MAX1536ETI+T ,3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-Down Regulator with Dynamic Output Voltage ControlApplicationso oMAX1536ETI -40 C to +85 C 28 Thin QFN 5mm x 5mmChipset/Graphics Cores Notebook Compu ..
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MAX1536ETI+T
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-Down Regulator with Dynamic Output Voltage Control
General DescriptionThe MAX1536 constant-off-time, pulse-width-modulated
(PWM) step-down DC-to-DC converter is ideal for use in
+5.0V and +3.3V to low voltages for notebook and sub-
notebook computers. The MAX1536 features an internal
PMOS power switch and internal synchronous rectifica-
tion for high efficiency and reduced component count. No
external Schottky diode is required across the internal
synchronous rectifier switch. The internal 54mΩPMOS
power switch and 47mΩNMOS synchronous-rectifier
switch easily deliver continuous load currents up to 3.6A.
The MAX1536 produces dynamically adjustable output
voltages for chipsets and graphics processor cores using
a logic-level control signal. The MAX1536 achieves effi-
ciencies as high as 96%.
The MAX1536 uses a unique current-mode, constant-off-
time, PWM control scheme. It has selectable Idle
ModeTMto maintain high efficiency during light-load
operation, or fixed-PWM mode for low output ripple. The
programmable constant-off-time architecture allows a
wide range of switching frequencies up to 1.4MHz, opti-
mizing performance trade-offs between efficiency, output
switching noise, component size, and cost. The
MAX1536 features a digital soft-start to limit surge cur-
rents during startup, a 100% duty-cycle mode for low-
dropout operation, and a low-power shutdown mode that
disconnects the input from the output and reduces supply
current below 1µA. The MAX1536 is available in a 28-pin
thin QFN package with an exposed backside pad.
________________________Applications
FeaturesDynamically Selectable Output Voltage from
+0.7V to VINInternal PMOS/NMOS Switches
54mΩ/47mΩOn-Resistance at VIN= +4.5V
63mΩ/53mΩOn-Resistance at VIN= +3.0V+3.0V to +5.5V Input Voltage Range1.4MHz Maximum Switching Frequency2V ±0.75% Reference OutputConstant-Off-Time PWM OperationSelectable Idle Mode/PWM Operation at Light
Loads100% Duty Factor in DropoutDigital Soft-Start Inrush Current Limiting<1µA Typical Shutdown Supply Current<750µA Quiescent Supply CurrentThermal Shutdown1% VOUTAccuracy Over Line and LoadExternal Reference InputPower-Good Window ComparatorSelectable Power-Good Blanking Time During
Output-Voltage Transition19-2729; Rev 1; 8/05
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Contr
Minimal Operating Circuit
Ordering InformationIdle Mode is a trademark of Maxim Integrated Products, Inc.
PART TEMP RANGEPIN-PACKAGEMAX1536ETI-40oC to +85oC28 Thin QFN 5mm x 5mm
MAX1536ETI+-40oC to +85oC28 Thin QFN 5mm x 5mm
MAX1536
VCC
SKIP
TOFF
PGOOD
SHDN
COMP
PGND
AGND
REF
REFIN
VIN
+3.0V TO +5.5V
VOUT
+0.7V TO VIN
Pin ConfigurationSHDN
SKIP
COMPININPGOODFBLANKV
AGND
PGND
N.C.
PGND
PGNDREF
REFIN
GATE
TOFF
N.C.
TOP VIEW
THIN QFNPGND161718192021654321
MAX1536
EXPOSED PADDLE
A "+" SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES.
Chipset/Graphics Cores
with Dual-Supply Voltages
Active Termination Buses
Notebook Computers
DDR Memory Termination
EVALUATION KIT
AVAILABLE+Denotes lead-free package.
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= VCC= VSHDN= +3.3V, VREFIN = +1.5V, SKIP= AGND, TA
= 0°C to +85°C, unless otherwise noted. Typicalvalues are at TA= +25°C.)
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.
