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MAX8553EEE+-MAX8554EEE+
4.5V to 28V Input, Synchronous PWM Buck Controllers for DDR Termination and Point-of-Load Applications
General DescriptionThe MAX8553 is a 4.5V to 28V input-voltage, synchro-
nous step-down controller that provides a complete
power-management solution for DDR memory. The
MAX8553 generates 1/2 VREFINvoltage for VTT and
VTTR. The VTT and VTTR tracking voltages are main-
tained within 1% of 1/2 VREFIN. The MAX8554 is a 4.5V to
28V input voltage, nontracking step-down controller with
a low 0.6V feedback threshold voltage. The MAX8553/
MAX8554 use Maxim’s proprietary Quick-PWM™ archi-
tecture for fast transient response and operate with
selectable pseudo-fixed frequencies. Both controllers
can operate without an external bias supply.
The controllers operate in synchronous-rectification mode
to ensure balanced current sourcing and sinking capabili-
ty of up to 25A. The MAX8553/MAX8554 also provide up
to 95% efficiency, making them ideal for server and point-
of-load applications. Additionally, a low 5µA shutdown
current allows for longer battery life in notebook applica-
tions. Lossless current monitoring is achieved by monitor-
ing the low-side MOSFET’s drain-to-source voltage. The
MAX8553/MAX8554 have an adjustable foldback current
limit to withstand a continuous output overload and short
circuit. Digital soft-start provides control of inrush current
during power-up. Overvoltage protection shuts the con-
verter down and discharges the output capacitor. The
MAX8553/MAX8554 come in space-saving 16-pin QSOP
packages.
ApplicationsWide-Input Power Supplies
Servers and Storage Applications
ASIC and CPU Core Voltages
Notebook and LCD-PC Power Supplies
DDR I and DDR II Memory Power Supplies
AGTL Bus Termination Supplies
FeaturesUp to 25A Output-Current CapabilityQuick-PWM Control for Fast Loop ResponseUp to 95% Efficiency4.5V to 28V Input Voltage RangeNo External Bias Supply Required0 to 3.6V Input REFIN Range (MAX8553)Automatically Sets VTT and VTTR to within ±1%
of 1/2 VREFIN- (MAX8553)Low 0.6V Feedback Threshold (MAX8554)200kHz/300kHz/400kHz/550kHz Selectable
Switching FrequenciesAdjustable Foldback Current LimitOvervoltage ProtectionDigital Soft-Start
MAX8553/MAX8554
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
Ordering InformationMAX8553EN/HSD
+5V
POK
VIN
VOUT
VTTR
REFIN
VTTRGND
POK
REFIN
BST
REF
ILIM
FSEL
PGND
VTT
PARTTEMP RANGEPIN-PACKAGE
MAX8553EEE-40°C to +85°C16 QSOP
MAX8554EEE-40°C to +85°C16 QSOP
Typical Operating Circuit19-3017; Rev 1; 5/05
Pin Configurations appear at end of data sheet.Quick-PWM is a trademark of Maxim Integrated Products, Inc.
MAX8553/MAX8554
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VV+= VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN= +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0V, ILIM = VL,
PGND = LX = GND, BST = VL, TA
= 0°C to +85°C.Typical values are at TA= +25°C, unless otherwise specified.)
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.
