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MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
General Description
Benefits and Features
The MAX20471, MAX20472, and MAX20472B are highefficiency low-voltage DC-DC converters that boost a 3.0V
to 4.0V input supply to between 3.8V and 5.25V (factoryconfigurable) at 500mA or 1A. The boost converters
achieve ±1.5% output error over load, line, and temperature range.
● Multiple Functions for Small Size
• Synchronous Boost Converter
• 3.8V to 5.25V Factory-Preset Output in 50mV
Steps
• 500mA and 1A Options
• 3V to 4V Operating Supply Voltage
• True Output Shutdown
• 2.2MHz Operation for the MAX20471, MAX20472
• 2.0MHz Operation for the MAX20472B
• Open-Drain Reset Output Pin (RESET)
• Spread-Spectrum Enable Pin (SSEN)
The devices feature a 2.2MHz (2.0MHz for MAX20472B)
fixed-frequency PWM mode for better noise immunity and
load-transient response, and a pulse-frequency modulation mode (skip) for increased efficiency during light-load
operation. The 2.2MHz/2.0MHz frequency operation allows for the use of all ceramic capacitors and minimizes
external components. The programmable spread-spectrum frequency modulation minimizes radiated electromagnetic emissions. Integrated low-RDSON switches improve efficiency at heavy loads and make the layout a
much simpler task with respect to discrete solutions.
Other features include true shutdown, soft-start, overcurrent, and overtemperature protections.
Applications
● Automotive Point of Load
● Automotive CAN Transceivers
● High-Precision
• ±1.5% Output Voltage Accuracy
• 93 ±2% UV Monitoring
• 107 ±2% OV Monitoring
• Good Load-Transient Performance
● Robust for the Automotive Environment
• Current-Mode, Forced-PWM and SKIP Operation
• Overtemperature and Short-Circuit Protection
• 12-Pin (3mm x 3mm) TDFN
• 12-Pin (3mm x 3mm) SWTDFN
• 8-Pin (0.150") SOIC (MAX20471 Only)
• -40°C to +125°C Automotive Temperature Range
Ordering Information appears at end of data sheet.
Simplified Block Diagram
3.3V
2.2µF
1µH
LX
3.3V
5V
AV
OUT
1µF
22µF
GND
EN
MAX20471
MAX20472/B
PGND
SYNC
50KΩ
SSEN
RESET
19-100163; Rev 13; 9/21
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
TABLE OF CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
12 TDFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
12 SWTDFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
8 SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
MAX20471/MAX20472/MAX20472B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
MAX20471 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Functional Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Diagram 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Enable Input (EN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
RESET Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Internal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Synchronization (SYNC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Soft-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Current-Limit/Short-Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
PWM/SKIP Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Overtemperature Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Boost Converter Short Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Startup into Short . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Short or Overload after Soft-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Input Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Inductor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Boost Output Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
PCB Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Circuit 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
www.maximintegrated.com
Maxim Integrated | 2
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Absolute Maximum Ratings
EN, SYNC to GND...................................................... -0.3V to 6V
AV to GND .................................................................. -0.3V to 6V
RESET to GND........................................................... -0.3V to 6V
OUT to PGND............................................................. -0.3V to 6V
SSEN to GND ..................................................-0.3V to VAV+0.3V
LX to PGND (Note 1) .................................... -0.3V to VOUT+0.3V
GND to PGND ......................................................... -0.3V to 0.3V
Maximum Continuous RMS Current ...................................... 2.5A
Output Short-Circuit Duration ..................................... Continuous
Continuous Power Dissipation (Note 2)
12-Pin TDFN-EP (derate 24.4 mW/°C > 70°C) ...........1951mW
12-Pin SWTDFN-EP (derate 24.4 mW/°C > 70°C) .....1951mW
8-Pin SOIC (derate 7.8mW/ºC > +70ºC) .......................623mW
Operating Temperature Range .............................-40°C to 125°C
Junction Temperature ....................................................... +150°C
Storage Temperature Range ..............................-65°C to +150°C
Soldering Temperature (reflow) ........................................ +300°C
Note 1: Self-protected from transient voltages exceeding these limits in circuit under normal operation.