VCC, IN, SHDN, SKIPto AGND................................-0.3V to +6V
OD, OD, GATE, PGOOD to AGND...........................-0.3V to +6V
COMP, FB, REF to AGND.........................................-0.3V to +6V
TOFF, REFIN, FBLANK to AGND.............................-0.3V to +6V
IN to VCC...............................................................-0.3V to +0.3V
PGND to AGND....................................................-0.3V to +0.3V
LX to PGND................................................-0.3V to (VIN+ 0.3V)
LX Current (Note 1).............................................................±5.7A
REF Short Circuit to AGND.........................................Continuous
Continuous Power Dissipation (TA= +70°C)
28-Pin Thin QFN (derated 20.8mW/°C above +70°C;
part mounted on 1in2of 1oz copper).........................1667mW
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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
PWM CONTROLLERInput VoltageVIN, VCC3.05.5V
Output Adjust RangeVOUTVREFINVINV
TA = +25°C to +85°C-30+3Feedback Voltage AccuracyVFB -
VREFIN
VCC = VIN = +3.0V to
+5.5V, ILOAD = 0TA = 0°C to +85°C-40+4mV
Feedback Load RegulationILOAD = 0 to 3.5A, VCC = VIN = +3.0V to +5.5V,
SKIP = VCC0.3%
FB Input Bias CurrentIFBVFB = 1.01 × VREFIN-50+50nA
DropoutVDOVCC = VIN = +3.0V, ILOAD = 3A, FB = AGND189330mV
VCC = VIN = +4.5V, ILOAD = 0.5A5490PMOS Switch On-ResistanceRPMOSVCC = VIN = +3.0V, ILOAD = 0.5A63110mΩ
VCC = VIN = +4.5V, ILOAD = 0.5A4780NMOS Switch On-ResistanceRNMOSVCC = VIN = +3.0V, ILOAD = 0.5A5390mΩ
Maximum Output CurrentIOU T ( R M S ) (Note 2)3.6A
Current-Limit ThresholdILIMIT(Note 3)4.04.85.5A
Idle Mode Current ThresholdSKIP = AGND0.210.601.00A
Zero-Cross Current ThresholdSKIP = AGND200mA
Switching FrequencyfSW(Note 2)1.4MHz
RTOFF = 30.1kΩ0.240.300.37
RTOFF = 110kΩ0.851.001.15Off-TimetOFFVFB ≥ 0.3 × VREFIN
RTOFF = 499kΩ3.84.55.2
Extended Off-TimeVFB < 0.3 × VREFIN4 × tOFFµs
On-TimetON(Note 2)0.3µs
Soft-Start Time(Note 3)3 × 256Cycles
Quiescent Supply CurrentICC + IINSKIP = AGND, VFB = 1.01 × VREFIN350750µA
Note 1:LX has clamp diodes to PGND and IN. Thermal limits dictate the maximum continuous current through these diodes.
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VIN= VCC= VSHDN= +3.3V, VREFIN = +1.5V, SKIP= AGND, TA
= 0°C to +85°C, unless otherwise noted. Typicalvalues are at TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSICC + IINSHDN = AGND; current into VCC and IN;
LX = 0 or +3.3V0.220
IINSHDN = AGND; current into IN; LX = 00.220Shutdown Supply Currents
ILXSHDN = AGND; current into LX; LX = +3.3V0.120
REFERENCEREF VoltageVREFVCC = VIN = +3.0V to +5.5V1.9852.0002.015V
REF Load RegulationIREF = -1µA to +50µA10mV
REFIN Input Voltage RangeVREFINV C C = V IN = + 3.0V to + 5.5V , V C C > V RE F IN + 1.35V 0.72.0V
REFIN Input Bias CurrentIREFINVREFIN = 1.5V, VFB = 1.01 × VREFIN-50+50nA
FAULT DETECTIONThermal ShutdownTSHDNRising, hysteresis = 15°C165°C
VCC and VIN rising, hysteresis 60mV typical2.42.62.8
VCC - VREFIN, VCC rising, hysteresis 60mV typical0.91.35Undervoltage Lockout
Threshold
VCC - VFB, VCC rising, hysteresis 60mV typical0.91.35
PGOOD Lower Trip ThresholdNo load, falling edge, hysteresis = 1% (Note 4)-12.5-10-8.0%
PGOOD Upper Trip ThresholdNo load, rising edge, hysteresis = 1% (Note 4)+8.0+10+12.5%
PGOOD Propagation DelaytPGOODFB forced 2% beyond PGOOD trip threshold5µs
PGOOD Output Low VoltageISINK = 1mA0.1V
PGOOD Leakage CurrentHigh-impedance state, forced to +5.5V1µA
FBLANK = VCC112150188
FBLANK = open or AGND75100125Fault Blanking TimetFBLANK
FBLANK = REF375063
INPUTS AND OUTPUTSSHDN, SKIP, GATE, VIN = VCC = +3.3V,
rising edge, hysteresis = 100mV0.91.31.6
Logic Input Threshold
V SHDN,
V SKIP,
VGATESHDN, SKIP, GATE, VIN = VCC = +5.0V,
rising edge, hysteresis = 100mV1.151.551.95
