19-5967; Rev 1; 9/11
EVALUATION KIT AVAILABLE
MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
General Description
The MAX15118 high-efficiency, current-mode step-down
regulator with integrated power switches operates from
2.7V to 5.5V and delivers up to 18A of output current in
a small 2mm x 3.5mm package. The MAX15118 offers
excellent efficiency with skip mode capability at light-
load conditions, yet provides unmatched efficiency
under heavy load conditions. The combination of small
size and high efficiency makes this device suitable for
both portable and nonportable applications.
The MAX15118 utilizes a current-mode control architecture
with a high-gain transconductance error amplifier, which
allows a simple compensation scheme and enables a
cycle-by-cycle current limit with fast response to line and
load transients. A factory-trimmed switching frequency of
1MHz (PWM operation) allows for a compact, all-ceramic
capacitor design.
Integrated switches with low on-resistance ensure high
efficiency at heavy loads while minimizing critical induc-
tances. The MAX15118’s simple layout and footprint
assure first-pass success in new designs.
Other features of the MAX15118 include a capacitor-
programmable soft-start to reduce inrush current, safe
startup into a prebiased output, an enable input, and a
power-good output for power sequencing.
The regulator is available in a 28-bump (4 x 7), 2.10mm
x 3.56mm WLP package, and is fully specified over the
-40NC to +85NC extended temperature range.
S
Continuous 18A Output Current
S
±1% Feedback Accuracy Over Load, Line, and
Temperature
S
Operates from 2.7V to 5.5V Supply
S
Input Undervoltage Lockout
S
Adjustable Output Range from 0.6V Up to 0.94 x V
IN
S
Programmable Soft-Start
S
Factory-Trimmed 1MHz Switching Frequency
S
Stable with Low-ESR Ceramic Output Capacitors
S
Safe-Startup into a Prebiased Output
S
External Reference Input
S
Selectable Skip Mode Option for Improved
Efficiency at Light Loads
S
Enable Input/PGOOD Output Allows Sequencing
S
Remote Ground Sense for Improved Accuracy
S
Thermal and Overcurrent Protection
S
Tiny 2.10mm x 3.56mm, 28-Bump WLP Package
Features
Applications
Notebooks
Servers
Distributed Power Systems
Ordering Information
appears at end of data sheet.
DDR Memory
Base Stations
Typical Operating Circuits
ON
OFF
EN
SKIP
AIN
V
IN
= 2.7V TO 5.5V
IN
C
IN
PGOOD
PGOOD
SS/REFIN
C
SS
PWM MODE OPERATION
GND
C
CC
COMP
R
C
C
C
R2
R
PULL
FB
LX
BST
C
BST
L
OUT
C
OUT
GSNS
R1
V
OUT
MAX15118
Typical Operating Circuits
continued at end of data sheet.
For related parts and recommended products to use with this part, refer to:
www.maxim-ic.com/MAX15118.related
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Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
ABSOLUTE MAXIMUM RATINGS
IN, PGOOD to GND ................................................-0.3V to +6V
EN, COMP, FB, SS/REFIN, GSNS, SKIP,
LX to GND ..............................................-0.3V to (V
IN
+ 0.3V)
LX to GND (for 50ns)........................................-1V to (V
IN
+ 1V)
LX to GND (for 10ns)........................................-2V to (V
IN
+ 2V)
BST to LX.................................................................-0.3V to +6V
BST to GND ...........................................................-0.3V to +12V
BST to IN .................................................................-0.3V to +6V
LX Continuous Current (Note 1) .........................................
Q26A
Output Short-Circuit Duration ...................................Continuous
Continuous Power Dissipation
WLP (derate 81.53mW/NC above +70NC)......................3.26W
Operating Temperature Range .......................... -40NC to +85NC
Junction Temperature (Note 2) .......................................+110NC
Storage Temperature Range............................ -65NC to +150NC
Bump Reflow Temperature (Note 3) ...............................+260NC
Note 1:
LX has internal clamp diodes to GND and IN. Applications that forward bias these diodes must take care not to exceed
the IC’s package power dissipation limits.
Note 2:
Limit the junction temperature to +110NC for continuous operation at maximum output current.
