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MAX1534ETE+T
High-Efficiency, Triple-Output, Keep-Alive Power Supply for Notebook Computers
General DescriptionThe MAX1534 is a high-efficiency, triple-output power
supply for keep-alive (always on) voltage rails. The
500mA buck regulator with an internal current-limited
0.5ΩPMOS steps down the battery or wall adapter
supply rail to a fixed 5V or an adjustable output voltage.
Two integrated low-voltage linear regulators follow this
output and provide two independent preset output volt-
ages of 3.3V and 1.8V, or adjustable output voltages.
The buck regulator utilizes a peak current-limit, pulse-
frequency modulation (PFM) architecture for highest
light-load efficiency to conserve battery life. High
switching frequencies (up to 200kHz) allow the use of
tiny surface-mount inductors and output capacitors.
Operation to 100% duty cycle minimizes dropout volt-
age (250mV at 500mA).
The low-dropout linear regulators use an internal
P-channel metal-oxide (PMOS) pass transistor to mini-
mize supply current and deliver up to 160mA each of
continuous current.
The MAX1534 includes a power-OK (POK) signal that
indicates all outputs are in regulation. The 4% accurate
threshold of the SHDNinput permits its use as a low-
battery detector.
The MAX1534 is available in a small 16-pin thin QFN
(4mm ✕4mm) package, occupying 33% less board
space than discrete solutions.
Applications
FeaturesOne Switching and Two Linear RegulatorsSwitching Regulator
+4.5V to +24V Input Voltage Range
Over 95% Efficiency
Up to 500mA Output Current
Up to 200kHz Switching Frequency
Fixed 5V or Adjustable Output Voltage
Internal 0.5ΩPMOS Switch
100% Maximum Duty Cycle for Low-Dropout
OperationTwo Low-Dropout Linear Regulators
Up to 160mA Output Current (Each)
3.3V/Adj Output Voltage for OUT1
1.8V/Adj Output Voltage for OUT2±1.5% Accurate Output Voltage±4% Accurate Shutdown for Low Battery
DetectionThermal Shutdown ProtectionPOK Output1mW Typical Standby Power
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
Ordering Information19-2662; Rev 0; 10/02
PARTTEMP RANGEPIN-PACKAGEMAX1534ETE-40°C to +85°C16 Thin QFN (4mm × 4mm)
MAX1534
POK
PRESET
ILIM
VOUT1 = +3.3V ALWAYS
VOUT3 = +5V ALWAYS
VIN = +7V TO +24V
VOUT2 = +1.8V ALWAYS
FB1
FB2
OUT1
OUT2LDOIN
FB3SHDN
GND
Typical Operating CircuitNotebook and Sub-
Notebook Computers
Wake-On LAN
2 to 4 Li+ Cells Battery-
Powered Devices
Hand-Held Devices
Keep-Alive Supplies
Standby Supplies
Pin Configuration appears at end of data sheet.
