MAX8664AEEP+ ,Low-Cost, Dual-Output, Step-Down Controller with Fast Transient ResponseApplicationsILIM2 ILIM1IN1Desktop and Notebook PCsOUT2 OUT1Graphic CardsDH2 DH1BST2 BST1ASIC/CPU/DS ..
MAX8664BEEP+ ,Low-Cost, Dual-Output, Step-Down Controller with Fast Transient ResponseELECTRICAL CHARACTERISTICS(V = 12V, R to GND = 56.1kΩ, REFIN2 = V , T = -40°C to +85°C, unless othe ..
MAX8668ETEQ+ ,1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual EnablesApplicationsMAX8667ETEAB+ T1633-4 AFICell Phones/SmartphonesMAX8667ETEAC+ T1633-4 AFMPDA and Palmto ..
MAX8668ETEX+T ,1.5MHz Dual Step-Down DC-DC Converters with Dual LDOs and Individual EnablesELECTRICAL CHARACTERISTICS(V = V = 3.6V, T = -40°C to +85°C, unless otherwise noted. Typical values ..
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MAX866ESA+ ,3.3V/5V or Adjustable Output, Single-Cell DC-DC ConvertersELECTRICAL CHARACTERISTICS(Circuit of Figure 2, V = 1.2V, I = 0mA, T = +25°C, unless otherwise note ..
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MAX8664AEEP+-MAX8664BEEP+
Low-Cost, Dual-Output, Step-Down Controller with Fast Transient Response
General DescriptionThe MAX8664 dual-output PWM controller is a low-cost,
high-performance solution for systems requiring dual
power supplies. It provides two individual outputs that
operate 180°out-of-phase to minimize input current
ripple, and therefore, capacitance requirements. Built-in
drivers are capable of driving external MOSFETs to
deliver up to 25A output current from each channel.
The MAX8664 operates from a 4.5V to 28V input volt-
age source and generates output voltages from 0.6V
up to 90% of the input voltage on each channel. Total
output regulation error is less than ±0.8% over load,
line, and temperature.
The MAX8664 operates with a constant switching fre-
quency adjustable from 100kHz to 1MHz. Built-in boost
diodes reduce external component count. Digital soft-
start eliminates input inrush current during startup. The
second output has an optional external REFIN2, facili-
tating tracking supply applications. Each output is
capable of sourcing and sinking current, making the
device a great solution for DDR applications.
The MAX8664 employs Maxim’s proprietary peak volt-
age-mode control architecture that provides superior
transient response during either load or line transients.
This architecture is easily stabilized using two resistors
and one capacitor for any type of output capacitors. Fast
transient response requires less output capacitance,
consequently reducing total system cost. The MAX8664B
latches off both controllers during a fault condition, while
the MAX8664A allows one controller to continue to func-
tion when there is a fault in the other controller.
ApplicationsDesktop and Notebook PCs
Graphic Cards
ASIC/CPU/DSP Power Supplies
Set-Top Box Power Supply
Printer Power Supply
Network Power Supply
POL Power Supply
Features±0.8% Output Accuracy Over Load and LineOperates from a Single 4.5V to 28V SupplySimple Compensation for Any Type of Output
CapacitorInternal 6.5V Regulator for Gate DriveIntegrated Boost DiodesAdjustable Output from 0.6V to 0.9 x VINDigital Soft-Start Reduces Inrush Current100kHz to 1MHz Adjustable Switching180°Out-of-Phase Operation Reduces Input
Ripple CurrentOvercurrent and Overvoltage ProtectionExternal Reference Input for Second ControllerPrebiased Startup Operation
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Ordering Information19-0796; Rev 0; 4/07
Note:This device operates over the -40°C to +85°C operating
temperature range.
+Denotes lead-free package.
