Two-Phase Desktop Core Supply Controllers with Controlled Change

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Two-Phase Desktop Core Supply Controllers with Controlled Change

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19-2498; 10/02
Two-Phase Desktop Core Supply Controllers with Controlled Change
MAX1937/MAX1938/MAX1939 comprise family synchronous, two-phase, step-down controllers capable delivering load currents 60A. controllers utilize Quick-PWMcontrol architecture conjunction with active load-current voltage positioning. Quick-PWM control provides instantaneous load-step response, while programmable voltage positioning allows converter utilize full transient regulation limits, reducing output capacitance requirement. phases operate 180° out-of-phase with effective 500kHz switching frequency, thus reducing input output current ripple, well reducing input filter capacitor requirements. MAX1937/MAX1938/MAX1939 compliant with Hammer, Intel, Voltage-Regulator Module (VRM) 9.0/9.1, AthlonMobile code specifications (see Table codes). internal provides ultra-high accuracy ±0.75%. controlled voltage transition implemented minimize both undervoltage overvoltage overshoot during input change. Remote sensing available high output-voltage accuracy. MOSFET switches driven gate-drive circuit minimize switching crossover conduction losses achieve efficiency high 90%. MAX1937/MAX1938/MAX1939 feature cycleby-cycle current limit ensure that current limit exceeded. Crowbar protection available protect against output overvoltage.
Features
±0.75% Output Voltage Accuracy Instant Load-Transient Response Efficiency Eliminates Heatsinks Output Current Input Range User-Programmable Voltage Positioning Controlled Voltage Transition 500kHz Effective Switching Frequency MAX1937: Hammer Compatible MAX1938: Intel 9.0/9.1 Compatible MAX1939: Athlon Mobile Compatible Soft-Start Power-Good (PWRGD) Output Cycle-by-Cycle Current Limit Output Overvoltage Protection (OVP) RDS(ON) RSENSE Current Sensing Remote Voltage Sensing 28-Pin QSOP Package
MAX1937/MAX1938/MAX1939
Ordering Information
PART MAX1937EEI MAX1938EEI MAX1939EEI TEMP RANGE -40°C +85°C -40°C +85°C -40°C +85°C PIN-PACKAGE QSOP QSOP QSOP
Applications
Notebook Desktop Computers Servers Workstations Blade Servers High-End Switches High-End Routers Macro Base Stations
VIEW
VID0 VID1 TIME VID2 VID3 VID4 VPOS ILIM BST1
Configuration
MAX1937 MAX1938 MAX1939
PGND BST2 PWRGD
Typical Application Circuits Functional Diagram appear data sheet.
GNDS
Quick-PWM trademark Maxim Integrated Products, Inc. Athlon trademark Advanced Micro Devices, Inc. Intel registered trademark Intel Corp.
QSOP
Maxim Integrated Products
pricing, delivery, ordering information, please contact Maxim/Dallas Direct! 1-888-629-4642, visit Maxim's website www.maxim-ic.com.
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
ABSOLUTE MAXIMUM RATINGS
.-0.3V +28V VDD, PWRGD, ILIM, .-0.3V GNDS, VPOS, REF, VID_, TIME .0.3V VVDD 0.3V PGND .-0.3V +0.3V CS1, .-2V +28V GND.-0.3V BST1, BST2 .-0.3V +35V BST1.-7V +0.3V BST2.-7V +0.3V LX1.-0.3V VBST1 0.3V LX2.-0.3V VBST2 0.3V DL1, PGND .-0.3V VVLG 0.3V Continuous Power Dissipation +70°C) 28-Pin QSOP (derate 20.8mW/°C above +70°C).860.2mW Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) .+300°C
Stresses beyond those listed under "Absolute Maximum Ratings" cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC 12V, VVDD PGND GNDS VID_ GND, CVPOS 47pF, CREF 0.1µF, VILIM +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER GENERAL Operating Range Operating Range Operating Range Operating Supply Current Operating Supply Current Operating Supply Current Shutdown Current Shutdown Current Shutdown Current TIME Output Voltage ILIM Input Bias VPOS Output Voltage REFERENCE Reference Voltage SOFT-START MAX1937 Ramp Period Soft-Start Voltage Step ERROR AMPLIFIER Input Resistance GNDS Input Bias Current Output Regulation Voltage Accuracy Resistance from -0.75 +0.75 MAX1938 MAX1939 -50µA IREF 50µA 1.987 2.000 2.013 VILIM 1.5V CS_= GND, VPOS connected through resistor VVLG VVDD above threshold switching) above threshold switching) above threshold switching) GND, VID_ connected 1.96 -250 1.96 2.00 MAX1937 MAX1938/MAX1939 2.04 +250 2.04 CONDITIONS UNITS
Two-Phase Desktop Core Supply Controllers with Controlled Change
ELECTRICAL CHARACTERISTICS (continued)
(VCC 12V, VVDD PGND GNDS VID_ GND, CVPOS 47pF, CREF 0.1µF, VILIM +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER FAULT PROTECTION Undervoltage Lockout (UVLO) Threshold UVLO Hysteresis UVLO Threshold UVLO Hysteresis Thermal Shutdown Reference UVLO Threshold Output Overvoltage Fault Threshold Output UVLO Threshold CURRENT LIMIT PGND CS_, VILIM 1.5V Current-Limit Threshold Input Offset Voltage Input Bias Current VOLTAGE POSITIONING VPOS Input Offset Voltage VPOS Gain VPOS Gain TIMER DRIVERS On-Time Minimum Off-Time GND, 1.5V high, high high Break-Before-Make Time high MAX1937/MAX1938 MAX1939 MAX1937/MAX1938 MAX1939 From VCS1, VCS2 -100mV; RVPOS From CS1, VCS1, VCS2 +13mV, -113mV; RVPOS 72.5 75.0 77.5 PGND CS_, VILIM PGND CS_, VILIM 0.5V Rising temperature, typical hysteresis 15°C Rising edge Falling edge Rising falling MAX1937/MAX1938 MAX1939 1.97 2.215 Rising falling 4.00 Rising falling 4.00 4.25 4.25 1.600 1.584 2.00 2.250 2.03 2.285 4.45 4.45 CONDITIONS UNITS
MAX1937/MAX1938/MAX1939
Rising falling percentage nominal regulation voltage
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
ELECTRICAL CHARACTERISTICS (continued)
(VCC 12V, VVDD PGND GNDS VID_ GND, CVPOS 47pF, CREF 0.1µF, VILIM +85°C, unless otherwise noted. Typical values +25°C.)
