MAX15026BETD+T ,Low-Cost, Small, 4.5V to 28V Wide Operating Range, DC-DC Synchronous Buck ControllerApplicationsV 2 13 LXCCSet-Top BoxesPGOOD312 BSTLCD TV Secondary SuppliesEN 4 11 DLMAX15026Switches ..
MAX15027ATB+T ,1.425V to 3.6V Input, 1A Low-Dropout Regulators with BIAS InputApplicationsPin ConfigurationsAutomotive (Dead-Man LDO)ServersTOP VIEWStorageNetworking +IN 1 10 OU ..
MAX15032ATA+ ,500kHz, 36V Output, 600mW PWM Step-Up DC-DC ConverterApplications Ordering InformationAvalanche Photodiode BiasingPIN- TOPPART TEMP RANGEPACKAGE MARKPIN ..
MAX15032ATA+T ,500kHz, 36V Output, 600mW PWM Step-Up DC-DC ConverterELECTRICAL CHARACTERISTICS(V = +3.3V, V = +3.3V, C = 10µF, PGND = GND = 0V, T = T = -40°C to +125°C ..
MAX15038ETG+ ,4A, 2MHz Step-Down Regulator with Integrated Switchesfeatures fixed-frequency PWM mode♦ Soft-Start Reduces Inrush Supply Currentoperation with a switchi ..
MAX15038ETG+T ,4A, 2MHz Step-Down Regulator with Integrated SwitchesApplicationsPGNDServer Power SuppliesCTL2POLsFBCTL1ASIC/CPU/DSP Core and I/O VoltagesFREQDDR Power ..
MAX412CSA+T ,Single/Dual/Quad, 28MHz, Low-Noise, Low-Voltage, Precision Op AmpsELECTRICAL CHARACTERISTICS(V+ = 5V, V- = -5V, T = +25°C, unless otherwise noted.)APARAMETER SYMBOL ..
MAX412ESA ,Single/Dual/Quad, 28MHz, Low-Noise, Low-Voltage, Precision Op AmpsFeatures
The MAX410/MAX412/MAX414 single/dual/quad op
amps set a new standard for noise perform ..
MAX412ESA+T ,Single/Dual/Quad, 28MHz, Low-Noise, Low-Voltage, Precision Op AmpsFeaturesThe MAX410/MAX412/MAX414 single/dual/quad op ♦ Voltage Noise: 2.4nV/√Hz (max) at 1kHzamps s ..
MAX4130EUK+ ,Single/Dual/Quad, Wide-Bandwidth, Low-Power, Single-Supply Rail-to-Rail I/O Op AmpsELECTRICAL CHARACTERISTICS (V = +2.7V to +6.5V, V = 0V, V = 0V, V = V /2, R tied to V /2, SHDN≥ 2V ..
MAX4130EUK+T ,Single/Dual/Quad, Wide-Bandwidth, Low-Power, Single-Supply Rail-to-Rail I/O Op AmpsApplications7 5CS GNDPin Configurations appear at end of data sheet.UCSP is a trademark of Maxim In ..
MAX4130EUK-T ,Single/Dual/Quad, Wide-Bandwidth, Low-Power, Single-Supply Rail-to-Rail I/O Op AmpsFeaturesThe MAX4130–MAX4134 family of operational amplifiers♦ 6-Bump UCSP (MAX4131)combines 10MHz g ..
MAX15026BETD+T
Low-Cost, Small, 4.5V to 28V Wide Operating Range, DC-DC Synchronous Buck Controller
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck ControllerEVALUATION KIT AVAILABLE
General DescriptionThe MAX15026 synchronous step-down controller oper-
ates from a 4.5V to 28V input voltage range and gener-
ates an adjustable output voltage from 85% of the input
voltage down to 0.6V while supporting loads up to 25A.
The device allows monotonic startup into a prebiased
bus without discharging the output and features adap-
tive internal digital soft-start.
The MAX15026 offers the ability to adjust the switching
frequency from 200kHz to 2MHz with an external resis-
tor. The MAX15026’s adaptive synchronous rectification
eliminates the need for an external freewheeling
Schottky diode. The device also utilizes the external
low-side MOSFET’s on-resistance as a current-sense
element, eliminating the need for a current-sense resis-
tor. This protects the DC-DC components from damage
during output overloaded conditions or output short-
circuit faults without requiring a current-sense resistor.
Hiccup-mode current limit reduces power dissipation
during short-circuit conditions. The MAX15026 includes
a power-good output and an enable input with precise
turn-on/turn-off threshold, which can be used for input
supply monitoring and for power sequencing.
Additional protection features include sink-mode cur-
rent limit and thermal shutdown.
Sink-mode current limit prevents reverse inductor cur-
rent from reaching dangerous levels when the device is
sinking current from the output.
