MAX1842 ,1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal SwitchesFeaturesThe MAX1742/MAX1842 constant-off-time, pulse-width-♦ ±1% Output Accuracymodulated (PWM) ste ..
MAX1842EEE ,1A/2.7A / 1MHz / Step-Down Regulators with Synchronous Rectification and Internal SwitchesFeaturesThe MAX1742/MAX1842 constant-off-time, pulse-width- ±1% Output Accuracymodulated (PWM) ste ..
MAX1842EEE+ ,1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal SwitchesApplications that forward-bias these diodes should take care not to exceedthe IC’s package power di ..
MAX1842EEE+T ,1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal SwitchesFeaturesThe MAX1742/MAX1842 constant-off-time, pulse-width-♦ ±1% Output Accuracymodulated (PWM) ste ..
MAX1842EEE-T ,1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal Switchesapplications requir-♦ 100% Duty Cycle During Low-Dropout Operationing small external component size ..
MAX1842EEE-T ,1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal SwitchesApplicationsTypical Configuration5V or 3.3V to Low-Voltage ConversionCPU I/O Ring OUTPUTINPUTIN 1.1 ..
MAX4736ELB+T ,0.6 Ohm, Low-Voltage, Single-Supply, Dual SPDT Analog SwitchApplicationsMAX4736EGC+ 12 QFN-EP* G1233+1● Power RoutingMAX4736ELB+ 10 μDFN L1022+1● Battery-Power ..
MAX4736EUB ,0.8 / Low-Voltage / Single-Supply / Dual SPDT Analog SwitchApplicationsPower RoutingOrdering InformationBattery-Powered SystemsPART TEMP RANGE PIN-PACKAGEAudi ..
MAX4736EUB ,0.8 / Low-Voltage / Single-Supply / Dual SPDT Analog SwitchELECTRICAL CHARACTERISTICS—Single 3V Supply(V+ = 2.7V to 3.6V, V = 1.4V, V = 0.5V, T = T to T , unl ..
MAX4736EUB+ ,0.6 Ohm, Low-Voltage, Single-Supply, Dual SPDT Analog SwitchElectrical Characteristics—Single 3V Supply(V+ = 2.7V to 4.2V, V = 1.4V, V = 0.5V, T = T to T , unl ..
MAX4736EUB+T ,0.6 Ohm, Low-Voltage, Single-Supply, Dual SPDT Analog Switchfeatures ● 1.8V CMOS Logic Compatible (3V Supply)low 0.6Ω on-resistance (R), with 0.1Ω R matching O ..
MAX4737EBE+T ,4.5 Ohm Quad SPST Analog Switches in UCSPApplications● Battery-Operated Equipment● Audio/Video-Signal Routing● Low-Voltage Data-Acquisition ..
MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with Synchronous Rectification and Internal Switches
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches19-1760; Rev 2; 9/05
General DescriptionThe MAX1742/MAX1842 constant-off-time, pulse-width-
modulated (PWM) step-down DC-DC converters are ideal
for use in 5V and 3.3V to low-voltage conversion neces-
sary in notebook and subnotebook computers. These
devices feature internal synchronous rectification for high
efficiency and reduced component count. They require
no external Schottky diode. The internal 90mΩPMOS
power switch and 70mΩNMOS synchronous-rectifier
switch easily deliver continuous load currents up to 1A.
The MAX1742/MAX1842 produce a preset 2.5V, 1.8V, or
1.5V output voltage or an adjustable output from 1.1V to
VIN. They achieve efficiencies as high as 95%.
The MAX1742/MAX1842 use 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 architec-
ture sets switching frequencies up to 1MHz, allowing the
user to optimize performance trade-offs between effi-
ciency, output switching noise, component size, and
cost. Both devices are designed for continuous output
currents up to 1A. The MAX1742 uses a peak current
limit of 1.3A (min) and is suitable for applications requir-
ing small external component size and high efficiency.
The MAX1842 has a higher current limit of 3.1A (min)
and is intended for applications requiring an occasional
burst of output current up to 2.7A. Both devices also fea-
ture an adjustable soft-start to limit surge currents during
startup, a 100% duty cycle mode for low-dropout opera-
tion, and a low-power shutdown mode that disconnects
the input from the output and reduces supply current
below 1µA. The MAX1742/MAX1842 are available in 16-
pin QSOP packages.
For similar devices that provide continuous output cur-
rents up to 2A and 3A, refer to the MAX1644 and
MAX1623 data sheets.
