MAX8643ETG+-MAX8643ETG+T Fast Delivery |IC PHOENIX CO.,LIMITED

MAX8643ETG+ ,3A, 2MHz Step-Down Regulator with Integrated SwitchesELECTRICAL CHARACTERISTICS(V = V = 3.3V, V = 0.5V, T = -40°C to +85°C. Typical values are at T = +2 ..
MAX8643ETG+T ,3A, 2MHz Step-Down Regulator with Integrated Switchesfeatures fixed-frequency PWM mode INoperation with a switching frequency range of 500kHz♦ Soft-Star ..
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MAX8643ETG+-MAX8643ETG+T
3A, 2MHz Step-Down Regulator with Integrated Switches
General Description
The MAX8643 high-efficiency switching regulator deliv-
ers up to 3A load current at output voltages from 0.6V
to (0.9 x VIN).The IC operates from 2.35V to 3.6V, mak-
ing it ideal for on-board point-of-load and postregula-
tion applications. Total output error is less than ±1%
over load, line, and temperature.
The MAX8643 features fixed-frequency PWM mode
operation with a switching frequency range of 500kHz
to 2MHz set by an external resistor. High-frequency
operation allows for an all-ceramic capacitor design.
The high operating frequency also allows for small-size
external components.
The low-resistance on-chip nMOS switches ensure high
efficiency at heavy loads while minimizing critical induc-
tances, making the layout a much simpler task with
respect to discrete solutions. Following a simple layout
and footprint ensures first-pass success in new designs.
The MAX8643 comes with a high-bandwidth (> 14MHz)
voltage-error amplifier. The voltage-mode control archi-
tecture and the voltage-error amplifier permit a type III
compensation scheme to be utilized to achieve maxi-
mum loop bandwidth, up to 20% of the switching fre-
quency. High loop bandwidth provides fast transient
response, resulting in less required output capacitance
and allowing for all-ceramic capacitor designs.
The MAX8643 provides two tri-state logic inputs to
select one of nine preset output voltages. The preset
output voltages allow customers to achieve ±1% out-
put-voltage accuracy without using expensive 0.1%
resistors. In addition, the output voltage can be set to
any customer value by either using two external resis-
tors at the feedback with 0.6V internal reference or
applying an external reference voltage to the REFIN
input. The MAX8643 offers programmable soft-start
time using one capacitor to reduce input inrush current.
The MAX8643 is available in a lead-free, 24-pin, 4mm x
4mm thin QFN package.
Applications
POLs
ASIC/CPU/DSP Core and I/O Voltages
DDR Power Supplies
Base-Station Power Supplies
Telecom and Networking Power Supplies
RAID Control Power Supplies
FeaturesInternal 37mΩRDSONMOSFETsContinuous 3A Output Current±1% Output Accuracy Over Load, Line,
and TemperatureOperates from 2.35V to 3.6V SupplyAdjustable Output from 0.6V to (0.9 x VIN)Soft-Start Reduces Inrush Supply Current500kHz to 2MHz Adjustable Switching FrequencyCompatible with Ceramic, Polymer, and
Electrolytic Output CapacitorsVID-Selectable Output Voltages
0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, and 2.5VFully Protected Against Overcurrent
and OvertemperatureSink/Source Current in DDR ApplicationLead-Free, 24-Pin, 4mm x 4mm
Thin QFN Package
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
Ordering Information
19-3970; Rev 3; 9/07
EVALUATION KIT
AVAILABLE
PARTTEMP
RANGEPIN-PACKAGEPKG
CODE
MAX8643ETG+-40°C to
+85°C
24 Thin QFN-EP*
4mm x 4mmT2444-4
+Denotes lead-free package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
OUTPUT
1.8V, 3A
INPUT
2.4V, 3.6V
BST
OUT
VDD
CTL1
CTL2
PGND
VDDCOMP
PWRGD
FREQ
REFIN
GND
MAX8643
Typical Operating Circuit
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= VDD= 3.3V, VFB= 0.5V, TA =-40°C to +85°C. Typical values are at TA= +25°C, circuit of Figure 1, unless otherwise noted.) (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, VDD, PWRGD to GND......................................-0.3V to +4.5V
COMP, FB, REFIN, OUT,
CTL_, EN, SS, FREQ to GND...................-0.3V to (VDD + 0.3V)
LX Current (Note 1).....................................................-4A to +4A
BST to LX..................................................................-0.3V to +4V
PGND to GND.......................................................-0.3V to +0.3V
Continuous Power Dissipation (TA= +70°C)
24-Pin TQFN-EP
(derated 27.8mW/°C above +70°C)........................2222.2mW
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
Note 1:LX has internal clamp diodes to GND and IN. Applications that forward bias these diodes should take care not to exceed
the IC’s package power dissipation limits.