The MAX15026 is available in a space-saving and ther-
mally enhanced 3mm x 3mm, 14-pin TDFN-EP pack-
age. The MAX15026 operates over the extended -40°C
to +85°C and automotive -40°C to +125°C temperature
ranges.
The MAX15026C is designed to provide additional mar-
gin for break-before-make times.
The MAX15026B/MAX15026C provide a soft-stop
feature to ramp down the output voltage at turn-off. The
soft-stop function is disabled in the MAX15026D.
ApplicationsSet-Top Boxes
LCD TV Secondary Supplies
Switches/Routers
Power Modules
DSP Power Supplies
Points-of-Load Regulators
Features4.5V to 28V or 5V ±10% Input Supply Range0.6V to (0.85 x VIN) Adjustable OutputAdjustable 200kHz to 2MHz Switching FrequencyAbility to Start into a Prebiased LoadLossless, Cycle-by-Cycle Valley Mode CurrentLimit with Adjustable, Temperature-CompensatedThresholdSink-Mode Current-Limit ProtectionAdaptive Internal Digital Soft-Start±1% Accurate Voltage ReferenceInternal Boost DiodeAdaptive Synchronous Rectification EliminatesExternal Freewheeling Schottky DiodeHiccup-Mode Short-Circuit ProtectionThermal ShutdownPower-Good Output and Enable Input for PowerSequencing±5% Accurate Enable Input ThresholdAEC-Q100 Qualified (MAX15026B)*EP
DRV
VCC
LIM
MAX15026
+14DHIN
312BSTPGOODGNDCOMPRTFB
TDFN
(3mm x 3mm)TOP VIEW
Pin Configuration
Ordering Information
PARTTEMP RANGEPIN-PACKAGEMAX15026BETD+-40°C to +85°C14 TDFN-EP*
MAX15026BETD/V+T-40°C to +85°C14 TDFN-EP*
MAX15026CETD+-40°C to +85°C14 TDFN-EP*
MAX15026BATD+-40°C to +125°C14 TDFN-EP*
MAX15026CATD+-40°C to +125°C14 TDFN-EP*
MAX15026DATD+-40°C to +125°C14 TDFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad. T = Tape and reel.
/V denotes an automotive qualified part.
MAX15026D recommended for new designs.
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VIN= 12V, RRT = 27kΩ, RLIM = 30kΩ, CVCC= 4.7µF, CIN= 1µF, TA= -40°C to +85°C (MAX15026B/CETD+, MAX15026BETD/V+), = TJ= -40°C to +125°C (MAX15026B/C/DATD+), unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)
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.
Note 1:Dissipation wattage values are based on still air with no heatsink. Actual maximum power dissipation is a function of heat
extraction technique and may be substantially higher. Package thermal resistances were obtained using the method
described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal consid-
erations, refer to www.maximintegrated.com/thermal-tutorial.
IN to GND...............................................................-0.3V to +30V
BST to GND............................................................-0.3V to +36V
LX to GND.................................................................-1V to +30V
EN to GND................................................................-0.3V to +6V
PGOOD to GND.....................................................-0.3V to +30V
BST to LX..................................................................-0.3V to +6V
DH to LX...............................................….-0.3V to (VBST + 0.3V)
DRV to GND.............................................................-0.3V to +6V
DL to GND................................................-0.3V to (VDRV+ 0.3V)
VCCto GND...............-0.3V to the lower of +6V and (VIN+ 0.3V)
All Other Pins to GND.................................-0.3V to (VCC+ 0.3V)
VCCShort Circuit to GND...........................................Continuous
DRV Input Current.............................................................600mA
PGOOD Sink Current............................................................5mA
Continuous Power Dissipation (TA= +70°C) (Note 1)
14-Pin TDFN-EP, Multilayer Board
(derate 24.4mW/°C above +70°C)..............................1951mW
Operating Temperature Range
MAX15026B/CETD+, MAX15026BETD/V+.......-40°C to +85°C