PARAMETER On-Resistance State On-Resistance State On-Resistance High State BST_ Leakage Current Leakage Current Level Threshold High Level Threshold Pullup Resistance PWRGD PWRGD Upper Trip Level PWRGD Lower Trip Level Output Level Output High Leakage CONTROLLED CHANGE On-the-Fly Change Slew Rate VID_ Change Frequency Range PWRGD Blanking Time VVDD 4.5V 5.5V RTIME 120k 25mV step RTIME RTIME 470k 6.17 2.35 23.5 6.67 2.63 26.3 7.25 2.99 29.9 10.0 12.5 -12.5 15.0 Internally pulled VBST_ 30V, VLX_ VBST_ 30V, VLX_ CONDITIONS VBST1 VBST2 UNITS
On-Resistance High State VBST_
Two-Phase Desktop Core Supply Controllers with Controlled Change
ELECTRICAL CHARACTERISTICS
(VVCC 12V, VVDD PGND GNDS GND, VID_= GND, CVPOS 47pF, CREF 0.1µF, VILIM -40°C +85°C, unless otherwise noted.) (Note
PARAMETER GENERAL Operating Range Operating Range Operating Range Operating Supply Current Operating Supply Current Operating Supply Current Shutdown Current Shutdown Current Shutdown Current TIME Output Voltage ILIM Input Bias VPOS Output Voltage REFERENCE Reference Voltage SOFT-START MAX1937 Ramp Period ERROR AMPLIFIER GNDS Input Bias Current Output Regulation Voltage Accuracy FAULT PROTECTION UVLO Threshold UVLO Threshold Output Overvoltage Fault Threshold Output UVLO Threshold CURRENT LIMIT PGND CS_, VILIM 1.5V Current-Limit Threshold PGND CS_, VILIM PGND CS_, VILIM 0.5V Rising falling Rising falling Rising falling MAX1937/MAX1938 MAX1939 4.00 4.00 1.97 2.215 4.45 4.45 2.03 2.285 MAX1938 MAX1939 -50µA IREF 50µA 1.98 2.02 VILIM GND, VPOS connected through resistor VVLG VVDD above threshold switching) above threshold switching) above threshold switching) GND, VID_ connected 1.96 -250 1.96 MAX1937 MAX1938/MAX1939 2.04 +250 2.04 CONDITIONS UNITS
MAX1937/MAX1938/MAX1939
Rising falling percentage nominal regulation voltage
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
ELECTRICAL CHARACTERISTICS (continued)
(VVCC 12V, VVDD PGND GNDS GND, VID_= GND, CVPOS 47pF, CREF 0.1µF, VILIM -40°C +85°C, unless otherwise noted.) (Note
PARAMETER Input Offset Voltage Input Bias Current VOLTAGE POSITIONING VPOS Input Offset Voltage VPOS Gain VPOS Gain TIMER DRIVERS On-Time Minimum Off-Time On-Resistance State On-Resistance State On-Resistance High State BST_ Leakage Current Leakage Current VID_ Level Threshold High Level Threshold Pullup Resistance PWRGD PWRGD Upper Trip Level PWRGD Lower Trip Level Output Level Output High Leakage CONTROLLED CHANGE On-the-Fly Change Slew Rate VID_ Change Frequency Range PWRGD Blanking Time VVDD 4.5V 5.5V RTIME 120k 25mV step RTIME RTIME 470k 6.17 2.35 23.5 7.25 2.99 29.9 Internally pulled VBST_ 30V, VLX_ VBST_ 30V, VLX_ From VCS1, VCS2 -100mV; RVPOS From CS1, VCS1, VCS2 +13mV, -113mV; RVPOS GND, 1.5V high, high VBST1 VBST2 72.5 77.5 CONDITIONS UNITS
On-Resistance High State VBST_
Note Specifications -40°C guaranteed design production tested.
Two-Phase Desktop Core Supply Controllers with Controlled Change
Typical Operating Characteristics
(VIN 12V, VOUT 1.45V, +25°C, unless otherwise noted.)