Pin Configuration appears at end of data sheet.PART PIN-
PACKAGE PKG
CODE FAULT
ACTIONMAX8664AEEP+ 20 QSOP E20-1 Independent
MAX8664BEEP+ 20 QSOP E20-1 Joint
DH1
BST1
DL1
BST2
FB2FB1
LX1
PGND
DH2
LX2
DL2
GND
IN1OUT2
IN2
OSC/EN12
ILIM2
PWRGDREFIN2
VCC
ILIM1
MAX8664
OUT1
Typical Operating Circuit
EVALUATION KITAVAILABLE
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN= 12V, ROSC/EN12to GND = 56.1kΩ, REFIN2 = VCC, TA= -40°C to +85°C, unless otherwise noted. Typical values are at = +25°C.) (Note 2)
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 implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN to GND...........................................................…-0.3V to +30V
VL to GND...................................................................-0.3 to +8V
IN, BST_ to VL........................................................-0.3V to +30V
VCC, FB_, PWRGD to GND.......................................-0.3V to +6V
VL to VCC....................................................................-2V to +8V
PGND to GND.......................................................-0.3V to +0.6V
DL_ to PGND...............................................-0.3V to (VVL+ 0.3V)
DH_ to PGND............................................-0.3V to (VBST_+ 0.3V)
BST_ to GND.............................................................-0.3V to 38V
BST_ to LX................................................................-0.3V to +8V
LX_ to PGND.................-1V (-2.5V for < 50ns transient) to +30V
DH_ to LX_................................................-0.3V to (VBST_+ 0.3V)
ILIM_ to GND...............................................-0.3V to (VIN+ 0.3V)
ILIM_ to LX_............................................................-0.6V to +30V
OSC/EN12, REFIN2 to GND.....................-0.3V to (VVCC+ 0.3V)
VL Continuous Current..............................................125mARMS
VCCContinuous Current..............................................10mARMS
Continuous Power Dissipation (TA= +70°C) (Note 1)
20-Pin QSOP (derate 11.0mW/°C above +70°C).........884mW
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
PARAMETERCONDITIONSMINTYPMAXUNITS
SUPPLY VOLTAGES7.228.0IN Supply VoltageIN = VL = VCC4.55.5V
VL Output Voltage7.2V < VIN < 28V, 0 < IVL < 60mA6.106.66.75V
VCC Output Voltage7.2V < VIN < 28V, 0 < ICC < 5mA4.55.05.5V
Rising3.43.53.6VVCC Undervoltage Lockout
(UVLO)Hysteresis350mV
VIN = 12V, IIN0.0950.2Standby Supply CurrentOSC/EN12 not
connectedVCC = VIN = VVL = 5V, IIN + IVL + IVCC0.080.2mA
VIN = 12V, IIN1.42.5Operating Supply CurrentNo switching,
VFB_ = 0.65VVCC = VIN = VVL = 5V, IIN + IVL+ IVCC1.11.8mA
REGULATOR SPECIFICATIONSTA = 0°C to +85°C0.59550.6000.6045
Reference AccuracyTA = -40°C to +85°C0.59300.6000.6070V
TA = 0°C to +85°C0.59520.6000.6048VREFIN2 = VVCCTA = -40°C to +85°C0.59250.6000.6075FB_ Regulation Accuracy
VREFIN2 = 1.000V0.9951.0001.005
REFIN2 to Internal Reference
Switchover ThresholdNot to be switched during operation2VVCC -
VVCC -
0.3V
RE FIN 2 M axi m um P r og r am V ol tag e1.3V
REFIN2 Disable Threshold50mV
FB Input Bias CurrentVFB = 0.5V3nA
REFIN2 Bias CurrentVREFIN2 = 0.65V3nA
FB Propagation DelayFB rising to DH falling90ns
Note 1:Package mounted on a multilayer PCB.
