the time of publication have typical ESR zero frequencies below 30kHz.
PAGE 27
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning PD (QH Re sistive) = VIN Generally, a small high-side MOSFET is desired to reduce switching losses at high input voltages. However, the RDS(ON) required to stay within package power-dissipation specifications often limits how small the MOSFET can be. Again, the optimum occurs when the switching losses equal the conduction (RDS(ON)) losses.
PAGE 28
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning simple low-pass RC filter with a 100ns time constant (100Ω x 1000pF) sufficiently reduces the noise on the current-sense signal (Figure 8). REF CREF Voltage-Positioning Compensation (CC) Q2 DL RAVPS VPCS CC RVPCS Applications Information CVPCS CCOMP RSENSE MAX1813 PGND GND Figure 8. Voltage-Positioning Block Diagram where D = V OUT /V IN is the regulator’s duty cycle.
PAGE 29
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning ESR STEP-DOWN AND STEP-UP (ISTEP x ESR) VOUT CAPACITIVE SAG (dV/dt = IOUT/COUT) RECOVERY from the hot CPU are beneficial. Effective efficiency is defined as the efficiency required of a non-voltagepositioned circuit to equal the total dissipation of a voltage-positioned circuit for a given CPU operating condition.
PAGE 30
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning A reasonable minimum value for h is 1.5, but adjusting this up or down allows trade-offs between VSAG, output capacitance, and minimum operating voltage.
PAGE 31
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning MAX1813 SUS VCC INV1 R3 30kΩ SUSPEND INV2 C1 10nF R2 80kΩ R1 120kΩ MAX1813 SKP/SDN INV3 ON/OFF tDELAY tDELAY SUSPEND ON/OFF SKIP (2.8V TO 6V) FORCED-PWM (1.4V TO 2.2V) SHUTDOWN (0 TO 0.5V) MAX1813 OPERATING MODE Figure 11. Three-State Operating Mode Control 2.7V TO 5.5V 1kΩ 3.0V TO 5.5V 100kΩ MAX1813 D4 D4 MAX1813 100kΩ D3 D3 ZMODE LOW VID = 01100 1.
PAGE 32
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning If the CPU’s VID pins float, the open-circuit pins can present a problem for the MAX1813’s internal mux. The processor’s VID pins can be used for the voltage-mode setting, together with suitable pullup resistors.
PAGE 33
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning MAX1813 3.15V TO 5.5V *OPTIONAL 4.7nF 1MΩ 1kΩ 1kΩ 1kΩ 1kΩ 1kΩ MAX1813 D4 100kΩ D3 CPU D2 100kΩ D1 D0 ZMODE CPU VID = 01100 → 1.15V (ZMODE LOW) ZMODE = HIGH = 1.25V ZMODE = LOW = 1.15V ZMODE HIGH VID = 01010 → 1.25V *TO REDUCE QUIESCENT CURRENT, 1kΩ PULLUP RESISTORS CAN BE REPLACED BY 1MΩ RESISTORS WITH 4.7nF CAPACATORS IN PARALLEL. Figure 14.
PAGE 34
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning QH DH L1 VOUT LX COUT R4 QL DL MAX1813 RVPCS R5 VPCS CVPCS RSENSE PGND GND FB CFB VOUT = VFB (1 + R4/R5) Figure 16. Adjusting VOUT with a Resistive-Divider Q1 DH L1 VOUT LX MAX1813 COUT Q2 DL RVPCS RFB MAX4634 VPCS R1 CVPCS RSENSE R2 PGND GND R3 R4 REF CREF LOGIC FB CFB ADD0 ADD1 INH CONTROL LOGIC Figure 17.
PAGE 35
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning MAX1813 Q1 DH L1 VOUT LX MAX1813 COUT Q2 DL RVPCS RFB VPCS MAX4634 CVPCS RSENSE R5 PGND R6 GND VCC MAX4322 R7 REF R8 CREF LOGIC FB CFB ADD0 ADD1 INH CONTROL LOGIC Figure 18. Adding a Negative Offset Voltage to V+ on the MAX1813, with the same attenuation factor as the output divider. The V+ input has a nominal 600kΩ input impedance, which should be considered when selecting resistor values.
PAGE 36
MAX1813 Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning about 2-3% at 600kHz when compared to the 300kHz voltage-positioned circuit, primarily due to the high-side MOSFET switching losses. approached in terms of fractions of centimeters, where a single mΩ of excess trace resistance causes a measurable efficiency penalty.
PAGE 37
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning plane where sensitive analog components, the GND pin, and VCC bypass capacitor go. The GND plane and PGND plane must meet only at a single point directly beneath the IC. These two planes are then connected to the high-power output ground with a short connection from PGND to the source of the low-side MOSFET (the middle of the star ground). This point must also be very close to the output capacitor ground terminal.
PAGE 38
Dynamically-Adjustable, Synchronous Step-Down Controller with Integrated Voltage Positioning QSOP.EPS MAX1813 Package Information Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.