MAX15058EWL+T [MAXIM]
Battery Charge Controller, Current-mode, 3A, 1150kHz Switching Freq-Max, BICMOS, PBGA9,;
| 型号： | MAX15058EWL+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Battery Charge Controller, Current-mode, 3A, 1150kHz Switching Freq-Max, BICMOS, PBGA9, 电池 信息通信管理 |
| 文件： | 总22页 (文件大小：1338K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EVALUATION KIT AVAILABLE
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
General Description
Features
● Internal 30mΩ (typ) R
The MAX15058 high-efficiency, current-mode, synchro-
nous step-down switching regulator with integrated power
switches delivers up to 3A of output current. The device
operates from 2.7V to 5.5V and provides an output volt-
age from 0.6V up to 94% of the input voltage, making
the device ideal for distributed power systems, portable
devices, and preregulation applications.
High-Side and 18mΩ
DS(ON)
(typ) Low-Side MOSFETs at 5V
● Continuous 3A Output Current Over Temperature
● 95% Efficiency with 3.3V Output at 3A
● 1% Output Voltage Accuracy Over Load, Line, and
Temperature
● Operates from 2.7V to 5.5V Supply
● Cycle-by-Cycle Overcurrent Protection
The MAX15058 utilizes a current-mode control architec-
ture with a high-gain transconductance error amplifier.
The current-mode control architecture facilitates easy
compensation design and ensures cycle-by-cycle current
limit with fast response to line and load transients.
● Adjustable Output from 0.6V to Up to 0.94 x V
● Programmable Soft-Start
IN
● Factory-Trimmed, 1MHz Switching Frequency
The MAX15058 offers selectable skip-mode functional-
ity to reduce current consumption and achieve a higher
● Stable with Low-ESR Ceramic Output Capacitors
● Safe-Startup Into Prebiased Output
● External Reference Input
efficiency at light output load. The low R
integrated
DS(ON)
switches ensure high efficiency at heavy loads while
minimizing critical inductances, making the layout design
a much simpler task with respect to discrete solutions.
Utilizing a simple layout and footprint assures first-pass
success in new designs.
● Skip-Mode Functionality
● Enable Input/Power-Good Output
● Fully Protected Against Overcurrent and
The MAX15058 features a 1MHz, factory-trimmed, fixed-
frequency PWM mode operation. The high switching fre-
quency, along with the PWM current-mode architecture,
allows for a compact, all-ceramic capacitor design.
Overtemperature
● Input Undervoltage Lockout
Ordering Information
The MAX15058 offers a capacitor-programmable soft-
start reducing inrush current, startup into PREBIAS opera-
tions, and a PGOOD open-drain output that can be used
as an interrupt and for power sequencing.
PART
TEMP RANGE
PIN-PACKAGE
MAX15058EWL+
-40°C to +85°C
9 WLP
+Denotes a lead(Pb)-free/RoHS-compliant package.
The MAX15058 is available in a 9-bump (3 x 3 array),
1.5mm x 1.5mm WLP package and is specified over the
-40°C to +85°C temperature range.
Typical Operating Circuit
INPUT
OUTPUT
1.8V/3A
2.8V TO 5.5V
IN
LX
Applications
● Distributed Power Systems
● Preregulators for Linear Regulators
● Portable Devices
● Notebook Power
● Server Power
MAX15058
GND
PGOOD
FB
ON
EN
ENABLE
OFF
COMP
SKIP
● IP Phones
SS/REFIN
19-5478; Rev 2; 7/11
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Absolute Maximum Ratings
IN, PGOOD to GND ................................................-0.3V to +6V
Continuous Power Dissipation (T = +70°C)
A
LX to GND..................................................-0.3V to (V + 0.3V)
9-Bump WLP Multilayer Board
IN
LX to GND...................................... -1V to (V + 0.3V) for 50ns
(derate 14.1mW/°C above T = +70°C)....................1127mW
IN
A
EN, COMP, FB, SS/REFIN, SKIP to GND .-0.3V to (V + 0.3V)
LX Current (Note 1).................................................... -6A to +6A
Output Short-Circuit Duration....................................Continuous
Operating Temperature Range........................... -40°C to +85°C
Storage Temperature Range............................ -65°C to +150°C
Soldering Temperature (reflow).......................................+260°C
IN
Note 1: LX has internal clamp diodes to GND and IN. Applications that forward bias these diodes should not exceed the IC’s pack-
age power dissipation limits.
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
PACKAGE TYPE: 9 WLP
Package Code
W91E1Z+1
Outline Number
21-0508
Land Pattern Number
Refer to Application Note 1891
THERMAL RESISTANCE, FOUR-LAYER BOARD
Junction to Ambient (θ
)
71°C/W
26°C/W
JA
Junction to Case (θ
)
JC
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
.
Maxim Integrated
│ 2
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Electrical Characteristics
(V = 5V, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
5.5
2
UNITS
V
IN Voltage Range
V
2.7
IN
IN Shutdown Supply Current
IN Supply Current
V
V
= 0V
0.2
µA
EN
I
= 5V, V = 0.65V, no switching
1.56
2.3
mA
IN
EN
FB
V
Undervoltage Lockout
IN
LX starts switching, V rising
2.6
2.7
V
IN
Threshold
V
Undervoltage Lockout
IN
LX stops switching, V falling
IN
200
mV
Hysteresis
ERROR AMPLIFIER
Transconductance
Voltage Gain
g
1.5
90
mS
dB
MV
A
VEA
FB Set-Point Accuracy
FB Input Bias Current
V
Over line, load, and temperature
594
600
606
mV
nA
FB
I
V
= 0.6V
-500
+500
FB
FB
COMP to Current-Sense
Transconductance
g
18
A/V
V
MC
COMP Clamp Low
V
= 0.65V, V = 0.6V
SS
0.94
FB
POWER SWITCHES
LX On-Resistance, High-Side
pMOS
30
18
5
mΩ
mΩ
A
LX On-Resistance, Low-Side
nMOS
High-Side Switch Current-Limit
Threshold
I
HSCL
Low-Side Switch Sink Current-
Limit Threshold
4
A
Low-Side Switch Source Current-
Limit Threshold
5
A
LX Leakage Current
RMS LX Output current
OSCILLATOR
V
= 0V
10
µA
A
EN
3
Switching Frequency
Maximum Duty Cycle
Minimum Controllable On-Time
f
850
1000
94
1150
kHz
%
SW
D
MAX
70
ns
Slope Compensation Ramp
Valley
1.15
320
V
Slope Compensation Ramp
Amplitude
V
Extrapolated to 100% duty cycle
mV
SLOPE
Maxim Integrated
│ 3
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Electrical Characteristics (continued)
(V = 5V, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ENABLE
EN Input High Threshold Voltage
EN Input Low Threshold Voltage
EN Input Leakage Current
V
V
V
V
rising
falling
= 5V
1.45
V
V
EN
0.4
EN
0.025
25
µA
µA
EN
SKIP Input Leakage Current
SOFT-START, PREBIAS, REFIN
Soft-Start Current
= V
= 5V
SKIP
EN
I
V
= 0.45V, sourcing
= 10mA, sinking
10
µA
SS
SS/REFIN
SS/REFIN Discharge Resistance
R
I
8.3
Ω
SS
SS/REFIN
SS/REFIN Prebias Mode Stop
Voltage
V
rising
0.58
V
V
SS/REFIN
External Reference Input Range
0
IN - 1.8
HICCUP
Number of Consecutive Current-
Limit Events to Hiccup
8
Events
Clock
Cycles
Timeout
1024
POWER-GOOD OUTPUT
PGOOD Threshold
V
V
rising
falling
0.535
0.555
28
0.575
60
V
FB
PGOOD Threshold Hysteresis
mV
mV
µA
FB
PGOOD V
I
= 5mA, V = 0.5V
20
OL
PGOOD
FB
PGOOD Leakage
V
= 5V, V = 0.65V
0.013
PGOOD
FB
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
150
20
°C
°C
Temperature falling
Note 2: Specifications are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by
A
design and characterization.
