MAX1843EGI ,2.7A / 1MHz / Low-Voltage / Step-Down Regulator with Internal Synchronous Rectification in QFN PackageApplicationsOrdering Information5V or 3.3V to Low-Voltage ConversionPART TEMP RANGE PIN-PACKAGECPU ..
MAX1843EGI-T ,2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in TQFN Packagefeatures♦ 95% Efficiencyan internal PMOS power switch and internal synchronous♦ Internal pMOS/nMOS ..
MAX1843ETI+ ,2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in TQFN PackageELECTRICAL CHARACTERISTICS (V = V = +3.3V, FBSEL = GND, T = 0°C to +85°C, unless otherwise noted. T ..
MAX1843ETI+T ,2.7A, 1MHz, Low-Voltage, Step-Down Regulator with Internal Synchronous Rectification in TQFN PackageApplicationsOrdering Information5V or 3.3V to Low-Voltage ConversionTEMP PIN- PKGPARTCPU I/O RingRA ..
MAX1844EEP+ ,High-Speed Step-Down Controller with Accurate Current Limit for Notebook ComputersELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V+ = 15V, V = V = 5V, SKIP = GND, T = 0°C to +85°C, ..
MAX1844EEP+T ,High-Speed Step-Down Controller with Accurate Current Limit for Notebook ComputersFeaturesThe MAX1844 pulse-width modulation (PWM) controller♦ Ultra-High Efficiencyprovides high eff ..
MAX4737EUD+ ,4.5 Ohm Quad SPST Analog Switches in UCSPapplications.● Low R ONThe MAX4737/MAX4738/MAX4739 feature 4.5Ω R ON• 4.5Ω (max) (+3V Supply) (max) ..
MAX4738EBE-T ,4.5? Quad SPST Analog Switches in UCSPELECTRICAL CHARACTERISTICS—Single +3V Supply(V+ = +2.7V to +3.6V, V = +1.4V, V = +0.5V, T = T to T ..
MAX4738EUD ,4.5? Quad SPST Analog Switches in UCSPapplications. Low RONThe MAX4737/MAX4738/MAX4739 feature 4.5Ω RON4.5Ω (max) (+3V Supply)(max) with ..
MAX4738EUD+ ,4.5 Ohm Quad SPST Analog Switches in UCSPFeaturesThe MAX4737/MAX4738/MAX4739 low-voltage, low on- ● USB 1.1 Signal Switchingresistance (R ), ..
MAX4738EUD+T ,4.5 Ohm Quad SPST Analog Switches in UCSPMAX4737/MAX4738/ 4.5Ω Quad SPST Analog Switches in UCSPMAX4739
MAX4739EBE-T ,4.5? Quad SPST Analog Switches in UCSPFeatures USB 1.1 Signal SwitchingThe MAX4737/MAX4738/MAX4739 low-voltage, low on-resistance (R ), ..
MAX1843EGI
2.7A / 1MHz / Low-Voltage / Step-Down Regulator with Internal Synchronous Rectification in QFN Package
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package19-1986; Rev 1; 3/02
General DescriptionThe MAX1843 constant-off-time, pulse-width modulated
(PWM) step-down DC-DC converter is ideal for use in 5V
and 3.3V to low-voltage conversion necessary in note-
book and subnotebook computers. This device features
an internal PMOS power switch and internal synchronous
rectification for high efficiency and reduced component
count. An external Schottky diode is not required. The
internal 90mΩpower switch and 70mΩNMOS synchro-
nous-rectifier switch easily deliver continuous load cur-
rents up to 2.7A. The MAX1843 produces a preset +2.5V,
+1.8V, or +1.5V output voltage or an adjustable output
from +1.1V to VIN. It achieves efficiencies as high as
95%.
The MAX1843 uses a unique current-mode, constant-off-
time, PWM control scheme, which includes Idle Mode™
to maintain high efficiency during light-load operation.
The programmable constant-off-time architecture sets
switching frequencies up to 1MHz, allowing the user to
optimize performance trade-offs between efficiency, out-
put switching noise, component size, and cost. The
MAX1843 features an adjustable soft-start to limit surge
currents 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 sup-
ply current below 1µA. The MAX1843 is available in a 28-
pin QFN package with an exposed backside pad.