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
PARAMETERCONDITIONSMINTYPMAXUNITS
PROTECTION FEATURESVFB1 rising0.75
Overvoltage Protection (OVP)
ThresholdVFB2 rising, VREFIN2 ≤ 1.3VREFIN2
+ 0.15
VREFIN2 = VVCC, VFB_ rising, MAX8664B
VFB1 rising, MAX8664A0.5000.5250.550VPower-Good (PWRGD) Threshold
Hysteresis5%
TA = +85oC60High-Side Current-Sense Program
Current (Note 3)TA = +25oC445060µA
TA = +25°C0.11.0ILIM LeakageTA = +85°C0.1µA
High-Side Current-Sense
Overcurrent Trip Adjustment Range0.050.40V
Internal Soft-Start TimeROSC/EN12 = 56.1kΩ, 400kHz2.5ms
RE FIN 2 Inter nal P ul l d ow n Resi stanceEngaged momentarily at startup1020Ω
Thermal-Shutdown ThresholdJunction temperature+160°C
DRIVER SPECIFICATIONSVVL = 6.5V1.352.1Sourcing current,
IDH = -50mAVIN = VVL = VVCC = 5V1.55
VVL = 6.5V0.91.4DH_ Driver Resistance
Sinking current,
IDH = 50mAVIN = VVL = VVCC = 5V1.0
VVL = 6.5V1.32Sourcing current,
IDL = -50mAVIN = VVL = VVCC = 5V1.5
VVL = 6.5V0.61.1DL_ Driver Resistance
Sinking current,
IDL = 50mAVIN = VVL = VVCC = 5V0.7
VVL = 6.5V132543Dead Time for Low-Side to
High-Side TransitionDL_ falling to DH_ risingVVL = 5V28ns
DH_ Minimum On-Time70108149ns
VBST - VLX = 7V, VLX = 28V, VFB_ = 0.55V1.252.3mABST CurrentOSC/EN12 not connected0.001µA
Internal Boost Switch Resistance6Ω
PWM CLOCK OSCILLATORPWM Clock-Frequency Accuracy-15+15%
PWM Clock-Frequency Adjustment
RangeROSC/EN12 = 226kΩ to 22.6kΩ1001000kHz
OSC/EN12 Disable Current1.52.5µA
ELECTRICAL CHARACTERISTICS (continued)(VIN= 12V, ROSC/EN12to GND = 56.1kΩ, REFIN2 = VCC, TA= -40°C to +85°C, unless otherwise noted. Typical values are at = +25°C.) (Note 2)
Note 2:Specifications at -40°C are guaranteed by design and not production tested.
Note 3:This current linearly compensates for the MOSFET temperature coefficient.
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
EFFICIENCY vs. LOAD CURRENT
(600kHz, FIGURE 2)MAX8664 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
VOUT = 2.5V
VOUT = 1.8V
NO LOAD ON THE
OTHER REGULATOR
EFFICIENCY vs. LOAD CURRENT
(1MHz, FIGURE 4)MAX8664 toc02
LOAD CURRENT (A)
EFFICIENCY (%)
VOUT1 = 2.5V
VOUT1 = 1.8V
VIN = 3.3V
VVL = 5V
NO LOAD ON OUT2
LOAD REGULATION
(600kHz, FIGURE 2)MAX8664 toc03
OUT1 LOAD CURRENT (A)
OUT1 VOLTAGE (%)68
IOUT2 = 8AIOUT2 = 4A
IOUT2 = 0A
POWER-UP WAVEFORMSMAX8664 toc08
VPRWGD
VOUT1
VOUT2
5V/div
2V/div
2V/div
10V/div
1ms/div
VIN
LINE REGULATION
(600kHz, FIGURE 2)MAX8664 toc04
INPUT VOLTAGE (V)
OUT1 VOLTAGE (%)
8A LOAD
NO LOAD
ROSC/EN12 vs. SWITCHING FRQUENCYMAX8664 toc05
OSC/EN12
(k
SWITCHING FREQUENCY (kHz)
OUT1 LOAD TRANSIENT (FIGURE 2)MAX8664 toc06
IOUT2
VOUT2
2A/div
100mV/div
20μs/div
2.5A2.5A5A
LOAD TRANSIENT
-3A TO +3A TO -3A (FIGURE 3)MAX8664 toc07
IOUT2
VOUT1
VOUT2
5A/div
50mV/div
50mV/div
100μs/div
-3A-3A
+3A
Typical Operating Characteristics(Circuit of Figure2, 600kHz, VIN= 12V, VOUT1= 2.5V, VOUT2= 1.8V, TA= +25°C, unless otherwise noted.)