EFFICIENCY LOAD CURRENT 1.45V OUTPUT
MAX1937 toc01
MAX1937/MAX1938/MAX1939
EFFICIENCY LOAD CURRENT 1.85V OUTPUT
MAX1937 toc02
FREQUENCY LOAD CURRENT
MAX1937 toc03
FREQUENCY (kHz)
EFFICIENCY
EFFICIENCY
VOUT 1.45V LOAD CURRENT
VOUT 1.85V LOAD CURRENT
VOUT 1.45V
LOAD CURRENT
FREQUENCY INPUT VOLTAGE
MAX1937 toc04
FREQUENCY TEMPERATURE
FREQUENCY (kHz) VOUT 1.45V ILOAD
MAX1937 toc05
FREQUENCY (kHz) ILOAD ILOAD
VOUT 1.45V
INPUT VOLTAGE
TEMPERATURE (°C)
INPUT CURRENT INPUT VOLTAGE
MAX1937 toc06
CURRENT VOLTAGE
MAX1937 toc07
1.80 1.75 CURRENT (mA) 1.70 1.65 1.60 1.55
INPUT CURRENT (µA)
VOUT 1.45V INPUT VOLTAGE
1.50 VOLTAGE
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Typical Operating Characteristics (continued)
(VIN 12V, VOUT 1.45V, +25°C, unless otherwise noted.)
CURRENT VOLTAGE SHUTDOWN
CURRENT (mA) VOUT VOLTAGE VID_ CONNECTED 1.350 LOAD CURRENT 1.375 1.400 RVPOS 120k
MAX1937 toc08
OUTPUT VOLTAGE LOAD CURRENT 1.45V OUTPUT
MAX1937 toc09
1.450
1.425 RVPOS 90.9k
CURRENT SHARING
MAX1937 toc10
CURRENT SHARING
MAX1937 toc11
INDUCTOR CURRENTS VOUT 1.45V +25°C
INDUCTOR CURRENTS VOUT 1.45V +80°C
LOAD CURRENT
LOAD CURRENT
INDUCTOR CURRENT WAVEFORMS WITH LOAD
MAX1937 toc12
INDUCTOR CURRENT WAVEFORMS WITH LOAD
MAX1937 toc13
OUTPUT RIPPLE VOLTAGE: 20mV/div
OUTPUT RIPPLE VOLTAGE: 20mV/div OUTPUT INDUCTOR CURRENTS: 10A/div
2µs/div
OUTPUT INDUCTOR CURRENTS: 10A/div VOUT 1.45V IOUT
VOUT 1.45V IOUT 2µs/div
Two-Phase Desktop Core Supply Controllers with Controlled Change
Typical Operating Characteristics (continued)
(VIN 12V, VOUT 1.45V, +25°C, unless otherwise noted.)
LOAD TRANSIENT
MAX1937 toc14
MAX1937/MAX1938/MAX1939
SOFT-START WAVEFORMS WITH LOAD
MAX1937 toc15
OUTPUT VOLTAGE: 50mV/div
SIGNAL OUTPUT VOLTAGE: 0.5V/div
INDUCTOR CURRENTS: 10A/div
TRANSIENT CONTROL SIGNAL: 47pF 91.1k 40µs/div 1ms/div
INDUCTOR CURRENT: 10A/div ENABLE SIGNAL
SOFT-START WAVEFORMS WITH LOAD
MAX1937 toc16
SHUTDOWN WAVEFORM WITH LOAD
MAX1937 toc17
SIGNAL OUTPUT VOLTAGE: 0.5V/div INDUCTOR CURRENT: 10A/div
SIGNAL OUTPUT VOLTAGE: 0.5V/div
INDUCTOR CURRENT: 10A/div ENABLE SIGNAL 1ms/div 20ms/div ENABLE SIGNAL
SHUTDOWN WAVEFORM WITH LOAD
MAX1937 toc18
CURRENT-SENSE THRESHOLD VILIM
SIGNAL CURRENT-SENSE THRESHOLD (mV) VILIM +25°C +80°C OUTPUT VOLTAGE: 0.5V/div INDUCTOR CURRENT: 10A/div
MAX1937 toc19
ENABLE SIGNAL 20ms/div
VOUT 1.45V
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Typical Operating Characteristics (continued)
(VIN 12V, VOUT 1.45V, +25°C, unless otherwise noted.)
CODE CHANGE ON-THE-FLY WITH LOAD 1.2V 1.45V 1.2V
MAX1937 toc20
CODE CHANGE ON-THE-FLY WITH LOAD 1.2V 1.45V 1.2V
MAX1937 toc21
SIGNAL
SIGNAL
OUTPUT VOLTAGE: 200mV/div CODE CHANGE CONTROL SIGNAL
OUTPUT VOLTAGE: 200mV/div
CONTROL SIGNAL
40µs/div
40µs/div
REFERENCE VOLTAGE TEMPERATURE
MAX1937 toc22
VOLTAGE TEMPERATURE
MAX1937 toc23
2.000
0.810
REFERENCE VOLTAGE
1.998
0.805 1.996 VOLTAGE VOUT 0.8V 0.800
1.994 VOUT 1.45V LOAD
1.992
0.795 LOAD 0.790
1.990 TEMPERATURE (°C)
TEMPERATURE (°C)
VOLTAGE TEMPERATURE
MAX1937 toc24
1.465
1.460 VOLTAGE
1.455
VOUT 1.45V
1.450 LOAD 1.445 TEMPERATURE (°C)
Two-Phase Desktop Core Supply Controllers with Controlled Change
Description
NAME VID0 VID1 TIME VID2 VID3 VID4 VPOS ILIM GNDS FUNCTION Voltage Identification Input Table Internal 100k pullup resistor VDD. Voltage Identification Input Table Internal 100k pullup resistor VDD. Connect external resistor (47k 470k) change slew-rate control. Voltage Identification Input Table Internal 100k pullup resistor VDD. Voltage Identification Input Table Internal 100k pullup resistor VDD. Voltage Identification Input Table Internal 100k pullup resistor VDD. Voltage Positioning. Connect resistor between VPOS output voltage-positioning droop, connect directly output voltage positioning. Connect 47pF capacitor from VPOS GND. Analog Power-Supply Input. Connect supply VDD. Current-Limit Threshold Phase. Connect ILIM default current limit 120mV, connect voltage-divider from adjust current limit. Setting Current Limit section. Ground Remote Ground Sense. Connect GNDS output ground load. applications, also connect resistor from GNDS PGND locally. Reference Output. Connect 0.1µF capacitor from GND. Enable Input. Leave unconnected drive high normal operation. Drive shutdown. Remote Feedback Sense. Connect output load. applications, also connect resistor from output locally. Power-Good Output. Open-drain output high impedance when output regulation pulled when output deviates more than 12.5% from voltage code. PWRGD also shutdown during fault condition. logic output, connect pullup resistor from PWRGD logic supply. High-Side MOSFET Gate-Driver Bootstrap Input. Connect 0.22µF higher value bypass capacitor from BST2 LX2. Keep trace length short possible. Connect Schottky diode between BST2 VLG. Selecting Capacitor section. High-Side MOSFET Gate-Drive Output. Connect high-side MOSFET gate. pulled shutdown. Inductor Connection. Connect switched side inductor. Negative Current-Sense Input. Connect current-sense resistor series with low-side MOSFET, connect low-side MOSFET's on-resistance current sensing. Low-Side MOSFET Gate-Driver Output. Connect low-side MOSFET gate. pulled shutdown. Power Ground. Connect power ground point where current-sense resistors low-side MOSFET sources connect. PGND used positive current-sense connection.
