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PDF MAX1928EUB15 Data sheet ( Hoja de datos )
| Número de pieza | MAX1928EUB15 | |
| Descripción | Low-Output-Voltage / 800mA / PWM Step-Down DC-DC Converters | |
| Fabricantes | Maxim Integrated | |
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19-2527; Rev 0; 7/02
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
General Description
The MAX1927/MAX1928 800mA step-down converters
power low-voltage microprocessors in compact equip-
ment requiring the highest possible efficiency. The
MAX1927/MAX1928 are optimized for generating low
output voltages (down to 750mV) at high efficiency
using small external components. The supply voltage
range is from 2.6V to 5.5V and the guaranteed minimum
output current is 800mA. 1MHz pulse-width modulation
(PWM) switching allows for small external components.
A unique control scheme minimizes ripple at light loads,
while maintaining a low 140µA quiescent current.
The MAX1927/MAX1928 include a low on-resistance
internal MOSFET switch and synchronous rectifier to
maximize efficiency and minimize external component
count. No external diode is needed. 100% duty-cycle
operation allows for a dropout voltage of only 340mV at
800mA. Other features include internal soft-start,
power-OK (POK) output, and selectable forced PWM
operation for lower noise at all load currents.
The MAX1928 is available with several preset output
voltages: 1.5V (MAX1928-15), 1.8V (MAX1928-18), and
2.5V (MAX1928-25). The MAX1927R has adjustable
output range down to 0.75V. The MAX1927/MAX1928
are available in a tiny 10-pin µMAX package.
Applications
WCDMA Handsets
PDAs and Palmtops
DSP Core Power
Battery-Powered Equipment
Features
o 800mA Output Current
o Output Voltages from 0.75V to 5V
o 2.6V to 5.5V Input Voltage Range
o Power-OK Output
o No Schottky Diode Required
o Selectable Forced PWM Operation
o 1MHz Fixed-Frequency PWM Operation
o 140µA Quiescent Current
o Soft-Start
o 10-Pin µMAX Package
Ordering Information
PART
MAX1927REUB
MAX1928EUB15
MAX1928EUB18
MAX1928EUB25
PRESET
OUTPUT
VOLTAGE
TEMP
RANGE
PIN-
PACKAGE
Adj. to 0.75V -40°C to +85°C 10 µMAX
1.5V
-40°C to +85°C 10 µMAX
1.8V
-40°C to +85°C 10 µMAX
2.5V
-40°C to +85°C 10 µMAX
Pin Configuration
TOP VIEW
PWM 1
GND 2
REF 3
FB 4
COMP 5
MAX1927R
MAX1928
10 POK
9 BATT
8 LX
7 PGND
6 SHDN
µMAX
Typical Operating Circuit
VIN
2.6V TO 5.5V
C1
BATT
PWM
LX
SHDN
FB
RC MAX1927R
COMP
POK
CC Cf
L1
VOUT
0.75V AT 800mA
C2
REF PGND
GND
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
(Circuits of Figure 3 and 4, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
MAX1927R
EFFICIENCY vs. LOAD CURRENT
100
VIN = 3.6V
90
80
70 VIN = 5V
60
50
40
1
VOUT = 3.3V
10 100
LOAD CURRENT (mA)
1000
MAX1928-15
EFFICIENCY vs. LOAD CURRENT
100
VIN = 2.7V
90
80
70 VIN = 5V
60 VIN = 3.6V
50
40
30
1
VOUT = 1.5V
10 100
LOAD CURRENT (mA)
1000
MAX1928-18
OUTPUT VOLTAGE vs. LOAD CURRENT
1.90
1.88
1.86
1.84
1.82
1.80
1.78
1.76
1.74
1.72 VIN = 3.6V
1.70
0 100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
MAX1928-25
EFFICIENCY vs. LOAD CURRENT
100
90 VIN = 3.6V
80
70 VIN = 5V
60
50
40
1
10 100
LOAD CURRENT (mA)
1000
MAX1927R
EFFICIENCY vs. LOAD CURRENT
100
90 VIN = 2.7V
80
70 VIN = 5V
60 VIN = 3.6V
50
40
30
1
VOUT = 1V
10 100
LOAD CURRENT (mA)
1000
NO-LOAD INPUT CURRENT
vs. INPUT VOLTAGE
400
350
300
250
200
150
100
50
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
MAX1928-18
EFFICIENCY vs. LOAD CURRENT
100
90 VIN = 2.7V
80 VIN = 3.6V
70
60 VIN = 5V
50
40
30
1
VOUT = 1.8V
10 100
LOAD CURRENT (mA)
1000
MAX1928-25
DROPOUT VOLTAGE vs. LOAD CURRENT
500
450
400
350
300
250
200
150
100
50
0
0
VIN = 2.5V
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
1.06
TA = +85°C
1.04
1.02
1.00 TA = +25°C
0.98
0.96 TA = -40°C
0.94
2.6 3.1 3.6 4.1 4.6 5.1 5.6
INPUT VOLTAGE (V)
_______________________________________________________________________________________ 5
5 Page 
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
Solving for Cf gives:
Cf
=
RESR × COUT
RC
or 22pF, whichever is greater.
Standard Application Circuits
Figures 3 and 4 are standard applications circuits for
the MAX1927/MAX1928. Figure 3 illustrates the preset
output voltages (MAX1928), while Figure 4 shows the
adjustable configuration (MAX1927). Table 2 lists part
numbers and suppliers for the components used in
these circuits.
PC Board Layout and Routing
High switching frequencies and large peak currents
make PC board layout a very important part of design.
Good design minimizes EMI, noise on the feedback
paths, and voltage gradients in the ground plane, all of
which can result in instability or regulation errors.
Connect the inductor, input filter capacitor, and output
filter capacitor as close together as possible and keep
their traces short, direct, and wide. Connect their
ground pins at a single common node in a star ground
configuration. The external voltage feedback network
should be very close to the FB pin, within 0.2in (5mm).
Keep noisy traces, such as those from the LX pin, away
from the voltage feedback network. Position the bypass
capacitors as close as possible to their respective pins
to minimize noise coupling. For optimum performance,
place input and output capacitors as close to the
device as possible. Connect GND and PGND to the
highest quality system ground. The MAX1928 evalua-
tion kit illustrates an example PC board layout and rout-
ing scheme.
Chip Information
TRANSISTORS: 3282
PROCESS: BiCMOS
Table 2. Suggested Parts/Suppliers
PART
PART NUMBER
MANUFACTURER
Inductor
CDRH3D16-4R7
Sumida
Input/Output Capacitors
COMP Capacitor
REF Capacitor
JMK212BJ106MG
GRM1881X1H561J
EMK107BJ104KA
Taiyo Yuden
Murata
Taiyo Yuden
PHONE
USA 847-956-0666
Japan 81-3-3607-5111
408-573-4150
770-436-1300
408-573-4150
WEBSITE
www.sumida.com
www.t-yuden.com
www.murata.com
www.t-yuden.com
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet MAX1928EUB15.PDF ] | |
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