MAX15026B/C/DATD+...................................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERAL4.528Input Voltage RangeVINVIN = VCC = VDRV4.55.5V
Quiescent Supply CurrentVFB = 0.9V, no switching1.752.75mA
Shutdown Supply CurrentIIN_SBYEN = GND290500µA
Enable to Output Delay480µs
VCC High to Output DelayEN = VCC375µs
VCC REGULATOR6V < VIN < 28V, ILOAD = 25mAOutput VoltageVCCVIN = 12V, 1mA < ILOAD < 70mA5.05.255.5V
VCC Regulator DropoutVIN = 4.5V, ILOAD = 70mA0.28V
VCC Short-Circuit Output CurrentVIN = 5V100200300mA
VCC Undervoltage LockoutVCC_UVLOVCC rising3.84.04.2V
VCC Undervoltage Lockout
Hysteresis400mV
ERROR AMPLIFIER (FB, COMP)FB Input Voltage Set-PointVFB585591597mV
FB Input Bias CurrentIFBVFB = 0.6V-250+250nA
FB to COMP TransconductancegMICOMP = ±20µA60012001800µS
Amplifier Open-Loop Gain80dB
Amplifier Unity-Gain BandwidthCapacitor from COMP to GND = 50pF4MHz
VCOMP-RAMP Minimum Voltage160mV
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
ENABLE (EN)EN Input HighVEN_HVEN rising1.141.201.26V
EN Input LowVEN_LVEN falling0.9971.051.103V
EN Input Leakage CurrentILEAK_ENVEN = 5.5V-1+1µA
OSCILLATORSwitching FrequencyfSWRRT = 27kΩ540600660kHz
1MHz Switching FrequencyRRT = 15.7kΩ0.911.1MHz
2MHz Switching FrequencyRRT = 7.2kΩ1.82.02.4MHz
Switching Frequency Adjustment
Range (Note 3)2002000kHz
RT VoltageVRT1.191.2051.22V
PWM Ramp Peak-to-Peak
AmplitudeVRAMP1.8V
PWM Ramp ValleyVVALLEY0.8V
Minimum Controllable On-Time65100ns
Maximum Duty CyclefSW = 600kHz8588%
Minimum Low-Side On-TimeRRT = 15.7kΩ75110150ns
OUTPUT DRIVERS/DRIVER SUPPLY (DRV)DRV Undervoltage LockoutVDRV_UVLOVDRV rising4.04.24.4V
DRV Undervoltage Lockout
Hysteresis400mV
Low, sinking 100mA, VBST = 5V13DH On-ResistanceHigh, sourcing 100mA, VBST = 5V1.54.5Ω
Low, sinking 100mA, VBST = 5.2V13DL On-ResistanceHigh, sourcing 100mA, VBST = 5.2V1.54.5Ω
Sinking4DH Peak CurrentCLOAD = 10nFSourcing3A
Sinking4DL Peak CurrentCLOAD = 10nFSourcing3A
DH/DL Break-Before-Make TimeDH at 1V (falling) to DL at 1V (rising)10 (18, Note 5)ns
DL/DH Break-Before-Make TimeDL at 1V (falling) to DH at 1V (rising)10 (20, Note 6)ns
SOFT-STARTSoft-Start Duration2048Switching
Cycles
Reference Voltage Steps64Steps
CURRENT LIMIT/HICCUPCurrent-Limit Threshold
Adjustment Range
Cycle-by-cycle valley current-limit
threshold adjustment range
valley limit = VLIM/10300mV
ELECTRICAL CHARACTERISTICS (continued)(VIN= 12V, RRT = 27kΩ, RLIM = 30kΩ, CVCC= 4.7µF, CIN= 1µF, TA= -40°C to +85°C (MAX15026B/CETD+, MAX15026BETD/V+), = TJ= -40°C to +125°C (MAX15026B/C/DATD+), unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSLIM Reference CurrentILIMVLIM = 0.3V to 3V (Note 4)455055µA
LIM Reference Current TempcoVLIM = 0.3V to 3V2300ppm/°C
Number of Consecutive Current-
Limit Events to Hiccup7Events
Soft-Start Timeout4096Switching
Cycles
Soft-Start Restart Timeout8192Switching
Cycles
Hiccup TimeoutOut of soft-start4096Switching
Cycles
Peak Low-Side Sink Current
LimitSink limit = 1.5V, RLIM = 30kΩ (Note 4)75mV
BOOSTBoost Switch ResistanceVIN = VCC = 5V, IBST = 10mA38Ω
POWER-GOOD OUTPUTPGOOD Threshold Rising9094.597.5% VFB
PGOOD Threshold Falling889294.5%VFB
PGOOD Output LeakageILEAK_PGDVIN = VPGOOD = 28V, VEN = 5V, VFB = 1V-1+1µA
PGOOD Output Low VoltageVPGOOD_LIPGOOD = 2mA, EN = GND0.4V
THERMAL SHUTDOWNThermal-Shutdown ThresholdTemperature rising+150°C
Thermal-Shutdown HysteresisTemperature falling20°C
ELECTRICAL CHARACTERISTICS (continued)(VIN= 12V, RRT = 27kΩ, RLIM = 30kΩ, CVCC= 4.7µF, CIN= 1µF, TA= -40°C to +85°C (MAX15026B/CETD+, MAX15026BETD/V+), = TJ= -40°C to +125°C (MAX15026B/C/DATD+), unless otherwise noted. Typical values are at TA= +25°C.) (Note 2)
Note 2:All devices are 100% tested at room temperature and guaranteed by design over the specified temperature range.