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
POWER-DOWN WAVEFORMSMAX8664 toc09
VPRWGD
VOUT1
VOUT2
5V/div
2V/div
2V/div
10V/div
1ms/div
VIN
ENABLE WAVEFORMS (FIGURE 2)MAX8664 toc10
VPRWGD
VOUT1
VOUT2
5V/div
5V/div
2V/div
2V/div
1ms/div
ENABLE
ENABLE WAVEFORMS (FIGURE 4)MAX8664 toc11
VPRWGD
VOUT1
VOUT2
5V/div
5V/div
1V/div
1V/div
400μs/div
ENABLE
SWITCHING WAVEFORMSMAX8664 toc12
IL1
IL2
10V/div
10V/div
5A/div
5A/div
2μs/div
VLX1
VLX2
FEEDBACK VOLTAGE
vs. TEMPERATUREMAX8664 toc13
FEEDBACK VOLTAGE (mV)
TEMPERATURE (°C)
NO LOAD
SHORT-CIRCUIT WAVEFORMSMAX8664 toc14
IL1
IIN
5A/div
2V/div
2A/div
5V/div
10μs/div
VOUT1
VPRWGD
OVERVOLTAGE PROTECTIONMAX8664 toc15
VDH1
IL1
10V/div
5V/div
10A/div
10V/div
20μs/div
VOUT1
VDL1
Typical Operating Characteristics (continued)(Circuit of Figure2, 600kHz, VIN= 12V, VOUT1= 2.5V, VOUT2= 1.8V, TA= +25°C, unless otherwise noted.)
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Pin Description
PINNAMEFUNCTIONDH1High-Side MOSFET Driver Output for Controller 1. Connect DH1 to the gate of the high-side MOSFET. DH1 is
low in shutdown and UVLO.LX1
External Inductor Connection for Controller 1. Connect LX1 to the switching node of the MOSFETs and
inductor. Make sure LX1 is close to the source of the high-side MOSFET(s) to form a Kelvin connection for
high-side current sensing. LX1 is high impedance during monotonic startup and shutdown.BST1Boost Capacitor Connection for the High-Side MOSFET Driver for Controller 1. Connect a 0.22µF ceramic
capacitor from BST1 to LX1.DL1Low-Side MOSFET Driver Output for Controller 1. Connect DL1 to the gate of the low-side MOSFET(s) for
controller 1. DL1 is low in shutdown and UVLO.
5VL
Low-Side Gate Drive Supply and Output of the 6.5V Linear Regulator. Connect a 4.7µF ceramic capacitor from
VL to PGND. When using a 4.5V to 5.5V supply, connect VL to IN. VL is the input to the VCC supply. Do not
load VL when IC is disabled.PGNDPower Ground. Connect to the power ground plane. Connect power and analog grounds at a single point near
the output capacitor’s ground.DL2Low-Side MOSFET Driver Output for Controller 2. Connect DL2 to the gate of the low-side MOSFET(s) for
controller 2. DL2 is low in shutdown and UVLO.BST2Boost Capacitor Connection for the High-Side MOSFET Driver for Controller 2. Connect a 0.22µF ceramic
capacitor from BST2 to LX2.LX2
External Inductor Connection for Controller 2. Connect LX2 to the switching node of the MOSFETs and
inductor. Make sure LX2 is close to the source of the high-side MOSFET(s) to form a Kelvin connection for
high-side current sensing. LX2 is high impedance during monotonic startup and shutdown.DH2High-Side MOSFET Driver Output for Controller 2. Connect DH2 to the gate of the high-side MOSFET(s) for
controller 2. DH2 is low in shutdown and UVLO.ILIM2Current-Limit Set for Controller 2. Connect a resistor from the drain of the high-side MOSFET(s) to ILIM2. See
the Setting the Overcurrent Threshold section.FB2
Feedback Input for Controller 2. Connect FB2 to the center of a resistor-divider connected between the output
of controller 2 and GND to set the desired output voltage. VFB2 regulates to VREFIN2 or the internal 0.6V
reference. To use the internal reference, connect REFIN2 to VCC.REFIN2
External Reference Input for Controller 2. To use the internal 0.6V reference, connect REFIN2 to VCC. To use
an external reference, connect REFIN2 through a resistor (> 1kΩ) to a reference voltage between 0V and
