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PDF MAX8744 Data sheet ( Hoja de datos )
| Número de pieza | MAX8744 | |
| Descripción | (MAX8744 / MAX8745) Main Power-Supply Controllers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX8744 (archivo pdf) en la parte inferior de esta página. Total 36 Páginas | ||
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19-3796; Rev 0; 4/06
EVAALVUAAILTAIOBNLEKIT
www.DataSheetH4U.ciomgh-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
General Description
The MAX8744/MAX8745 are dual step-down, switch-
mode, power-supply (SMPS) controllers with synchro-
nous rectification, intended for main 5V/3.3V power
generation in battery-powered systems. Fixed-frequen-
cy operation with optimal interleaving minimizes input
ripple current from the lowest input voltages up to the
26V maximum input. Optimal 40/60 interleaving allows
the input voltage to go down to 8.3V before duty-cycle
overlap occurs, compared to 180° out-of-phase regula-
tors where the duty-cycle overlap occurs when the
input drops below 10V.
Output current sensing provides peak current-limit pro-
tection, using either an accurate sense resistor or using
lossless inductor DCR current sensing. A low-noise
mode maintains high light-load efficiency while keeping
the switching frequency out of the audible range.
An internal, fixed 5V, 100mA linear regulator powers up
the MAX8744/MAX8745 and their gate drivers, as well
as external keep-alive loads. When the main PWM reg-
ulator is in regulation, an automatic bootstrap switch
bypasses the internal linear regulator, providing current
up to 200mA. An additional adjustable linear-regulator
driver with an external pnp transistor may be used with
a secondary winding to provide a 12V supply, or pow-
ered directly from the main outputs to generate low-
voltage outputs as low as 1V.
Independent enable controls and power-good signals
allow flexible power sequencing. Voltage soft-start
gradually ramps up the output voltage and reduces
inrush current, while soft-shutdown gradually ramps the
output voltage down, preventing negative voltage dips.
The MAX8744/MAX8745 feature output undervoltage
and thermal-fault protection. The MAX8744 also
includes output overvoltage-fault protection.
The MAX8744/MAX8745 are available in a 32-pin, 5mm
x 5mm, thin QFN package. The exposed backside pad
improves thermal characteristics for demanding linear
keep-alive applications.
Applications
Main Power Supplies
2 to 4 Li+ Cell Battery-Powered Devices
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
Features
♦ Fixed-Frequency, Current-Mode Control
♦ 40/60 Optimal Interleaving
♦ Internal BST Switches
♦ Internal 5V, 100mA Linear Regulator
♦ Auxiliary Linear-Regulator Driver (12V or
Adjustable Down to 1V)
♦ Dual Mode™ Feedback—3.3V/5V Fixed or
Adjustable Output Voltages
♦ 200kHz/300kHz/500kHz Switching Frequency
♦ Undervoltage and Thermal-Fault Protection
♦ Overvoltage-Fault Protection (MAX8744 Only)
♦ 6V to 26V Input Range
♦ 2V ±0.75% Reference Output
♦ Independent Enable Inputs and Power-Good
Outputs
♦ Soft-Start and Soft-Shutdown (Voltage Ramp)
♦ 8µA (typ) Shutdown Current
Ordering Information
PART
TEMP RANGE
MAX8744ETJ+ -40°C to +85°C
MAX8745ETJ+ -40°C to +85°C
+Denotes lead-free package.
PIN-
PACKAGE
32 Thin QFN
(5mm x 5mm)
32 Thin QFN
(5mm x 5mm)
PKG
CODE
T3255-4
T3255-4
Pin Configuration
TOP VIEW
24 23 22 21 20 19 18 17
DH3 25
16 DH5
BST3 26
15 BST5
PGOOD3 27
14 PGOOD5
CSL3 28
CSH3 29
FB3 30
MAX8744
MAX8745
13 CSL5
12 CSH5
11 FB5
FBA 31
OUTA 32
+
10 SKIP
9 FSEL
1 2345678
Dual Mode is a trademark of Maxim Integrated Products, Inc.