Note 2: 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 considerations, refer to www.maximintegrated.com/thermal-tutorial.
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.
Package Information
12 TDFN
Package Code
TD1233+2C
Outline Number
21-0664
Land Pattern Number
90-0397
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
41°C/W
Junction to Case (θJC)
8.5°C/W
12 SWTDFN
Package Code
TD1233Y+2C
Outline Number
21-100176
Land Pattern Number
90-100072
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
41°C/W
Junction to Case (θJC)
8.5°C/W
8 SOIC
Package Code
S8+2C
Outline Number
21-0041
Land Pattern Number
90-0096
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θJA)
128.4°C/W
Junction to Case (θJC)
36°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates
RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
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
considerations, refer to www.maximintegrated.com/thermal-tutorial.
www.maximintegrated.com
Maxim Integrated | 3
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Electrical Characteristics
(VAV = 3.3V, EN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted., Typical values are at TA = +25°C under normal conditions
unless otherwise noted. (Note 3))
PARAMETER
Supply Voltage Range
UVLO
SYMBOL
VIN
CONDITIONS
(Note 4)
VUVLOR
Rising
VUVLOF
Falling
Shutdown Supply
Current
ISD
EN = LOW
Supply Current
IIN
EN = high, IOUT = 0mA, SYNC low
PWM Switching
Frequency
fSW
Spread Spectrum
SS
Internally Generated
Internally Generated, MAX20472B
MIN
TYP
3
2.48
2.55
MAX
UNITS
4.25
V
2.9
2.475
0.1
2
130
µA
µA
2
2.2
2.4
1.88
2.0
2.12
SSEN high
V
±3
MHz
%
OUT
Voltage Accuracy
VOUT
ILOAD = 0A to IMAX, 3V ≤ VAV ≤ 4.25V
pMOS On-Resistance
RHS
VAV = 3.3V, ILX = 0.18A
nMOS On-Resistance
RLS
VAV = 3.3V, ILX = 0.18A
nMOS Current-Limit
Threshold
ILIM1
MAX20471
1.4
1.8
4
ILIM2
MAX20472/MAX20472B
2.8
4.2
7
pMOS Turn Off
Threshold
-1.5
+1.5
150
100
IZX
VAV = 6V, LX = PGND or OUT, TA =
25°C
%
mΩ
mΩ
A
50
mA
0.1
μA
LX Leakage Current
ILXLKG
Maximum Duty Cycle
DCMAX
OUT Discharge
Resistance
RDISCH
VEN = 0V (connected to OUT)
300
Ω
SKIP Threshold
THSKIP
Percentage of nMOS current-limit
threshold (MAX20471/MAX20472 only)
15
%
Soft-Start Time
tSS
1.9
ms
165
°C
15
°C
90
%
THERMAL OVERLOAD
Thermal Shutdown
Temperature
TSHDN
Hysteresis
THYST
TJ rising
RESET
OV Threshold
OVACC
Rising, % of nominal output
105
107
109
%
UV Threshold
UVACC
Falling, % of nominal output
91
93
95
%
tHOLD1
Option 1 (default)
0.5
tHOLD2
Option 2
3.7
tHOLD3
Option 3
7.4
14.8
Active Hold Period
tHOLD4
Option 4
Delay Filter
tUVDEL
10% below/above threshold
Output-High Leakage
Current
IRLKG
TA = 25°C
Output Low Level
VROL
Sinking -2mA, 3V ≤ VAV ≤ 4.25V
www.maximintegrated.com
ms
10
-0.5
0.1
µs
+0.5
μA
0.2
V
Maxim Integrated | 4
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Electrical Characteristics (continued)
(VAV = 3.3V, EN = 3.3V, TA = TJ = -40°C to +125°C, unless otherwise noted., Typical values are at TA = +25°C under normal conditions
unless otherwise noted. (Note 3))
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ENABLE AND SYNC INPUTS
Input High Level
VIH
Input Low Level
VIL
Input Hysteresis
VHYST
EN Pulldown Current
IENPD
SYNC Input Pulldown
RSYNCPD
SYNC Input Frequency
Range
fSYNC
1.5
V
0.5
V
2
µA
0.1
VAV = 3.3V
0.5
EN high
1
V
100
1.7
kΩ
2.6
MHz
Note 3: All units are 100% production tested at +25˚C. All temperature limits are guaranteed by design and characterization.