1.3V. An RC lowpass filter is recommended when using an external reference and soft-start is not provided by
the external reference. For tracking applications, connect REFIN2 to the center of a resistor voltage-divider
between the output of controller 1 and GND (see Figure 3). Connect REFIN2 to GND to disable controller 2.OSC/EN12
Switching Frequency Set Input. Connect a 22.6kΩ to 226kΩ resistor from OSC/EN12 to GND to set the
switching frequency between 1000kHz and 100kHz. Connect a switch in series with this resistor for
enable/shutdown control. When the switch is open, the IC enters low-power shutdown mode. In shutdown,
OSC/EN12 is internally driven to approximately 800mV.INInternal 6.5V Linear Regulator Input. Connect IN to a 7.2V to 28V supply, and connect a 0.47µF or larger
ceramic capacitor from IN to PGND. When using a 4.5V to 5.5V supply, connect IN to VL.GNDAnalog Ground. Connect to the analog ground plane. Connect the analog and power ground planes at a
single point near the output capacitor’s ground.
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Pin Description (continued)
PINNAMEFUNCTIONVCC
Internal Analog Supply. VCC regulates to 1.5V below VVL. Connect a 1µF ceramic capacitor from VCC to GND.
When using a 4.5V to 5.5V supply, connect a 10Ω resistor from VCC to IN. VCC is used to power the IC’s
internal circuitry.PWRGD
Open-Drain Power-Good Output. PWRGD is high impedance when controllers 1 and 2 (using the internal
reference) are in regulation. PWRGD is low if the outputs are out of regulation, if there is a fault condition, or if
the IC is shut down. PWRGD does not reflect the status of output 2 in the MAX8664A or when REFIN2 is
connected to an external reference in the MAX8664B.FB1Feedback Input for Controller 1. Connect FB1 to the center of a resistor-divider connected between the output
of controller 1 and GND to set the desired output voltage. VFB1 regulates to 0.6V.ILIM1Current-Limit Set for Controller 1. Connect a resistor from the drain of the high-side MOSFET(s) to ILIM1. See
the Setting the Overcurrent Threshold section.
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient ResponseCONTROL
LOGIC
CONTROL
LOGIC
THERMAL
SHUTDOWN
THERMAL
SHUTDOWN
VOLTAGE
REFERENCE
BIAS
GENERATOR
OSCILLATOR
SHUTDOWN
CONTROL
LOGIC
UVLO
CIRCUITRY
FB1
REF1 - 0.1V
VCC
REFIN2
OSC/EN12
PGND
LX1
ILIM1
BST1
PWM
COMPARATOR 1
PWM
COMPARATOR 2
BST CAP
CHARGING SWITCH
BST CAP
CHARGING SWITCH
CURRENT-LIMIT
COMPARATOR
CURRENT-LIMIT
COMPARATOR
LX1
IF VREFIN2 > 2.0V
OPEN S1 AND CLOSE S2.
OTHERWISE, CLOSE S1
AND OPEN S2.
LX2
ILIM2
BST2
SOFT-START 1
FB2
0.6V
REF
CLOCK 1
DL1
50μA
50μA
DH1
DH2
DL2
LX2
FB1VL
VCCGND
FB2
REF2 - 0.1V
6.5V LDO
PWRGD4μA
REF2
REFEN
SHUTDOWN 1
SHUTDOWN 1
CLOCK 2
CLOCK 1
CLOCK 2
SOFT-START
SHUTDOWN 2
SHUTDOWN 2
REF
THERMAL
SHUTDOWN
50mV
ENABLE2
ENABLE
1.5V
Figure1. Functional Diagram
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Detailed DescriptionThe MAX8664 dual-output PWM controller is a low-cost
solution for dual power-supply systems. It provides two
individual outputs that operate 180°out-of-phase to
minimize input capacitance requirements. Built-in dri-
vers are capable of driving external MOSFETs to deliv-
er up to 25A of current from each output. The MAX8664
operates from a 4.5V to a 5.5V or a 7.2V to 28V input
and generates output voltages from 0.6V up to 90% of
the input voltage on each channel. Total output error is
less than ±0.8% over load, line, and temperature.
