MAX8744 Datasheet, PDF (1/36 Pages) Maxim Integrated Products – High-Efficiency, Quad Output, Main Power-Supply Controllers for Notebook Computers

19-3796; Rev 0; 4/06
EVAALVUAAILTAIOBNLEKIT
High-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.