Note 4: FPWM operation is only guaranteed up to 4.0V supply voltage. Supply voltages higher than 4.0V will exhibit skip mode
behavior even with SYNC = HIGH for FPWM operation.
www.maximintegrated.com
Maxim Integrated | 5
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Typical Operating Characteristics
(AVVDD = +3.3V, VDDIO = +1.8V, VREFP - VREFN = VREF = 2.5V; No Line-Frequency Rejection, Continuous-Conversion Mode, Internal
Clock; TA = TMIN to TMAX unless otherwise noted.)
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Maxim Integrated | 6
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Pin Configurations
EN
AV
GND
GND
RESET
TOP VIEW
SYNC
MAX20471/MAX20472/MAX20472B
12
11
10
9
8
7
MAX20471
MAX
MAX20472/B
20472/B
1
2
3
4
5
6
SSEN
OUTS
OUT
LX
LX
PGND
+
TDFN-EP
SWTDFN-EP
3mm x 3mm
MAX20471
TOP VIEW
EN
1
8 SYNC
OUT
2
LX
3
6 GND
PGND
4
5 RESET
MAX20471
7 AV
SOIC
(0.150")
Pin Description
PIN
MAX20471/
MAX20472/
MAX20472B
MAX20471
1
—
SSEN
Spread Spectrum Enable. Connect to VAV to enable spread spectrum.
2
—
OUTS
Output Voltage Feedback Pin. Connect this pin to the output capacitor.
NAME
FUNCTION
3
2
OUT
4, 5
3
LX
6
4
PGND
Power Ground.
7
5
RESET
Open–Drain RESET Output. To obtain a logic signal, pull up RESET with an
external resistor.
8
—
9
6
10
7
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GND
AV
Output Voltage.
Inductor Connection. Connect LX to the switched side of the inductor.
Ground. Connect all ground pins to the EP.
Analog Ground. Connect all ground pins to the EP.
Analog Power Input Supply. Connect a 1μF ceramic capacitor from VAV to GND.
Maxim Integrated | 7
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Pin Description (continued)
PIN
MAX20471/
MAX20472/
MAX20472B
MAX20471
11
1
EN
12
8
SYNC
SYNC Input. Connect SYNC to GND or leave unconnected to enable skip-mode
operation under light loads. Connect SYNC to VAV or an external clock to enable
fixed-frequency forced-PWM-mode operation.
EP
Exposed Pad. Connect the exposed pad to ground. Connecting the exposed pad
to ground does not remove the requirement for proper ground connections to
PGND. The exposed pad is attached with epoxy to the substrate of the die,
making it an excellent path to remove heat from the IC.
-
—
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NAME
FUNCTION
Active-High Enable. Drive EN HIGH for normal operation.