Maxim Integrated
│ 4
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Typical Operating Characteristics
(V = 5V, V
= 1.8V, I
= 3A, Circuit of Figure 5, T = +25°C, unless otherwise noted.)
IN
OUT
LOAD
A
EFFICIENCY vs. LOAD CURRENT
(SKIP MODE)
EFFICIENCY vs. LOAD CURRENT
(PWM MODE)
EFFICIENCY vs. OUTPUT CURRENT
(FORCED PWM)
100
95
90
85
80
75
70
100
95
90
85
80
75
100
95
90
85
80
75
V
= 3.3V
V
= 2.5V
OUT
OUT
V
= 2.5V
OUT
V
= 1.5V
OUT
V = 1.8V
OUT
V
OUT
= 1.8V
V
= 1.8V
V
= 1.5V
OUT
OUT
V
OUT
= 1.2V
V
= 1.5V
OUT
V
= 1.2V
V
= 2.5V
OUT
OUT
V
= 1.2V
OUT
V
= 3.3V
OUT
V
= 5V
V
IN
= 5V
V
= 3.3V
IN
IN
0
0.5
1.0
1.5
2.0
2.5
3.0
0
0.5
1.0
1.5
2.0
2.5
3.0
0
0.5
1.0
1.5
2.0
2.5
3.0
2.7
0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
EFFICIENCY vs. OUTPUT CURRENT
(SKIP MODE)
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
100
95
90
85
80
75
1100
V
= 2.5V
OUT
1080
1060
1040
1020
1000
980
V
OUT
= 1.8V
V
= 1.5V
OUT
V
= 1.2V
OUT
960
940
920
V
= 3.3V
IN
900
0
0.5
1.0
1.5
2.0
2.5
3.0
3.2
3.7
4.2
4.7
5.2
OUTPUT CURRENT (A)
INPUT VOLTAGE (V)
OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
1.89
1.87
1.85
1.83
1.81
1.79
1.77
1.75
1.89
1.87
1.85
1.83
1.81
1.79
1.77
1.75
V
= 3.3V
= 5V
OUT
V
OUT
I
= 0.5A
OUT
2.7
3.2
3.7
4.2
4.7
5.2
0.5
1.0
1.5
2.0
2.5
3.0
SUPPLY VOLTAGE (V)
OUTPUT CURRENT (A)
Maxim Integrated
│ 5
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Typical Operating Characteristics (continued)
(V = 5V, V
= 1.8V, I
= 3A, Circuit of Figure 5, T = +25°C, unless otherwise noted.)
IN
OUT
LOAD A
LOAD-TRANSIENT RESPONSE
SWITCHING WAVEFORMS (I
= 3A)
OUT
MAX15058 toc08
MAX15058 toc09a
V
OUT
20mV/div
AC-COUPLED
50mV/div
AC-COUPLED
I
LX
1AV/div
1A/div
0A
V
LX
5V/div
100µs/div
400ns/div
SWITCHING WAVEFORM IN SKIP MODE
(I = 10mA)
SWITCHING WAVEFORMS (I
= 3A)
OUT
OUT
MAX15058 toc09b
MAX15058 toc10
V
OUT
20mV/div
AC-COUPLED
V
OUT
50mV/div
AC-COUPLED
I
LX
1AV/div
I
LX
1A/div
0A
V
LX
V
LX
5V/div
5V/div
V
IN
= 3.3V
400ns/div
10µs/div
INPUT AND OUTPUT
WAVEFORMS (I
= 3A)
SHUTDOWN WAVEFORM
MAX15058 toc12
OUT
MAX15058 toc11
V
ENABLE
5V/div
INPUT
20mV/div
AC-COUPLED
V
OUT
1V/div
I
LX
OUTPUT
100mV/div
AC-COUPLED
1A/div
V
PGOOD
5V/div
400ns/div
10µs/div
Maxim Integrated
│ 6
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Typical Operating Characteristics (continued)
(V = 5V, V
= 1.8V, I
= 3A, Circuit of Figure 5, T = +25°C, unless otherwise noted.)
IN
OUT
LOAD A
SOFT-START WAVEFORMS
(PWM MODE) (I = 3A)
SOFT-START WAVEFORMS
(SKIP MODE) (I = 3A)
OUT
OUT
MAX15058 toc13a
MAX15058 toc13b
V
V
ENABLE
ENABLE
5V/div
5V/div
V
OUT
V
OUT
1V/div
1V/div
I
LX
I
LX
1A/div
1A/div
V
V
PGOOD
PGOOD
5V/div
5V/div
200µs/div
200µs/div
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
SHORT-CIRCUIT HICCUP MODE
MAX15058 toc15
100
90
80
70
60
50
40
30
20
10
0
V
EN
= 0V
I
IN
500mA/div
V
OUT
200mV/div
I
OUT
5A/div
2.7
3.2
3.7
4.2
4.7
5.2
200µs/div
INPUT VOLTAGE (V)
RMS INPUT CURRENT
vs. INPUT VOLTAGE
FB VOLTAGE vs. TEMPERATURE
606
604
602
600
598
596
594
200
160
120
80
40
NO LOAD
SHORT CIRCUIT ON OUTPUT
0
-40 -20
0
20
40
60
80
2.8 3.1 3.4 3.7 4.0 4.3 4.6 4.9 5.2 5.5
INPUT VOLTAGE (V)
AMBIENT TEMPERATURE (°C)
Maxim Integrated
│ 7
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Typical Operating Characteristics (continued)
(V = 5V, V
= 1.8V, I
= 3A, Circuit of Figure 5, T = +25°C, unless otherwise noted.)
