Document
19-3796; Rev 0; 4/06
KIT ATION EVALU E L B A AVAIL
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High-Efficiency, Quad Output, Main PowerSupply Controllers for Notebook Computers
General Description 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
MAX8744/MAX8745
PGOODA
LDO5
DL3
DL5
LX3
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.
24 DH3 25 BST3 26 PGOOD3 27 CSL3 28 CSH3 29 FB3 30 FBA 31 OUTA 32 1 ONA +
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22
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17 16 15 14 13 DH5 BST5 PGOOD5 CSL5 CSH5 FB5 SKIP FSEL
Applications
Main Power Supplies 2 to 4 Li+ Cell Battery-Powered Devices Notebook and Subnotebook Computers PDAs and Mobile Communicators
MAX8744 MAX8745
LX5
TOP VIEW
PGND
The MAX8744/MAX8745 are dual step-down, switchmode, power-supply (SMPS) controllers with synchronous rectification, intended for main 5V/3.3V power generation in battery-powered systems. Fixed-frequency 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 regulators where the duty-cycle overlap occurs when the input drops below 10V. Output current sensing provides peak current-limit protection, 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 regulator 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 powered directly from the main outputs to generate lowvoltage 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.
Ordering Information
PART MAX8744ETJ+ MAX8745ETJ+ TEMP RANGE -40°C to +85°C -40°C to +85°C PINPACKAGE PKG CODE
32 Thin QFN T3255-4 (5mm x 5mm) 32 Thin QFN T3255-4 (5mm x 5mm)
+Denotes lead-free package.
Pin Configuration
IN
12 11 10 9
2 DRVA
3 ILIM
4 SHDN
5 ON3
6 ON5
7 REF
8 GND
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.
www.DataSheet4U.com High-Efficiency, Quad Output, Main PowerSupply Controllers for Notebook Computers
MAX8744/MAX8745
ABSOLUTE MAXIMUM RATINGS
IN, SHDN, DRVA, OUTA to GND............................-0.3V to +28V LDO5, ON3, ON5, ONA to GND ..............................-0.3V to +6V PGOODA, PGOOD3, PGOOD5 to GND...................-0.3V to +6V CSL3, CSH3, CSL5, CSH5 to GND ..........................-0.3V to +6V REF, FB3, FB5, FBA to GND...................-0.3V to (VLDO5 + 0.3V) SKIP, FSEL, ILIM to GND........................-0.3V to (VLDO5 + 0.3V) DL3, DL5 to PGND..................................-0.3V to (VLDO5 + 0.3V) BST3, BST5 to PGND .............................................-0.3V to +34V BST3 to LX3..............................................................-0.3V to +6V DH3 to LX3 ..............................................-0.3V to (VBST3 + 0.3V) BST5 to LX5..............................................................-0.3V to +6V DH5 to LX5 ..............................................-0.3V to (VBST5 + 0.3V) GND to PGND .......................................................-0.3V to +0.3V BST3, BST5 LDO5 .................................................-0.3V to +0.3V LDO Short Circuit to GND ..........................................Momentary REF Short Circuit to GND ........................