Applications5V or 3.3V to Low-Voltage Conversion
CPU I/O Ring
Chipset Supplies
Notebook and Subnotebook Computers
Features±1% Output Accuracy95% EfficiencyInternal PMOS and NMOS Switches
90mΩOn-Resistance at VIN= 4.5V
110mΩOn-Resistance at VIN= 3VOutput Voltage
2.5V, 1.8V, or 1.5V Pin Selectable
1.1V to VINAdjustable3V to 5.5V Input Voltage Range600μA (max) Operating Supply Current<1μA Shutdown Supply CurrentProgrammable Constant-Off-Time Operation1MHz (max) Switching FrequencyIdle-Mode Operation at Light LoadsThermal Shutdown Adjustable Soft-Start Inrush Current Limiting100% Duty Cycle During Low-Dropout OperationOutput Short-Circuit Protection16-Pin QSOP Package
Ordering InformationIdle Mode is a trademark of Maxim Integrated Products.
Typical ConfigurationTOFF
COMP
VCC
FBSELSHDN
PGND
GND
REFMAX1742
MAX1842
OUTPUT
1.1V TO
VIN
INPUT
3V TO
5.5V
0.01μF
1μF
2.2μF470pF
10Ω
Pin Configuration appears at end of data sheet.
EVALUATION KIT
AVAILABLE
PARTTEMP RANGEPIN-PACKAGE
MAX1742EEE-40°C to +85°C16 QSOP
MAX1742EEE+-40°C to +85°C16 QSOP
MAX1842EEE-40°C to +85°C16 QSOP
MAX1842EEE+-40°C to +85°C16 QSOP
+ Denotes lead-free package.
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
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.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput Voltage VIN, VCC 3.0 5.5 V
TA = +25°C
to +85°C2.5002.5252.550
FBSEL =
VCCTA = +0°C
to +85°C2.4872.5252.563
TA = +25°C
to +85°C1.5001.5151.530
FBSEL =
unconnectedTA = +0°C
to +85°C1.4921.5151.538
TA = +25°C
to +85°C1.8001.8181.836
FBSEL =
REFTA = +0°C
to +85°C1.7911.8181.845
TA = +25°C
to +85°C1.0891.1001.111
Preset Output VoltageVOUT
VIN = 3V to
5.5V,
ILOAD = 0
to 1A for
MAX1742,
ILOAD = 0
to 2.5A for
MAX1842,
VFB = VOUT
FBSEL =
GNDTA = +0°C
to +85°C1.0841.1001.117V
Adjustable Output Voltage
Range
VIN = VCC = 3V to 5.5V, ILOAD = 0,
FBSEL = GNDVREFVINV
AC Load Regulation Error2%DC Load Regulation Error 0.4 %Dropout Voltage VDO VIN = VCC = 3V, ILOAD = 1A 250 mV
TA = +25°C to +85°C 1.089 1.100 1.111 Reference Voltage VREFTA = +0°C to +85°C 1.084 1.100 1.117 VReference Load Regulation ΔVREF IREF = -1µA to +10µA 0.5 2 mVVIN = 4.5V 90 200 PMOS Switch
On-Resistance RON, P ILX = 0.5A VIN = 3V 110 250VIN = 4.5V 70 150 NMOS Switch
On-Resistance RON, N ILX = 0.5A VIN = 3V 80 200mΩ
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)
SSOP (derate 16.7mW/°C above +70°C;
part mounted on 1 in.2of 1oz. copper)...............................1W
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +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.
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
ELECTRICAL CHARACTERISTICS (continued)(VIN= VCC= 3.3V, FBSEL = GND, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMAX1742 1.3 1.5 1.7 Current-Limit Threshold ILIMIT MAX1842 3.1 3.6 4.1 ARMS LX Output Current 3.1 AMAX1742 0.1 0.3 0.5 Idle Mode Current Threshold IIM MAX1842 0.3 0.6 0.9 ASwitching Frequency f (Note 2) 1 MHz
No-Load Supply CurrentIIN + ICCVFB = 1.2V350600µAShutdown Supply Current ICC(SHDN) SHDN = GND <1 5 µAPMOS Switch Off-Leakage
Current IIN SHDN = GND 15 µAThermal Shutdown Threshold TSHDN Hysteresis = 15°C 160 °CUndervoltage Lockout Threshold VUVLO VIN falling, hysteresis = 90mV 2.5 2.6 2.7 VFB Input Bias Current IFB VFB = 1.2V 0 60 250 nARTOFF = 110kΩ 0.9 1.00 1.1RTOFF = 30.1kΩ 0.24 0.30 0.37 Off-Time Default Period tOFFRTOFF = 499kΩ 3.8 4.5 5.2µsOff-Time Startup Period tOFF FB = GND 4 ✕ tOFF µsOn-Time Period tON (Note 2) 0.4 µsSS Source Current ISS 4 5 6 µASS Sink Current ISS VSS = 1V 100 µASHDN Input Current I SHDN V SHDN = 0 to VCC -1 1 µASHDN Input Low Threshold VIL 0.8 VSHDN Input High Threshold VIH 2.0 VFBSEL Input Current -4 +4 µA
FBSEL = GND0.2
FBSEL = REF0.91.3
FBSEL = unconnected0.7 ✕ VCC
- 0.2
0.7 ✕ VCC
+0.2FBSEL Logic Thresholds
FBSEL = VCCVCC
- 0.2
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
ELECTRICAL CHARACTERISTICS(VIN= VCC= 3.3V, FBSEL = GND, TA
= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 3)
Note 2:Recommended operating frequency, not production tested.