PARAMETERCONDITIONSMINTYPMAXUNITS
IN/VDD
IN and VDD Voltage Range2.353.60V
VIN = 2.5V44.6IN Supply CurrentfS = 1MHz, no load (includes
gate-drive current)VIN = 3.3V5.5mA
VIN = 2.5V1.42.3VDD Supply CurrentfS = 1MHzVIN = 3.3V2mA
Total Shutdown Current from IN
and VDDVIN = VDD = VBST - VLX = 3.6V, VEN = 0V13µA
VDD rising22.1
VDD falling1.81.9VVDD Undervoltage Lockout
ThresholdLX starts/stops switching
Deglitching2µs
BST
TA = +25°C5BST Supply CurrentVBST = VDD = VIN = 3.6V,
VLX = 3.6V or 0V, VEN = 0VTA = +85°C10µA
PWM COMPARATOR
PWM Comparator Propagation
Delay10mV overdrive20ns
COMP
COMP Clamp Voltage, HighVIN = 2.35V to 3.6V2V
COMP Slew Rate1.4V/µs
PWM Ramp Amplitude1V
COMP Shutdown ResistanceFrom COMP to GND, VEN = VSS = 0V8Ω
ERROR AMPLIFIER
Preset Output-Voltage AccuracyREFIN = SS-1
Select
from
Table 1%
FB Regulation Accuracy Using
External ResistorsCTL1 = CTL2 = GND0.5940.6000.606V
FB to OUT ResistorAll VID settings except CTL1 = CTL2 = GND5811kΩ
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
ELECTRICAL CHARACTERISTICS (continued)
(VIN= VDD= 3.3V, VFB= 0.5V, TA =-40°C to +85°C. Typical values are at TA= +25°C, circuit of Figure 1, unless otherwise noted.) (Note 2)
PARAMETERCONDITIONSMINTYPMAXUNITS
Open-Loop Voltage Gain1kΩ from COMP to GND115dB
Error-Amplifier Unity-Gain
BandwidthParallel 10kΩ, 40pF from COMP to GND (Note 3)1426MHz
VDD = 2.35V to 2.6V0 VDD - 1.65Error-Amplifier Common-Mode
Input RangeVDD = 2.6V to 3.6V0 VDD - 1.7V
Sourcing1000Error-Amplifier Minimum Output
CurrentVCOMP = 1VSinking-500µA
FB Input Bias CurrentVFB = 0.7V, CTL1 = CTL2 =TA = +25°C-200-40nA
CTL_
VCTL_ = 0V-7CTL_ Input Bias CurrentVCTL_ = VDD+7µA
Rising0.75
High-Impedance ThresholdFallingVDD
- 1.2V
HysteresisAll VID transitions50mV
REFIN
REFIN Input Bias CurrentVREFIN = 0.6VTA = +25°C-500-100nA
VDD = 2.3V to 2.6V0 VDD - 1.65REFIN Common-Mode RangeVDD = 2.6V to 3.6V0 VDD - 1.7V
REFIN Offset VoltageCTL1 = CTL2 = GND, TA = +25°C-3+3mV
LX (ALL PINS COMBINED)
VIN = VBST - VLX = 2.5V39LX On-Resistance, High SideILX = -2AVIN = VBST - VLX = 3.3V3758mΩ
VIN = 2.5V36LX On-Resistance, Low SideILX = 2AVIN = 3.3V3455mΩ
LX Current-Limit ThresholdVIN = 2.5V, high-side sourcing45.5A
VLX = 0V-2TA = +25°CVLX = 3.6V+2
VLX = 0V1LX Leakage CurrentVIN = 3.6V, VEN = VSS = 0V
TA = +85°CVLX = 3.6V1
RFREQ = 50kΩ0.911.1LX Switching FrequencyVIN = 2.5V to 3.3VRFREQ = 23.2kΩ1.82.02.2MHz
Frequency Range5002000kHz
LX Minimum Off-TimeVIN = 2.5V to 3.3V4075ns
LX Maximum Duty CycleRFREQ = 50kΩ, VIN = 2.5V to 3.3V9396%
LX Minimum On-Time80ns
RMS LX Output Current3A
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
PARAMETERCONDITIONSMINTYPMAXUNITS
ENABLE
EN Input Logic-Low, Falling1.20.7V
EN Input Logic-High, Rising1.71.4V
EN Hysteresis200mV
TA = +25°C1EN, Input CurrentVEN = 0V or 3.6V,
VDD = 3.6VTA = +85°C0.01µA
SS Charging CurrentVSS = 0.45V789µA
SS Discharge Resistance500Ω
THERMAL SHUTDOWN
Thermal-Shutdown Threshold+165°C
Thermal-Shutdown Hysteresis20°C
POWER-GOOD (PWRGD)
Power-Good Threshold VoltageVFB falling, 3mV hysteresis879093%
Power-Good Falling-Edge Deglitch48Clock
cycles
PWRGD Output-Voltage LowIPWRGD = 4mA0.030.15V
PWRGD Leakage CurrentVDD = VPWRGD = 3.6V, VFB = 0.9V0.01µA
OVERCURRENT LIMIT
Current-Limit Startup Blanking128Clock
cycles
Restart Time1024Clock
cycles
Note 2:Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by
design and characterization.