Maxim Integrated | 8
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Functional Diagrams
Diagram 1
CS AMP
SKIP
COMP
CLK
OUT
OUT
RAMP
GENERATOR
ILIM
COMP
CONTROL LOGIC
PGND
LX
PV
LX
PWM
COMP
VREF
VREF
SOFT-START
GENERATOR
PGND
FPWM CLK
EAMP
PGND
OUTS
OUTS
UV/OV
ZX, NEG ILIM
GND
GND
VREF
SYNC
SSEN
CLK
OTP
TRIMBITS
VAV
OSC
FPWM
POK
VOLTAGE
REFERENCE
VREF
UVLO
AV
RESET
EN
MAIN
CONTROL
LOGIC
www.maximintegrated.com
PGND
Maxim Integrated | 9
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Detailed Description
The MAX20471, MAX20472, and MAX20472B are high-efficiency, low-voltage 500mA and 1A synchronous DC-DC boost
converter ICs that boost the 3.0V to 4.0V input supply to a fixed output voltage between 3.8V and 5.25V. The boost
converters have True Shutdown™, so the output voltage will be 0V when off. The ICs achieve ±1.5% output error over
load, line, and temperature ranges.
The ICs feature either a 2.2MHz (MAX20471/MAX20472) or a 2.0MHz (MAX20472B) fixed-frequency FPWM mode
for better noise immunity and load-transient response, as well as pulse-frequency operation that allows the use of allceramic capacitors, thus minimizing external components. The programmable spread-spectrum frequency modulation
minimizes radiated electromagnetic emissions. The spread modulation is factory set to pseudorandom. Integrated low
RDS(ON) switches improve efficiency at heavy loads, which makes the layout a much simpler task with respect to discrete
solutions.
The ICs contain high-accuracy, factory-set OV/UV thresholds for each output mapped to the RESET pin. There are
diagnostics on the RESET and OUT pins to guarantee high reliability and fail-safe operation. In light-load applications,
a logic input (SYNC) allows the ICs to operate either in skip mode for reduced current consumption, or fixed-frequency
FPWM mode to eliminate frequency variation and help minimize EMI.
Enable Input (EN)
The EN input activates the ICs’ channels from their low-power shutdown state. EN has an input threshold of 1.0V (typ),
with hysteresis of 100mV (typ). When EN goes high, the associated output voltage ramps up with the programmed softstart time.
RESET Output
The device features individual open-drain, active-low reset outputs for each output that asserts low when the
corresponding output voltage is outside of the UV/OV window. RESET remains asserted for a fixed timeout period after
the output rises up to its regulated voltage. The fixed timeout period is selectable between 0.5ms, 3.7ms, 7.4ms, or
14.8ms (see the Selector Guide). To obtain a logic signal, place a resistor pullup between RESET pins to the system I/O
voltage.
Internal Oscillator
The device has a spread-spectrum oscillator that varies the internal operating frequency up by ±3% relative to the
internally generated typical operating frequency. This function does not apply to externally applied oscillation frequency.
The spread frequency generated is pseudorandom with a repeat rate well below the audio band. Spread spectrum on
MAX20471ASAA is enabled as an internal setting. Contact customer support for more details.
Synchronization (SYNC)
The ICs have an on-chip oscillator that provides a 2.2MHz/2.0MHz switching frequency. Depending on the condition of
the SYNC pin for the MAX20471/MAX20472, two operation modes exist. If SYNC is unconnected or at GND and the
load current is below the skip-mode current threshold, the ICs will operate in a highly efficient pulse-skipping mode. If
the current is above the threshold, the ICs automatically change to FPWM mode. If SYNC is at VAV or has a frequency
applied to it, the ICs will always operate in FPWM mode. The ICs can be switched during operation between FPWM or
skip mode by pulling SYNC up to VAV or down to GND.
For the MAX20472B, the SYNC pin operates differently. If the SYNC is unconnected or at GND for the MAX20472B the
device will remain in pulse-skipping operation regardless of load current. If SYNC pin for the MAX20472B is at VAV or
has a frequency applied to it, the device will always operate in FPWM mode.
Soft-Start
The IC includes a fixed soft-start of 1.9ms. Soft-start time limits start-up inrush current by forcing the output voltage to
ramp up towards its regulation point.
