MAX1733EUK+T Fast Delivery |IC PHOENIX CO.,LIMITED

MAX1733EUK+T ,Low-Voltage, Step-Down DC-DC Converters in SOT23ELECTRICAL CHARACTERISTICS(V = +2.7V to +5.5V, SHDN = IN, T = 0°C to +85°C. Typical values are at T ..
MAX1733EUK-T ,Low-Voltage / Step-Down DC-DC Converters in SOT23ApplicationsGuide, then insert the proper designator into the blanks above tocomplete the part numb ..
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MAX4562EEE ,Serially Controlled / Clickless Audio/Video Switchesfeatures 30Ω max on-resistance (R ), 5Ω RON ON' 30Ω max On-Resistancematch, and 5Ω R flatness. Audi ..
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MAX4565CAP ,Quad/Dual / Low-Voltage / Bidirectional RF/Video SwitchesGeneral Description ________

MAX1733EUK+T
Low-Voltage, Step-Down DC-DC Converters in SOT23
General Description
The MAX1733/MAX1734 step-down DC-DC converters
deliver over 250mA to outputs as low as 1.25V. These
converters use a unique proprietary current-limited con-
trol scheme that achieves over 90% efficiency. These
devices maintain extremely low quiescent supply cur-
rent (40µA), and their high 1.2MHz (max) operating fre-
quency permits small, low-cost external components.
This combination of features makes the MAX1733/
MAX1734 excellent high-efficiency alternatives to linear
regulators in space-constrained applications.
Internal synchronous rectification greatly improves effi-
ciency and eliminates the external Schottky diode
required in conventional step-down converters. Both
devices also include internal digital soft-start to limit
input current upon startup and reduce input capacitor
requirements.
The MAX1733 provides an adjustable output voltage
(1.25V to 2.0V). The MAX1734 provides factory-preset
output voltages (see Selector Guide). Both are avail-
able in space-saving 5-pin SOT23 packages.
Applications
Cellular, PCS, and Cordless Telephones
PDAs, Palmtops, and Handy-Terminals
Battery-Powered Equipment
Features250mA Guaranteed Output CurrentSynchronous Rectifier for Over 90% EfficiencyTiny 5-Pin SOT23 Package40µA Quiescent Supply Current0.01µA Logic-Controlled ShutdownUp to 1.2MHz Switching FrequencyFixed 1.8V or 1.5V Outputs (MAX1734)Adjustable Output Voltage (MAX1733)±1.5% Initial Accuracy2.7V to 5.5V Input RangeSoft-Start Limits Startup Current
MAX1733/MAX1734
Low-Voltage, Step-Down DC-DC Converters
in SOT23
GND
OUT (FB)
( ) ARE FOR MAX1733 ONLY.
SHDNLXIN
MAX1733
MAX1734
SOT23-5
TOP VIEW
Pin Configuration
OUT
VOUT AT
250mA
INPUT
+2.7V TO +5.5VIN
MAX1734
SHDN
GND
10μH
22μF2.2μFypical Operating Circuit
19-1586; Rev 0; 7/00
Note:The MAX1734 offers two output voltages. See the Selector
Guide, then insert the proper designator into the blanks above to
complete the part number.
Ordering InformationPART TEMP. RANGE PIN-PACKAGE
MAX1733EUK-T-40°C to +85°C5 SOT23-5A X1 7 3 4 E U K_ _- T-40°C to +85°C5 SOT23-5
Selector Guide
PARTVOUT (V)TOP MARK
MAX1733EUKAdjustableADKY
MAX1734EUK181.8ADKW
MAX1734EUK151.5ADKX
MAX1733/MAX1734
Low-Voltage, Step-Down DC-DC Converters
in SOT23
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= +2.7V to +5.5V, SHDN= IN, TA= 0°C to +85°C.Typical values are at TA= +25°C, unless otherwise noted.)
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.