Logic Input CurrentSHDN, SKIP, GATE-0.5+0.5µA
FBLANK = VCCVCC - 0.2
FBLANK = REF1.82.2
FBLANK = open0.81.2FBLANK Logic ThresholdsVFBLANK
FBLANK = AGND0.2
FBLANK Input CurrentIFBLANKFBLANK forced to AGND or VCC-5+5µA
OD On-ResistanceRODGATE = VCC1025Ω
OD Leakage CurrentGATE = AGND, VOD = +5.5V-50+50nA
OD On-ResistanceR ODGATE = AGND1025Ω
OD Leakage CurrentGATE = VCC, V OD = +5.5V-50+50nA
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= VCC= VSHDN= +3.3V, VREFIN = +1.5V, SKIP= AGND, TA
= -40°C to +85°C, unless otherwise noted.) (Note 5)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
PWM CONTROLLERInput VoltageVIN, VCC3.05.5V
Feedback Voltage AccuracyVFB -
VREFINVCC = VIN = +3.0V to +5.5V, ILOAD = 0-4+4mV
FB Input Bias CurrentIFBVFB = 1.01 × VREFIN-50+50nA
DropoutVDOVCC = VIN = +3.0V, ILOAD = 3A, FB = AGND330mV
VCC = VIN = +4.5V, ILOAD = 0.5A90PMOS Switch On-ResistanceRPMOSVCC = VIN = +3.0V, ILOAD = 0.5A110mΩ
VCC = VIN = +4.5V, ILOAD = 0.5A80NMOS Switch On-ResistanceRNMOSVCC = VIN = +3.0V, ILOAD = 0.5A90mΩ
Maximum Output CurrentIOU T ( R M S ) (Note 2)3.6A
Current-Limit ThresholdILIMIT(Note 3)4.05.7A
Idle Mode Current ThresholdSKIP = AGND0.211.00A
Switching FrequencyfSW(Note 2)1.4MHz
RTOFF = 30.1kΩ0.240.37
RTOFF = 110kΩ0.851.15Off-TimetOFFVFB ≥ 0.3 × VREFIN
RTOFF = 499kΩ3.85.2
On-TimetON(Note 2)0.3µs
Quiescent Supply CurrentICC + IINSKIP = AGND, VFB = 1.01 × VREFIN750µA
ICC + IINSHDN = AGND; current into VCC and IN;
LX = 0 or +3.3V20
IINSHDN = AGND; current into IN; LX = 020Shutdown Supply Currents
ILXSHDN = AGND; current into LX; LX = +3.3V20
REFERENCEREF VoltageVREFVCC = VIN = +3.0V to +5.5V1.982.02V
REFIN Input Voltage RangeVREFINVCC = VIN = +3.0V to +5.5V,
VCC > VREFIN + 1.35V0.72.0V
FAULT DETECTIONPGOOD Lower Trip ThresholdNo load, falling edge, hysteresis = 1% (Note 4)-12.5-8%
PGOOD Upper Trip ThresholdNo load, rising edge, hysteresis = 1% (Note 4)+8+12.5%
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
Note 2:Guaranteed by design and not production tested.
Note 3:To limit input surge currents, the current-limit threshold is set to 25% of its final value (25% x 4.8A = 1.2A) when the
MAX1536 is enabled or powered up. The current-limit threshold is increased by 25% every 256 LX cycles. The current-limit
threshold is at its final level of 4.8A after 768 LX cycles. See the Internal Soft-Start Circuitsection.
Note 4:The upper and lower PGOOD thresholds are expressed as a ratio of VFBwith respect to VREFIN.
Note 5:Specifications to -40°C are guaranteed by design and are not production tested.xFBREFIN
REFIN100%
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VIN= VCC= VSHDN= +3.3V, VREFIN = +1.5V, SKIP= AGND, TA
= -40°C to +85°C, unless otherwise noted.) (Note 5)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
INPUTS AND OUTPUTSSHDN, SKIP, GATE, VIN = VCC = +3.3V,
rising edge, hysteresis = 100mV0.91.6
Logic Input Threshold S HDN, S KIP,
V GATESHDN, SKIP, GATE, VIN = VCC = +5.0V,
rising edge, hysteresis = 100mV1.151.95
FBLANK = VCCVCC - 0.2
FBLANK = REF1.82.2
FBLANK = open0.81.2FBLANK Logic ThresholdsVFBLANK
FBLANK = AGND0.2
OD On-ResistanceRODGATE = VCC25Ω
OD On-ResistanceR O DGATE = AGND25Ω
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 5V, L = 1.5μH)
MAX1536 toc01
OUTPUT CURRENT (A)
EFFICIENCY (%)40
VOUT = 0.7V
RTOFF = 200kΩ
VOUT = 1.8V
RTOFF = 93.1kΩ
VOUT = 2.5V
RTOFF = 54.9kΩ
PWM MODE
IDLE MODE
OUTPUT VOLTAGE vs. OUTPUT CURRENT
(VIN = 5V, L = 1.5μH)
MAX1536 toc02
OUTPUT CURRENT (A)
OUTPUT VOLTAGE (V)
RTOFF = 93.1kΩ
PWM MODEIDLE MODE
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 3.3V, L = 1.2μH)
MAX1536 toc03
OUTPUT CURRENT (A)
EFFICIENCY (%)40
VOUT = 0.7V
RTOFF = 165kΩ
VOUT = 1.8V
RTOFF = 75kΩ
VOUT = 2.5V
RTOFF = 42.2kΩ
PWM MODE
IDLE MODE
Typical Operating Characteristics(MAX1536 Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