Note 3:Specifications from 0°C to -40°C are guaranteed by design, not production tested.
PARAMETERSYMBOLCONDITIONSMINMAXUNITSInput Voltage VIN 3.0 5.5 V
VIN = 3V to 5.5V,
FBSEL = VCC2.4752.575
FBSEL = unconnected1.4851.545
FBSEL = REF1.7821.854
Preset Output VoltageVOUT
ILOAD = 0 to 1A
for MAX1742,
ILOAD = 0 to 2.5A
for MAX1842,
VFB = VOUTFBSEL = GND1.0781.122V
Adjustable Output Voltage
Range
VIN = VCC = 3V to 5.5V, ILOAD = 0,
FBSEL = GNDVREFVINVReference Voltage VREF 1.078 1.122 VVIN = 4.5V 200 PMOS Switch
On-Resistance RON, P ILX = 0.5A VIN = 3V 250VIN = 4.5V 150 NMOS Switch
On-Resistance RON, N ILX = 0.5A VIN = 3V 200mΩMAX1742 1.2 1.8 Current-Limit Threshold ILIMIT MAX1842 2.9 4.3MAX1742 0.05 0.55 Idle Mode Current Threshold IIM MAX1842 0.2 1.0A
No-Load Supply CurrentIIN + ICCVFB = 1.2V600µA
FB Input Bias CurrentIFBVFB = 1.2V0300nA
Off-Time Default PeriodtOFFRTOFF = 110kΩ0.851.15µs
Typical Operating Characteristics(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal SwitchesMAX1742
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 5.0V, L = 6.0μH)
MAX1742 toc01
OUTPUT CURRENT (A)
EFFICIENCY (%)
VOUT = 1.8V, RTOFF = 75kΩ,
f = 833kHz
VOUT = 1.5V, RTOFF = 100kΩ, f = 692kHz
VOUT = 2.5V, RTOFF = 47kΩ, f = 926kHz
MAX1742
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 3.3V, L = 3.9μH)
MAX1742 toc02
OUTPUT CURRENT (A)
EFFICIENCY (%)
VOUT = 2.5V, RTOFF = 36kΩ, f = 456kHz
VOUT = 1.8V, RTOFF = 43kΩ, f = 869kHz
VOUT = 1.5V, RTOFF = 56kΩ, f = 833kHz
MAX1742
EFFICIENCY vs.OUTPUT CURRENT
(fPWM = 270kHz)
MAX1742 toc03
OUTPUT CURRENT (A)
EFFICIENCY (%)
VIN = 5V, VOUT = 1.8V,
L = 15μH, RTOFF = 240kΩ
VIN = 3.3V, VOUT = 1.8V,
L = 10μH, RTOFF = 160kΩ
MAX1742
NORMALIZED OUTPUT ERROR
vs. OUTPUT CURRENT
MAX1742 toc04
OUTPUT CURRENT (A)
NORMALIZED OUTPUT ERROR (%)
VIN = 5V, VOUT = 1.5V, L = 6μH
VIN = 3.3V, VOUT = 1.5V
MAX1742
SWITCHING FREQUENCY
vs. OUTPUT CURRENT
MAX1742 toc05
OUTPUT CURRENT (A)
FREQUENCY (kHz)
VIN = 5V, VOUT = 2.5V, L = 6μH
VIN = 5V, VOUT = 1.5V, L = 6μH
VIN = 3.3V, VOUT = 1.5V, L = 3.9μH
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
MAX1742
STARTUP AND SHUTDOWNIINPUT
1A/div
VOUTPUT
1V/div
VSS
2V/div
MAX1742 toc06
1ms/div
VSHDN
5V/div
MAX1742
LOAD-TRANSIENT RESPONSEVOUTPUT
AC-COUPLED,
50mV/div
0.5A/div
MAX1742 toc07
10μs/div
MAX1742
LINE-TRANSIENT RESPONSEVINPUT
2V/div
VOUTPUT
20mV/div
AC-COUPLED
MAX1742 toc08
20μs/div
IOUT = 1A, VOUT = 1.5V, RTOFF = 100kΩ, L = 6μH
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1742 toc09
VIN (V)
NO-LOAD SUPPLY CURRENT, I
+ I
CC
SHUTDOWN SUPPLY CURRENT, I
+ I
CC
(nA)
NO LOAD
SHUTDOWN
Typical Operating Characteristics (continued)(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
OFF-TIME vs. RTOFF
MAX1742 toc10
RTOFF (kΩ)
tOFF
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switchesypical Operating Characteristics (continued)(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
MAX1842
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 5.0V, L = 2.5μH)