V+, EN/HSD, EN, HSD to GND...............................-0.3V to +30V
PGND to GND.......................................................-0.3V to +0.3V
VTT, REFIN, POK, OUT, FB, VL to GND...................-0.3V to +6V
REF, VTTR, DL, ILIM, FSEL to GND............-0.3V to (VVL + 0.3V)
LX to PGND...............................................................-2V to +30V
BST to GND............................................................-0.3V to +36V
DH to LX...................................................................-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
REF Short Circuit to GND...........................................Continuous
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derated 8.3mW/°C above +70°C)........667mW
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
PARAMETERCONDITIONSMINTYPMAXUNITSV+ Input Voltage RangeVL not connected to V+628V
V+ Input Voltage RangeVL connected to V+4.55.5V
EN/HSD Input Voltage RangeMAX8553 enabled1.528.0V
EN Input Voltage RangeMAX8554 enabled1.528.0V
EN Input Current23µA
HSD Input Voltage RangeMAX8554 enabled1.528.0V
HSD Input Current2040µA
REFIN Input Voltage Range03.6V
V+ Supply Current (MAX8553)VVTT = +1.35V0.81.2mA
V+ Supply Current (MAX8554)VFB = 630mV0.620.90mA
REFIN Supply Current125250µA
EN/HSD Supply Current510µA
VL Supply CurrentVVL = VV+ = 5.5V, VVTT = +1.35V0.81.2mA
V+ Shutdown Supply CurrentEN/HSD = GND35µA
REFIN Shutdown Supply CurrentEN/HSD = GND1µA
VL Shutdown Supply CurrentVVL = VV+ = +5.5V, VEN/HSD = 0V512µA
VL Undervoltage-Lockout ThresholdRising edge, typical hysteresis = 40mV4.054.254.40V
VTTVTT Input Bias CurrentVVTT = +1.25V-0.150µA
VTT Feedback Voltage Range01.8V
VREFIN = VEN/HSD = +1.8V49.55050.5VTT Feedback Voltage AccuracyVREFIN = VEN/HSD = +3.6V49.55050.5% VRE FIN
FB Input Bias CurrentMAX8554, VFB = +600mV-0.150µA
MAX8553/MAX8554
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)(VV+= VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN= +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0V, ILIM = VL,
PGND = LX = GND, BST = VL, TA
= 0°C to +85°C.Typical values are at TA= +25°C, unless otherwise specified.)
PARAMETERCONDITIONSMINTYPMAXUNITSFB Regulation VoltageMAX8554, VOUT = +2.5V, FSEL unconnected0.5980.6070.616V
Output Adjust RangeMAX8554 (Note 1)0.63.5V
VTT Line RegulationVEN/HSD ±10%, VVTT = +1.25V, IOUT = 0A±0.325%
FB Line RegulationMAX8554, VHSD ±10%, VOUT = +2.5V,
IOUT = 0A, FSEL unconnected±0.325%
VTT Load Regulation0 < IOUT < +7A, VVTT = +1.25V0.2%
FB Load RegulationMAX8554, 0 < IOUT < +7A, VOUT = +2.5V,
FSEL unconnected0.2%
REFERENCEReference Output VoltageVV+ = VVL = +4.5 to +5.5V, IREF = 01.972.002.03V
Reference Load RegulationVV+ = VVL = +5V, IREF = 0 to 50µA10mV
Reference UVLOVV+ = VVL = +5V, reference rising, hysteresis = 27mV1.51.61.7V
VTTRVTTR Output Voltage Range01.8V
IVTTR = -5mA to +5mA49.55050.5
IVTTR = -25mA to +25mA, VREFIN = +1.8V495051VTTR Output Accuracy
IVTTR = -25mA to +25mA, VREFIN = +3.6V49.55050.5
% VRE FIN Thermal Shutdown Rising temperature, typical hysteresis = 15°C +160 °C
SOFT-STARTILIM Ramp Period Ramps the ILIM trip threshold from 20% to 100% in
20% increments0.8 1.73.0msOutput Predischarge Period Rising edge of EN/HSD to the start of internal digital
soft-start0.8 1.73.0ms
OSCILLATORFSEL = VL 200 FSEL = unconnected 300 FSEL = REF 400 Oscillator FrequencyFSEL = GND 550 kHzFSEL = VL 2.18 2.5 2.83FSEL unconnected 1.45 1.67 1.89FSEL = REF 1.09 1.25 1.41 On-Time MAX8553, VVTT = +1.25V
(Note 2)FSEL = GND 0.82 0.91 1.00µsFSEL = VL 0.89 1.02 1.16FSEL unconnected 0.61 0.71 0.80FSEL = REF 0.43 0.49 0.56 On-Time MAX8554, VOUT = +2.5V
(Note 2)FSEL = GND 0.33 0.37 0.41µsOff-Time (Note 2) 350 400 ns
MAX8553/MAX8554
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)(VV+= VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN= +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0V, ILIM = VL,
PGND = LX = GND, BST = VL, TA
= 0°C to +85°C.Typical values are at TA= +25°C, unless otherwise specified.)