THIN QFN
5mm x 5mm
________________________________________________________________ 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  
www.DataSheetH4U.ciomgh-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = 12V, both SMPS enabled, FSEL = REF, SKIP = GND, ILIM = LDO5, FBA = LDO5, IREF = ILDO5 = IOUTA =
no load, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Output Undervoltage Protection
Trip Threshold
With respect to error-comparator
threshold
65 70 75
%
Output Undevoltage Fault
Propagation Delay
tUVP
50mV overdrive
10 µs
Output Undervoltage Protection
Blanking Time
PGOOD_ Lower Trip Threshold
PGOOD_ Propagation Delay
PGOOD_ Output Low Voltage
PGOOD_ Leakage Current
Thermal-Shutdown Threshold
GATE DRIVERS
DH_ Gate-Driver On-Resistance
DL_ Gate-Driver On-Resistance
DH_ Gate-Driver Source/Sink
Current
DL_ Gate-Driver Source Current
DL_ Gate-Driver Sink Current
Dead Time
tBLANK
tPGOOD_
IPGOOD_
tSHDN
From rising edge of ON_ with respect to
fSW
With respect to error-comparator
threshold, hysteresis = 1% (typ)
Falling edge, 50mV overdrive
Rising edge, 50mV overdrive
ISINK = 1mA
High state, PGOOD_ forced to 5.5V
Hysteresis = 15°C
RDH BST_ – LX_ forced to 5V
DL_, high state
RDL DL_, low state
IDH
DH_ forced to 2.5V, BST_ – LX_ forced to
5V
IDL (SOURCE) DL_ forced to 2.5V
IDL (SINK) DL_ forced to 2.5V
tDEAD
DH_low to DL_high
DL_low to DH_high
5000
-12
15
15
6144
-10
10
1
+160
1.3
1.7
0.6
2
1.7
3.3
45
44
7000 1/fOSC
-8 %
µs
0.4 V
1 µA
°C
5Ω
5
Ω
3
A
A
A
ns
Internal BST_ Switch On-
Resistance
BST_ Leakage Current
INPUTS AND OUTPUTS
SHDN Input Trip Level
ONA Logic Input Voltage
ON3, ON5 Input Voltage
RBST
IBST = 10mA
VBST_ = 26V
Rising trip level
Falling trip level
Hysteresis = 600mV (typ)
High
Low
SMPS off level/clear fault level
Delay start level
SMPS on level
5
2 20
1.1 1.6 2.2
0.96 1 1.04
2.4
0.8
0.8
1.9 2.1
2.4
Ω
µA
V
V
V
_______________________________________________________________________________________ 5
5 Page 
www.DataSheetH4U.ciomgh-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 12V, SKIP = GND, FSEL = REF, TA = +25°C, unless otherwise noted.)
SMPS DELAYED STARTUP SEQUENCE
SMPS DELAYED STARTUP SEQUENCE
SOFT-START WAVEFORM
3.3V
0
MAX8744 toc16
A
3.3V
0
(ON3 = REF)
MAX8744 toc17
A
3.3V
0
(ON5 = REF)
MAX8744 toc18
A
5V
5V
B
5V
B
B
0 00
0
C0
C
0
C
12V 3.3V 3.3V
0
D
0
D
0
D
5A 0 E 0 E
0E
400μs/div
A. ON3 AND ON5, 5V/div
B. 5V OUTPUT (VOUT5), 5V/div
C. PGOOD5, 5V/div
D. AUX LDO OUTPUT
(VOUTA), 10V/div
E. L5 INDUCTOR CURRENT,
5A/div
1ms/div
A. ON5, 5V/div
B. 5V OUTPUT (VOUT5), 5V/div
C. PGOOD5, 5V/div
ON3 = REF
D. 3.3V OUTPUT (VOUT3),
5V/div
E. PGOOD3, 5V/div
1ms/div
A. ON3, 5V/div
B. 5V OUTPUT (VOUT5), 5V/div
C. PGOOD5, 5V/div
ON5 = REF
D. 3.3V OUTPUT (VOUT3),
5V/div
E. PGOOD3, 5V/div
SMPS SHUTDOWN WAVEFORMS
MAX8744 toc19
3.3V
A
5V
B
0
5A
1A
5.1V
5.0V
OUT5 LOAD TRANSIENT
MAX8744 toc20
A
B
3A
1A
3.35V
3.30V
OUT3 LOAD TRANSIENT
MAX8744 toc21
A
B
0 C 4.9V
5A
3.25V
3.3V 1A C 3A C
0D
1A
5V
0
12V
E
12V
D
D
00
1ms/div
A. SHDN, 5V/div
B. 5V OUTPUT (VOUT5), 5V/div
C. PGOOD5, 5V/div
NO LOAD
D. 3.3V OUTPUT (VOUT3),
5V/div
E. PGOOD3, 5V/div
20μs/div
A. IOUT5 = 1A TO 5A, 5A/div
B. VOUT5, 50mV/div
C. INDUCTOR CURRENT,
5A/div
D. LX5, 10V/div
20μs/div
A. IOUT3 = 1A TO 3A, 5A/div
B. VOUT3, 50mV/div
C. INDUCTOR CURRENT,
5A/div
D. LX3, 10V/div
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 36 Páginas | |
| PDF Descargar | [ Datasheet MAX8744.PDF ] | |
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