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PDF MAX8742 Data sheet ( Hoja de datos )
| Número de pieza | MAX8742 | |
| Descripción | (MAX8741 / MAX8742) 500kHz Multi-Output Power-Supply Controllers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX8742 (archivo pdf) en la parte inferior de esta página. Total 33 Páginas | ||
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19-3262; Rev 0; 4/04
500kHzwww.DataSheet4U.com Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
General Description
The MAX8741/MAX8742 are buck-topology, step-down,
switch-mode, power-supply controllers that generate
logic-supply voltages in battery-powered systems. These
high-performance, dual/triple-output devices include on-
board power-up sequencing, power-good signaling with
delay, digital soft-start, secondary winding control, low-
dropout circuitry, internal frequency-compensation net-
works, and automatic bootstrapping.
Up to 97% efficiency is achieved through synchronous
rectification and Maxim’s proprietary Idle Mode™ control
scheme. Efficiency is greater than 80% over a 1000:1
load-current range, which extends battery life in system
suspend or standby mode. Excellent dynamic response
corrects output load transients within five clock cycles.
Strong 1A on-board gate drivers ensure fast external
n-channel MOSFET switching.
These devices feature a logic-controlled and synchroniz-
able, fixed-frequency, pulse-width-modulation (PWM)
operating mode. This reduces noise and RF interference
in sensitive mobile communications and pen-entry appli-
cations. Asserting the SKIP pin enables fixed-frequency
mode, for lowest noise under all load conditions.
The MAX8741/MAX8742 include two PWM regulators,
adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V
modes. All these devices include secondary feedback
regulation, and the MAX8742 contains a 12V/120mA lin-
ear regulator. The MAX8741 includes a secondary feed-
back input (SECFB), plus a control pin (STEER) that
selects which PWM (3.3V or 5V) receives the secondary
feedback signal. SECFB provides a method for adjusting
the secondary winding voltage regulation point with an
external resistor-divider, and is intended to aid in creating
auxiliary voltages other than fixed 12V.
The MAX8741/MAX8742 contain internal output overvolt-
age- and undervoltage-protection features.
________________________Applications
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Desktop CPU Local DC-DC Converters
Features
♦ 97% Efficiency
♦ 4.2V to 30V Input Range
♦ 2.5V to 5.5V Dual Adjustable Outputs
♦ Selectable 3.3V and 5V Fixed or Adjustable
Outputs (Dual Mode™)
♦ 12V Linear Regulator
♦ Adjustable Secondary Feedback (MAX8741)
♦ 5V/50mA Linear-Regulator Output
♦ Precision 2.5V Reference Output
♦ Programmable Power-Up Sequencing
♦ Power-Good (RESET) Output
♦ Output Overvoltage Protection
♦ Output Undervoltage Shutdown
♦ 333kHz/500kHz Low-Noise, Fixed-Frequency
Operation
♦ Low-Dropout, 98% Duty-Factor Operation
♦ 2.5mW Typical Quiescent Power (12V Input,
Both SMPSs On)
♦ 4µA Typical Shutdown Current
PART
MAX8741EAI
MAX8741ETJ
MAX8742EAI
MAX8742ETJ
Ordering Information
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
32 Thin QFN 5mm x 5mm
28 SSOP
32 Thin QFN 5mm x 5mm
INPUT
5V (RTC)
Functional Diagram
5V
LINEAR
12V
LINEAR
12V
3.3V 3.3V 5V
SMPS
SMPS
5V
Idle Mode is a trademark of Maxim Integrated Products, Inc.