PARAMETERCONDITIONSMINTYPMAXUNITS
CURRENT LIMITLX to PGND, ILIM = VL80100115
LX to PGND, RILIM = 100kΩ355065Current-Limit Threshold (Positive
Direction)
LX to PGND, RILIM = 400kΩ160200230
Current-Limit Threshold (Negative
Direction)
LX to PGND, ILIM = VL, with respect to positive
current-limit threshold-130-110-90%
ILIM Input Current5µA
FAULT DETECTIONMAX8553 (VREFIN > +1V)576063% VRE FIN
MAX8553 (VREFIN ≤ +1V)0.5760.6000.624Overvoltage Threshold
MAX85540.6960.7200.744V
VL REGULATOROutput Voltage +6V < VV+ <+28V, 1mA < IVL < 35mA 4.80 5.0 5.33 VLine Regulation +6V < VV+ < +28V, IVL = 10mA 0.2 %RMS Output Current 35 mABypass Capacitor ESR < 100mΩ 2.2 µF
DRIVERDH Gate-Driver On-ResistanceVBST - VLX = +5V1.42.5Ω
DL Gate-Driver On-Resistance
(Source)DL high state1.63.0Ω
DL Gate-Driver On-Resistance
(Sink)DL low state0.751.25Ω
DL rising32Dead TimeDL falling30ns
FSEL LOGICLogic Input Current-3+3µA
Logic Low (GND)0.5V
Logic REF LevelFSEL = REF1.652.35V
Logic Float LevelFSEL unconnected3.153.85V
Logic VL LevelFSEL = VLVVL - 0.4V
EN/HSD OR EN LOGICEN/HSD or EN Shutdown CurrentMax IEN/HSD for VEN/HSD < +0.8V or VEN < +0.8V0.53.0µA
Logic HighVVL = VV+ = +4.5 to +5.5V, 100mV hysteresis1.5V
Logic LowVVL = VV+ = +4.5 to +5.5V0.8V
MAX8553/MAX8554
4.5V to 28V Input, Synchronous PWM Buck Controllers
for DDR Termination and Point-of-Load Applications
ELECTRICAL CHARACTERISTICS (continued)(VV+= VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN= +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0V, ILIM = VL,
PGND = LX = GND, BST = VL, TA
= 0°C to +85°C.Typical values are at TA= +25°C, unless otherwise specified.)
PARAMETERCONDITIONSMINTYPMAXUNITS
POWER-OK OUTPUTUpper VTT and VTTR ThresholdMAX8553555657% VRE FIN
Lower VTT and VTTR ThresholdMAX8553434445% VRE FIN
Upper ThresholdMAX85540.6460.6720.698V
Lower ThresholdMAX85540.5040.5280.552V
POK Output Low LevelISINK = 2mA0.4V
POK Output High LeakageVPOK = +5V5µA
ELECTRICAL CHARACTERISTICS (VV+ = VHSD = +12V, VEN/HSD = VREFIN = +2.5V, VEN = +5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND
= LX = POK = GND, BST = VL, TA
= -40°C to +85°C, unless otherwise specified.) (Note 3)
PARAMETERCONDITIONSMINMAXUNITSV+ Input Voltage RangeVL not connected to V+628V
V+ Input Voltage RangeVL connected to V+4.55.5V
EN/HSD Input Voltage RangeMAX8553 enabled1.528.0V
EN Input Voltage RangeMAX8554 enabled1.528.0V
EN Input Current3µA
HSD Input Voltage RangeMAX8554 enabled1.528.0V
HSD Input Current40µA
REFIN Input Voltage Range03.6V
V+ Supply Current (MAX8553)VVTT = +1.35V1.2mA
V+ Supply Current (MAX8554)VFB = 630mV0.90mA
REFIN Supply Current250µA
EN/HSD Supply Current10µA
VL Supply CurrentVVL = VV+ = 5.5V, VVTT = +1.35V1.2mA
V+ Shutdown Supply CurrentEN/HSD = GND5µA
REFIN Shutdown Supply CurrentEN/HSD = GND1µA
VL Shutdown Supply CurrentVVL = VV+ = +5.5V, VEN/HSD = 0V12µA
VL Undervoltage-Lockout ThresholdRising edge, typical hysteresis = 40mV4.054.40V
VTTVTT Input Bias CurrentVVTT = +1.25V-0.20µA
VTT Feedback Voltage Range01.8V
VREFIN = VEN/HSD = +1.8V49.550.5VTT Feedback Voltage AccuracyVREFIN = VEN/HSD = +3.6V49.550.5% VRE FIN
FB Input Bias CurrentMAX8554, VFB = +600mV-0.20µA
FB Regulation VoltageMAX8554, VOUT = +2.5V, FSEL unconnected0.5980.616V
Output Adjust RangeMAX8554 (Note 1)0.63.5V