IN, SHDNto GND.....................................................-0.3V to +6V
OUT, FB, LX to GND....................................-0.3V to (VIN+ 0.3V)
OUT Short Circuit to GND..........................................Continuous
Continuous Power Dissipation (TA= +70°C)
5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW
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
Input Voltage RangeVIN2.75.5V
Startup VoltageVSTART2.0V
VIN rising1.851.95UVLO ThresholdVUVLOVIN falling1.551.65V
UVLO Hysteresis200mV
Quiescent Supply CurrentIINNo switching, no load (FB/OUT above trip
point)4070μA
Shutdown Supply CurrentISHDNSHDN = GND0.014μA
Outp ut V ol tag e Range ( MAX 1733) VOUT1.252.0V
IOUT = 0, TA = +25°C-1.5+1.5Output Voltage Accuracy
(MAX1734)IOUT = 0 to 250mA-3+3%
Load RegulationIOUT = 0 to 250mA0%/mA
Line RegulationVIN = 2.7V to 5.5V0%/V
OUT Sense Current (MAX1734)VOUT = VREG, VIN = V SHDN= 5V48μA
TA = +25°C, VIN = 3.6V1.2311.2501.269FB Feedback Threshold
(MAX1733)VFBVIN = 3.6V1.2201.280V
FB Leakage Current (MAX1733)IFBVFB = 1.5V0.0010.2μA
SHDN Input High VoltageVIH2.7V < VIN < 5.5V1.6V
SHDN Input Low VoltageVIL2.7V < VIN < 5.5V0.4V
SHDN Leakage CurrentISHDNSHDN = GND or IN0.0011μA
High-Side Current LimitILIMP300425535mA
Low-Side Current LimitILIMN200325430mA
ILX = -50mA, VIN = 3.0V0.71.4High-Side On-ResistanceRONPILX = -50mA, VIN = 5.5V0.51.1Ω
ILX = -50mA, VIN = 3.0V1.02Rectifier On-ResistanceRONNILX = -50mA, VIN = 5.5V0.81.6Ω
Rectifier Off-Current ThresholdILXOFF40mA
LX Leakage CurrentILXLEAKVIN = 5.5V, VLX = 0 to VIN0.15μA
LX Reverse Leakage CurrentILXLK,RIN unconnected, VLX = 5.5V, SHDN = GND0.15μA
Minimum On-TimetON(MIN)VIN = 3.6V0.280.40.5μs
Minimum Off-TimetOFF( M IN) VIN = 3.6V0.280.40.5μs
MAX1733/MAX1734
Low-Voltage, Step-Down DC-DC Converters
in SOT23
Note 1:All devices are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.
ELECTRICAL CHARACTERISTICS
(VIN= +2.7V to +5.5V, SHDN= IN, TA= -40°C to +85°C,unless otherwise noted.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINMAXUNITS
Input Voltage RangeVIN2.75.5V
Startup VoltageVSTART2.0V
VIN rising, 200mV typical hysteresis1.95UVLO ThresholdVUVLOVIN falling1.55V
Quiescent Supply CurrentIINNo switching (FB/OUT above trip point)70μA
Shutdown Supply CurrentISHDNSHDN = GND4μA
Outp ut V ol tag e Range ( MAX 1733) VOUT1.252.0V
Output Voltage Accuracy
(MAX1734)IOUT = 0 to 250mA-3+3%
OUT Sense Current (MAX1734)IOUTVOUT = VREG, VIN = V SHDN = 5V8μA
FB Feedback Threshold
(MAX1733)VFBVIN = 3.6V1.2101.280V
FB Leakage Current (MAX1733)IFBVFB = 1.5V0.2μA
SHDN Input High VoltageVIH2.7V < VIN < 5.5V1.6V
SHDN Input Low VoltageVIL2.7V < VIN < 5.5V0.4V
SHDN Leakage CurrentISHDNSHDN = GND or IN1μA
High-Side Current LimitILIMP300565mA
Low-Side Current LimitILIMN200430mA
ILX = -50mA, VIN = 3.0V1.4High-Side On-ResistanceRONPILX = -50mA, VIN = 5.5V1.1Ω
ILX = -50mA, VIN = 3.0V2Rectifier On-ResistanceRONNILX = -50mA, VIN = 5.5V1.6Ω
LX Leakage CurrentILXLEAKVIN = 5.5V, VLX = 0 to VIN5μA
LX Reverse Leakage CurrentILXLK,RIN unconnected, VLX = 5.5V, SHDN = GND5μA
Minimum On-TimetON(MIN)0.250.55μs
Minimum Off-TimetOFF( M IN) 0.250.55μs
MAX1733/MAX1734
Low-Voltage, Step-Down DC-DC Converters
in SOT23
Typical Operating Characteristics
(CIN= 2.2µF ceramic, COUT= 22µF tantalum, L = 10µH, unless otherwise noted.)