Note 3:Select RRTas: where fSWis in Hertz.
Note 4:TA= +25°C.
Note 5:10ns for MAX15026B, 18ns for the MAX15026C/D.
Note 6:10ns for MAX15026B, 20ns for the MAX15026C/D.17.3101x10)x(fRT7SW×−()2
EFFICIENCY vs. LOAD CURRENT
(MAX15026B/C)MAX15026 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
VOUT = 3.3V
VOUT = 1.2V
VOUT = 5V
VOUT = 1.8V
EFFICIENCY vs. LOAD CURRENT
(VIN = 12V, VCC = VDRV = 5V)MAX15026 toc02
LOAD CURRENT (A)
EFFICIENCY (%)6842012
VOUT = 3.3VVOUT = 1.2VVOUT = 5V
VOUT = 1.8V
VOUT vs. LOAD CURRENT
MAX15026 toc03
LOAD CURRENT (A)
% OUTPUT FROM NOMINAL6842012
VCC vs. LOAD CURRENT
MAX15026 toc04
LOAD CURRENT (mA)
(V)204060
VCC LINE REGULATION
MAX15026 toc05
VIN (V)
(V)2015105
5mA
50mA
VCC vs. TEMPERATUREMAX15026 toc06
TEMPERATURE (°C)
(V)3510-15
SWITCHING FREQUENCY
vs. RESISTANCE
MAX15026 toc07
SWITCHING FREQUENCY (kHz)604020
SWITCHING FREQUENCY
vs. TEMPERATURE
MAX15026 toc08
SWITCHING FREQUENCY (kHz)3510-15
RRT = 7.2kΩ
RRT = 15.7kΩ
RRT = 27kΩ
RRT = 85kΩ
SUPPLY CURRENT
vs. SWITCHING FREQUENCYMAX15026 toc09
SUPPLY CURRENT (mA)
10010,000
Typical Operating Characteristics(VIN= 12V, TA= +25°C. The following TOCs are for MAX15026B/C/D, unless otherwise noted.) (See the circuit of Figure 5.)
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Typical Operating Characteristics (continued)(VIN= 12V, TA= +25°C. The following TOCs are for MAX15026B/C/D, unless otherwise noted.) (See the circuit of Figure 5.)
LIM REFERENCE CURRENT
vs. TEMPERATUREMAX15026 toc10
TEMPERATURE (°C)
LIM REFERENCE CURRENT (3510-15
SINK AND SOURCE CURRENT-LIMIT
THRESHOLDS vs. RESISTANCE (RILIM)
MAX15026 toc11
RESISTANCE (kΩ)
CURRENT-LIMIT THRESHOLDS (V)5040302010
SINK CURRENT-LIMIT
SOURCE CURRENT-LIMIT
LOAD TRANSIENT ON OUTMAX15026 toc12
400µs/div
AC-COUPLEDVOUT
200mV/div
IOUT
10A
STARTUP AND DISABLE FROM EN
(RLOAD = 1.5Ω)MAX15026 toc13
4ms/div
VOUT
1V/div
VIN
5V/div
PGOOD
5V/div
STARTUP RISE TIME
(MAX15026B)MAX15026 toc14
1ms/div
VIN
5V/div
VOUT
1V/div
POWER-DOWN FALL TIMEMAX15026 toc15
4ms/div
VIN
5V/div
VOUT
1V/div
STARTUP RISE TIME
(MAX15026C/D)MAX15026 toc16
VIN
5V/div
VOUT
1V/div0V OUTPUT
SOFT-START WITH 0.5V
PREBIAS AT NO LOAD (MAX15026C/D)MAX15026 toc17
VIN
5V/div
VOUT
1V/div0.5V OUTPUT PREBIAS
OUTPUT SHORT-CIRCUIT BEHAVIOR MONITOR
OUTPUT VOLTAGE AND CURRENTMAX15026 toc18
500mV/div
VOUT
IOUT
20A/div
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Pin Description
PINNAMEFUNCTION1INRegulator Input. Bypass IN to GND with a 1µF minimum ceramic capacitor. Connect IN to VCC when
operating in the 5V ±10% range.
2VCC
5.25V Linear Regulator Output. Bypass VCC to GND with a minimum of 4.7µF low-ESR ceramic
capacitor to ensure stability up to the regulated rated current when VCC supplies the drive current at
DRV. Bypass VCC to GND when VCC supplies the device core quiescent current with a 2.2µF
minimum ceramic capacitor.PGOODOpen-Drain Power-Good Output. Connect PGOOD with an external resistor to any supply voltage.