The MAX8664 operates with a constant switching fre-
quency adjustable from 100kHz to 1MHz. Built-in boost
diodes reduce external component count. Digital soft-
start eliminates input inrush current during startup. The
second output has an optional REFIN2 input that takes
an external reference voltage, facilitating tracking supply
applications. Each output is capable of sourcing and
sinking current. Internal 6.5V and 5V linear regulators
provide power for gate drive and internal IC functions.
The MAX8664 has built-in protection against output over-
voltage, overcurrent, and thermal faults. The MAX8664B
latches off both controllers during a fault condition, while
the MAX8664A allows one controller to continue to func-
tion when there is a fault in the other controller.
The MAX8664 employs Maxim’s proprietary peak-volt-
age mode control architecture that provides superior
transient response during either load or line transients.
This architecture is easily stabilized using two resistors
and one capacitor for any type of output capacitors.
Fast transient response requires less output capaci-
tance, consequently reducing total system cost.
DC-DC Controller ArchitectureThe peak-voltage mode PWM control scheme ensures
stable operation, simple compensation for any output
capacitor, and fast transient response. An on-chip inte-
grator removes any DC error due to the ripple voltage.
This control scheme is simple: when the output voltage
falls below the regulation threshold, the error compara-
tor begins a switching cycle by turning on the high-side
switch at the rising edge of the following clock cycle.
This switch remains on until the minimum on-time
expires and the output voltage is in regulation or the
current-limit threshold is exceeded. At this point, the
low-side synchronous rectifier turns on and remains on
until the rising edge of the first clock cycle after the out-
put voltage falls below the regulation threshold.
Internal Linear RegulatorsThe internal VL low-dropout linear regulator of the
MAX8664A and MAX8664B provides the 6.5V supply
used for the gate drive. Connect a 4.7µF ceramic
capacitor from VL to PGND. When using a 4.5V to 5.5V
input supply, connect VL directly to IN.
The 5V supply used to power IC functions (VCC) is gen-
erated by an internal 1.5V shunt regulator from VL.
Connect a 2.2µF ceramic capacitor from VCCto GND.
When using a 4.5V to 5.5V input supply, connect VCC
to IN through a 10Ωresistor.
High-Side Gate-Drive Supply (BST_)The gate-drive voltage for the high-side MOSFETs is
generated using a flying capacitor boost circuit. The
capacitor between BST_ and LX_ is charged to the VL
voltage through the integrated BST_ diode during the
low-side MOSFET on-time. When the low-side MOSFET
is switched off, the BST_ voltage is shifted above the
LX_ voltage to provide the necessary turn-on voltage
(VGS) for the high-side MOSFET. The controller closes
a switch between BST_ and DH_ to turn the high-side
MOSFET on.
Voltage ReferenceAn internal 0.6V reference sets the feedback regulation
voltage. Controller 1 always uses the internal reference.
An external reference input is provided for controller 2.
To use the external reference, connect a 0 to 1.3V sup-
ply to REFIN2. This facilitates tracking applications. To
use the internal 0.6V reference for controller 2, connect
REFIN2 to VCC.
Undervoltage Lockout (UVLO)When the VCCsupply voltage drops below the UVLO
threshold (3.15V falling typ), the undervoltage lockout
(UVLO) circuitry inhibits the switching of both con-
trollers, and forces the DL and DH gate drivers low.
When VCCrises above the UVLO threshold (3.5V rising
typ), the controllers begin the startup sequence and
resume normal operation.