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ABSOLUTE MAXIMUM RATINGSStresses 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, ILIM, PRESET, SHDNto GND...........................-0.3V to +25V
FB1, FB2, FB3, LDOIN, BP to GND..........................-0.3V to +6V
OUT1, OUT2, POK to GND...................-0.3V to (VLDOIN+ 0.3V)
LX to GND.......................................................-2V to (VIN+ 0.3V)
OUT1, OUT2 Short Circuit to GND.............................Continuous
Peak IN Current........................................................................2A
Maximum IN DC Current...................................................500mA
Continuous Power Dissipation (TA= +70°C)
16-Pin Thin QFN (derate 16.9mW/°C
above +70°C)............................................................1349mW
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
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= 12V, ILIM = GND, PRESET= GND, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA=
+25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput Voltage RangeVIN4.524V
Input Supply CurrentIINNo load, FB3 = 5.2V, LDOIN = GND1530µA
Input Supply Current in
DropoutIIN(DROP)N o l oad , FB3 = V IN = 4.5V , LD O IN = G N D 60110µA
Shutdown Supply CurrentSHDN = GND3.57µA
VIN rising3.64.04.4Input UVLO ThresholdVUVLOVIN falling3.53.94.3V
BUCK REGULATORTA = +25°C to +85°C4.925.005.08FB3 Voltage Accuracy (Preset
Mode) (Note 1)PRESET = GNDTA = 0°C to +85°C4.905.005.10V
TA = +25°C to +85°C0.9851.001.015FB3 Set Voltage (Adjustable
Mode) (Note 1)VFB3PRESET = INTA = 0°C to +85°C0.981.001.02V
FB3 Bias CurrentIFB3VFB3 = 5.5V3.56.25µA
LX Switch Minimum Off-TimetOFF(MIN)0.220.420.62µs
LX Switch Minimum On-TimetON(MIN)0.50µs
LX Switch Maximum On-TimetON(MAX)91011µs
VIN = 6V0.51.0LX Switch On-ResistanceRLXVIN = 4.5V0.61.2Ω
ILIM = IN80010001200LX Current LimitILX(PEAK)ILIM = GND425500575mA
LX Zero-Crossing Threshold-75+75mV
LX Zero-Crossing TimeoutLX does not rise above threshold30µs
TA = +25°C1LX Switch Leakage CurrentVIN = 24V, not
switchingTA = 0°C to +85°C10µA
Dropout VoltageVOUT3(DROPOUT)ILX(DC) = 500mA250mV
Line RegulationVIN = 8V to 24V, ILX(DC) = 200mA0.1%/V
Load RegulationILX(DC) = 80mA to 400mA0.9%
LINEAR REGULATORSLDOIN Input VoltageVLDOIN2.55.5V
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VIN= 12V, ILIM = GND, PRESET= GND, TA
= 0°C to +85°C, unless otherwise noted. Typical values are at TA+25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSOUT1 Voltage Accuracy
(Preset Mode)VOUT1PRESET = GNDIOUT1 = 100µA to
160mA3.203.303.37V
OUT2 Voltage Accuracy
(Preset Mode)VOUT2PRESET = GNDIOUT2 = 100µA to
160mA1.741.801.84V
FB1, FB2 Set Voltage
(Adjustable Mode)VFB1, VFB2PRESET = INIOUT_ = 100µA to
160mA0.971.001.02V
FB1, FB2 Bias CurrentPRESET = IN, VFB1 = VFB2 = 1.1V-25+25nA
OUT1, OUT2 Adjustable Output
Voltage Range
VOUT1,
VOUT2PRESET = IN1.0VLDOINV
Maximum OUT1 Output CurrentIOUT1(MAX)Continuous160mA
OUT1 Current Limit160550mA
Maximum OUT2 Output CurrentIOUT2(MAX)Continuous160mA