Note 3:
The WLP package is constructed using a unique set of package techniques that impose a limit on the thermal profile. The
device can be exposed to during board-level solder attach and rework. This limit permits only the use of the solder pro-
files recommended in the industry-standard specification JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection
reflow. Preheating is required. Hand or wave soldering is not allowed.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion 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 THERMAL CHARACTERISTICS (Note 4)
WLP
Junction-to-Ambient Thermal Resistance (q
JA
) .......20.6°C/W
Junction-to-Case Thermal Resistance (q
JC
) ..................12.3°C/W
Note 4:
Package thermal resistances were obtained using the MAX15118 evaluation board.
DC ELECTRICAL CHARACTERISTICS
(V
IN
= 5V, see the
Typical Operating Circuits,
T
A
= -40NC to +85NC. Typical values are at T
A
= +25NC, unless otherwise noted.) (Note 5)
PARAMETER
IN Voltage Range
IN Supply Current
IN Shutdown Current
IN Undervoltage Lockout
Threshold
IN Undervoltage Lockout
Threshold Hysteresis
ERROR AMPLIFIER
Transconductance
Voltage Gain
FB Setpoint Voltage
FB Input Bias Current
COMP to Current-Sense
Transconductance
COMP Clamp Low Voltage
Slope Compensation Ramp
Amplitude
V
SLOPE
g
M
A
VEA
V
FB
I
FB
g
MC
V
FB
= 0.65V, V
SS/REFIN
= 0.6V
Over line, load, and temperature
0.594
-500
150
0.97
130
1.2
90
0.600
0.606
+500
mS
dB
V
nA
A/V
V
mV
SYMBOL
V
IN
I
IN
I
SHDN
V
UVLO
V
EN
= V
IN
, V
FB
= 0.65V, no switching
V
EN
= 0V
V
IN
rising, LX starts switching
V
IN
falling, LX stops switching
CONDITIONS
MIN
2.7
4.8
0.01
2.6
200
TYP
MAX
5.5
7
3
2.68
UNITS
V
mA
FA
V
mV
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Maxim Integrated Products
2
MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
DC ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, see the
Typical Operating Circuits,
T
A
= -40NC to +85NC. Typical values are at T
A
= +25NC, unless otherwise noted.) (Note 5)
PARAMETER
GROUND SENSE
GSNS Output Current
POWER SWITCHES
High-side switch
Current-Limit Threshold
LX Leakage Current
BST Leakage Current
BST On-Resistance
LX RMS Output Current
OSCILLATOR
Switching Frequency
Maximum Duty Cycle
Minimum Controllable On-Time
ENABLE FUNCTIONALITY
EN Input High Threshold
EN Input Low Threshold
EN Input Leakage Current
SKIP FUNCTIONALITY (Note 6)
SKIP Input High Threshold
SKIP Input Low Threshold
SKIP Pulldown Resistor
Minimum LX On-Current in Skip
Mode
Zero-Crossing LX Threshold
SOFT-START AND PREBIAS FUNCTIONALITY
Soft-Start Current
SS/REFIN Discharge Resistance
SS/REFIN Prebias Mode Stop
Voltage
SS/REFIN External Reference
Input Range
HICCUP MODE
Number of Consecutive Current-
Limit Events to Hiccup Mode
Hiccup Mode Timeout
N
HIC
8
1024
Events
Clock
Cycles
I
SS
R
SS
V
SS/REFIN
= 0.45V, sourcing
I
SS/REFIN
= 10mA, sinking
V
SS/REFIN
rising
6.8
10
7
0.58
V
IN
-
2.5
12.5
FA
I
V
V
V
SKIP
rising
V
SKIP
falling
0.4
210
3.6
0.5
1.4
V
V
kI
A
A
V
IH
V
IL
V
EN
rising
V
EN
falling
0.4
-1
+1
1.4
V
V
FA
f
SW
D
MAX
t
ON
PWM mode
Skip mode
850
1000
94
85
70
1150
kHz
%
ns
R
ON_BST
Low-side switch, sinking
Low-side switch, sourcing
V
EN
= 0V
V
EN
= 0V
I
BST
= 50mA
18
0.63
24
24
24
3
3
FA
FA
I
A
A
V
SS/REFIN
= 0.6V, V
GSNS
= 0V
56
FA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated Products
3
MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
DC ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, see the
Typical Operating Circuits,
T
A
= -40NC to +85NC. Typical values are at T
A
= +25NC, unless otherwise noted.) (Note 5)
PARAMETER
POWER-GOOD OUTPUT
PGOOD Threshold
PGOOD Threshold Hysteresis
PGOOD Output Voltage Low
PGOOD Leakage Current
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
T
SHDN
Die temperature rising
+150
20
NC
NC
V
PG_OL
I
PG_LK
V
FB
falling, PGOOD deasserts
V
FB
rising
I
PGOOD
= 5mA, V
EN
= 0V
V
PGOOD
= 5.5V, V
FB
= 0.65V
0.514
0.530
25
18
50
1
0.542
V
mV
mV
FA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Note 5:
All devices are 100% production tested at T
A
= +25NC. Limits over the operating temperature range are guaranteed by design.
