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PDF MAX15109 Data sheet ( Hoja de datos )
| Número de pieza | MAX15109 | |
| Descripción | Current-Mode Synchronous Step-Down Switching Regulator | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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19-5918; Rev 0; 6/11
High-Efficiency, 8A, Current-Mode Synchronous
Step-Down Switching Regulator with VID Control
General Description
The MAX15109 high-efficiency, current-mode, synchro-
nous step-down switching regulator with integrated
power switches deliver up to 8A of output current. This
regulator operates from 2.7V to 5.5V and provides four
output voltages using two VID control inputs.
This 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.
This regulator offers skip-mode functionality to reduce
current consumption and achieve a higher efficiency at
light loads. The low RDS(ON) integrated switches ensure
high efficiency at heavy loads while minimizing critical
inductance, making the layout design a much simpler
task with respect to discrete solutions. The high switching
frequency (1MHz), along with the PWM current-mode archi-
tecture allows for a compact, all-ceramic capacitor design.
The IC features a capacitor-programmable slew-rate
control to reduce input current at the startup and when
the output changes state under VID control. 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
Notebook Power
Applications
Features
S Continuous 8A Output Current
S Efficiency Over 90%
S ±1% Accuracy Over Load, Line, and Temperature
S Operates from a 2.7V to 5.5V Supply
S VID Control Inputs for Selecting Output Voltage
S Programmable Slew-Rate Control
S Safe Startup into Prebiased Output
S 1MHz Switching Frequency
S Stable with Low-ESR Ceramic Output Capacitors
S Enable Input and Power-Good Output for Power-
Supply Sequencing
S Cycle-by-Cycle Overcurrent Protection Faults
S Fully Protected 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
MAX15109EWP+ -40NC to +85NC
20 WLP
+Denotes a lead(Pb)-free/RoHS-compliant package.
Typical Operating Circuit
2.7V TO
5.5V
VID0
VID1
VID0
VID1
IN
LX
FB
PGND
OUTPUT
MAX15109
INX
PGOOD
COMP
SS
________________________________________________________________ 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.
1 page  
High-Efficiency, 8A, Current-Mode Synchronous
Step-Down Switching Regulator with VID Control
Typical Operating Characteristics (continued)
(Circuit of Typical Application Circuit, TA = +25NC, unless otherwise noted.)
LOAD-TRANSIENT RESPONSE
(VIN = 5V, VOUT = 0.9V)
MAX15109 toc06
SWITCHING WAVEFORMS
(IOUT = 8A, VIN = 5V)
MAX15109 toc07
40µs/div
VOUT
10mV/div
AC-COUPLED
4A
IOUT
2A
400ns/div
VOUT
10mV/div
AC-COUPLED
ILX
5A/div
VLX
5V/div
SWITCHING WAVEFORM IN SKIP MODE
(IOUT = 10mA, VIN = 5V)
MAX15109 toc08
VOUT
10mV/div
AC-COUPLED
ILX
2A /div
VLX
5V/div
40µs/div
SOFT-START WAVEFORMS
(NO LOAD, SKIP MODE)
MAX15109 toc10a
VEN
2V/div
VLX
5V/div
SHUTDOWN WAVEFORM
(ILOAD = 8A)
MAX15109 toc09
VEN
2V/div
VLX
5V/div
ILX
5A/div
10µs/div
VOUT
500mV/div
VPGOOD
2V/div
SOFT-START WAVEFORMS
(ILOAD = 8A)
MAX15109 toc10b
VEN
2V/div
VLX
5V/div
200µs/div
VOUT
500mV/div
VPGOOD
5V/div
200µs/div
VOUT
500mV/div
VPGOOD
5V/div
_______________________________________________________________________________________ 5
5 Page 
High-Efficiency, 8A, Current-Mode Synchronous
Step-Down Switching Regulator with VID Control
Programmable Soft-Start (SS)
The IC utilizes a soft-start feature to slowly ramp up the
regulated output voltage to reduce input inrush current
during startup. Connect a capacitor from SS to PGND to
set the startup time. See the Output Voltage Transition
Timing section for capacitor selection details.
Error Amplifier
A high-gain error amplifier provides accuracy for the
voltage feedback loop regulation. Connect a compen-
sation network between COMP and SGND. See the
Compensation Design Guidelines section. The error
amplifier transconductance is 1.4mS. COMP clamp low
is set to 0.8V, just below the PWM ramp compensation
valley, helping COMP to rapidly return to the correct set
point during load and line transients.
PWM Comparator
The PWM comparator compares COMP voltage to the
current-derived ramp waveform (LX current to COMP
voltage transconductance value is 25A/V). To avoid
instability due to subharmonic oscillations when the duty
cycle is around 50% or higher, a compensation ramp
is added to the current-derived ramp waveform. The
compensation ramp slope (0.3V x 1MHz = 0.3V/Fs) is
equivalent to half of the inductor current down-slope in
the worst case (load 2A, current ripple 30% and maxi-
mum duty-cycle operation of 95%). The compensation
ramp valley is set to 1V.
Overcurrent Protection and Hiccup
When the converter output is connected to ground or the
device is overloaded, each high-side MOSFET current-
limit event (14A) turns off the high-side MOSFET and
turns on the low-side MOSFET. A 3-bit counter incre-
ments on each current-limit event. The counter is reset
after three consecutive events of high-side MOSFET
turn-on without reaching the current limit. If the current-
limit condition persists, the counter fills up reaching eight
events. The control logic then discharges SS, stops both
high-side and low-side MOSFETs and waits for a hiccup
period (1024 clock cycles) before attempting a new soft-
start sequence. The hiccup-mode also operates during
soft-start.
Thermal Shutdown Protection
The IC contains an internal thermal sensor that limits the
total power dissipation to protect it in the event of an
extended thermal fault condition. When the die tempera-
ture exceeds +160NC, the thermal sensor shuts down
the device, turning off the DC-DC converter to allow the
die to cool. After the die temperature falls by 25NC, the
device restarts, following the soft-start sequence.
Skip Mode Operation
The IC operates in skip mode. When in skip mode, LX
output becomes high impedance when the inductor
current falls below 0.7A. The inductor current does not
become negative. During a clock cycle, if the inductor
current falls below the 0.7A threshold (during off-time),
the low side turns off. At the next clock cycle, if the
output voltage is above the 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 (330ns). In this way, the system skips cycles,
reducing the 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 for details. In skip mode,
power dissipation is reduced and efficiency improved at
light loads because the internal power MOSFETs do not
switch at every clock cycle.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet MAX15109.PDF ] | |
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