OUT2 Current Limit160550mA
LDOIN CurrentIOUT1 = IOUT2 = 0, VLDOIN = 5.5V165265µA
LDO_ Dropout VoltageIOUT_ = 80mA (Note 2)120240mV
LDO_ Line RegulationVLDOIN = (VOUT_ + 0.4V) or
+2.5V to +5.5V, IOUT_ = 1mA-0.20+0.2%/V
FAULT DETECTIONPOK ThresholdOUT1, OUT2, and FB3 rising edge,
1% hysteresis (Note 3)-13-11-9%
POK Propagation DelayFalling edge, 50mV overdrive10µs
POK Output Low VoltageISINK = 1mA0.4V
POK Leakage CurrentHigh state, forced to 5.5V1µA
Thermal Shutdown ThresholdTypical hysteresis = 15°C+160°C
INPUTS AND OUTPUTSSHDN Input Trip LevelRising trip level, 100mV hysteresis0.961.01.04V
Input Leakage CurrentV SHDN, V PRESET, VILIM = 0 or 24V-1+1µA
Low0.5VPRESET, ILIM Logic LevelsHigh2.2V
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= 12V, ILIM = GND, PRESET= GND, TA
= -40°C to +85°C, unless otherwise noted.) (Note 4)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSInput Voltage RangeVINVIN4.524V
VIN rising3.64.4Input Undervoltage Lockout
ThresholdVUVLOVIN falling3.54.3V
BUCK REGULATORFB3 Voltage Accuracy (Preset
Mode)PRESET = GND4.855.15V
FB3 Set Voltage (Adjustable
Mode)VFB3PRESET = IN0.971.03V
LX Switch Minimum Off-TimetOFF(MIN)0.220.62µs
LX Switch Maximum On-TimetON(MAX)812µs
VIN = 6V1.0LX Switch On-ResistanceRLXVIN = 4.5V1.2Ω
ILIM = IN8001200LX Current LimitILX(PEAK)ILIM = GND425575mA
LINEAR REGULATORSLDOIN Input VoltageVLDOIN2.55.5V
LDOIN UVLOVUVLO(LDO)VLDOIN rising, hysteresis = 40mV (typ)2.152.40V
OUT1 Voltage Accuracy (Preset
Mode)VOUT1PRESET = GNDIOUT1 = 100µA to
160mA3.203.40V
OUT2 Voltage Accuracy (Preset
Mode)VOUT2PRESET = GNDIOUT2 = 100µA to
160mA1.741.86V
FB1, FB2 Set Voltage (Adjustable
Mode)VFB1, VFB2PRESET = INIOUT_ = 100µA to
160mA0.971.03V
OUT1, OUT2 Adjustable Output
Voltage Range
VOUT1,
VOUT2PRESET = IN1.0VLDOINV
Maximum OUT1 Output CurrentIOUT1(MAX)Continuous160mA
OUT1 Current Limit160550mA
Maximum OUT2 Output CurrentIOUT2(MAX)Continuous160mA
OUT2 Current Limit160550mA
LDO_ Dropout VoltageIOUT_ = 80mA (Note 2)250mV
LDO_ Line RegulationVLDOIN = (VOUT_ + 0.4V) or +2.5V
to +5.5V, IOUT_ = 1mA-0.2+0.2%/V
FAULT DETECTIONPOK ThresholdOUT1, OUT2, and FB3 rising edge, 1%
hysteresis (Note 3)-13-8%
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)(Circuit of Figure 1, VIN= 12V, ILIM = GND, PRESET= GND, TA
= -40°C to +85°C, unless otherwise noted.) (Note 4)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
INPUTS AND OUTPUTSSHDN Input Trip LevelRising trip level, 100mV hysteresis0.961.04V
Low0.5VPRESET, ILIM Logic LevelsHigh2.2V
Note 1:The output voltage at light loads has a DC regulation level higher than the error comparator threshold by half the ripple volt-
age.
Note 2:The dropout voltage is defined as VLDOIN- VOUT_when VLDOIN= VOUT_(NOM). Specification only applies when VOUT_≥
2.5V.
Note 3:OUT1, OUT2 DC set point, FB3 set point at the DC trip threshold of buck regulator.
Note 4:Specifications to -40°C are guaranteed by design, not production tested.
Typical Operating Characteristics(Circuit of Figure 1, VIN= +12V, PRESET= GND, TA = +25°C, unless otherwise noted.)