4ENActive-High Enable Input. Pull EN to GND to disable the output. Connect EN to VCC for always-on
operation. EN can be used for power sequencing and as a UVLO adjustment input.LIMCurrent-Limit Adjustment. Connect a resistor from LIM to GND to adjust current-limit threshold from
30mV (RLIM = 6kΩ) to 300mV (RLIM = 60kΩ). See the Setting the Valley Current Limit section.COMPCompensation Input. Connect compensation network from COMP to FB or from COMP to GND. See
the Compensation section.
7FBFeedback Input. Connect FB to a resistive divider between output and GND to adjust the output
voltage between 0.6V and (0.85 x Input Voltage). See the Setting the Output Voltage section.
8RTOscillator Timing Resistor Input. Connect a resistor from RT to GND to set the oscillator frequency
from 200kHz to 2MHz. See the Setting the Switching Frequency section.GNDGroundDRVDrive Supply Voltage. DRV is internally connected to the anode terminal of the internal boost diode.
Bypass DRV to GND with a 2.2µF minimum ceramic capacitor (see the Typical Application Circuits).DLLow-Side Gate-Driver Output. DL swings from DRV to GND. DL is low during UVLO.BSTBoost Flying Capacitor. Connect a ceramic capacitor with a minimum value of 100nF between BST
and LX.LX
External Inductor Connection. Connect LX to the switching side of the inductor. LX serves as the
lower supply rail for the high-side gate driver and as a sensing input of the drain to source voltage
drop of the synchronous MOSFET.DHHigh-Side Gate-Driver Output. DH swings from LX to BST. DH is low during UVLO.
—EPExposed Pad. Internally connected to GND. Connect EP to a large copper plane at GND potential to
improve thermal dissipation. Do not use EP as the only GND ground connection.
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Functional DiagramOSCILLATOR
DC-DC
AND
OSCILLATOR
ENABLE
LOGIC
VREF
ENABLE
COMPARATOR
OSC_ENABLE
BANDGAP
GENERATOR
VCC
UVLO
DRV
UVLO
THERMAL
SHUTDOWN
AND ILIM
CURRENT
GEN
UVLO
BGAP_OK
BGAP_OK
EN_INT
VL_OK
VDRV_OK
SHUTDOWN
VIN_OK
VREF
VIN_OK
VIN_OK
IBIAS
VBGAP
BGAP_OK
BGAP_OK
VDRV
VIN_OK
VBGAP
LIM
VCC
INTERNAL
VOLTAGE
REGULATOR
MAIN
BIAS
CURRENT
GENERATOR
VREF = 0.6V
VBGAP = 1.24V
BANDGAP
REFERENCE
ENABLE
SOFT-START/
SOFT-STOP
LOGIC AND
HICCUP LOGIC
VREF
HICCUP
ENABLEDH_DL_ENABLE
VREF
VREF
DH_DL_ENABLE
HICCUP
TIMEOUT
FB1
DAC_VREF
PWM
COMPARATOR
RAMP
GENERATOR
SINK
CURRENT-LIMIT
COMPARATOR
PGOOD
COMPARATOR
VALLEY
CURRENT-LIMIT
COMPARATOR
PWM
PWM
CONTROL
LOGIC
BOOST
DRIVER
HIGH-
SIDE
DRIVER
LOW-
SIDE
DRIVER
RAMP
GATEP
HICCUP TIMEOUT
HICCUP
LIM/20
LIM/10
COMP
BST
DRV
GND
PGOOD
GND
MAX15026
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Detailed DescriptionThe MAX15026 synchronous step-down controller oper-
ates from a 4.5V to 28V input voltage range and gener-
ates an adjustable output voltage from 85% of the input
voltage down to 0.6V while supporting loads up to 25A.
As long as the device supply voltage is within 5.0V to
5.5V, the input power bus (VIN) can be as low as 3.3V.
The MAX15026 offers adjustable switching frequency
from 200kHz to 2MHz with an external resistor. The
adjustable switching frequency provides design flexi-
bility in selecting passive components. The MAX15026
adopts an adaptive synchronous rectification to elimi-
nate an external freewheeling Schottky diode and
improve efficiency. The device utilizes the on-resis-
tance of the external low-side MOSFET as a current-
sense element. The current-limit threshold voltage is
resistor-adjustable from 30mV to 300mV and is temper-
ature-compensated, so that the effects of the MOSFET
RDS(ON) variation over temperature are reduced. This
current-sensing scheme protects the external compo-
nents from damage during output overloaded condi-
tions or output short-circuit faults without requiring a
current-sense resistor. Hiccup-mode current limit
reduces power dissipation during short-circuit condi-
tions. The MAX15026 includes a power-good output
and an enable input with precise turn-on/-off threshold
to be used for monitoring and for power sequencing.