EFFICIENCY vs.
LOAD CURRENT (VOUT = 1.8V)
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.6V
VIN = 2.7V
MAX1733/4-01
EFFICIENCY vs.
LOAD CURRENT (VOUT = 1.5V)
MAX1733/4-02
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.6V
VIN = 2.7V
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1733/4-03
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
VOUT = 1.5V, TA = -40°C
VOUT = 1.5V, TA = +25°C
VOUT = 1.8V, TA = +85°C
VOUT = 1.8V, TA = +25°C
OUTPUT ACCURACY vs.
LOAD CURRENT (VOUT = 1.8V)
MAX1733/4-04
LOAD CURRENT (mA)
OUTPUT ACCURACY (%)
VIN = 3.6V, TA = -40°C
VIN = 5.0V, TA = +25°C
VIN = 3.6V, TA = +85°C
VIN = 2.7V, TA = +25°C
OUTPUT ACCURACY vs.
LOAD CURRENT (VOUT = 1.5V)
MAX1733/4-05
LOAD CURRENT (mA)
OUTPUT ACCURACY (%)
VIN = 3.6V, TA = -40°C
VIN = 2.7V, TA = +25°C
VIN = 3.6V, TA = +85°C
VIN = 5.0V, TA = +25°C
SWITCHING FREQUENCY
vs. SUPPLY VOLTAGE
MAX1733/4-06
SUPPLY VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
VOUT = 1.8V
VOUT = 1.5V
ILOAD = 50mA TO 250mA
LIGHT-LOAD SWITCHING WAVEFORMS
MAX1733/4-07
400ns/div
VLX
2V/div
VOUT
AC-COUPLED
20mV/div
VIN = 3.6V, VOUT = 1.8V, ILOAD = 20mA
HEAVY-LOAD SWITCHING WAVEFORMS
MAX1733/4-08
400ns/div
VLX
2V/div
VOUT
AC-COUPLED
20mV/div
VIN = 3.6V, VOUT = 1.8V, ILOAD = 200mA
MAX1733/MAX1734
Low-Voltage, Step-Down DC-DC Converters
in SOT23
Typical Operating Characteristics (continued)
(CIN= 2.2µF ceramic, COUT= 22µF tantalum, L = 10µH, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
MAX1733/4-12
4μs/div
VOUT
AC-COUPLED
50mV/div
ILOAD
100mA/div
VIN = 3.6V, VOUT = 1.8V, ILOAD = 20mA TO 200mA
LIGHT-LOAD LINE-TRANSIENT RESPONSE
MAX1733/4-10
4μs/div
VOUT
AC-COUPLED
50mV/div
VIN
AC-COUPLED
200mV/div
VIN = 3.4V TO 3.8V, VOUT = 1.8V, ILOAD = 20mA
HEAVY-LOAD LINE-TRANSIENT RESPONSE
MAX1733/4-11
4μs/div
VOUT
AC-COUPLED
50mV/div
VIN
AC-COUPLED
200mV/div
VIN = 3.4V TO 3.8V, VOUT = 1.8V, ILOAD = 200mA
SOFT-START AND SHUTDOWN RESPONSE
MAX1733/4-09
200μs/div
VOUT
1V/div
VIN = 3.6V, VOUT = 1.8V, RLOAD = 7Ω
VSHDN
5V/div
IIN
100mA/div
Pin Description
PINNAMEFUNCTION
1INSupply Voltage Input. Input range from +2.7V to +5.5V. Bypass with a 2.2μF ceramic capacitor to
GND.GNDGroundSHDNActive-Low Shutdown Input. Connect SHDN to IN for normal operation. In shutdown, LX becomes
high impedance and quiescent current drops to 0.01μA.MAX1733 Voltage Feedback Input. FB regulates to 1.25V nominal. Connect FB to an external
voltage-divider between the output voltage and GND.4
OUTMAX1734 Voltage Sense Input. OUT is connected to an internal voltage-divider.LXInductor Connection
MAX1733/MAX1734
Detailed Description
The MAX1733/MAX1734 step-down DC-DC converters
deliver over 250mA to outputs as low as 1.25V. They
use a unique proprietary current-limited control scheme
that maintains extremely low quiescent supply current
(40µA), and their high 1.2MHz (max) operating frequen-
cy permits small, low-cost external components. Figure
2 is a simplified functional diagram.