IN
OUT
LOAD A
SOFT-START WAVEFORMS
(EXTERNAL REFIN) (PWM MODE)
SOFT-START WAVEFORMS
(EXTERNAL REFIN) (SKIP MODE)
MAX15058 toc18a
MAX15058 toc18b
V
V
SS/REFIN
SS/REFIN
500mV/div
500mV/div
V
OUT
V
OUT
1V/div
1V/div
NO LOAD
NO LOAD
I
LX
I
LX
1A/div
1A/div
V
V
PGOOD
PGOOD
5V/div
5V/div
200µs/div
200µs/div
STARTING INTO A PREBIASED OUTPUT
(I = 2A)
STARTING INTO A PREBIASED OUTPUT
(NO LOAD)
OUT
MAX15058 toc19
MAX15058 toc20a
V
ENABLE
V
ENABLE
5V/div
5V/div
V
OUT
V
OUT
1V/div
1V/div
I
LX
I
LX
1A/div
1A/div
V
PGOOD
V
PGOOD
PWM MODE
PWM MODE
200µs/div
5V/div
5V/div
200µs/div
STARTING INTO A PREBIASED OUTPUT
STARTING INTO A PREBIASED OUTPUT
(NO LOAD)
HIGHER THAN SET OUTPUT
MAX15058 toc20b
MAX15058 toc21
1.8V
V
OUT
V
ENABLE
500mV/div
5V/div
V
OUT
1V/div
I
L
1A/div
I
LX
1A/div
V
SS/REFIN
500mV/div
V
PGOOD
5V/div
SKIP MODE
10Ω LOAD AT OUT
200µs/div
400µs/div
Maxim Integrated
│ 8
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Typical Operating Characteristics (continued)
(V = 5V, V
= 1.8V, I
= 3A, Circuit of Figure 5, T = +25°C, unless otherwise noted.)
IN
OUT
LOAD A
CASE TEMPERATURE
vs. AMBIENT TEMPERATURE
INPUT CURRENT IN SKIP MODE
vs. OUTPUT VOLTAGE
100
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
NO LOAD
80
60
40
20
0
V
V
= 5.0V
CC
= 3.3V
2.2
CC
-20
-40
-40
-20
0
20
40
60
80
1.2
1.7
2.7
3.2
AMBIENT TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
Maxim Integrated
│ 9
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Pin Configuration
TOP VIEW
(BUMPS ON BOTTOM)
MAX15058
GND
LX
A2
IN
A1
A3
COMP
B1
SKIP
B2
EN
B3
FB
C1
SS/REFIN PGOOD
C2
C3
WLP
Pin Description
BUMP
NAME
FUNCTION
Analog Ground/Low-Side Switch Source Terminal. Connect to the PCB copper plane at one point near the
input bypass capacitor return terminal.
A1
GND
Inductor Connection. Connect LX to the switched side of the inductor. LX is high impedance when the IC is
in shutdown mode.
A2
A3
LX
IN
Input Power Supply. Input supply range is from 2.7V to 5.5V. Bypass with a minimum 10µF ceramic capacitor
to GND. See Figures 5 and 6.
Voltage Error-Amplifier Output. Connect the necessary compensation network from COMP to GND. See
the Closing the Loop: Designing the Compensation Circuitry section.
B1
B2
B3
COMP
SKIP
EN
Skip-Mode Input. Connect to EN to select skip mode or leave unconnected for normal operation.
Enable Input. EN is a digital input that turns the regulator on and off. Drive EN high to turn on the regulator.
Connect to IN for always-on operation.
Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to GND to set
C1
C2
C3
FB
the output voltage from 0.6V up to 94% of V
.
IN
Soft-Start/External Voltage Reference Input. Connect a capacitor from SS/REFIN to GND to set the startup
SS/REFIN time. See the Setting the Soft-Start Time section for details on setting the soft-start time. Apply a voltage
reference from 0V to V - 1.5V to drive soft-start externally.
IN
Open-Drain Power-Good Output. PGOOD goes high when FB is above 555mV and pulls low if FB is below
527mV.
PGOOD
Maxim Integrated
│ 10
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Block Diagram
SKIP
EN
IN
HIGH-SIDE
CURRENT LIMIT
SHDN
SKPM
BIAS
GENERATOR
EN LOGIC, IN UVLO
THERMAL SHDN
SKIP-MODE
LOGIC
LX
VOLTAGE
REFERENCE
CURRENT-SENSE
AMPLIFIER
LX
IN
IN
STRONG PREBIASED
FORCED START
SKPM
CK
0.58V
LX
CONTROL
LOGIC
SS/REFIN
IN
SS/REFIN BUFFER
0.6V
GND
10µA
LOW-SIDE SOURCE-SINK
CURRENT LIMIT AND ZERO-
CROSSING COMPARATOR
PWM
COMPARATOR
ERROR AMPLIFIER
SINK
SOURCE
FB
ZX
∑
COMP
RAMP
CK
SKPM
OSCILLATOR
RAMP GEN
MAX15058
PGOOD
POWER-GOOD
COMPARATOR
0.555V RISING,
0.527V FALLING
Maxim Integrated
│ 11
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
reached. The low-side MOSFET turns on for the remain-
der of the oscillation cycle.
Detailed Description
The MAX15058 high-efficiency, current-mode switch-
ing regulator can deliver up to 3A of output current. The
MAX15058 provides output voltages from 0.6V to 0.94 x
Starting into a Prebiased Output
The MAX15058 can soft-start into a prebiased output
without discharging the output capacitor. In safe pre-
biased startup, both low-side and high-side MOSFETs
remain off to avoid discharging the prebiased output.
PWM operation starts when the voltage on SS/REFIN
crosses the voltage on FB.
V
IN
from 2.7V to 5.5V input supplies, making the device
ideal for on-board point-of-load applications.
The MAX15058 delivers current-mode control architec-
ture using a high-gain transconductance error amplifier.