The MAX15026 features internal digital soft-start that
allows prebias startup without discharging the output.
The digital soft-start function employs sink current limit-
ing to prevent the regulator from sinking excessive cur-
rent when the prebias voltage exceeds the
programmed steady-state regulation level. The digital
soft-start feature prevents the synchronous rectifier
MOSFET and the body diode of the high-side MOSFET
from experiencing dangerous levels of current while the
regulator is sinking current from the output. The
MAX15026 shuts down at a junction temperature of
+150°C to prevent damage to the device.
DC-DC PWM ControllerThe MAX15026 step-down controller uses a PWM volt-
age-mode control scheme (see the Functional Diagram).
Control-loop compensation is external for providing max-
imum flexibility in choosing the operating frequency and
output LC filter components. An internal transconduc-
tance error amplifier produces an integrated error volt-
age at COMP that helps to provide higher DC accuracy.
The voltage at COMP sets the duty cycle using a PWM
comparator and a ramp generator. On the rising edge of
an internal clock, the high-side n-channel MOSFET turns
or the maximum duty cycle is reached. During the on-
time of the high-side MOSFET, the inductor current
ramps up. During the second-half of the switching cycle,
the high-side MOSFET turns off and the low-side n-chan-
nel MOSFET turns on. The inductor releases the stored
energy as the inductor current ramps down, providing
current to the output. Under overload conditions, when
the inductor current exceeds the selected valley current-
limit threshold (see the Current-Limit Circuit (LIM) sec-
tion), the high-side MOSFET does not turn on at the
subsequent clock rising edge and the low-side MOSFET
remains on to let the inductor current ramp down.
Internal 5.25V Linear RegulatorAn internal linear regulator (VCC) provides a 5.25V nomi-
nal supply to power the internal functions and to drive
the low-side MOSFET. Connect IN and VCC together
when using an external 5V ±10% power supply. The
maximum regulator input voltage (VIN) is 28V. Bypass IN
to GND with a 1µF ceramic capacitor. Bypass the output
of the linear regulator (VCC) with a 4.7µF ceramic capac-
itor to GND. The VCCdropout voltage is typically 125mV.
When VINis higher than 5.5V, VCCis typically 5.25V. The
MAX15026 also employs an undervoltage lockout circuit
that disables the internal linear regulator when VCCfalls
below 3.6V (typ). The 400mV UVLO hysteresis prevents
chattering on power-up/power-down.
The internal VCClinear regulator can source up to
70mA to supply the IC, power the low-side gate driver,
recharge the external boost capacitor, and supply small
external loads. The current available for external loads
depends on the current consumed by the MOSFET
gate drivers.
For example, when switching at 600kHz, a MOSFET
with 18nC total gate charge (at VGS = 5V) requires
(18nC x 600kHz) = 11mA. The internal control functions
consume 5mA maximum. The current available for
external loads is:
(70 – (2 x 11) – 5)mA ≅43mA
MOSFET Gate Drivers (DH, DL)DH and DL are optimized for driving large-size n-chan-
nel power MOSFETs. Under normal operating condi-
tions and after startup, the DL low-side drive waveform
is always the complement of the DH high-side drive
waveform, with controlled dead-time to prevent cross-
conduction or shoot-through. An adaptive dead-time
circuit monitors the DH and DL outputs and prevents
the opposite-side MOSFET from turning on until the
other MOSFET is fully off. Thus, the circuit allows the
high-side driver to turn on only when the DL gate driver
has turned off, preventing the low-side (DL) from turn-
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck ControllerThe adaptive driver dead-time allows operation without
shoot-through with a wide range of MOSFETs, minimiz-
ing delays and maintaining efficiency. There must be a
low-resistance, low-inductance path from DL and DH to
the MOSFET gates for the adaptive dead-time circuits
to function properly. The stray impedance in the gate
discharge path can cause the sense circuitry to inter-
pret the MOSFET gate as off while the VGSof the
MOSFET is still high. To minimize stray impedance, use
very short, wide traces.
Synchronous rectification reduces conduction losses in
the rectifier by replacing the normal low-side Schottky
catch diode with a low-resistance MOSFET switch. The
MAX15026 features a robust internal pulldown transis-
tor with a typical 1ΩRDS(ON)to drive DL low. This low
on-resistance prevents DL from being pulled up during
the fast rise time of the LX node, due to capacitive cou-
pling from the drain to the gate of the low-side synchro-
nous rectifier MOSFET.
High-Side Gate-Drive Supply (BST)
and Internal Boost SwitchAn internal switch between BST and DH turns on to
boost the gate voltage above VINproviding the neces-
sary gate-to-source voltage to turn on the high-side
MOSFET. The boost capacitor connected between BST
and LX holds up the voltage across the gate driver dur-
ing the high-side MOSFET on-time.