Note 6:
Connect SKIP to EN for skip mode functionality. Connect SKIP to GND for PWM mode functionality.
Typical Operating Characteristics
(V
IN
= 5V, V
OUT
= 1.5V, C
SS
= 0.1µF, see the
Typical Operating Circuits,
T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 5V, PWM MODE)
MAX15118 toc01
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 3.3V, PWM MODE)
MAX15118 toc02
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 5V, SKIP MODE)
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
V
OUT
= 2.5V
V
OUT
= 1.8V
V
OUT
= 1.5V
V
OUT
= 1.2V
V
OUT
= 0.8V
V
OUT
= 3.3V
MAX15118 toc03
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
2
4
6
8
V
OUT
= 3.3V
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
V
OUT
= 0.8V
V
OUT
= 2.5V
100
V
OUT
= 2.5V
V
OUT
= 1.8V
V
OUT
= 1.5V
V
OUT
= 1.2V
V
OUT
= 0.8V
V
OUT
= 1.8V
V
OUT
= 1.5V
V
OUT
= 1.2V
10
12
14
16
18
0
2
4
6
8
10
12
14
16
18
0
2
4
6
8
10
12
14
16
18
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
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Maxim Integrated Products
4
MAX15118
High-Efficiency, 18A, Current-Mode Synchronous
Step-Down Regulator with Integrated Switches
Typical Operating Characteristics (continued)
(V
IN
= 5V, V
OUT
= 1.5V, C
SS
= 0.1µF, see the
Typical Operating Circuits,
T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(V
IN
= 3.3V, SKIP MODE)
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0
2
4
6
8
10
12
14
16
18
OUTPUT CURRENT (A)
900
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
INPUT VOLTAGE (V)
V
OUT
= 1.8V
V
OUT
= 1.5V
V
OUT
= 1.2V
V
OUT
= 0.8V
V
OUT
= 2.5V
MAX15118 toc04
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
T
A
= +85°C
MAX15118 toc05
100
1100
SWITCHING FREQUENCY (kHz)
1050
T
A
= +25°C
1000
T
A
= -40°C
950
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
(PWM MODE, V
OUT
= 1.5V)
MAX15118 toc06a
OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
(SKIP MODE,
V
OUT
= 1.5V)
MAX15118 toc06b
1.520
1.515
OUTPUT VOLTAGE (V)
1.510
1.505
1.500
1.495
1.490
1.485
1.480
2.7
3.1
3.5 3.9 4.3 4.7
SUPPLY VOLTAGE (V)
5.1
I
LOAD
= 18A
I
LOAD
= 10A
1.53
1.52
OUTPUT VOLTAGE (V)
1.51
1.50
1.49
1.48
1.47
2.7
3.1
3.5
3.9
4.3
4.7
5.1
I
LOAD
= 10A
I
LOAD
= 2A
NO LOAD
5.5
5.5
SUPPLY VOLTAGE (V)
OUTPUT VOLTAGE ERROR
vs. SUPPLY VOLTAGE
MAX15118 toc07
OUTPUT VOLTAGE vs. OUTPUT CURRENT
(PWM MODE, V
OUT
= 1.5V)
MAX15118 toc08a
0.50
0.40
OUTPUT VOLTAGE ERROR (%)
0.30
0.20
0.10
0
-0.10
-0.20
-0.30
-0.40
-0.50
2.90
3.55
4.20
V
OUT
= 1.5V
V
OUT
= 1.8V
I
LOAD
= 18A
4.85
V
OUT
= 1.2V
NORMALIZED AT V
IN
= 3.5V
1.53
1.52
OUTPUT VOLTAGE (V)
V
IN
= 5V
1.51
1.50
1.49
1.48
1.47
V
IN
= 3.3V
5.50
0
2
4
6
8
10
12
14
16
18
SUPPLY VOLTAGE (V)
OUTPUT CURRENT (A)
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Maxim Integrated Products
5
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