BUCK OUTPUT VOLTAGE
vs. LOAD CURRENT, CIRCUIT 1
MAX1534 toc01
IOUT3 (mA)
OUT3
(V)
VIN = 12V
VIN = 20V
VIN = 6V
(tON LIMITED)ILIM = IN
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 1
MAX1534 toc02
IOUT3 (mA)
EFFICIENCY (%)70
ILIM = IN
VIN = 6V
VIN = 12V
VIN = 20V
BUCK EFFICIENCY
vs. LOAD CURRENT, CIRCUIT 2
MAX1534 toc03
IOUT3 (mA)
EFFICIENCY (%)70
VIN = 12V
VIN = 20V
VIN = 7V
ILIM = GND
BUCK EFFICIENCY vs. LOAD CURRENT
CIRCUIT 1, VIN = 12V
MAX1534 toc04
IOUT3 (mA)
EFFICIENCY (%)
L = 15μH
L = 10μH
L = 22μH
ILIM = IN
SWITCHING FREQUENCY
vs. VIN, CIRCUIT 1, ILIM = IN
MAX1534 toc05
VIN (V)
FREQUENCY (kHz)
IOUT3 = 500mA
IOUT3 = 250mA
IOUT3 = 100mA
IOUT3 = 50mA
IOUT3 = 10mA
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computersypical Operating Characteristics (continued)(Circuit of Figure 1, VIN= +12V, PRESET= GND, TA = +25°C, unless otherwise noted.)
NO-LOAD SUPPLY CURRENT
vs. VIN, CIRCUIT 1, ILIM = GND
MAX1534 toc07
VIN (V)
SUPPLY CURRENT (
SHDN = IN
SHDN = GND
SHDN = IN
VOUT3 NOT CONNECTED
TO VLDOIN
PEAK SWITCH CURRENT
vs. VIN, CIRCUIT 1, ILIM = IN
MAX1534 toc08
VIN (V)
PEAK SWITCH CURRENT (A)
L = 10μH
L = 15μHL = 22μH
IOUT3 = 300mA
40μs/div
BUCK LOAD TRANSIENTILX
1A/div
VOUT3
200mV/div
AC-COUPLED
IOUT3
500mA/div
MAX1534 toc09
10V
500mA
VLX
10V/div
VIN = 12V, IOUT3 = 100mA TO 450mA
100μs/div
LINE TRANSIENT15V
10VVOUT3
200mV/div
AC-COUPLED
VIN
5V/div
MAX1534 toc10
ILX
500mA/div
VIN = 10V TO 15V, IOUT3 = 300mA
100μs/div
LINE TRANSIENT NEAR DROPOUT10VVOUT3
200mV/div
AC-COUPLED
VIN
5V/div
MAX1534 toc11
ILX
500mA/div
VIN = 5.2V TO 10V, IOUT3 = 300mA
SWITCHING FREQUENCY
vs. LOAD CURRENT, CIRCUIT 1, ILIM = IN
MAX1534 toc06
IOUT3 (mA)
FREQUENCY (kHz)
VIN = 20V
VIN = 12V
VIN = 7V
LDO DROPOUT VOLTAGE
vs. LOAD CURRENT
MAX1534 toc12
IOUT1 (mA)
DROPOUT VOLTAGE (mV)
LDO DROPOUT VOLTAGE vs. VOUT1
MAX1534 toc13
VOUT1 (V)
DROPOUT VOLTAGE (mV)
IOUT1 = 80mA
LDO PSRR vs. FREQUENCY
MAX1534 toc14
FREQUENCY (kHz)
PSRR (dB)
100Ω LOAD
20μs/div
LDO LOAD TRANSIENT150mA
VOUT1
20mV/div
AC-COUPLED
MAX1534 toc15
IOUT1
50mA/div
VLDOIN = 5V, IOUT1 = 10mA TO 150mA
MAX1534
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers100μs/div
STARTUP WAVEFORMSSHDN
MAX1534 toc16
ILX
1A/div
VIN = 12V, ROUT1 = 33Ω, ROUT2 = 18Ω, ROUT3 = 50Ω
5V/div
VOUT3
2V/div
VOUT1
2V/div
VOUT2
2V/div
POK
5V/div
100μs/div
SHUTDOWN WAVEFORMSSHDN
MAX1534 toc17ILX
1A/div
VIN = 12V, ROUT1 = 33Ω, ROUT2 = 18Ω, ROUT3 = 50Ω
5V/div
VOUT_
2V/div
POK
5V/div
VOUT3
VOUT1
VOUT2
Typical Operating Characteristics (continued)(Circuit of Figure 1, VIN= +12V, PRESET= GND, TA = +25°C, unless otherwise noted.)