The charge lost by the boost capacitor for delivering the
gate charge is replenished when the high-side MOSFET
turns off and LX node goes to ground. When LX is low,
an internal high-voltage switch connected between
VDRVand BST recharges the boost capacitor. See the
Boost Capacitorsection in the Applications Information
to choose the right size of the boost capacitor.
Enable Input (EN), Soft-Start,
and Soft-StopDrive EN high to turn on the MAX15026. A soft-start
sequence starts to increase step-wise the reference
voltage of the error amplifier. The duration of the soft-
start ramp is 2048 switching cycles and the resolution
is 1/64th of the steady-state regulation voltage allowing
a smooth increase of the output voltage. A logic-low on
EN initiates a soft-stop sequence by stepping down the
reference voltage of the error amplifier. After the soft-
stop sequence is completed, the MOSFET drivers are
both turned off. See Figure 1. The soft-stop feature is
disabled in the MAX15026D.
Connect EN to VCCfor always-on operation. Owing to
the accurate turn-on/-off thresholds, EN can be used as
UVLO adjustment input, and for power sequencing
together with the PGOOD output.
When the valley current limit is reached during soft-start
the MAX15026 regulates to the output impedance times
the limited inductor current and turns off after 4096
clock cycles. When starting up into a large capacitive
load (for example) the inrush current will not exceed the
current-limit value. If the soft-start is not completed
before 4096 clock cycles, the device will turn off. The
device remains off for 8192 clock cycles before trying
to soft-start again. This implementation allows the soft-
start time to be automatically adapted to the time nec-
essary to keep the inductor current below the limit while
charging the output capacitor.
Power-Good Output (PGOOD)The MAX15026 includes a power-good comparator to
monitor the output voltage and detect the power-good
threshold, fixed at 94.5% of the nominal FB voltage. The
open-drain PGOOD output requires an external pullup
resistor. PGOOD sinks up to 2mA of current while low.
PGOOD goes high (high-impedance) when the regula-
tor output increases above 94.5% of the designed nom-
inal regulated voltage. PGOOD goes low when the
regulator output voltage drops to below 92% of the
nominal regulated voltage. PGOOD asserts low during
hiccup timeout period.
Startup into a Prebiased OutputWhen the MAX15026 starts into a prebiased output, DH
and DL are off so that the converter does not sink cur-
rent from the output. DH and DL do not start switching
until the PWM comparator commands the first PWM
pulse. The first PWM pulse occurs when the ramping
reference voltage increases above the FB voltage.
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck Controller
Current-Limit Circuit (LIM)The current-limit circuit employs a valley and sink cur-
rent-sensing algorithm that uses the on-resistance of
the low-side MOSFET as a current-sensing element, to
eliminate costly sense resistors. The current-limit circuit
is also temperature compensated to track the on-resis-
tance variation of the MOSFET over temperature. The
current limit is adjustable with an external resistor at
LIM, and accommodates MOSFETs with a wide range
of on-resistance characteristics (see the Setting the
Valley Current Limit section). The adjustment range is
from 30mV to 300mV for the valley current limit, corre-
sponding to resistor values of 6kΩto 60kΩ. The valley
current-limit threshold across the low-side MOSFET is
precisely 1/10th of the voltage at LIM, while the sink
current-limit threshold is 1/20th of the voltage at LIM.
Valley current limit acts when the inductor current flows
towards the load, and LX is more negative than GND
during the low-side MOSFET on-time. If the magnitude
of current-sense signal exceeds the valley current-limit
threshold at the end of the low-side MOSFET on-time,
the MAX15026 does not initiate a new PWM cycle and
lets the inductor current decay in the next cycle. The
controller also rolls back the internal reference voltage
so that the controller finds a regulation point deter-
mined by the current-limit value and the resistance of
the short. In this manner, the controller acts as a con-
stant current source. This method greatly reduces
inductor ripple current during the short event, which
reduces inductor sizing restrictions, and reduces the
possibility for audible noise. After a timeout, the device
goes into hiccup mode. Once the short is removed, the
internal reference voltage soft-starts back up to the nor-
VCCCDE
2048 CLK
CYCLES
2048 CLK
CYCLESGHIAUVLO
VOUT
DAC_VREF
UVLOUndervoltage threshold value is provided in
the Electrical Characteristics table.
Internal 5.25V linear regulator output.
Active-high enable input.
Regulator output voltage.
Regulator internal soft-start and soft-stop signal.
Regulator high-side gate-driver output.
Regulator low-side gate-driver output.
VCC rising while below the UVLO threshold.
EN is low.
VCC
VOUT
DAC_VREF
SYMBOLDEFINITIONVCC is higher than the UVLO threshold. EN is low.