Note 3:Guaranteed by design.
ELECTRICAL CHARACTERISTICS (continued)
(VIN= VDD= 3.3V, VFB= 0.5V, TA =-40°C to +85°C. Typical values are at TA= +25°C, circuit of Figure 1, unless otherwise noted.) (Note 2)
Typical Operating Characteristics
(Typical values are at VIN= VDD= 3.3V, VOUT= 1.8V, RFREQ= 50kΩ, IOUT= 3A, and TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
EFFICIENCY (%)
MAX8643 toc01
VOUT = 1.8V
VOUT = 2.5V
VIN = VDD = 3.3V
VOUT = 1.2V
EFFICIENCY vs. OUTPUT CURRENT
EFFICIENCY (%)
MAX8643 toc02
VOUT = 1.5V
VOUT = 1.88V
VIN = VDD = 2.5V
VOUT = 1.2V
Typical Operating Characteristics (continued)
(Typical values are at VIN= VDD= 3.3V, VOUT= 1.8V, RFREQ= 50kΩ, IOUT= 3A, and TA = +25°C, unless otherwise noted.)
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
FREQUENCY vs. INPUT VOLTAGE
INPUT VOLTAGE (V)
FREQUENCY (kHz)
MAX8643 toc04
+25°C-40°C+85°C
+25°C-40°C+85°C
LOAD REGULATION
LOAD CURRENT (A)
OUTPUT VOLTAGE CHARGE (%)
MAX8643 toc05
VOUT = 1.8V
VOUT = 1.2V
VOUT = 2.5V
VIN = VDD = 3.3V
LOAD TRANSIENT
40μs/div
MAX8643 toc06
IOUT
VOUT
1A/div
AC-COUPLED
50mV/div
VIN = VDD = 3.3V
SWITCHING WAVEFORMS
100ns/div
MAX8643 toc07
VLX
ILX
VOUT
2V/div
2A/div
AC-COUPLED
20mV/div
SOFT-START WAVEFORMS
400µs/div
MAX8643 toc08
VOUT
VEN
1V/div
2V/div
RLOAD = 1Ω
SHUTDOWN WAVEFORMS
10μs/div
MAX8643 toc09
VOUT
VEN
1V/div
2V/div
RLOAD = 1Ω
EFFICIENCY vs. OUTPUT CURRENT
OUTPUT CURRENT (A)
EFFICIENCY (%)
MAX8643 toc03
VOUT = 1.2V
VOUT = 1.5V
VOUT = 1.8V
VIN = 2.5V
VDD = 3.3V
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
Typical Operating Characteristics (continued)
(Typical values are at VIN= VDD= 3.3V, VOUT= 1.8V, RFREQ= 50kΩ, IOUT= 3A, and TA = +25°C, unless otherwise noted.)