The current-mode control architecture facilitates easy
compensation design and ensures cycle-by-cycle current
limit with fast response to line and load transients.
The MAX15058 can start into a prebiased voltage higher
than the nominal set point without abruptly discharging
the output. Forced PWM operation starts when the SS/
REFIN voltage reaches 0.58V (typ), forcing the converter
to start. In case of prebiased output, below or above the
output nominal set point, if low-side sink current-limit
threshold (set to the reduced value of -0.4A (typ) for the
first 32 clock cycles and then set to -5A (typ)) is reached,
the low-side switch turns off before the end of the clock
period, and the high-side switch turns on until one of the
following conditions is satisfied:
The MAX15058 features a 1MHz fixed switching frequen-
cy, allowing for all-ceramic capacitor designs and fast
transient responses. The high operating frequency mini-
mizes the size of external components. The MAX15058 is
available in a 1.5mm x 1.5mm (3 x 3 array) x 0.5mm pitch
WLP package.
The MAX15058 offers a selectable skip-mode functional-
ity to reduce current consumption and achieve a higher
efficiency at light output loads. The low R
inte-
DS(ON)
grated switches (30mΩ high-side and 18mΩ low-side, typ)
ensure high efficiency at heavy loads while minimizing
critical inductances, making the layout design a much
simpler task with respect to discrete solutions. Utilizing a
simple layout and footprint assures first-pass success in
new designs.
● High-side source current hits the reduced high-side
current limit (0.4A, typ); in this case, the high-side
switch is turned off for the remaining time of the clock
period.
● The clock period ends. Reduced high-side current
limit is activated to recirculate the current into the
high-side power switch rather than into the internal
high-side body diode, which could be damaged. Low-
side sink current limit is provided to protect the low-
side switch from excessive reverse current during
prebiased operation.
The MAX15058 features 1MHz ±15%, factory-trimmed,
fixed-frequency PWM mode operation. The MAX15058
also offers capacitor-programmable, soft-start reducing
inrush current, startup into PREBIAS operation, and a
PGOOD open-drain output for sequencing with other
devices.
In skip mode operation, the prebias output needs to be
lower than the set point.
Controller Function—PWM Logic
The controller logic block is the central processor that
determines the duty cycle of the high-side MOSFET
under different line, load, and temperature conditions.
Under normal operation, where the current-limit and
temperature protection are not triggered, the controller
logic block takes the output from the PWM comparator
and generates the driver signals for both high-side and
low-side MOSFETs. The control logic block controls the
break-before-make logic and all the necessary timing.
Enable Input
The MAX15058 features independent device enable con-
trol and power-good signal that allow for flexible power
sequencing. Drive the enable input (EN) high to enable
the regulator, or connect EN to IN for always-on opera-
tion. Power-good (PGOOD) is an open-drain output that
asserts when V
is above 555mV (typ), and deasserts
FB
low if V is below 527mV (typ).
FB
Programmable Soft-Start (SS/REFIN)
The high-side MOSFET turns on at the beginning of the
oscillator cycle and turns off when the COMP voltage
crosses the internal current-mode ramp waveform, which
is the sum of the slope compensation ramp and the
current-mode ramp derived from inductor current (current-
sense block). The high-side MOSFET also turns off if the
maximum duty cycle is 94%, or when the current limit is
The MAX15058 utilizes a soft-start feature to slowly ramp
up the regulated output voltage to reduce input inrush cur-
rent during startup. Connect a capacitor from SS/REFIN
to GND to set the startup time (see the Setting the Soft-
Start Time section for capacitor selection details).
Maxim Integrated
│ 12
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
200mA (typ). The inductor current does not become nega-
tive. If during a clock cycle the inductor current falls below
Error Amplifier
A high-gain error amplifier provides accuracy for the
voltage-feedback loop regulation. Connect the necessary
compensation network between COMP and GND (see
the Compensation Design Guidelines section). The error-
amplifier transconductance is 1.5mS (typ). COMP clamp
low is set to 0.94V (typ), just below the slope ramp com-
pensation valley, helping COMP to rapidly return to the
correct set point during load and line transients.
the 200mA threshold (during off-time), the low side turns
off. At the next clock cycle, if the output voltage is above
set point, the PWM logic keeps both high-side and low-
side MOSFETs off. If instead the output voltage is below
the set point, the PWM logic drives the high-side on for a
minimum fixed on-time (300ns typ). In this way the system
can skip cycles, reducing frequency of operations, and
switches only as needed to service load at the cost of
an increase in output voltage ripple (see the Skip Mode
Frequency and Output Ripple section). In skip mode,
power dissipation is reduced and efficiency is improved
at light loads because power MOSFETs do not switch at
every clock cycle.
PWM Comparator
The PWM comparator compares COMP voltage to the
current-derived ramp waveform (LX current to COMP volt-
age transconductance value is 18A/V typ). To avoid insta-
bility due to subharmonic oscillations when the duty cycle
is around 50% or higher, a slope compensation ramp is
added to the current-derived ramp waveform. Confirm
the compensation ramp slope (0.3V x 1MHz = 0.3V/µs)
is equivalent to half the inductor current downslope in the
worst case (load 3A, current ripple 30% and maximum
duty-cycle operation of 94%). The slope compensation
ramp valley is set to 1.15V (typ).
Applications Information
Setting the Output Voltage
The MAX15058 output voltage is adjustable from 0.6V
up to 94% of V by connecting FB to the center tap of a
IN
resistor-divider between the output and GND (Figure 1).
Choose R1 and R2 so that the DC errors due to the FB
input bias current (±500nA) do not affect the output volt-
age accuracy. With lower value resistors, the DC error
is reduced, but the amount of power consumed in the
resistor-divider increases. A typical value for R2 is 10kΩ,
but values between 5kΩ and 50kΩ are acceptable. Once
R2 is chosen, calculate R1 using:
Overcurrent Protection and Hiccup
When the converter output is shorted or the device is
overloaded, each high-side MOSFET current-limit event
(5A typ) turns off the high-side MOSFET and turns on
the low-side MOSFET. On each current-limit event a 3-bit
counter is incremented. The counter is reset after three
consecutive high-side MOSFETs turn on without reach-
ing current limit. If the current-limit condition persists, the
counter fills up reaching eight events. The control logic
then discharges SS/REFIN, stops both high-side and low-
side MOSFETs, and waits for a hiccup period (1024 clock
cycles typ) before attempting a new soft-start sequence.
The hiccup mode is also enabled during soft-start time.
VOUT
R1 = R2×
−1
V
FB
where the feedback threshold voltage, V
= 0.6V (typ).