MAX1937/MAX1938/MAX1939
PWRGD
BST2
PGND
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Description (continued)
NAME FUNCTION Driver Power-Supply Input. Connect 4.5V 6.5V supply powering low-side MOSFET gate drive, bootstrap circuit driving high-side MOSFETs. Ensure that VVLG greater than equal VVDD. Low-Side MOSFET Gate-Driver Output. Connect low-side MOSFET gate. pulled shutdown. Negative Current-Sense Input. Connect current-sense resistor series with low-side MOSFET connect low-side MOSFET's on-resistance current sensing. Inductor Connection. Connect switched side inductor. High-Side MOSFET Gate-Drive Output. Connect high-side MOSFET gate. pulled shutdown. High-Side MOSFET Gate-Driver Bootstrap Input. Connect 0.22µF higher value bypass capacitor from BST1 LX1. Keep trace length short possible. Connect Schottky diode between BST1 VLG. Selecting Capacitor section. Input Voltage Sense. Connect input supply high-side MOSFET drain. voltage sensed used on-time.
BST1
Detailed Description
MAX1937/MAX1938/MAX1939 family synchronous, two-phase step-down controllers capable delivering load currents 60A. controllers Quick-PWM control architecture conjunction with active load current voltage positioning. Quick-PWM control provides instantaneous load-step response, while programmable voltage positioning allows converter utilize full transient regulation limits, reducing output capacitance requirement. Furthermore, phases operate 180° out-of-phase with effective 500kHz switching frequency, thus reducing input output current ripple, well reducing input filter capacitor requirements. MAX1937/MAX1938/MAX1939 compliant with Hammer, Intel 9.0/VRM 9.1, Athlon Mobile code specifications (see Table codes). internal provides ultra-high accuracy ±0.75%. controlled voltage transition implemented minimize both undervoltage overvoltage overshoot during input change. Remote sensing available high output-voltage accuracy. MOSFET switches driven with gate-drive circuit minimize switching crossover conduction losses achieve efficiency high 90%. MAX1937/MAX1938/ MAX1939 feature cycle-by-cycle current limit ensure current limit exceeded. Crowbar protection available protect against output overvoltage.
On-Time One-Shot
heart Quick-PWM core one-shot that sets high-side switch on-time. This fast, low-jitter, one-shot circuitry varies on-time response input output voltages. high-side switch on-time inversely proportional voltage applied directly proportional output voltage. This algorithm results nearly constant switching frequency, despite lack fixed-frequency clock generator. benefits constant switching frequency twofold: frequency selected avoids noise-sensitive regions, inductor ripple current operating point remains relatively constant, resulting easy design methodology predictable output voltage ripple: VOUT VDROP VVCC
where constant VDROP voltage drop across low-side MOSFET's on-resistance plus drop across current-sense resistor (VDROP 75mV), used. on-time one-shot good accuracy operating point specified Electrical Characteristics. Ontimes operating points removed from conditions specified Electrical Characteristics vary over wide range. example, regulators slower with input voltages greater than because very short on-times required.
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Table Programmed Output Voltage
VID4 VID3 VID2 VID1 VID0 VOUT MAX1937 1.550 1.525 1.500 1.475 1.450 1.425 1.400 1.375 1.350 1.325 1.300 1.275 1.250 1.225 1.200 1.175 1.150 1.125 1.100 1.075 1.050 1.025 1.000 0.975 0.950 0.925 0.900 0.875 0.850 0.825 0.800 Shutdown MAX1938 1.850 1.825 1.800 1.775 1.750 1.725 1.700 1.675 1.650 1.625 1.600 1.575 1.550 1.525 1.500 1.475 1.450 1.425 1.400 1.375 1.350 1.325 1.300 1.275 1.250 1.225 1.200 1.175 1.150 1.125 1.100 Shutdown MAX1939 2.000 1.950 1.900 1.850 1.800 1.750 1.700 1.650 1.600 1.550 1.500 1.450 1.400 1.350 1.300 Shutdown 1.275 1.250 1.225 1.200 1.175 1.150 1.125 1.100 1.075 1.050 1.025 1.000 0.975 0.950 0.925 Shutdown
Note: above table, zero indicates VID_ connected driven low, indicates VID_ driven high connected.
