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MAX8744 Fiches technique(PDF) 1 Page - Maxim Integrated Products |
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MAX8744 Fiches technique(HTML) 1 Page - Maxim Integrated Products |
1 / 36 page 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. 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 High-Efficiency, Quad Output, Main Power- Supply Controllers for Notebook Computers ________________________________________________________________ Maxim Integrated Products 1 19-3796; Rev 0; 4/06 +Denotes lead-free package. MAX8744 MAX8745 THIN QFN 5mm x 5mm TOP VIEW 29 30 28 27 12 11 13 14 12 + CSL3 45 6 7 23 24 22 20 19 18 CSH3 FB3 PGOOD5 CSL5 CSH5 FB5 3 21 31 10 FBA SKIP 32 9 OUTA FSEL PGOOD3 26 15 BST5 BST3 25 16 DH5 8 17 DH3 Pin Configuration Ordering Information PART TEMP RANGE PIN- PACKAGE PKG CODE MAX8744ETJ+ -40°C to +85°C 32 Thin QFN (5mm x 5mm) T3255-4 MAX8745ETJ+ -40°C to +85°C 32 Thin QFN (5mm x 5mm) T3255-4 Dual Mode is a trademark of Maxim Integrated Products, Inc. EVALUATION KIT AVAILABLE |
Numéro de pièce similaire - MAX8744 |
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Description similaire - MAX8744 |
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