FB
When regulating for an output of 0.6V in skip mode, short
FB to OUT and keep R2 connected from FB to GND.
Inductor Selection
Thermal-Shutdown Protection
A high-valued inductor results in reduced inductor ripple
current, leading to a reduced output ripple voltage.
However, a high-valued inductor results in either a larger
physical size or a high series resistance (DCR) and
a lower saturation current rating. Typically, choose an
inductor value to produce a current ripple equal to 30%
of load current. Choose the inductor with the following
formula:
The MAX15058 contains an internal thermal sensor that
limits the total power dissipation to protect the device in
the event of an extended thermal fault condition. When
the die temperature exceeds +150°C (typ), the thermal
sensor shuts down the device, turning off the DC-DC
converter to allow the die to cool. After the die tempera-
ture falls by 20°C (typ), the device restarts, following the
soft-start sequence.
Skip Mode Operation
V
V
OUT
OUT
L =
× 1−
The MAX15058 operates in skip mode when SKIP is con-
nected to EN. When in skip mode, LX output becomes
high impedance when the inductor current falls below
f
×LIR ×I
V
SW
LOAD
IN
where f
is the internally fixed 1MHz switching frequen-
cy, and LIR is the desired inductor current ratio (typically
SW
Maxim Integrated
│ 13
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
FEEDBACK
DIVIDER
ERROR AMPLIFIER
POWER MODULATOR
SLOPE
OUTPUT FILTER
AND LOAD
COMPENSATION
RAMP
V
IN
V
OUT
g
MC
∑
FB
R1
*C
FF
I
L
V
FB
V
OUT
COMP
V
Q
HS
LS
I
OUT
L
DCR
PWM
CONTROL
LOGIC
R2
COMP
ESR
Q
COMPARATOR
R
LOAD
R
C
R
OUT
g
MV
C
OUT
C
C
V
COMP
I
OUT
G
MOD
AVEA(dB)/20
= 10 /g
R
OUT
MV
NOTE: THE G
STAGE SHOWN ABOVE MODELS THE AVERAGE CURRENT OF
MOD
REF
THE INDUCTOR, I , INJECTED INTO THE OUTPUT LOAD, I , e.g., I = I .
OUT OUT
L
L
THIS CAN BE USED TO SIMPLIFY/MODEL THE MODULATION/CONTROL/POWER
STATE CIRCUITRY SHOWN WITHIN THE BOXED AREA.
*NOTE: C IS OPTIONAL AND DESIGNED TO EXTEND THE
FF
REGULATOR’S GAIN BANDWIDTH AND INCREASED PHASE
MARGIN FOR SOME LOW-DUTY CYCLE APPLICATIONS.
Figure 1. Peak Current-Mode Regulator Transfer Model
set to 0.3). In addition, the peak inductor current, I
,
to be less than 2% of the minimum input voltage, f
is
SW
L_PK
must always be below the minimum high-side current-limit
value, I , and the inductor saturation current rating,
the switching frequency (1MHz), and I
is the output
LOAD
load. The impedance of the input capacitor at the switch-
ing frequency should be less than that of the input source
so high-frequency switching currents do not pass through
the input source, but are instead shunted through the
input capacitor.
HSCL
I
.
L_SAT
Ensure that the following relationship is satisfied:
1
I
= I
+
∆I < min I
I
(
)
L_PK
LOAD
L
HSCL_, L_SAT
2
The input capacitor must meet the ripple current require-
ment imposed by the switching currents. The RMS input
ripple current is given by:
Input Capacitor Selection
The input capacitor reduces the peak current drawn from
the input power supply and reduces switching noise in the
device. The total input capacitance must be equal to or
greater than the value given by the following equation to
keep the input ripple voltage within the specification and
minimize the high-frequency ripple current being fed back
to the input source:
V
× V − V
(
)
OUT
IN
OUT
I
=
I
RIPPLE
LOAD
V
IN
where I
is the input RMS ripple current.
RIPPLE
Output Capacitor Selection
The key selection parameters for the output capacitor are
capacitance, ESR, ESL, and voltage rating. The param-
eters affect the overall stability, output ripple voltage, and
transient response of the DC-DC converter. The output
ripple occurs due to variations in the charge stored in
the output capacitor, the voltage drop due to the capaci-
I
V
OUT
V
IN
LOAD
C
=
×
IN
f
× ∆V
SW
IN_RIPPLE
where ∆V
is the maximum-allowed input ripple
IN_RIPPLE
voltage across the input capacitors and is recommended
Maxim Integrated
│ 14
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
tor’s ESR, and the voltage drop due to the capacitor’s
ESL. Estimate the output-voltage ripple due to the output
capacitance, ESR, and ESL as follows:
on the inductor and output capacitor values. After a short
time, the controller responds by regulating the output volt-
age back to the predetermined value.
Use higher C
values for applications that require light
OUT
V
V
OUT
1
OUT
×L
load operation or transition between heavy load and light
load, triggering skip mode, causing output undershooting
or overshooting. When applying the load, limit the output
undershoot by sizing C
formula:
∆V
=
× 1−
× R
+
ESR_COUT
OUT
f
V
8× f
× C
SW
IN
SW
OUT
For ceramic capacitors, ESR contribution is negligible:
1
according to the following
OUT
R
<<
ESR_OUT
∆I
8× f
× C
OUT
LOAD
x ∆V
OUT
SW
C
≅
OUT
3f
CO
For tantalum or electrolytic capacitors, ESR contribution
is dominant:
where ∆I
is the total load change, f
is the regula-
LOAD
CO
tor unity-gain bandwidth (or zero crossover frequency),
and ∆V is the desired output undershooting. When
removing the load and entering skip mode, the device
cannot control output overshooting, since it has no sink
current capability; see the Skip Mode Frequency and
1
R
>>
ESR_OUT
OUT
8× f
× C
OUT
SW
Use these equations for initial output-capacitor selec-
tion. Determine final values by testing a prototype or an
evaluation circuit. A smaller ripple current results in less
output-voltage ripple. Since the inductor ripple current is
a factor of the inductor value, the output-voltage ripple
decreases with larger inductance. Use ceramic capacitors
for low ESR and low ESL at the switching frequency of
the converter. The ripple voltage due to ESL is negligible
when using ceramic capacitors.
Output Ripple section to properly size C
.