While on-time input output voltage, other factors contribute switching frequency. on-time guaranteed Electrical Characteristics influenced switching delays external high-side MOSFET. Resistive losses inductor, both MOSFETs, output capacitor ESR, board copper losses
output ground, tend raise switching frequency higher output currents. Switch dead-time also increase effective on-time, reducing switching frequency. This effect occurs when inductor current reverses light negative load currents. With reversed inductor current, inductor's
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
causes high earlier than normal, extending on-time period equal rising dead-time. When controller operates continuous mode, dead-time longer factor, actual switching frequency VOUT VDROP1 (VVCC VDROP1 VDROP2 Once regulation achieved, controller returns 180° out-of-phase operation. minimum current-adaptive phase-selection algorithm used determine which phase used start first out-of-phase cycle. Once output voltage returns nominal output voltage regulation value, subsequent cycle starts with phase that lowest inductor current. example, current-sense inputs indicate that phase lower inductor current than phase controller turns phase high-side MOSFET first when returning normal operation.
where VDROP1 parasitic voltage drops inductor discharge path, including synchronous rectifier, inductor, board resistances; VDROP2 resistances charging path, including high-side MOSFET, inductor, board resistances.
Differential Voltage Sensing Error Comparator
MAX1937/MAX1938/MAX1939 differential sensing output voltage achieve highest possible accuracy output voltage. This allows error comparator sense actual voltage load, that controller compensate losses power output ground lines. GNDS used differential output voltage sensing. controller triggers next cycle (turn high-side MOSFET) when error comparator (VFB VGNDS less than regulation voltage), below current-limit threshold, minimum off-time one-shot timed out. Traces from GNDS should routed close each other away possible from sources noise (such inductors high di/dt traces). noise these connections cannot prevented, then filters. filter connect series resistor from positive sense trace connect 1000pF capacitor from right pin. GNDS, connect series resistor from negative sense trace GNDS, connect 1000pF capacitor from GNDS GNDS pin. applications, connect resistor from output locally board), connect resistor from GNDS PGND locally board). GNDS also connect output load (off board, microprocessor). This provides benefits differential output voltage sensing mentioned above safety regulating output voltage board case external sense connections disconnected.
Synchronized 2-Phase Operation
phases MAX1937/MAX1938/MAX1939 operate 180° out-of-phase reduce input filtering requirements, reduce electromagnetic interference (EMI), improve efficiency. This effectively lowers cost saves board space, making MAX1937/ MAX1938/MAX1939 ideal cost-sensitive applications. With dual synchronized out-of-phase operation, MAX1937/MAX1938/MAX1939s' high-side MOSFETs turn 180° out-of-phase. instantaneous input current peaks both regulators overlap, resulting reduced input voltage ripple ripple current. This reduces input capacitance requirement, allowing fewer less expensive capacitors, reduces shielding requirements EMI. 180° out-of-phase waveforms shown Typical Operating Characteristics. Each phase operates with 250kHz switching frequency. Since regulators operate 180° out-of-phase, effective switching 500kHz seen input output. addition being higher frequency (compared single-phase regulator), both input output ripple have lower amplitude.
Phase Overlap
minimize crosstalk noise phases, maximum duty cycle MAX1937/MAX1938/ MAX1939 less than 50%. provide fast transient response, these devices have phase-overlap mode that allows phases operate phase when heavy-load transient detected. In-phase operation continues until output voltage returns nominal output voltage regulation value.
External Linear Regulator
linear regulator (U2) used step down main supply. output this linear regulator connected provide power low-side gate drive bootstrap circuit. Using this supply improves efficiency providing stronger gate drive than supply. reduce switching noise VLG,
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
INPUT: 10µF CERAMIC CAPACITORS TAIYO YUDEN TMK432BJ106MM 100µF OS-CON SANYO 16SP100M IRLR7811W 0.66µH VOUT OUTPUT 0.8V 1.55V
KA78M06 2.2µF
CVLG
CBST1 0.22µF
CENTRAL CMHD4448 2.2µF 2.2µF
CVDD 0.01µF RTIME 120k
VID0 VID1 VID2 VID3 VID4
VID0 VID1 VID2 VID3 VID4 MAX1937
BST1
CENTRAL CMPSH-3A
SUMIDA CDEP134-6 FAIRCHILD ISL9N303AS3ST RCS1
PGND BST2
CBST2 0.22µF
RCS2 FAIRCHILD ISL9N303AS3ST 0.66µH SUMIDA CDEP134-6 1RLR7811W
CVPOS 47pF CREF 0.47µF RVPOS 51.1k
TIME
VPOS
200k
ILIM GNDS
GNDS
PWRGD
100k 390µF SP-CAP PANASONIC EEFUE0D391XR CERAMIC CAPACITORS TAIYO YUDEN LMK212BJ105MG PWRGD COUT
Figure MAX1937 Application Circuit
connect capacitor (CVLG) from PGND. Place this capacitor close possible pin. MAX1937/MAX1938/MAX1939 also require external supply connected VDD. diode with forward voltage drop about (D1) used stepdown supply power shown Figure diode connects between linear regulator output filter used filter voltage (R1, CVDD, C3). board layout, place CVDD close possible pin.
High-Side Gate-Drive Supply (BST_)
drive voltage high-side MOSFETs generated using bootstrap circuit. capacitor, CBST_, should sized properly minimize ripple voltage switching. ripple voltage should less than 200mV. more information selecting capacitors circuit, Selecting Capacitor section. minimize forward voltage drop across bootstrap diodes (D2), Schottky diodes. recommended value boost capacitors (CBST_) 0.22µF.