Dual Mode is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
ON/OFF
POWER-UP POWER-
SEQUENCE GOOD
RESET
________________________________________________________________ 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  
500kHzwww.DataSheet4U.com Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
ELECTRICAL CHARACTERISTICS
(V+ = 15V, both PWMs on, SYNC = VL, VL load = 0, REF load = 0, SKIP = 0, TA = -40°C to +85°C, unless otherwise noted.) (Note 6)
PARAMETER
MAIN SMPS CONTROLLERS
Input Voltage Range
3V Output Voltage in Adjustable Mode
CONDITIONS
V+ = 4.2V to 30V, CSH3 - CSL3 = 0,
CSL3 connected to FB3
MIN TYP MAX UNITS
4.2
2.42
30.0
2.58
V
V
3V Output Voltage in Fixed Mode
V+ = 4.2V to 30V, 0 < CSH3 - CSL3
< 80mV, FB3 = 0
3.20
3.47 V
5V Output Voltage in Adjustable Mode
V+ = 4.2V to 30V, CSH5 - CSL5 = 0,
CSL5 connected to FB5
2.42
2.58 V
5V Output Voltage in Fixed Mode
Output Voltage Adjust Range
Adjustable-Mode Threshold Voltage
Current-Limit Threshold
Oscillator Frequency
Maximum Duty Factor
SYNC Input Frequency Range
FLYBACK CONTROLLER
VDD Regulation Threshold
SECFB Regulation Threshold
VDD Shunt Threshold
VDD Shunt Sink Current
12V LINEAR REGULATOR (MAX8742)
12OUT Output Voltage
Quiescent VDD Current
INTERNAL REGULATOR AND REFERENCE
VL Output Voltage
VL Undervoltage-Lockout Fault Threshold
VL Switchover Threshold
REF Output Voltage
REF Load Regulation
REF Sink Current
REF Fault-Lockout Voltage
V+ Operating Supply Current
V+ = 5.3V to 30V, 0 < CSH5 - CSL5
< 80mV, FB5 = 0
Either SMPS
Dual-mode comparator
CSH3 - CSL3 or CSH5 - CSL5
SKIP = VL or VDD < 13V or SECFB < 2.44V
SYNC = VL
SYNC = 0
SYNC = VL
SYNC = 0 (Note 2)
Falling edge (MAX8742)
Falling edge (MAX8741)
Rising edge, hysteresis = 1% (MAX8742)
VDD = 20V (MAX8742)
13V < VDD < 18V, 0mA < ILOAD < 100mA
VDD = 18V, run mode, no 12OUT load
SHDN = V+, RUN/ON3 = TIME/ON5 = 0,
5.4V < V+ < 30V, 0 < ILOAD < 50mA
Falling edge, hysteresis = 1%
Rising edge of CSL5, hysteresis = 1%
No external load (Note 4)
0 < ILOAD < 50µA
0 < ILOAD < 5mA
Falling edge
VL switched over to CSL5, 5V SMPS on
4.85
REF
0.5
80
-50
450
283
95
97
400
13
2.44
18
10
11.65
4.7
3.5
4.2
2.45
10
1.8
5.25
5.5
1.1
120
-150
550
383
583
V
V
V
mV
kHz
%
kHz
14
2.60
20
V
V
V
mA
12.50
100
V
µA
5.1
3.7
4.7
2.55
12.5
100.0
2.4
50
V
V
V
V
mV
µA
V
µA
_______________________________________________________________________________________ 5
5 Page 
500kHzwww.DataSheet4U.com Multi-Output Power-Supply Controllers
with High Impedance in Shutdown
INPUT
7V TO 24V
C3
5V OUTPUT
C1
R1
C4
0.1µF
L1
Q1
Q2
5V ON/OFF
3.3V ON/OFF
ON/OFF
10Ω
4.7µF
0.1µF
0.1µF
V+ SHDN SECFB VL
SYNC
BST5 BST3
DH5 DH3
LX5 LX3
DL5 MAX8741
DL3
PGND
GND
CSH5
CSL5
CSH3
CSL3
FB3
FB5
TIME/ON5
RUN/ON3
RESET
SKIP
STEER
REF SEQ
1µF
0.1µF
5V ALWAYS ON
4.7µF
0.1µF
Q3
C5
0.1µF
L2
Q4
R2 3.3V OUTPUT
C2
RESET OUTPUT
2.5V ALWAYS ON
Figure 1. Standard 3.3V/5V Application Circuit (MAX8741)
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 33 Páginas | |
| PDF Descargar | [ Datasheet MAX8742.PDF ] | |
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