OUT
Skip Mode Frequency and Output Ripple
In skip mode, the switching frequency (f
) and output
SKIP
ripple voltage (V
) shown in Figure 2 are cal-
OUT-RIPPLE
culated as follows:
t
is a fixed time (300ns, typ); the peak inductor current
ON
reached is:
Load-transient response also depends on the selected
output capacitance. During a load transient, the output
V
− V
L
IN
OUT
I
=
× t
ON
SKIP−LIMIT
instantly changes by ESR x ∆I
. Before the control-
LOAD
ler can respond, the output deviates further, depending
I
L
I
SKIP-LIMIT
I
LOAD
t
t
t
= n × t
OFF2 CK
ON
OFF1
V
OUT
V
OUT-RIPPLE
Figure 2. Skip Mode Waveform
Maxim Integrated
│ 15
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
t
is the time needed for inductor current to reach the
As a result, the inductor’s pole frequency is shifted
beyond the gain bandwidth of the regulator. System
stability is provided with the addition of a simple series
capacitor-resistor from COMP to GND. This pole-zero
combination serves to tailor the desired response of the
closed-loop system. The basic regulator loop consists of a
power modulator (comprising the regulator’s pulse-width
modulator, current sense and slope compensation ramps,
control circuitry, MOSFETs, and inductor), the capacitive
output filter and load, an output feedback divider, and a
voltage-loop error amplifier with its associated compensa-
tion circuitry. See Figure 1.
OFF1
zero-current crossing limit (~0A):
L ×I
SKIP−LIMIT
t
=
OFF1
V
OUT
During t
charge equal to (see Figure 2):
and t , the output capacitor stores a
OFF1
ON
1
1
2
L x I
−I
SKIP−LIMIT LOAD
x
+
(
)
V
− V
V
IN
OUT
OUT
∆Q
=
OUT
2
The average current through the inductor is expressed as:
During t
(= n x t , number of clock cycles skipped),
CK
OFF2
output capacitor loses this charge:
I
= G
× V
MOD COMP
L
where I is the average inductor current and G
is the
MOD
∆Q
L
OUT
t
=
⇒
OFF2
power modulator’s transconductance.
I
LOAD
2
For a buck converter:
1
1
L x I
−I
x
+
(
)
SKIP−LIMIT LOAD
V
− V
V
OUT
IN
OUT
V
= R
×I
LOAD L
t
=
OUT
OFF2
2 xI
LOAD
where R
is the equivalent load resistor value.
LOAD
Combining the above two relationships, the power modu-
lator’s transfer function in terms of V with respect to
COMP
Finally, frequency in skip mode is:
1
OUT
V
is:
f
=
SKIP
t
+ t
+ t
OFF1 OFF2
ON
V
R
×I
LOAD L
OUT
=
= R
× G
LOAD MOD
V
I
L
COMP
Output ripple in skip mode is:
G
MOD
V
= V
+ V
OUT−RIPPLE
COUT−RIPPLE
− I
ESR−RIPPLE
The peak current-mode controller’s modulator gain is
attenuated by the equivalent divider ratio of the load
resistance and the current-loop gain’s impedance.
I
x t
(
)
SKIP−LIMIT
LOAD
ON
=
C
OUT
G
becomes
+ R
x I
(
− I
LOAD
MOD
)
ESR,COUT
SKIP−LIMIT
1
L x I
G
DC = g
×
MC
SKIP−LIMIT
(
)
MOD
V
=
+ R
ESR,COUT
OUT−RIPPLE
R
LOAD
C
x V − V
(
)
)
1+
× K × 1− D − 0.5
OUT
IN
OUT
(
)
S
f
×L
SW
x I
(
− I
SKIP−LIMIT
LOAD
where R
= V
, f
is the switching
LOAD
OUT/IOUT(MAX) SW
frequency, L is the output inductance, D is the duty cycle
(V /V ), and K is a slope compensation factor calcu-
lated from the following equation:
To limit output ripple in skip mode, size C
the above formula. All the above calculations are appli-
cable only in skip mode.
based on
OUT
OUT IN
S
Compensation Design Guidelines
S
V
× f
×L × g
MC
SLOPE
S
N
SLOPE SW
K
= 1+
= 1+
S
The MAX15058 uses a fixed-frequency, peak-current-
mode control scheme to provide easy compensation
and fast transient response. The inductor peak current is
monitored on a cycle-by-cycle basis and compared to the
COMP voltage (output of the voltage error amplifier). The
regulator’s duty cycle is modulated based on the induc-
tor’s peak current value. This cycle-by-cycle control of
the inductor current emulates a controlled current source.
V
− V
(
)
IN OUT
where:
V
SLOPE
S
=
= V
× f
SLOPE
SLOPE SW
t
SW
V
(
− V
OUT
)
IN
S
=
N
L × g
MC
Maxim Integrated
│ 16
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
1ST ASYMPTOTE
R2 × (R1 + R2) × 10
-1
AVEA(dB)/20
-1 -1
SW
× g × R
MC
× {1 + R
× [K × (1 - D) - 0.5] × (L × f ) }
LOAD
LOAD
S
2ND ASYMPTOTE
-1
-1
-1 -1
SW
R2 × (R1 + R2) × g × (2C ) × g × R
× {1 + R
× [K × (1 - D) - 0.5] × (L × f ) }
MV
C
MC
LOAD
LOAD
S
GAIN
3RD ASYMPTOTE
-1
-1
-1 -1
× [K × (1 - D) - 0.5] × (L × f ) } ×
R2 × (R1 + R2) × g × (2C ) × g × R
× {1 + R
-1 -1 -1
SW
MV
-1
C
MC
LOAD
LOAD
S
SW
(2C
× {R
+ [K × (1 - D) - 0.5] × (L × f ) } )
OUT
LOAD
S
4TH ASYMPTOTE
-1
-1 -1
× [K × (1 - D) - 0.5] × (L × f ) } ×
R2 × (R1 + R2) × g × R × g × R
× {1 + R
MV
-1
C
MC
LOAD
LOAD
S
SW
-1 -1 -1
(2GC
× {R
+ [K × (1 - D) - 0.5] × (L × f ) } )
OUT
LOAD
S
SW
3RD POLE (DBL) 2ND ZERO
-1
(2C ESR)
0.5 × f
SW
OUT
UNITY
FREQUENCY
1ST POLE
AVEA(dB)/20
f
CO
-1 -1
)]
MV
[2 × (10
C
- g
2ND POLE
f
*
PMOD
5TH ASYMPTOTE
-1
-1 -1
× [K × (1 - D) - 0.5] × (L × f ) }
R2 × (R1 + R2) × g × R × g × R
× {1 + R
SW
×
MV
-1
C
MC
LOAD
LOAD
-1 -1 -1
S
SW
1ST ZERO
-1
2
-2
(2C
× {R
+ [K × (1 - D) - 0.5] × (L × f ) } ) × (0.5 × f ) × (2f)
OUT
LOAD
S
SW
(2 C R )
C
C
NOTE:
AVEA(dB)/20
