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PDF MAX15041 Data sheet ( Hoja de datos )

Número de pieza MAX15041
Descripción Step-Down DC-DC Regulator
Fabricantes Maxim Integrated Products 
Logotipo Maxim Integrated Products Logotipo



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No Preview Available ! MAX15041 Hoja de datos, Descripción, Manual

19-4815; Rev 0; 7/09
www.DataSheet4U.com
Low-Cost, 3A, 4.5V to 28V Input, 350kHz, PWM
Step-Down DC-DC Regulator with Internal Switches
General Description
The MAX15041 low-cost, synchronous DC-DC convert-
er with internal switches delivers an output current up to
3A. The MAX15041 operates from an input voltage of
4.5V to 28V and provides an adjustable output voltage
from 0.6V to 90% of VIN, set with two external resistors.
The MAX15041 is ideal for distributed power systems,
preregulation, set-top boxes, television, and other con-
sumer applications.
The MAX15041 features a peak-current-mode PWM con-
troller with internally fixed 350kHz switching frequency
and a 90% maximum duty cycle. The current-mode con-
trol architecture simplifies compensation design, and
ensures a cycle-by-cycle current limit and fast response
to line and load transients. A high-gain transconductance
error amplifier allows flexibility in setting the external com-
pensation by using a type III compensation scheme,
thereby allowing the use of all ceramic capacitors.
This synchronous buck regulator features internal
MOSFETs that provide better efficiency than asynchro-
nous solutions, while simplifying the design relative to
discrete controller solutions. In addition to simplifying
the design, the integrated MOSFETs minimize EMI,
reduce board space, and provide higher reliability by
minimizing the number of external components.
The MAX15041 also features thermal shutdown and
overcurrent protection (high-side sourcing and low-side
sinking), and an internal 5V LDO with undervoltage
lockout. In addition, this device ensures safe startup
when powering into a prebiased output.
Other features include an externally adjustable soft-start
that gradually ramps up the output voltage and reduces
inrush current. Independent enable control and power-
good signals allow for flexible power sequencing.
The MAX15041 is available in a space-saving, high-
power, 3mm x 3mm, 16-pin TQFN-EP package and is
fully specified from -40°C to +85°C.
Applications
Distributed Power Systems
Wall Adapters
Preregulators
Set-Top Boxes
Televisions
xDSL Modems
Consumer Products
Features
Up to 3A of Continuous Output Current
±1% Output Accuracy Over Temperature
4.5V to 28V Input Voltage Range
Adjustable Output Voltage Range from 0.606V to
0.9 x VIN
Internal 170mRDS-ON High-Side and 105m
RDS-ON Low-Side Power Switches
Fixed 350kHz Switching Frequency
Up to 93% Efficiency
Cycle-By-Cycle Overcurrent Protection
Programmable Soft-Start
Stable with Low-ESR Ceramic Output Capacitors
Safe Startup into Prebiased Output
Enable Input and Power-Good Output
Fully Protected Against Overcurrent and
Overtemperature
VDD LDO Undervoltage Lockout
Space-Saving, Thermally Enhanced, 3mm x 3mm
Package
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
TOP
MARK
MAX15041ETE+ -40°C to +85°C 16 TQFN-EP* AGV
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Typical Operating Circuit
INPUT
12V
PGOOD
IN BST
EN
MAX15041 LX
VDD
PGND
PGOOD
SS
FB
COMP
SGND
OUTPUT
1.8V AT 3A
Pin Configuration appears at end of data sheet.
________________________________________________________________ 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




MAX15041 pdf
www.DataSheet4U.com
Low-Cost, 3A, 4.5V to 28V Input, 350kHz, PWM
Step-Down DC-DC Regulator with Internal Switches
Typical Operating Characteristics (continued)
(VIN = 12V, VOUT = 3.3V, CVDD = 1µF, CIN = 22µF, TA = +25°C, circuit of Figure 3 (see Table 1 for values), unless otherwise specified.)
INPUT SUPPLY CURRENT
vs. INPUT VOLTAGE
16
L = 4.7FH
15 ILOAD = 0A
14
13
12
11
10
0
5 10 15 20
INPUT VOLTAGE (V)
25
10
9
8
7
6
5
4
3
2
1
0
0
SHUTDOWN WAVEFORMS
MAX15041 toc12
VEN
5V/div
VOUT
2V/div
IL
2A/div
VPGOOD
5V/div
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
5 10 15 20
INPUT VOLTAGE (V)
25
SHUTDOWN CURRENT
vs. TEMPERATURE
4.0
3.5
3.0
2.5
2.0
1.5
1.0
-40
-15 10 35 60
TEMPERATURE (NC)
OUTPUT SHORT-CIRCUIT WAVEFORMS
MAX15041 toc13
VOUT
2V/div
IIN
5A/div
IL
5A/div
VSS
2V/div
85
100µs/div
10µs/div
SWITCHING WAVEFORMS
MAX15041 toc14
VLX
10V/div
1µs/div
IL
2A/div
VOUT
AC-COUPLED
50mV/div
SOFT-START WAVEFORMS
MAX15041 toc15
VEN
5V/div
VOUT
2V/div
400µs/div
IL
2A/div
VPGOOD
5V/div
_______________________________________________________________________________________ 5