MAX1534
Detailed DescriptionThe MAX1534 regulator provides efficient light-load
power conversion for notebook computers or hand-held
devices that require keep-alive power or standby
power. The main step-down buck regulator uses a
unique peak current-limited control scheme, providing
high efficiency at light loads over a wide load range.
Operation up to 100% duty cycle allows the lowest pos-
sible dropout voltage, increasing the usable supply
voltage range. Under no load, the MAX1534 consumes
only 1mW, and in shutdown mode, it draws only 3.5µA.
The internal 24V switching MOSFET, internal current
sensing, and a high-switching frequency minimize PC
board space and component costs.
The MAX1534 includes two low-noise, low-dropout,
low-quiescent-current linear regulators. The linear regu-
lators are available with preset output voltages of 3.3V
and 1.8V. Each linear regulator can supply loads up to
160mA.
High-Efficiency, Triple-Output, Keep-Alive
Power Supply for Notebook Computers
Pin Description
PINNAMEFUNCTIONSHDN
Shutdown Control Input. Drive SHDN above 1V to start up, and below 0.9V to shut down. LX is high
impedance in shut down, and supply current reduces to 3.5µA. Connect SHDN to IN for automatic
startup. SHDN can be connected to IN through a resistive voltage-divider to implement a
programmable undervoltage lockout.POK
Open-Drain Power-OK (POK) Output. POK asserts low while any output voltage is below the reset
threshold. Connect a 100kΩ pullup resistor to OUT_. POK is driven low in shut down. If not used,
leave this pin unconnected.GNDGround. Connect backside pad to GND.ILIMPeak LX Current Control Input. Connect to IN for 1000mA peak LX current. Connect to GND for
500mA peak LX current.
5, 8LXInductor Connection. Connect LX to external inductor and diode as shown in Figure 1. Both LX pins
must be connected together on the PC board.
6, 7INBuck Regulator Input Supply Voltage. Input voltage range is 4.5V to 24V. Both IN pins must be
connected together on the PC board.OUT2Regulated LDO2 Output Voltage. Sources up to 160mA guaranteed. Bypass with 2.2µF (<0.2Ω
typical ESR) ceramic capacitor to GND.LDOINInput Supply for both LDOs. Supply voltage can range from 2.5V to 5.5V. Bypass with 2.2µF capacitor
to GND (see Capacitor Selection and LDO Stability).OUT1Regulated LDO1 Output Voltage. Sources up to 160mA guaranteed. Bypass with 2.2µF (<0.2Ω
typical ESR) ceramic capacitor to GND.BPLDO Reference Noise Bypass. Bypass with a low-leakage 0.01µF ceramic capacitor for reduced
noise at both outputs.FB1Feedback Input for LDO1. For a fixed 3.3V output, connect PRESET and FB1 to GND. For an
adjustable output, connect PRESET = IN and connect a resistive divider between OUT1 and GND.FB2Feedback Input for LDO2. For a fixed 1.8V output, connect PRESET and FB2 to GND. For an
adjustable output, connect PRESET = IN and connect a resistive divider between OUT2 and GND.PRESET
Preset Feedback Select Input. Connect to GND for the preset 5V buck output voltage, preset 3.3V
OUT1 output voltage, and preset 1.8V OUT2 output voltage. Connect PRESET to IN to select
adjustable feedback mode for all three regulators.FB3Buck Outp ut Feed b ack Inp ut. For a fi xed 5.0V outp ut, connect P RE SE T to G N D and FB3 to O U T3. For
an ad j ustab l e outp ut, connect P RE SE T to IN and connect a r esi sti ve d i vi d er b etw een O U T3 and GN D .