INPUT CURRENT vs. INPUT VOLTAGE
INPUT VOLTAGE (V)
INPUT CURRENT (
MAX8643 toc10
VEN = 0V
CURRENT LIMIT vs. OUTPUT VOLTAGE
OUTPUT VOLTAGE (V)
CURRENT LIMIT (A)
MAX8643 toc11
HICCUP CURRENT LIMIT
400μs/div
MAX8643 toc12
IIN
IOUT
VOUT
5A/div
1A/div
1V/div
RMS INPUT CURRENT DURING SHORT CIRCUIT
vs. INPUT VOLTAGE (C4 = 0.022μF)
INPUT VOLTAGE (V)
RMS INPUT CURRENT (A)
MAX8643 toc13
0.50VOUT = 0V
EXPOSED PAD TEMPERATURE
vs. AMBIENT TEMPERATURE
TEMPERATURE (°C)
EXPOSED PAD TEMPERATURE (
MAX8643 toc1420406080100
VOUT = 1.8V
3A LOAD
MEASURED ON A MAX8643EVKIT
FEEDBACK VOLTAGE vs. TEMPERATURE
TEMPERATURE (°C)
FEEDBACK VOLTAGE (V)
MAX8643 toc15
SOFT-START WITH REFIN
200μs/div
MAX8643 toc16
VPWRGD
VOUT
VREFIN
IIN
1V/div
2V/div
1A/div
0.5V/div
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
Pin Description
PINNAMEFUNCTION
1, 7GNDAnalog Circuit Ground
2VDDSupply Voltage and Bypass Input. Connect VDD to IN with a 10Ω resistor. Connect a 1µF ceramic
capacitor from VDD to GND.
3, 4CTL1,
CTL2
Preset Output Voltage Selection Input. CTL1 and CTL2 set the output voltage to one of nine preset
voltages. See Table 1 for preset voltages.REFIN
External Reference Input. Connect REFIN to SS to use the internal 0.6V reference. Connecting REFIN to an
external reference voltage forces FB to regulate the voltage applied to REFIN. REFIN is internally pulled to
GND when the IC is in shutdown mode.
6SSSoft-Start Input. Connect a capacitor from SS to GND to set the startup time. See the Soft-Start and REFIN
section for details on setting the soft-start time.COMPOutput of the Voltage-Error Amplifier. Connect the necessary compensation network from COMP to FB.
COMP is internally pulled to GND when the IC is in shutdown mode.
9FB
Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to GND to set
the output voltage from 0.6V to 90% of VIN. Connect FB through an RC network to the output when using
CTL1 and CTL2 to select any of nine preset voltages.OUTOutput Voltage Sense. Connect to the output. Leave OUT unconnected when an external resistor-divider
is used.FREQOscillator Frequency Selection. Connect a resistor from FREQ to GND to select the switching frequency.PWRGDow er - G ood O utp ut. O p en- d r ai n outp ut that i s hi g h i m p ed ance w hen V F B ≥ 90% of V R E F IN or 0.6V . P W RGD i snter nal l y p ul l ed l ow w hen V F B fal l s b el ow 90% of i ts r eg ul ati on p oi nt. P W RG D i s i nter nal l y p ul l ed l ow w hen the
IC i s i n shutd ow n m od e, V D D or V I N i s b el ow the U V LO thr eshol d , or the IC i s i n ther m al shutd ow n.BSTHigh-Side MOSFET Driver Supply. Bypass BST to LX with a 0.1µF capacitor.
14, 15, 16LXInductor Connection. All LX pins are internally connected together. Connect all LX pins to the output
inductor. LX is high impedance when the IC is in shutdown mode.
17–20PGNDPower Ground. Connect all PGND pins externally to the power ground plane.
21, 22, 23INPower-Supply Input. Input supply range is from 2.35V to 3.6V. Bypass with 22µF ceramic capacitance to
PGND externally. See the Typical Application Circuit.ENEnable Input. Logic input to enable/disable the MAX8643.EPExposed Paddle. Connect to a large ground plane to optimize thermal performance.
MAX8643
3A, 2MHz Step-Down Regulator
with Integrated Switches
Block Diagram
CONTROL
LOGIC
PGND
BST
THERMAL
SHUTDOWN
SOFT-START
VOLTAGE
REFERENCE
BIAS
GENERATOR
OSCILLATOR
1VP-P
SHUTDOWN
CONTROL
UVLO
CIRCUITRY
VDD
SHDN
0.9 x VREFIN
COMP
GND
PWRGD
FREQ
ERROR
AMPLIFIERPWM
COMPARATOR
CURRENT-LIMIT
COMPARATOR
ILIM THRESHOLD
BST CAPACITOR
CHARGING SWITCH
COMP LOW
DETECTOR
REFIN
VID
VOLTAGE-
CONTROL
CIRCUITRY
OUT
CTL2
CTL1
8kΩ
MAX8643

Partno	Mfg	Dc	Qty	Available	Descript
MAX8643ETG+	MAXIM	N/a	10000	avai	3A, 2MHz Step-Down Regulator with Integrated Switches
MAX8643ETG+T	MAXIM	N/a	27	avai	3A, 2MHz Step-Down Regulator with Integrated Switches