MAX1536ETI ,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 ..
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 ..
MAX1538ETI ,4.75 to 28 V,power-source selector for dual-battery systemFeaturesThe MAX1538 selector provides power-source control ♦ Automatically Detects and Responds tof ..
MAX1538ETI+ ,Power-Source Selector for Dual-Battery SystemsELECTRICAL CHARACTERISTICS(V = V = V = 16.8V, C = 1µF, V = V = 0.93V, V = V = 28V, V = V = V = 0,BA ..
MAX1538ETI+T ,Power-Source Selector for Dual-Battery SystemsFeaturesThe MAX1538 selector provides power-source control ♦ Automatically Detects and Responds tof ..
MAX153CAP ,1Msps, レP-Compatible, 8-Bit ADC with 1レA Power-DownGeneral Description
The MAX153 high-speed, microprocessor (wF')-corrr
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MAX4173FEUT-T ,Low-Cost / SOT23 / Voltage-Output / High-Side Current-Sense AmplifierMAX4173T/F/H19-1434; Rev 1; 5/99Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
MAX4173HESA ,Low-Cost / SOT23 / Voltage-Output / High-Side Current-Sense AmplifierFeaturesThe MAX4173 low-cost, precision, high-side current-' Low-Cost, Compact Current-Sense Soluti ..
MAX4173HESA+ ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierFeaturesThe MAX4173 low-cost, precision, high-side current-♦ Low-Cost, Compact Current-Sense Soluti ..
MAX4173HESA+T ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifierfeatures a voltage output that eliminates the need forRange, Functional Down to 0V, Independent ofg ..
MAX4173HEUT ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierMAX4173 Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense Amplifier
MAX4173HEUT+T ,Low-Cost, SOT23, Voltage-Output, High-Side Current-Sense AmplifierApplicationsRS+ RS-+3V TO +28VNotebook ComputersVCCPortable/Battery-Powered Systems0.1μFSmart Batte ..
MAX1536ETI
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 Control
Minimal Operating CircuitIdle Mode is a trademark of Maxim Integrated Products, Inc.
Chipset/Graphics Cores
with Dual-Supply Voltages
Active Termination Buses
Notebook Computers
DDR Memory Termination
+Denotes lead-free package.
LCJ/JH 9/22/05 (P1)
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
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.)
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)
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.
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)
Typical Operating Characteristics
(MAX1536 Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Controlypical Operating Characteristics (continued)
(MAX1536 Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
Typical Operating Characteristics (continued)
(MAX1536 Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
Pin Description
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
Standard Application Circuit
The MAX1536 standard application circuit (Figure 1)
generates a dynamically adjustable output voltage typical
of graphic processor core requirements. See Table 1
for component selections. Table 2 lists the component
manufacturers.
Detailed Description
The MAX1536 synchronous, current-mode, constant-
off-time, PWM DC-to-DC converter steps down an input
voltage (VIN) from +3.0V to +5.5V to an output voltage
from +0.7V to VIN. The MAX1536 output delivers up to
3.6A of continuous current. An internal 54mΩPMOS
power switch and an internal 47mΩNMOS synchro-
nous rectifier switch improve efficiency, reduce compo-
nent count, and eliminate the need for an external
Schottky diode (Figure 2).
Modes of Operation
The MAX1536 has two modes of operation: constant-
off-time PWM mode, and pulse-skipping Idle Mode.
The logic level on the SKIPinput and the current
through the PMOS switch determine the MAX1536
mode of operation.
Forced-PWM mode keeps the switching frequency rel-
atively constant and is desirable in applications that
must always keep the frequency of conducted and
radiated emissions in a narrow band. Visit Maxim’s
website at for more information on
how to control electromagnetic interference (EMI).
Pulse-skipping Idle Mode has a dynamic switching fre-
quency under light loads and is desirable in applica-
tions that require high efficiency at light loads.
Forced-PWM Mode (SKIP= VCC)
Connect SKIPto VCCto force the MAX1536 to operate
in low-noise, constant-off-time PWM mode. Constant-
off-time PWM architecture provides a relatively con-
stant switching frequency (see the Frequency Variation
with Output Currentsection). A single resistor (RTOFF)
sets the PMOS power switch off-time that results in a
switching frequency up to 1.4MHz optimizing perfor-
mance trade-offs in efficiency, switching noise, compo-
nent size, and cost.
PWM mode regulates the output voltage by increasing
the PMOS switch on-time to increase the amount of energy
transferred to the load per cycle. At the end of each off-
time, the PMOS switch turns on and remains on until the
output is in regulation or the current through the switch
increases to the 4.8A current limit. When the PMOS
switch turns off, it remains off for the programmed off-
time (tOFF), and the NMOS synchronous switch turns on.
The NMOS switch remains on until the end of tOFF. Since
either the NMOS or the PMOS switch is always on in
PWM mode, the inductor current is continuous.
Idle Mode (SKIP= AGND)
Connect SKIPto AGND to allow the MAX1536 to auto-
matically switch between high-efficiency Idle Mode
under light loads and PWM mode under heavy loads.
The transition from PWM mode to Idle Mode occurs
when the load current is half the Idle Mode current
threshold (600mA typ).
In Idle Mode operation, the switching frequency is
reduced to increase efficiency. The inductor current is
discontinuous in this mode and the MAX1536 only initi-
ates an LX switching cycle when VFB< VREFIN. When
VFBfalls below VREFIN, the PMOS switch turns on and
remains on until output is in regulation and the current
through the switch increases to the Idle Mode current
threshold (600mA typ). When the PMOS switch turns
off, the NMOS synchronous switch turns on and remains
on until the current through the switch decreases to the
zero-cross-current threshold of 200mA.
100% Duty-Cycle Operation
When the input voltage drops near the output voltage,
the LX duty cycle increases until the PMOS switch is on
continuously. The dropout voltage in 100% duty cycle
is the output current multiplied by the on-resistance of
the internal PMOS switch and parasitic resistance in
the inductor. The PMOS switch remains on continuously
as long as the current limit is not reached.
Internal Soft-Start Circuit
Soft-start allows a gradual increase of the current-limit
level at startup to reduce input surge currents. When
the MAX1536 is enabled or powered up, its current-
limit threshold is set to 25% of its final value (25% of
4.8A = 1.2A). The current-limit threshold is increased
by 25% every 256 LX cycles. The current-limit thresh-
old reaches its final level of 4.8A after 768 LX cycles or
when the output voltage is in regulation, whichever
occurs first. Additionally, when VFB< 0.3 ×VREFIN, the
PMOS switch remains off for the extended off-time of 4 ×
tOFF. As a result of this soft-start feature, the main output
capacitor charges up relatively slowly. The exact time of
the output rise depends on the nominal switching fre-
quency, output capacitance, and the load current. See
the startup waveformsin theTypical Operating
Characteristics.
Short-Circuit/Overload Protection
The MAX1536 can sustain a constant short circuit or
overload. Under a short-circuit or overload condition,
when VFB< 0.3 ×VREFIN, the MAX1536 uses an
MAX1536
3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step-
Down Regulator with Dynamic Output Voltage Control
Table 1. Recommended Component Values (IOUT= 3.6A)
*In single-output voltage applications, OD, OD, and GATE are general-purpose gates. If OD and ODare not used, connect GATE to
AGND and leave OD and ODopen.
**The output voltage changes between two set points depending on VGATE. See the Setting Dynamic Output Voltages with REFIN section.
Figure 1. MAX1536 Standard Application Circuit