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
MOSFET Drivers
drivers optimized driving large high-side larger low-side MOSFETs N4). This consistent with duty-cycle operation controller. low-side drive waveform always complement high-side drive waveform, with fixed dead-time between MOSFET turning other turning prevent cross-conduction shoot-through current. internal transistor that drives robust with (typ) on-resistance. This helps prevent from being pulled during fast rise time node capacitive coupling from drain gate low-side synchronous-rectifier MOSFET. However, some combinations high-side low-side MOSFETs cause excessive gate-drain coupling, leading poor efficiency, EMI, shoot-through currents. This often remedied adding resistor (typically less than series with BST_, which increases turn-on time high-side MOSFET without degrading turn-off time.
Current Balancing
current balancing between phases depends accuracy current-sense elements offset current-balance amplifier. maximum offset current-balance amplifier (VCBOFFSET) ±3mV. current-balance accuracy calculated from: Current-balance accuracy VCBOFFSET RCS) where peak inductor current value current-sense resistor. current-balance accuracy most important full load. With load current 25A) current-sense resistors, worst-case current-balance accuracy Current-balance accuracy 0.003 0.002) on-resistance low-side MOSFETs used current sensing, part-to-part variation MOSFET on-resistance significant factor current balance. matching between MOSFETs should order 15%, worst case. Thus, even current-balance amplifier offset, DC-current balance could 15%. practice, little help received from thermal ballasting MOSFETs. That say, positive temperature coefficient on-resistance MOSFETs reduces mismatch current between phases.
Current-Limit Circuit
MAX1937/MAX1938/MAX1939 either onresistance low-side MOSFETs current-sense resistor monitor inductor current. Using lowside MOSFETs' on-resistance current-sense element provides lossless inexpensive solution ideal high-efficiency cost-sensitive applications. disadvantage this method that on-resistance MOSFETs vary from part part, overtemperature, which means cannot counted high accuracy. high accuracy needed, current-sense resistors, which provide accurate current limit under conditions reduce efficiency slightly because power lost resistors. current-limit circuit employs "valley" currentsensing algorithm monitor inductor current. current-sense signal does drop below currentlimit threshold, controller does initiate cycle. This limits maximum value IVALLEY current current-limit threshold (Figure current-limit threshold adjustable over wide range, allowing range current-sense resistor values. voltage ILIM sets current-limit threshold between PGND VILIM. 10mV 200mV adjustment range corresponds ILIM voltages from 100mV ILIM voltage resistor-divider between GND. Setting Current Limit section details.
Voltage Positioning (VPOS)
During load transient, output voltage instantly changes output capacitors times change load current (VOUT -ESRCOUT ILOAD). Conventional DC-DC converters respond regulating output voltage back nominal state after load transient occurs (Figure However, requires that output voltage remain within specific voltage band. Dynamically positioning output voltage allows fewer output capacitors reduces power consumption under heavy load. conventional (nonvoltage-positioned) circuit, total output voltage deviation from light load full load back light load VP-P1 (ESRCOUT ILOAD) VSAG VSOAR where SOAR defined Output Capacitor Selection section. Setting converter regulate lower voltage when under load allows larger voltage step when output current suddenly decreases. total voltage change voltage-positioned circuit VP-P2 (ESRCOUT ILOAD) VSAG +VSOAR
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
VOLTAGE POSITIONING OUTPUT
IPEAK 1.4V ILOAD INDUCTOR CURRENT
IVALLEY 1.4V
TIME
CONVENTIONAL CONVERTER (50mV/div) VOLTAGE-POSITIONED OUTPUT (50mV/div)
Figure Inductor Current Waveform
Figure Voltage-Positioning Nonvoltage-Positioning Waveforms
maximum allowable voltage change during transient fixed supply range (VP-P1 VP-P2). This means that voltage-positioned circuit tolerates twice output capacitors. Because specification achieved paralleling several capacitors, fewer capacitors needed voltage-positioned circuit. Figure shows transient response regions. additional benefit voltage positioning reduced power consumption high-load currents. Because output voltage lower under heavy load, draws less current. result lower power dissipation CPU.
case shutdown code, only held low. rest controller enabled. When driven high, startup sequence begins. Once reference voltage rises above 1.6V UVLO threshold, controller begins switching starts ramp output voltage. output voltage ramped 25mV steps every 50µs until output reaches nominal output voltage.
Fault Conditions
MAX1937/MAX1938/MAX1939 contain internal circuitry protect themselves surrounding circuitry from damage from output overvoltage output undervoltage conditions. When either these conditions occurs, pulled low, driven high, PWRGD pulled low. These pins remain this state until either power cycled toggled high-low-high.
Voltage Reference (REF)
reference provided MAX1937/MAX1938/ MAX1939 through pin. capable sourcing sinking 50µA. addition providing reference used setting current limit voltage positioning. Connect 0.47µF capacitor from GND. This capacitor should placed close possible pin. UVLO provided reference voltage. reference voltage must rise above 1.600V activate controller. controller disabled reference voltage falls below 1.584V.
Setting Output Voltage (VID_)
internal used output regulation voltage. 5-bit code inputs VID0-VID4 used specify output voltage. Some codes disable output. There internal 100k pullup resistor each VID_ inputs. Connecting VID_ sets logic (0); connecting VID_ leaving unconnected sets logic high (1). external pullup resistors speed low-tohigh logic transition, lower logic voltages. Table list codes corresponding output regulation voltages each parts. VID_ codes MAX1937 comply with Hammer code. VID_ codes MAX1938
Enable Input (EN) Soft-Start
When low, held (turning MOSFETs), leaving high impedance. addition, reference turned PWRGD pulled low. shutdown, total current consumption about 50µA (typ).