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Maxim Integrated | 10
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Current-Limit/Short-Circuit Protection
The device features current limit that protects the device against short-circuit and overload conditions at the output. In
the event of a short-circuit or overload condition, the high-side MOSFET remains on until the inductor current reaches
the high-side MOSFET’s current-limit threshold. The converter then turns on the low-side MOSFET to allow the inductor
current to ramp down. Once the inductor current crosses below the low-side MOSFET current-limit threshold, the
converter turns on the high-side MOSFET again. This cycle repeats until the short or overload condition is removed.
PWM/SKIP Modes
The device features an input (SYNC) that puts the converter either in SKIP mode for forced PWM mode of operation.
See Pin Descriptions for mode detail. In PWM mode of operation, the converter switches at a constant frequency with
variable on-time. In SKIP mode of operation, the converter’s switching frequency is load dependent until the output load
reaches a certain threshold. At higher load current, the switching frequency does not change and the operating mode is
similar to the PWM mode. SKIP mode helps improve efficiency in light-load applications by allowing the converter to turn
on the high-side switch only when the output voltage falls below a set threshold. As such, the converter does not switch
MOSFETs on and off as often as is the case in the PWM mode. Consequently, the gate charge and switching losses are
much lower in SKIP mode.
Overtemperature Protection
Thermal overload protection limits the total power dissipation in the MAX20471, MAX20472, and MAX20472B. When
the junction temperature exceeds 165°C (typ), an internal thermal sensor shuts down the internal bias regulator and the
step-down controller, allowing the IC to cool. The thermal sensor turns on the IC again after the junction temperature
cools by 15°C.
Boost Converter Short Protection
The boost has protection against startup into short and also protection against short/overload after startup.
Startup into Short
After the boost is enabled, the internal pMOS rectifier is configured as a 2A (typ) current source. This mode of operation is
referred to as “charge mode” and is used to charge the output to within 600mV of the input. Under normal circumstances,
charge mode is successful and the boost begins switching soft-start to 5.0V. If the output is shorted or overloaded,
charge mode will be unable to charge the output to within 600mV of the input. If charge mode lasts for more than 1.9ms,
the boost shuts off and automatically attempts restart after 120ms. This automatic restart is called “hiccup mode” and
continues indefinitely. Disabling then reenabling the boost overrides the 120ms timer and retries immediately.
Short or Overload after Soft-Start
After soft-start is complete, the boost continues monitoring to ensure that the output is always greater than the 600mV
input. If a short or overload condition pulls the output below the 600mV input, the boost stops switching and re-enters the
charge-mode configuration. If the output continues to fall below 3.125V, independent of the input voltage, the boost shuts
off and enters hiccup mode, as described above.
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Maxim Integrated | 11
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Applications Information
Input Capacitor
The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on
the input caused by the circuit’s switching. A 2.2µF X7R ceramic capacitor is recommended for the DC-DC input. A 1µF
X7R ceramic capacitor is recommended for the VAV pin.
Inductor Selection
Use a 1µH inductor for MAX20472/MAX20471 and MAX20472B. For a ferrite core, the saturation current should be
greater than the maximum current limit. For a soft-saturation core, the saturation current can be less than the maximum
current limit as long as the inductance at the maximum current limit is greater than 50% of the nominal inductance.
Boost Output Capacitor
The MAX20471, MAX20472, and MAX20472B are designed to be stable with low-ESR ceramic capacitors. Other
capacitor types are not recommended, as the ESR zero can affect stability of the device. The output-capacitor
calculations below are guidelines based on nominal conditions. The phase margin must be measured on the final circuit
to verify that proper stability is achieved.
55 µ sec
COUT_MIN = V
OUT
110 µ sec
COUT_NOM = V
OUT
PCB Layout Guidelines
When laying out the PCB, keep the DC-DC power components close together and the routes short to minimize loop area.
The output capacitor, power inductor, and input capacitor should be placed close to the IC package. The output capacitor
experiences the greatest amount of ripple current, and should be placed closest to the IC. The higher current-carrying
traces, such as the input (LX) and OUT, should be wide. Vias should connect the exposed pad of the ICs to provide
optimal ground and thermal dissipation connections. A large ground plane should be placed directly below the power
traces.