-1
R
= 10
× g
MV
OUT
-1
-1 -1 -1
f
= [2C
× (ESR + {R + [K × (1 - D) - 0.5] × (L × f ) } )]
LOAD S SW
PMOD
OUT
6TH ASYMPTOTE
-1
-1 -1
R2 × (R1 + R2) × g × R × g × R
× {1 + R
-1 -1
× [K × (1 - D) - 0.5] × (L × f ) } ×
LOAD S SW
MV
C
MC
LOAD
WHICH FOR
ESR << {R
-1
2
-2
ESR × {R
+ [K × (1 - D) - 0.5] × (L × f ) } × (0.5 × f ) × (2f)
S SW SW
LOAD
-1
-1 -1
+ [K × (1 - D) - 0.5] × (L × f ) }
LOAD
S
SW
BECOMES
-1
-1
-1 -1 -1
f
f
= [2C
= (2C
× {R
LOAD
+ [K × (1 - D) - 0.5] × (L × f ) } ]
PMOD
PMOD
OUT
OUT
S
SW
-1
× R
)
+ [K × (1 - D) - 0.5] × (2C
× L × f )
LOAD
S
OUT
SW
Figure 3. Asymptotic Loop Response of Current-Mode Regulator
As previously mentioned, the power modulator’s dominant
pole is a function of the parallel effects of the load resis-
tance and the current-loop gain’s equivalent impedance:
which can be expressed as:
1
K
× 1− D − 0.5
(
)
S
f
≈
+
PMOD
2π × C
×R
2π × f
×L × C
OUT
LOAD
SW
OUT
1
f
=
PMOD
−1
K × 1− D − 0.5
(
)
1
Note: Depending on the application’s specifics, the
amplitude of the slope compensation ramp could have a
significant impact on the modulator’s dominate pole. For
low duty-cycle applications, it provides additional damp-
ing (phase lag) at/near the crossover frequency (see the
Closing the Loop: Designing the Compensation Circuitry
section). There is no equivalent effect on the power modu-
S
2π × C
× ESR +
+
OUT
R
f
×L
LOAD
SW
And knowing that the ESR is typically much smaller than
the parallel combination of the load and the current loop:
−1
K
× 1− D − 0.5
(
)
1
S
ESR <<
+
lator zero, f
.
ZMOD
R
f
× L
LOAD
SW
1
1
f
= f
=
ZESR
ZMOD
f
≈
PMOD
2π × C
×ESR
−1
OUT
K
× 1− D − 0.5
(
)
1
S
2π × C
×
+
OUT
R
f
×L
LOAD
SW
Maxim Integrated
│ 17
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
The effect of the inner current loop at higher frequencies
is modeled as a double-pole (complex conjugate) fre-
The dominant poles and zeros of the transfer loop gain
are shown below:
quency term, G
(s), as shown:
SAMPLING
g
MV
1
f
=
P1
AVEA(dB)/20
G
s =
( )
SAMPLING
2π ×10
× C
C
2
s
s
+
+1
1
2
π × f
× Q
C
f
=
SW
π × f
(
)
P2
SW
K × 1−D −0.5
(
)
1
S
−1
2π × C
+
OUT
where the sampling effect quality factor, Q , is:
C
R
f
×L
LOAD
SW
1
1
f
=
f
(
)
P3
SW
Q
=
C
2
π × K × 1− D − 0.5
(
)
S
1
f
=
Z1
And the resonant frequency is:
ωSAMPLING(s) = π × f
2π × C R
C
C
1
SW
f
=
Z2
2π × C
ESR
or:
OUT
f
SW
2
f
=
SAMPLING
The order of pole-zero occurrence is:
< f ≤ f < f ≤ f < f
Z2
Having defined the power modulator’s transfer function,
the total system transfer can be written as follows (see
Figure 3):
f
P1 P2
Z1
CO
P3
Under heavy load, f , approaches f . Figure 3 shows
P2
Z1
a graphical representation of the asymptotic system
closed-loop response, including dominant pole and zero
locations.
Gain(s) = G (s) × G (s) × G
(DC) × G
(s) ×
FILTER
FF
EA
MOD
(s)
G
SAMPLING
where:
The loop response’s fourth asymptote (in bold, Figure 3)
is the one of interest in establishing the desired crossover
frequency (and determining the compensation component
values). A lower crossover frequency provides for stable
closed-loop operation at the expense of a slower load-
and line-transient response. Increasing the crossover
frequency improves the transient response at the (poten-
tial) cost of system instability. A standard rule of thumb
sets the crossover frequency between 1/10 and 1/5 of
the switching frequency. First, select the passive power
and decoupling components that meet the application’s
requirements. Then, choose the small-signal compen-
sation components to achieve the desired closed-loop
frequency response and phase margin as outlined in the
Closing the Loop: Designing the Compensation Circuitry
section.
sC R1+1
R2
(
)
FF
G
s =
( )
×
FF
sC R1|| R2 +1
R1+ R2
(
)
FF
Leaving C empty, G (s) becomes:
FF
FF
R2
G
s =
( )
FF
R1+ R2
Also:
sC R +1
(
)
AVEA(dB)/20
C C
G
s = 10
( )
×
EA
AVEA(dB)/20
10
sC
R
+
+1
C
C
g
MV
which simplifies to:
sC R +1
(
)
AVEA(dB)/20
C C
G
s = 10
( )
×
EA
Closing the Loop: Designing the
Compensation Circuitry
AVEA(dB)/20
10
sC
+1
C
g
MV
1) Select the desired crossover frequency. Choose f
CO
approximately 1/10 to 1/5 of the switching frequency
(f ).
SW
AVEA(dB)/20
10
when R <<
C
g
MV
2) Determine R by setting the system transfer’s fourth
C
asymptote gain equal to unity (assuming f
> f
,
Z1
sC
ESR +1
CO
(
)
OUT
G
s = R
( )
×
LOAD
FILTER
f
, and f ) where:
−1
P2
P1
K × 1− D − 0.5
(
)
1
S
sC
+
+1
OUT
R
f
× L
LOAD
SW
Maxim Integrated
│ 18
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Using C the zero-pole order is adjusted as follows:
FF
R
K
1− D − 0.5
(
)
LOAD
S
1+
L × f
R1+ R2
R2
SW
1
1
R
=
×
× 2πf
C
×
C
CO OUT
f
< f ≤ f
<
<
≈
P1 P2
Z1
g
× g
×R
MV
MC
LOAD
2πC R1 2πC (R1|| R2)
FF
FF
f
< f < f
P3 Z2
CO
1
Confirm the desired operation of C empirically. The
FF
ESR +
K
1− D − 0.5
(
)
1
phase lead of C diminishes as the output voltage is
S
FF
+
a smaller multiple of the reference voltage, e.g., below
about 1V. Do not use C when V
R
L × f
LOAD
SW
= V
.