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
CAPACITIVE SOAR (dV/dt IOUT/COUT) VOLTAGE STEP (ISTEP RESR)
Design Procedure
Output Inductor Selection
most applications, inductor value 0.5µH recommended. inductance desired amount inductor current ripple (LIR). larger inductance value minimizes output ripple current increases efficiency, slows transient response. best compromise size, cost, efficiency, recommended (LIR 0.4). inductor value found from:
VOUT
CAPACITIVE (dV/dt IOUT/COUT)
RECOVERY
ILOAD
VOUT VOUT
ILOAD(MAX)
Figure Transient Response Regions
Intel 9.0/9.1 Athlon. MAX1939 Athlon Mobile.
where actual switching frequency phase. selected inductor should have lowest possible equivalent resistance saturation current greater than peak inductor current (IPEAK). IPEAK found from: IPEAK ILOAD(MAX)
VID_ Change Slew Rate (TIME)
MAX1937/MAX1938/MAX1939 allow VID_ code changed while converter operating (on-thefly). slew rate which output voltage changing controlled through TIME. slew rate adjusted externally connecting 470k resistor (RTIME) from TIME GND. slew rate, select RTIME resistor using following equation: RTIME
Output Capacitor Selection
output capacitor must have enough meet output ripple load-transient requirements. Also, capacitance value must high enough absorb inductor energy going from full-load no-load condition without tripping circuit. core power supplies other applications where output subject large load transients, output capacitor's size typically depends much needed prevent output from dipping under load transient. Ignoring finite capacitance: RESR VSTEP(MAX) ILOAD(MAX) actual capacitance value required relates physical size needed achieve ESR, well chemistry capacitor technology. Thus, capacitor usually selected voltage rating rather than capacitance value (this true OSCONs, capacitors, POSCAPs, other electrolytic capacitors). Generally, ceramic capacitors recommended bulk output capacitance make excellent high-frequency decoupling capacitors. Once enough capacitance added meet overshoot requirement, undershoot rising load edge
where slew rate output voltage V/µs. output voltage stepped down 25mV steps until reaches voltage code.
Power-Good Output (PWRGD)
PWRGD open-drain output that pulled when output voltage deviates more than 12.5% from regulation voltage (set VID_ inputs). PWRGD pulled shutdown, input UVLO, during startup. fault condition forces PWRGD until fault cleared, reset cycling power momentarily toggling logic-level output voltages, connect external pullup resistor between PWRGD logic power supply. 100k resistor works well most applications.
Two-Phase Desktop Core Supply Controllers with Controlled Change
(VSAG) longer problem. amount overshoot from stored inductor energy calculated VSOAR I2PEAK COUT VOUT tems that powered from very impedance sources. Multiple smaller value capacitors used parallel satisfy capacitance requirements.
MAX1937/MAX1938/MAX1939
Selecting Capacitor
capacitors must large enough handle gate-charging requirements high-side MOSFETs. most applications, 0.22µF ceramic capacitors recommended. capacitors needed keep voltage BST_ pins from dropping much when high-side MOSFET gates charged. capacitor value that prevents VBST_ from dropping more than 100mV 200mV adequate. capacitance needed BST_ capacitor calculated from: CBST VBST
where IPEAK peak inductor current. undershoot rising load edge load transient calculated from:
I2LOAD OFF(MIN) VSAG (VIN VOUT COUT VOUT OFF(MIN)
where ILOAD change load current, 4µs. ensure stability, make sure that zero frequency created output capacitance, output capacitor exceed 50kHz. zero frequency found from: fzESR ESRCOUT COUT
where total gate charge high-side MOSFET VBST_ amount that voltage BST_ drops when gate charged. using multiple MOSFETs parallel, gate charges QGH.
Setting Current Limit
Current limit sets maximum value inductor "valley" current. IVALLEY calculated from following equation: IVALLEY ILOAD(MAX)
Currently, aluminum electrolytic, Sanyo POSCAP, Panasonic capacitors have zero frequencies well below 50kHz. When using ceramic capacitors, might necessary series resistance ensure that zero below 50kHz.
Input Capacitor Selection
input capacitor reduces peak currents drawn from power source reduces noise voltage ripple input caused circuit's switching. input capacitor must meet ripple current requirement (IRMS) imposed switching currents defined following equation: IRMS LOAD VOUT (VIN VOUT
current-limit threshold (ILIMIT) must higher than valley current: ILIMIT IVALLEY current-limit threshold voltage ILIM value current-sense resistors: ILIMIT VILIM
maximum value when input voltage equals twice output voltage IRMS(MAX) ILOAD most applications, nontantalum capacitors (ceramic, aluminum electrolytic, polymer, OS-CON) preferred input because their robustness with high inrush currents typical sys-
where VILIM voltage ILIM (0.1V value current-sense resistor. on-resistance low-side MOSFET used current sensing, then maximum value on-resistance (overtemperature part-to-part variation) must used RCS.