Output Overcurrent ProtectionWhen the MAX8664 detects an overcurrent condition,
DH is immediately pulled low. If the overcurrent condition
persists for four consecutive cycles, the controller latch-
es off and both DH_ and DL_ are pulled low. During soft-
start, when FB_ is less than 300mV, the controller latches
off on the first overcurrent condition. The protection cir-
cuit detects an overcurrent condition by sensing the
drain-source voltage across the high-side MOSFET(s).
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient ResponseThe threshold that trips overcurrent protection is set by a
resistor connected from ILIM_ to the drain of the high-
side MOSFET(s). ILIM_ sinks 50µA (typ) through this
resistor. When the drain-source voltage exceeds the volt-
age drop across this resistor during the high-side
MOSFET(s) on-time, an overcurrent fault is triggered. To
prevent glitches from falsely tripping the overcurrent pro-
tection, connect a filter capacitor (0.01µF typically) in
parallel with the overcurrent-setting resistor.
Output Overvoltage Protection (OVP)During an overvoltage event on one or both of its out-
puts, the MAX8664 latches off the controller. This
occurs when the feedback voltage exceeds its normal
regulation voltage by 150mV for 10µs. In this state, the
low-side MOSFET(s) are on and the high-side MOS-
FET(s) are off to discharge the output. To clear the
latch, cycle EN or the input power.
Thermal-Overload ProtectionThermal-overload protection limits total power dissipa-
tion in the MAX8664. When the junction temperature
exceeds +160°C, an internal thermal sensor shuts down
the device, pulling DH_ and DL_ low for both controllers.
To restart the controller, cycle EN or input power.
Power-Good Output (PWRGD)PWRGD is an open-drain output that is pulled low when
the output voltage rises above the PWRGD upper
threshold or falls below the PWRGD falling threshold.
PWRGD is held low in shutdown, when VCCis below the
UVLO threshold, during soft-start, and during fault con-
ditions. PWRGD does not reflect the status of controller
2 in the MAX8664A, or when REFIN2 is connectedto an
external reference with either version. See Table1 for
PWRGD operation of the circuits of Figures 2–5 during
fault conditions. For logic-level output voltages, con-
nect an external pullup resistor between PWRGD and
the logic power supply. A 100kΩresistor works well in
most applications.
Fault-Shutdown ModesWhen an overvoltage or overcurrent fault occurs on one
controller of the MAX8664A, the second controller con-
tinues to operate. With the MAX8664B, a fault in one
controller latches off both controllers automatically, and
PWRGD is pulled low. See Table1 for the fault-shut-
down modes of the circuits shown in Figures 2–5.
Table1. Fault Shutdown Modes for Circuits of Figures 2–5
MAX8664A (INDEPENDENT)MAX8664B (JOINT)CIRCUITCONTROLLER 1 FAULTCONTROLLER 2 FAULTCONTROLLER 1 FAULTCONTROLLER 2 FAULTFigure 2,
Figure 5
(Independent)
Controller 2 remains on.
PWRGD is pulled low.
Controller 1 remains on.
PWRGD remains high.
Controller 2 is shut down.
PWRGD is pulled low.
Controller 1 is shut down.
PWRGD is pulled low.
Figure 3
(Tracking)
Controller 2 shuts down.
PWRGD is pulled low.
Controller 1 remains on.
PWRGD remains high.
Controller 2 is shut down.
PWRGD is pulled low.
Controller 1 is shut down.
PWRGD is pulled low.
Figure 4
(Sequenced)
Controller 2 shuts down.
PWRGD is pulled low.
Controller 1 remains on.
PWRGD remains high.
Controller 2 is shut down.
PWRGD is pulled low.
Controller 1 is shut down.
PWRGD is pulled low.