MAX1842 toc11
OUTPUT CURRENT (A)
VOUT = 1.5V, RTOFF = 1OOkΩ,
fPWM = 770kHz
VOUT = 1.8V, RTOFF = 75kΩ,
fPWM = 910kHz
VOUT = 2.5V, RTOFF = 47kΩ,
fPWM = 1070kHz
EFFICIENCY (%)
MAX1842
EFFICIENCY vs. OUTPUT CURRENT
(VIN = 3.3V, L = 1.5μH)
MAX1842 toc12
OUTPUT CURRENT (A)
VOUT = 2.5V, RTOFF = 56kΩ,
fPWM = 1000kHz
VOUT = 2.5V, RTOFF = 39kΩ,
fPWM = 610kHz
VOUT = 1.8V, RTOFF = 43kΩ,
fPWM = 1050kHz
EFFICIENCY (%)
MAX1842
EFFICIENCY vs. OUTPUT CURRENT
(fPWM = 270kHz)
MAX1842 toc13
IOUT (A)
VIN = 3.3V, VOUT = 1.8V,
L = 4.7μH, RTOFF = 160kΩ
EFFICIENCY (%)
VIN = 5V, VOUT = 1.8V, L = 5.6μH,
RTOFF = 240kΩ
MAX1842
NORMALIZED OUTPUT ERROR
vs. OUTPUT CURRENTMAX1842 toc14
OUTPUT CURRENT (A)
VIN = 3.3V, VOUT = 1.5V, L = 1.5μH
VIN = 5V, VOUT = 1.5V, L = 2.5μH
NORMALIZED OUTPUT ERROR (%)
MAX1842
SWITCHING FREQUENCY
vs. OUTPUT CURRENT
MAX1842 toc15
OUTPUT CURRENT (A)
FREQUENCY (kHz)
VIN = 5V, VOUT = 2.5V, L = 2.5μH
VIN = 3.3V, VOUT = 1.5V, L = 1.5μH
VIN = 5V, VOUT = 1.5V, L = 2.5μH
MAX1842
STARTUP AND SHUTDOWNVSS
2V/div
MAX1842 toc16
VSHDN
5V/div
ROUT = 0.5Ω, RTOFF = 56kΩ
IINPUT
1A/div
VOUTPUT
1V/div
1ms/div
MAX1742/MAX1842
1A/2.7A, 1MHz, Step-Down Regulators with
Synchronous Rectification and Internal Switches
NAMEFUNCTIONSHDNShutdown Control Input. Drive SHDNlow to disable the reference, control circuitry, and internal
MOSFETs. Drive high or connect to VCCfor normal operation.
PIN
Pin Description
MAX1842
LOAD-TRANSIENT RESPONSEVOUTPUT
50mV/div
2A/div
MAX1842 toc17
10μs/div
MAX1842
LINE-TRANSIENT RESPONSEVINPUT
2V/div
VOUTPUT
20mV/div
AC-COUPLED
MAX1842 toc18
20μs/div
IOUT = 2.5A, VOUT = 1.5V, RTOFF = 100kΩ, L = 2.2μH
2, 4INSupply Voltage Input—for the internal PMOS power switch.
3, 14, 16LXConnection for the drains of the PMOS power switch and NMOS synchronous-rectifier switch. Connect
the inductor from this node to the output filter capacitor and load.SSSoft-Start. Connect a capacitor from SS to GND to limit inrush current during startup.COMPIntegrator Compensation. Connect a capacitor from COMP to VCCfor integrator compensation. See
Integrator Amplifiersection.TOFFOff-Time Select Input. Sets the PMOS power switch off-time during constant-off-time operation. Connect a
resistor from TOFF to GND to adjust the PMOS switch off-time.FBFeedback Input—for both preset-output and adjustable-output operating modes. Connect directly to
output for fixed-voltage operation or to a resistive divider for adjustable operating modes.GNDAnalog GroundREFReference Output. Bypass REF to GND with a 1µF capacitor.FBSELFeedback Select Input. Selects output voltage. See Table 3 for programming instructions.VCCAnalog Supply Voltage Input. Supplies internal analog circuitry. Bypass VCCwith a 10Ωand 2.2µF low-
pass filter. See Figure 1.
13, 15PGNDPower Ground. Internally connected to the internal NMOS synchronous-rectifier switch.
ypical Operating Characteristics (continued)(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)