Applications5V or 3.3V to Low-Voltage Conversion
CPU I/O Ring
Chipset Supplies
Notebook and Subnotebook Computers
Features±1% Output AccuracyUp to 1MHz Switching Frequency95% EfficiencyInternal PMOS/NMOS Switches
90mΩ/70mΩOn-Resistance at VIN= +4.5V
110mΩ/80mΩOn-Resistance at VIN= +3VOutput Voltage
+2.5V, +1.8V, or +1.5V Pin Selectable
+1.1V to VINAdjustable+3V to +5.5V Input Voltage Range350µA Operating Supply Current<1µA Shutdown Supply CurrentProgrammable Constant-Off-Time OperationIdle Mode Operation at Light LoadsThermal Shutdown Adjustable Soft-Start Inrush Current Limiting100% Duty Cycle During Low-Dropout OperationOutput Short-Circuit Protection28-Pin QFN Package
Ordering InformationIdle Mode is a trademark of Maxim Integrated Products.
Pin Configurationypical Configuration
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS (VIN= VCC= +3.3V, FBSEL = GND, TA
= 0°C to +85°C, unless otherwise noted. Typical values 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 to GND........................................................-0.3V to +6V
IN to VCC.............................................................................±0.3V
GND to PGND.....................................................................±0.3V
All Other Pins to GND.................................-0.3V to (VCC+ 0.3V)
LX Current (Note 1).............................................................±4.7A
REF Short Circuit to GND Duration............................Continuous
ESD Protection.....................................................................±2kV
Continuous Power Dissipation (TA= +70°C)
28-Pin QFN (derate 20mW/°C above +70°C, part mounted
on 1in2of 1oz copper)......................................................1.6W
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s)................................+300°C
Note 1:LX has internal clamp diodes to PGND and IN. Applications that forward bias these diodes should take care not to exceed the
IC’s package power dissipation limits.
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
ELECTRICAL CHARACTERISTICS(VIN
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
ELECTRICAL CHARACTERISTICS (continued)
Note 3:Specifications from 0°C to -40°C are guaranteed by design, not production tested.
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN PackageSUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1843 toc01
VIN (V)
NO-LOAD SUPPLY CURRENT, I
+ I
CC
SHUTDOWN SUPPLY CURRENT, I
+ I
CC
(nA)
Typical Operating Characteristics (continued)(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
Detailed DescriptionThe MAX1843 synchronous, current-mode, constant-off-
time, PWM DC-DC converter steps down input voltages
of +3V to +5.5V to a preset output voltage of +2.5V,
+1.8V, or +1.5V, or to an adjustable output voltage from
+1.1V to VIN. It delivers up to 2.7A of output current.
Internal switches composed of a 0.09ΩPMOS power
switch and a 0.07ΩNMOS synchronous-rectifier switch
improve efficiency, reduce component count, and elimi-
nate the need for an external Schottky diode.
The MAX1843 optimizes efficiency by operating in con-
stant-off-time mode under heavy loads and in Maxim’s
proprietary idle mode under light loads. A single resistor-
programmable constant-off-time control sets switching
frequencies up to 1MHz, allowing the user to optimize
performance trade-offs in efficiency, switching noise,
component size, and cost. Under low-dropout conditions,
the device operates in a 100% duty-cycle mode, where
the PMOS switch remains continuously on. Idle mode
enhances light-load efficiency by skipping cycles, thus
reducing transition and gate-charge losses.
When power is drawn from a regulated supply, constant-
off-time PWM architecture essentially provides constant-
frequency operation. This architecture has the inherent
advantage of quick response to line and load transients.
The MAX1843’s current-mode, constant-off-time PWM
architecture regulates the output voltage by changing
the PMOS switch on-time relative to the constant off-
time. Increasing the on-time increases the peak induc-
tor current and the amount of energy transferred to the
load per pulse.
Modes of OperationThe current through the PMOS switch determines the
mode of operation: constant-off-time mode (for load
currents greater than half the idle mode threshold, of
idle mode), or idle mode (for load currents less than
half the idle-mode threshold). Current sense is
achieved through a proprietary architecture that elimi-
nates current-sensing I2R losses.
Pin Description
MAX1843
2.7A, 1MHz, Low-Voltage, Step-Down Regulator with
Internal Synchronous Rectification in QFN Package
Constant-Off-Time ModeConstant-off-time operation occurs when the current
through the PMOS switch is greater than the idle-mode
threshold current (which corresponds to a load current of
half the idle mode threshold). In this mode, the regulation
comparator turns the PMOS switch on at the end of each
off-time, keeping the device in continuous-conduction
mode. The PMOS switch remains on until the output is in
regulation or the current limit is reached. When the
PMOS switch turns off, it remains off for the programmed
off-time (tOFF). To control the current under short-circuit
conditions, the PMOS switch remains off for approxi-
mately 4 x tOFFwhen VOUT< VOUT(NOM) / 4.
Figure 2. Functional Diagram
Figure 1. Typical Circuit