FF
OUT
FB
and where the ESR is much smaller than the parallel
combination of the equivalent load resistance and the
current loop impedance, e.g.,:
Setting the Soft-Start Time
The soft-start feature ramps up the output voltage slowly,
reducing input inrush current during startup. Size the C
SS
capacitor to achieve the desired soft-start time, t , using:
SS
1
ESR <<
K
1− D − 0.5
(
)
1
S
I
× t
SS
SS
FB
+
C
=
SS
R
L × f
LOAD
SW
V
R
becomes:
C
I
, the soft-start current, is 10µA (typ) and V , the out-
SS FB
put feedback voltage threshold, is 0.6V (typ). When using
large C capacitance values, the high-side current
limit can trigger during the soft-start period. To ensure the
2πf
× C
R1+ R2
R2
CO
OUT
MC
OUT
R
=
×
C
g
× g
MV
correct soft-start time, t , choose C
satisfy:
large enough to
SS
SS
3) Determine C by selecting the desired first sys-
C
tem zero, f , based on the desired phase margin.
Z1
V
×I
Typically, setting f
ficient phase margin.
below 1/5 of f
provides suf-
Z1
CO
OUT SS
− I
C
>> C
×
OUT
SS
(I
) × V
OUT
HSCL_
FB
f
1
CO
5
I
is the typical high-side MOSFET current-limit
HSCL_
value.
f
=
≤
Z1
C
2π × C R
C
C
An external tracking reference with steady-state value
between 0V and V - 1.8V can be applied to SS/REFIN.
In this case, connect an RC network from external track-
ing reference and SS/REFIN, as shown in Figure 4. The
recommended value for R
therefore:
IN
5
≥
C
2π × f
×R
C
CO
is approximately 1kΩ. R
SS
SS
is needed to ensure that, during hiccup period, SS/REFIN
can be internally pulled down.
4) For low duty-cycle applications, the addition of
a phase-leading capacitor (C in Figure 1) helps
FF
When an external reference is connected to SS/REFIN,
the soft-start must be provided externally.
mitigate the phase lag of the damped half-frequency
double pole. Adding a second zero near to but below
the desired crossover frequency increases both the
closed-loop phase margin and the regulator’s unity-
gain bandwidth (crossover frequency). Select the
capacitor as follows:
R
SS
V
1
REF_EXT
SS/REFIN
C
=
FF
C
SS
2π × f
× R1|| R2
(
)
MAX15058
CO
This guarantees the additional phase-leading zero
occurs at a frequency lower than f from:
CO
1
Figure 4. RC Network for External Reference at SS/REFIN
f
=
PHASE_LEAD
2π × C ×R1
FF
Maxim Integrated
│ 19
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
INPUT
2.8V TO 5.5V
L
1µH
OUT
(ICE IN06142)
OUTPUT
1.8V AT 3A
IN
LX
C
IN
22µF
1.2Ω
R
20kΩ
C
PULL
OUT
MAX15058
22µF x 2
C
R
1
FF
1nF
100pF
8.06kΩ
PGOOD
GND
ON
FB
ENABLE
EN
OFF
R
2
COMP
4.02kΩ
SKIP
R
C
5.36kΩ
SS/REFIN
C
22nF
SS
C
1nF
C
Figure 5. Application Circuit for PWM Mode Operation
2) Place capacitors on IN and SS/REFIN as close as pos-
sible to the IC and the corresponding pad using direct
traces.
Power Dissipation
The MAX15058 is available in a 9-bump WLP package
and can dissipate up to 1127mW at T = +70°C. When
A
the die temperature exceeds +150°C, the thermal-shut-
down protection is activated (see the Thermal-Shutdown
Protection section).
3) Keep the high-current paths as short and wide as
possible. Keep the path of switching current short
and minimize the loop area formed by LX, the output
capacitors, and the input capacitors.
Layout Procedure
4) Connect IN, LX, and GND separately to a large copper
area to help cool the IC to further improve efficiency.
Careful PCB layout is critical to achieve clean and stable
operation. It is highly recommended to duplicate the
MAX15058 Evaluation Kit layout for optimum perfor-
mance. If deviation is necessary, follow these guidelines
for good PCB layout:
5) Ensure all feedback connections are short and direct.
Place the feedback resistors and compensation com-
ponents as close as possible to the IC.
6) Route high-speed switching nodes (such as LX) away
from sensitive analog areas (such as FB and COMP).
1) Connect the signal and ground planes at a single point
immediately adjacent to the GND bump of the IC.
Maxim Integrated
│ 20
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
INPUT
2.8V TO 5.5V
L
1µH
OUT
(ICE IN06142)
OUTPUT
1.8V AT 3A
IN
LX
C
IN
22µF
1.2Ω
C
R
20kΩ
OUT
PULL
MAX15058
22µF x 2
R
C
1
FF
1nF
8.06kΩ
100pF
PGOOD
EN
GND
ON
FB
ENABLE
OFF
R
2
COMP
4.02kΩ
SKIP
R
C
5.36kΩ
SS/REFIN
C
22nF
SS
C
1nF
C
Figure 6. Application Circuit for Skip Mode Operation
Chip Information
PROCESS: BiCMOS
Maxim Integrated
│ 21
www.maximintegrated.com
MAX15058
High-Efficiency, 3A, Current-Mode Synchronous,
Step-Down Switching Regulator
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
DESCRIPTION
CHANGED
0
1
12/10
3/11
Initial release
—
Revised Package Information section.
20
Changed the 1.65mm x 1.65mm, 9-bump package information to 1.5mm x 1.5mm,
9-bump package information. Inserted Typical Operating Circuit on page one.
2
7/11
1, 11
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
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.
2011 Maxim Integrated Products, Inc.
│ 22
相关型号：
MAX15059AETE+T
Switching Regulator, Current-mode, 1.3A, 420kHz Switching Freq-Max, BICMOS, TQFN-16
MAXIM
©2020 ICPDF网 联系我们和版权申明