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PDF MAX15108A Data sheet ( Hoja de datos )
| Número de pieza | MAX15108A | |
| Descripción | Synchronous Step-Down Switching Regulator | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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EVALUATION KIT AVAILABLE
MAX15108A
High-Efficiency, 8A, Current-Mode
Synchronous Step-Down Switching Regulator
General Description
The MAX15108A high-efficiency, current-mode, syn-
chronous step-down switching regulator with integrated
power switches delivers up to 8A of output current. The
regulator operates from 2.7V to 5.5V and provides an
output voltage from 0.6V up to 95% of the input voltage,
making the device ideal for distributed power systems,
portable devices, and preregulation applications.
The IC utilizes a current-mode control architecture
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.
The low RDS(ON) integrated switches ensure high effi-
ciency at heavy loads while minimizing critical induc-
tance, making the layout design a much simpler task
with respect to discrete solutions. The IC’s simple layout
and footprint assures first-pass success in new designs.
The regulator features a 1MHz, factory-trimmed fixed-
frequency PWM mode operation. The high switching
frequency, along with the PWM current-mode architecture
allows for a compact, all ceramic capacitor design.
The IC features a capacitor-programmable soft-start
to reduce input inrush current. Internal control circuitry
ensures safe-startup into a prebiased output. Power
sequencing is controlled with the enable input and
power-good output.
The IC is available in a 20-bump (4 x 5 array), 2.5mm x
2mm, WLP package and is fully specified over the -40NC
to +85NC temperature range.
Distributed Power Systems
DDR Memory
Base Stations
Portable Devices
Notebook Power
Server Power
Applications
Features
S Continuous 8A Output Current
S Efficiency Up to 96%
S ±1% Accuracy Over Load, Line, and Temperature
S Operates from a 2.7V to 5.5V Supply
S Adjustable Output from 0.6V to 0.95 x VIN
S Programmable Soft-Start
S Safe Startup into Prebiased Output
S External Reference Input
S 1MHz Switching Frequency
S Stable with Low-ESR Ceramic Output Capacitors
S Forced PWM Mode
S Enable Input and Power-Good Output for Power-
Supply Sequencing
S Cycle-by-Cycle Overcurrent Protection
S Fully Protected Features Against Overcurrent and
Overtemperature
S Input Undervoltage Lockout
S 20-Bump (4 x 5 Array), 2.5mm x 2mm, WLP
Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX15108AEWP+ -40NC to +85NC
20 WLP
+Denotes a lead(Pb)-free/RoHS-compliant package.
2.7V TO
5.5V
Typical Operating Circuit
LX
EN PGND
IN MAX15108A
FB
INX
PGOOD
COMP
OUTPUT
SS
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.
19-6702; Rev 0; 6/13
1 page  
MAX15108A
High-Efficiency, 8A, Current-Mode
Synchronous Step-Down Switching Regulator
Typical Operating Characteristics (continued)
(Circuit of Typical Application Circuit, TA = +25NC, unless otherwise noted.)
SWITCHING WAVEFORMS
(IOUT = 8A, VIN = 5V)
MAX15108A toc08
VOUT
10mV/div
AC-COUPLED
ILX
5A/div
VLX
2V/div
400ns/div
SOFT-START WAVEFORMS (ILOAD = 8A)
MAX15108A toc10
VEN
2V/div
1ms/div
VLX
2V/div
ILX
5A/div
VOUT
1V/div
VPGOOD
2V/div
OVERLOAD HICCUP MODE
INPUT SHUTDOWNMACX1U51R08RA tEocN12T
vs. SUPPLY VOLTAGE
2.0
IIN
2A/div
1.6
1.2
VOUT = 0V ONLY IN A SHORT
0.8
VOUT
1V/div
IOUT
0.4 10A/div
400µs/div
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
Maxim Integrated
SUPPLY VOLTAGE (V)
SHUTDOWN WAVEFORM (ILOAD = 8A)
MAX15108A toc09
VEN
2V/div
VLX
5V/div
ILX
5A/div
10µs/div
VOUT
VPGOOD
1V/div
INPUT SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
2.0
1.6
1.2
0.8
0.4
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
RMS INPUT CURRENT
vs. SUPPLY VOLTAGE
1.0
0.9 SHORT-CIRCUIT ON OUTPUT
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2.7 3.1 3.5 3.9 4.3 4.7 5.1
SUPPLY VOLTAGE (V)
5.5
5
5 Page 
MAX15108A
High-Efficiency, 8A, Current-Mode
Synchronous Step-Down Switching Regulator
Input Capacitor Selection
For a step-down converter, the input capacitor CIN helps
to keep the DC input voltage steady, in spite of discon-
tinuous input AC current. Use low-ESR capacitors to
minimize the voltage ripple due to ESR.
Size CIN using the following formula:
=CIN
fSW
×
ILOAD
∆VIN_RIPPLE
×
VOUT
VIN
Make sure that the selected capacitance can accom-
modate the input ripple current given by:
IRM=S
IO ×
VOUT × (VIN - VOUT )
VIN
If necessary, use multiple capacitors in parallel to meet
the RMS current rating requirement.
Output Capacitor Selection
Use low-ESR ceramic capacitors to minimize the voltage
ripple due to ESR. Use the following formula to estimate
the total output voltage peak-to-peak ripple:
∆VOUT=
VOUT
fSW × L
×
1-
VOUT
VIN
×
RESR_COUT
+
8
×
1
fSW ×
COUT
Select the output capacitors to produce an output ripple
voltage that is less than 2% of the set output voltage.
Setting the Soft-Start Startup Time
The soft-start feature ramps up the output voltage slowly,
reducing input inrush current during startup. Size the
CSS capacitor to achieve the desired soft-start time, tSS,
using:
C SS
=
ISS x t SS
VFB
ISS, the soft-start current, is 10FA, and VFB, the output
feedback voltage threshold, is 0.6V. When using large
COUT capacitance values, the high-side current limit can
trigger during the soft-start period. To ensure the correct
soft-start time, tSS, choose CSS large enough to satisfy:
C SS
>>
COUT
×
VOUT × ISS
(IHSCL_MIN - IOUT)
×
VFB
IHSCL_MIN is the minimum high-side switch current-limit
value.
FEEDBACK
DIVIDER
VOUT
ERROR AMPLIFIER
POWER MODULATOR
COMPENSATION
RAMP
VIN
R1 FB
COMP
C
gMC
CONTROL
R2 LOGIC
PWM
gMV
ROUT
RC *CCC
COMPARATOR
QHS
LO
QLS
DCR
IL
CC
ROUT = AVEA/gMV
REF *CCC IS OPTIONAL.
VCOMP GMOD
VOUT
IL
NOTE: THE GMOD STAGE SHOWN ABOVE MODELS THE AVERAGE CURRENT OF
THE INDUCTOR INJECTED INTO THE OUTPUT LOAD. THIS REPRESENTS A
SIMPLIFICATION FOR THE POWER MODULATOR STAGE DRAWN ABOVE.
Figure 1. Peak Current-Mode Regulator Transfer Model
Maxim Integrated
OUTPUT FILTER
AND LOAD
VOUT
ESR
COUT
RLOAD
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX15108A.PDF ] | |
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