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient ResponseMAX8664
ILIM1
C20
10μF
DH1C17
1μF
C18
1μF
LX1
BST1
DL1
PGND
ILIM2
DH2
LX2
BST2
ENABLE
OFFDL2
FB1
INPUT
10.8V TO 13.2V
POWER-GOOD
TO SYSTEM
VCC
C19
0.01μF
51.1kΩ
L1
1μH
3.92kΩ
1.15kΩ
1500pF
OUT1
2.5V/8A
2.7kΩ
R10
39.2kΩ
VCC
REFIN2
C13
0.22μF
C25
680pF
R37
GND
PWRGD
10kΩ
2N7002
OSC/EN12
FB2
C14
4.7μF
10μF
1000μF
C23
0.1μF
47μF
47μF
47μF
C21
10μF
C16
0.01μF
3.92kΩ
R38
C26
680pFR8
1.82kΩ
L2
1μH
51.1kΩ
C12
1500μF
OUT2
1.8V/8A
3.01kΩ
C15
0.22μF
10μF
C22
0.1μF
C11
47μF
C10
47μF
47μF
C27
0.47μF
Figure 2. Low-Cost, 600kHz Typical Application Circuit
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient Response
Table2. Component List for Figure2
DESIGNATIONQTYDESCRIPTIONC1, C3,
C20, C21410µF ±20%, 16V X5R ceramic
capacitors (1206)1
1000µF ±20%, 16V electrolytic
capacitor (8mm diameter,
20mm height)
C5, C1221500pF, 50V C0G ceramic
capacitors (0603)
C6–C11647µF ±20%, 6.3V X5R ceramic
capacitors (1206)
C13, C1520.22µF ±10%, 25V X7R ceramic
capacitors (0603)
C1414.7µF ±10%, 6.3V X5R ceramic
capacitor (0805)
C16, C1920.01µF ±10%, 50V X7R ceramic
capacitors (0603)
C1711µF ±20%, 16V X5R ceramic
capacitor (0603)
C1811µF ±20%, 6.3V X5R ceramic
capacitor (0603)
C22, C2320.1µF ±20%, 16V X7R ceramic
capacitors (0603)
DESIGNATIONQTYDESCRIPTIONC25, C262680pF, 50V C0G ceramic capacitors
(0603)
C2710.47µF ±10%, 16V ceramic
capacitor (0603)
L1, L221µH inductors
TOKO FDV0630-1R0M
N1–N44n-channel MOSFETs (8-pin SO)
International Rectifier IRF78211n-channel MOSFET (SOT23)
Central 2N700212.74kΩ ±1% resistor (0603)1301kΩ ±1% resistor (0603)
R3, R6251.1kΩ ±1% resistors (0603)
R4, R723.92kΩ ±1% resistors (0603)11.15kΩ ±1% resistor (0603)11.82kΩ ±1% resistor (0603)110kΩ ±5% resistor (0603)
R10139.2kΩ ±1% resistor (0603)
R37, R3823Ω ±5% resistors (0805)1MAX8664 (20-pin QSOP)
MAX8664
Low-Cost, Dual-Output, Step-Down
Controller with Fast Transient ResponseFB1
PWRGD
VCC
GND
OSC/EN12
REFIN2
ILIM2
FB2
ILIM1
DH1
LX1
BST1
DL1
PGND
DH2
LX2
BST2
DL2
VCC
INPUT
10V TO 14V
POWER-GOOD
TO SYSTEM
ENABLE
OUT1
1.8V/20A
OUT2
0.9V/6A
1μF
1μF
C13
4.7μF
10kΩ
0.01μF
3.16kΩ
10μF
0.015μF
10kΩ
3.57kΩ
0.56μH
C15
0.01μF
0.47μH
R13
10kΩ
C19
4700pF
24.3kΩ
R11
14.7kΩ
2N7002
OUT1
1kΩ
1kΩ
C12
1000pF
R10
44.2kΩ
OFF
0.22μF
C18
0.22μF
C14
2200pF
10μF
1000μF
C16
10μF
C17
10μF
C11
10μF
470μF
C10
470μF
C22
10μF
C20
680μF
C21
680μFN4
2.74kΩ
MAX8664
R12
C23
2200pF
Figure3. 500kHz Tracking Circuit for DDR2 Applications