Typical Application Circuits
Circuit 1
3.3V
2.2µF
1µH
LX
3.3V
5V
AV
OUT
1µF
22µF
GND
EN
MAX20471
MAX20472/B
PGND
SYNC
50KΩ
SSEN
RESET
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Maxim Integrated | 12
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Ordering Information
TEMP RANGE
PINPACKAGE
VOUT (V)
tHOLD (μs)
INPUT CURRENT
LIMIT (A)
MAX20471ATCA/V+
-40°C to +125°C
12 TDFN-EP*
5
500
1.8
MAX20471ATCB/V+
-40°C to +125°C
12 TDFN-EP*
5.15
500
1.8
MAX20471ATCB/VY+
-40°C to +125°C
12 SWTDFNEP*
5.15
500
1.8
MAX20471ATCA/VY+
-40°C to +125°C
12 SWTDFNEP*
5
500
1.8
MAX20471ASAA/V+
-40°C to +125°C
8 SOIC
5
500
1.8
MAX20472ATCA/V+
-40°C to +125°C
12 TDFN-EP*
5
500
4.2
MAX20472ATCB/V+
-40°C to +125°C
12 TDFN-EP*
5.15
500
4.2
MAX20472ATCC/V+
-40°C to +125°C
12 TDFN-EP*
3.85
500
4.2
MAX20472ATCA/VY+
-40°C to +125°C
12 SWTDFNEP*
5
500
4.2
MAX20472BATCC/V+
-40°C to +125°C
12 TDFN-EP*
3.85
500
4.2
MAX20472ATCE/V+
-40°C to +125°C
12 TDFN-EP*
5
14800
4.2
PART NUMBER
Note: For variants with different options, contact factory.
/V Denotes an automotive qualified part.
Y Denotes side-wettable.
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
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Maxim Integrated | 13
MAX20471, MAX20472,
MAX20472B
Low Voltage Synchronous Boost Converter
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/17
Initial Release
—
1
1/18
Changed part in Ordering Information table from MAX20471ASA/V+** to
MAX20471ASAA/V+** and removed future product status from MAX20472ATCA/V*
9
2
5/18
Updated Internal Oscillator section and added Boost Converter Short Protection,
Startup into Short, and Short or Overload after Soft-Start sections
7, 8
3
6/18
Added MAX20472ATCB/V+** (future product) to Ordering Information table.
10
4
9/18
Removed all references to MAX20473 and 2A convertor operation; updated Pin
Configuration; updated Functional Diagram; updated Inductor Selection and Output
Capacitor sections; updated Typical Application Circuit; removed MAX20473ATCA/
V+** and future-part designation for MAX20471ATCB/V+ from the Ordering
Information table
5
11/18
Removed future-part designation for MAX20472ATCB/V+ from the Ordering
Information table
11
6
12/18
Updated Package Information table
2
7
3/19
Added information for SWTDFN package to Benefits and Features, Absolute
Maximum Ratings, Package Information, Pin Configurations, and Ordering
Information; added MAX20472ATCC/V+** to Ordering Information
8
6/19
Removed future-part designation from MAX20471ASAA/V+ in the Ordering
Information table
11
9
8/19
Added notes to Ordering Information table
11
9.1
PAGES
CHANGED
DESCRIPTION
Corrected Revision Date for Rev 9 in Revision History
1–11
1, 2, 6, 11
11
10
6/20
Added MAX20472B
1–14
11
8/20
Updated Package Information, Ordering Information
12
9/20
Updated Benefits and Features, Absolute Maximum Ratings, Electrical Characteristics, Pin
Description, Detailed Description, and Applications Information; removed future-product
notation from MAX20471ATCA/VY+T in Ordering Information
1, 3, 4, 5, 7,
8, 10, 12,
13
13
9/21
Updated Electrical Characteristics, Detailed Description, and Ordering Information
4, 5, 10, 13
3, 14
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max
limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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