Control Scheme
The MAX1733/MAX1734 use a proprietary, current-lim-
ited control scheme to ensure high-efficiency, fast tran-
sient response, and physically small external
components. This control scheme is simple: when the
output voltage is out of regulation, the error comparator
begins a switching cycle by turning on the high-side
switch. This switch remains on until the minimum on-
time of 400ns expires and the output voltage regulates
or the current-limit threshold is exceeded. Once off, the
high-side switch remains off until the minimum off-time
of 400ns expires and the output voltage falls out of reg-
ulation. During this period, the low-side synchronous
rectifier turns on and remains on until either the high-
side switch turns on again or the inductor current
approaches zero. The internal synchronous rectifier
eliminates the need for an external Schottky diode.
This control scheme allows the MAX1733/MAX1734 to
provide excellent performance throughout the entire
load-current range. When delivering light loads, the
high-side switch turns off after the minimum on-time to
reduce peak inductor current, resulting in increased
efficiency and reduced output voltage ripple. When
delivering medium and higher output currents, the
MAX1733/MAX1734 extend either the on-time or the off-
time, as necessary to maintain regulation, resulting in
nearly constant frequency operation with high efficien-
cy and low output voltage ripple.
Shutdown Mode
Connecting SHDNto GND places the MAX1733/
MAX1734 in shutdown mode and reduces supply cur-
rent to 0.01µA. In shutdown, the control circuitry, inter-
nal switching MOSFET, and synchronous rectifier turn
off and LX goes high impedance. Connect SHDNto IN
for normal operation.
Soft-Start
The MAX1733/MAX1734 have internal soft-start circuitry
that limits current draw at startup, reducing transients on
the input source. Soft-start is particularly useful for higher
impedance input sources, such as Li+ and alkaline cells.
Soft-start is implemented by starting with the current limit
at 25% of its full current value and gradually increasing it
in 25% steps until the full current limit is reached. See
Soft-Start and Shutdown Response in the Typical
Operating Characteristicssection.
Design Information
Setting the Output Voltage (MAX1733)
Select an output voltage for the MAX1733 by connect-
ing FB to a resistive divider between the output and
Low-Voltage, Step-Down DC-DC Converters
in SOT23
Figure 1. MAX1733 Typical Application Circuit
VOUT
2.2μF
22μF
10μHIN
MAX1733
SHDN
GND
INPUT
+2.7V TO +5.5V
SHDN
CONTROL
LOGIC
VREF
OUT (FB)
GND( ) ARE FOR MAX1733 ONLY.
CURRENT
LIMIT
SHUTDOWN
CONTROL
DIGITAL
SOFT-START
MAX1733
MAX1734
Figure 2. Simplified Functional Diagram

Partno	Mfg	Dc	Qty	Available	Descript
MAX1733EUK+T \|MAX1733EUKT	MAXIM/PBF	N/a	45000	avai	Low-Voltage, Step-Down DC-DC Converters in SOT23