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
VILIM from 0.5V connecting ILIM resistor-divider from GND. Select resistors such that current through divider least 5µA: 400k typical value 200k; then solve using: VILIM VILIM PD(HS)COND VOUT I2LOADMAX RDS(ON)
where RDS(ON) on-resistance high-side MOSFET input voltage. minimize conduction losses, select MOSFET with RDS(ON). Switching losses also major contributor power dissipation high-side MOSFET. Switching losses difficult precisely calculate should measured circuit. estimate switching losses, following equation: PD(HS)SW (IPEAK fall IVALLEY trise where IPEAK IVALLEY maximum peak valley inductor currents, tFALL tRISE fall rise times high-side MOSFET, switching frequency (about 250kHz). total power dissipated high-side MOSFET then found from: PD(HS) PD(HS)COND PD(HS)SW power dissipation low-side MOSFET highest duty cycles (high input voltage, output voltage), mainly because conduction losses: I2LOADMAX PD(LS)COND RDS(ON) Switching losses low-side MOSFET small because voltage being clamped body diode. Switching losses estimated from: PD(LS)SW LOADMAX where ILOADMAX/2 maximum average inductor current, time/cycle that low-side MOSFET conducts through body diode, forward voltage drop across body diode. total power dissipation low-side MOSFET PD(LS) PD(LS)COND PD(LS)SW
Setting Voltage Positioning
Voltage positioning dynamically changes outputvoltage point response load current. When output loaded, signals back from current-sense inputs adjust output voltage point, thereby decreasing power dissipation. load-transient response this control loop extremely fast well controlled, amount voltage change accurately confined within limits stipulated microprocessor power-supply guidelines. understand benefits dynamically adjusting output voltage, Voltage Positioning (VPOS) section. amount output voltage change adjusted external gain resistor (RVPOS). Connect RVPOS between VPOS. output voltage changes response load current follows: VOUT VVID gm(VPOS) RVPOS where VVID programmed output voltage code (Table voltage-positioning transconductance (gm(VPOS)) typically 20µS. value current-sense resistor connected from PGND. on-resistance low-side MOSFETs used instead current-sense resistors current sensing, then maximum on-resistance low-side MOSFETs equation above.
MOSFET Power Dissipation
Power dissipation high-side MOSFET worst high duty cycles (maximum output voltage, minimum input voltage). major factors contribute highside power dissipation, conduction losses, switching losses. Conduction losses because current flowing through resistance, calculated from:
Power Dissipation
During normal operation, power dissipation controller mostly from gate drivers. This calculated from following equation: PGATE VVLG QGL)
Two-Phase Desktop Core Supply Controllers with Controlled Change
where approximately 250kHz, gate charge high-side MOSFET, gate charge low-side MOSFET. values used gate charge gate drive voltage (VVLG). above equation phases converter. multiple MOSFETs used parallel, gate charges each MOSFET find total gate charge used above equation. Make sure that maximum power dissipation exceeded (see Absolute Maximum Ratings). rent traces short wide reduce resistance these traces. Also make gate-drive connections (DH_ DL_) short wide, measuring squares (50mils 100mils wide MOSFET from controller IC). Kelvin sense connections current-sense resistors. Place capacitor, capacitor, BST_ diode capacitor close possible from input capacitors, bypass with additional 0.1µF greater ceramic capacitor close pin. example board layout, refer MAX1937 MAX1938 evaluation kit.
MAX1937/MAX1938/MAX1939
Applications Information
Board Layout Guidelines
properly designed board layout important switching DC-DC converter circuit. possible, mount MOSFETs, inductor, input/output capacitors, current-sense resistor side board. Connect ground these devices close together power ground plane. Make other ground connections separate analog ground plane. Connect analog ground plane power ground single point. help dissipate heat, place high-power components (MOSFETs, inductor, current-sense resistor) large board area, heat sink. Keep high cur-
Chip Information
TRANSISTOR COUNT: 6243 PROCESS: BiCMOS
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Functional Diagram
ENABLE/ SHUTDOWN
BIAS
ON-TIME COMPUTE
ON-TIME ONE-SHOT TIME ONE-SHOT BST1
12.5%
12.5% PWRGD CONTROL LOGIC
PGND
BST2
VPOS
CURRENT BALANCE
ERROR UVLO/ OVLO
CURRENT LIMIT
GNDS
VID0-VID4
TIME
ILIM
Two-Phase Desktop Core Supply Controllers with Controlled Change
MAX1938 Typical Application Circuit
INPUT: 10µF CERAMIC CAPACITORS TAIYO YUDEN TMK432BJ106MM 330µF SANYO 25MV330WX
MAX1937/MAX1938/MAX1939
KA78M06
CVLG
2.2µF
CENTRAL CMHD4448 2.2µF 2.2µF
3X1RLR7811W CBST1 0.22µF
CVDD 0.01µF RTIME 120k
0.5µH VOUT OUTPUT 0.8V 1.55V
VID0 VID1 VID2 VID3 VID4
VID0 VID1 VID2 VID3 VID4 MAX1938
BST1
CENTRAL CMPSH-3A
TECHNOLOGIES HM73-40R50 FAIRCHILD 1SL9N303AS3ST RCS1
PGND BST2
CBST2 0.22µF 1RLR7811W
RCS2 FAIRCHILD 1SL9N303AS3ST 0.5µH TECHNOLOGIES HM73-40R50 1RLR7811W
CVPOS 47pF CREF 0.47µF RVPOS 51.1k
TIME
VPOS
200k
82.5k
ILIM GNDS
GNDS
PWRGD
100k 560µF/4V OS-CAN CAPACITORS SANYO SP560M CERAMIC CAPACITORS TAIYO YUDEN: LMK212BJ105MG PWRGD
Two-Phase Desktop Core Supply Controllers with Controlled Change MAX1937/MAX1938/MAX1939
Package Information
(The package drawing(s) this data sheet reflect most current specifications. latest package outline information, www.maxim-ic.com/packages.)
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
_Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600 2002 Maxim Integrated Products Printed registered trademark Maxim Integrated Products.

Two-Phase Desktop Core Supply Controllers with Controlled Change

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