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MAX15041 arduino
www.DataSheet4U.com
Low-Cost, 3A, 4.5V to 28V Input, 350kHz, PWM
Step-Down DC-DC Regulator with Internal Switches
Inductor Selection
A larger inductor value results in reduced inductor ripple
current, leading to a reduced output ripple voltage.
However, a larger inductor value results in either a larger
physical size or a higher series resistance (DCR) and a
lower saturation current rating. Typically, inductor value
is chosen to have current ripple equal to 30% of load
current. Choose the inductor with the following formula:
L
=
VOUT
fSW × IL
× ⎛⎝⎜1
VOUT
VIN
⎠⎟
where fSW is the internally fixed 350kHz switching fre-
quency, and IL is the estimated inductor ripple current
(typically set to 0.3 x ILOAD). In addition, the peak
inductor current, IL_PK, must always be below both the
minimum high-side MOSFET current-limit value,
IHSCL_MIN (5A, typ), and the inductor saturation current
rating, IL_SAT. Ensure that the following relationship is
satisfied:
1
IL _ PK = ILOAD + 2 × IL < min(IHSCL _ MIN,IL _ SAT )
Diode Selection
The MAX15041 requires an external bootstrap steering
diode. Connect the diode between VDD and BST. The
diode should have a reverse voltage rating, higher than
the converter input voltage and a 200mA minimum cur-
rent rating. Typically, a fast switching or Schottky diode
is used in this application, but a simple low-cost diode
(1N4007) suffices.
Input Capacitor Selection
For a step-down converter, input capacitor CIN helps to
keep the DC input voltage steady, in spite of discontin-
uous input AC current. Low-ESR capacitors are pre-
ferred to minimize the voltage ripple due to ESR.
Size CIN using the following formula:
CIN
=
fSW
×
ILOAD
VIN _ RIPPLE
×
VOUT
VIN
Output-Capacitor Selection
Low-ESR capacitors are recommended to minimize the
voltage ripple due to ESR. Total output-voltage peak-to-
peak ripple is estimated by the following formula:
VOUT
=
VOUT
fSW × L
× ⎛⎝⎜1
VOUT
VIN
⎠⎟
×
⎝⎜RESR _ COUT
+
8×
1
fSW ×
COUT
⎠⎟
For ceramic capacitors, ESR contribution is negligible:
RESR _ COUT
<<
8×
1
fSW ×
COUT
For tantalum or electrolytic capacitors, ESR contribution
is dominant:
RESR _ COUT
>>
8×
1
fSW ×
COUT
Compensation Design Guidelines
The MAX15041 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
inductor’s peak current value. This cycle-by-cycle con-
trol of the inductor current emulates a controlled current
source. 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 sim-
ple series capacitor-resistor from COMP to SGND. 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,
compensation ramp, control circuitry, MOSFETs, and
inductor), the capacitive output filter and load, an out-
put feedback divider, and a voltage-loop error amplifier
with its associated compensation circuitry. See Figure 1
for a graphical representation.
The average current through the inductor is expressed as:
IL = GMOD × VCOMP
where IL is the average inductor current and GMOD is
the power modulator’s transconductance. For a buck
converter:
V OUT = RLOAD × IL
where RLOAD is the equivalent load resistor value.
Combining the two previous equations, the power mod-
ulator’s transfer function in terms of VOUT with respect
to VCOMP is:
VOUT
VCOMP
=
RLOAD
IL
× IL
= RLOAD
× GMOD
⎝⎜ GMOD ⎠⎟
______________________________________________________________________________________ 11

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