EN is pulled high. DH and DL start switching.
Normal operation.
VCC drops below UVLO.
VCC goes above the UVLO threshold. DH and DL
start switching. Normal operation.
EN is pulled low. VOUT enters soft-stop.
EN is pulled high. DH and DL start switching.
Normal operation.
VCC drops below UVLO.
SYMBOLDEFINITIONFigure 1. Power-On/-Off Sequencing for MAX15026B/C.
MAX15026
Low-Cost, Small, 4.5V to 28V Wide Operating
Range, DC-DC Synchronous Buck ControllerSink current limit is implemented by monitoring the volt-
age drop across the low-side MOSFET when LX is more
positive than GND. When the voltage drop across the
low-side MOSFET exceeds 1/20th of the voltage at LIM
at any time during the low-side MOSFET on-time, the
low-side MOSFET turns off, and the inductor current
flows from the output through the body diode of the high-
side MOSFET. When the sink current limit activates, the
DH/DL switching sequence is no longer complementary.
Carefully observe the PCB layout guidelines to ensure
that noise and DC errors do not corrupt the current-
sense signals at LX and GND. Mount the MAX15026
close to the low-side MOSFET with short, direct traces
making a Kelvin-sense connection so that trace resis-
tance does not add to the intended sense resistance of
the low-side MOSFET.
Hiccup-Mode Overcurrent ProtectionHiccup-mode overcurrent protection reduces power dis-
sipation during prolonged short-circuit or deep overload
conditions. An internal three-bit counter counts up on
each switching cycle when the valley current-limit
threshold is reached. The counter counts down on each
switching cycle when the threshold is not reached, and
stops at zero (000). The counter reaches 111 (= 7
events) when the valley mode current-limit condition
persists. The MAX15026 stops both DL and DH drivers
and waits for 4096 switching cycles (hiccup timeout
delay) before attempting a new soft-start sequence. The
hiccup-mode protection remains active during the soft-
start time.
Undervoltage LockoutThe MAX15026 provides an internal undervoltage lockout
(UVLO) circuit to monitor the voltage on VCC. The UVLO
circuit prevents the MAX15026 from operating when VCC
is lower than VUVLO. The UVLO threshold is 4V, with
400mV hysteresis to prevent chattering on the rising/falling
edge of the supply voltage. DL and DH stay low to inhibit
switching when the device is in undervoltage lockout.
Thermal-Overload ProtectionThermal-overload protection limits total power dissipation
in the MAX15026. When the junction temperature of the
device exceeds +150°C, an on-chip thermal sensor shuts
down the device, forcing DL and DH low, allowing the
device to cool. The thermal sensor turns the device on
again after the junction temperature cools by 20°C. The
regulator shuts down and soft-start resets during thermal
shutdown. Power dissipation in the LDO regulator and
excessive driving losses at DH/DL trigger thermal-over-
load protection. Carefully evaluate the total power dissi-
pation (see the Power Dissipation section) to avoid
unwanted triggering of the thermal-overload protection in
normal operation.
Applications Information
Effective Input Voltage RangeThe MAX15026 operates from input supplies up to 28V
and regulates down to 0.6V. The minimum voltage con-
version ratio (VOUT/VIN) is limited by the minimum con-
trollable on-time. For proper fixed-frequency PWM
operation, the voltage conversion ratio must obey the
following condition,
where tON(MIN) is 125ns and fSWis the switching fre-
quency in Hertz. Pulse-skipping occurs to decrease the
effective duty cycle when the desired voltage conver-
sion does not meet the above condition. Decrease the
switching frequency or lower VINto avoid pulse skipping.
The maximum voltage conversion ratio is limited by the
maximum duty cycle (Dmax):
where VDROP1is the sum of the parasitic voltage drops
in the inductor discharge path, including synchronous
rectifier, inductor, and PCB resistance. VDROP2is the
sum of the resistance in the charging path, including
high-side switch, inductor, and PCB resistance. In
practice, provide adequate margin to the above condi-
tions for good load-transient response.
Setting the Output VoltageSet the MAX15026 output voltage by connecting a
resistive divider from the output to FB to GND (Figure
2). Select R2from between 1kΩand 50kΩ. Calculatewith the following equation:
where VFB = 0.591V (see the Electrical Characteristics
table) and VOUTcan range from 0.591V to (0.85 x VIN).
Resistor R1also plays a role in the design of the Type III
compensation network. Review the values of R1and R2
when using a Type III compensation network (see the
Type III Compensation Network (See Figure 4)section).V
OUT1=⎛⎜⎞⎟⎡⎢⎢⎥⎥DDV(1D)V
OUTmaxmaxDROP2maxDROP1<×+×−−tfOUTON(MIN)SWI>×
