MAX8550A 19-3313 Rev 0 5/04 Integrated DDR Power-Supply Solution for Desktops, Notebooks, and Graphic Cards General Description Features Buck Controller The MAX8550A integrates a synchronous-buck PWM controller to generate V , a sourcing and sinking LDO Quick-PWM with 100ns Load-Step Response DDQ linear regulator to generate V , and a 10mA reference TT Up to 95% Efficiency output buffer to generate V . The buck controller drives TTR 2V to 28V Input Voltage Range two external n-channel MOSFETs to generate output volt- ages down to 0.7V from a 2V to 28V input with output cur- 1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable Output rents up to 15A. The LDO can sink or source up to 1.5A Up to 600kHz Selectable Switching Frequency continuous and 3A peak current. Both the LDO output Programmable Current Limit with Foldback and the 10mA reference buffer output can be made to Capability track the REFIN voltage. These features make the MAX8550A ideally suited for DDR memory applications in 1.7ms Digital Soft-Start desktops, notebooks, and graphic cards. Independent Shutdown and Standby Controls The PWM controller in the MAX8550A utilizes Maxims Overvoltage/Undervoltage-Protection Option proprietary Quick-PWM architecture with programma- Power-Good Window Comparator ble switching frequencies of up to 600kHz. This control LDO Section scheme handles wide input/output voltage ratios with ease and provides 100ns response to load transients Fully Integrated VTT and VTTR Capability while maintaining high efficiency and a relatively con- VTT Has 3A Sourcing/Sinking Capability stant switching frequency. The MAX8550A offers fully VTT and VTTR Outputs Track V / 2 REFIN programmable UVP/OVP and skip-mode options ideal in portable applications. Skip mode allows for improved All-Ceramic Output-Capacitor Designs efficiency at lighter loads. 1.0V to 2.8V Input Voltage Range The VTT and VTTR outputs track to within 1% of V / 2. REFIN Power-Good Window Comparator The high bandwidth of this LDO regulator allows excel- lent transient response without the need for bulk capac- Ordering Information itors, thus reducing cost and size. The buck controller and LDO regulators are provided with PART TEMP RANGE PIN-PACKAGE independent current limits. Adjustable lossless foldback MAX8550AETI -40C to +85C 28 TQFN 5mm 5mm current limit for the buck regulator is achieved by monitor- ing the drain-to-source voltage drop of the low-side MOSFET. Additionally, overvoltage and undervoltage pro- Pin Configuration tection mechanisms are built in. Once the overcurrent condition is removed, the regulator is allowed to enter TOP VIEW soft-start again. This helps minimize power dissipation during a short-circuit condition. The MAX8550A allows flexible sequencing and standby power management TON 1 21 DL using the SHDN and STBY inputs, which support all OVP/UVP 2 20 BST DDRs operating states. 3 19 LX REF The MAX8550A is available in a small 5mm 5mm, 28- pin thin QFN package. ILIM 4 18 DH MAX8550A POK1 5 17 V IN Applications 6 16 POK2 OUT DDR I and DDR II Memory Power Supplies 7 15 FB Desktop Computers STBY Notebooks and Desknotes Graphic Cards Game Consoles 5mm x 5mm Thin QFN RAID Networking Typical Operating Circuit appears at end of data sheet. Quick-PWM is a trademark of Maxim Integrated Products, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE SS 8 28 TPO SHDN VTTS 9 27 VTTR 10 26 AV DD SKIP PGND2 11 25 VTT GND 12 24 VTTI PGND1 13 23 REFIN 14 22 V DDIntegrated DDR Power-Supply Solution for Desktops, Notebooks, and Graphic Cards ABSOLUTE MAXIMUM RATINGS V to GND .............................................................-0.3V to +30V VTTS to GND............................................-0.3V to (AV + 0.3V) IN DD V AV , VTTI to GND.........................................-0.3V to +6V PGND1, PGND2, TP0 to GND...............................-0.3V to +0.3V DD, DD SHDN, REFIN to GND ..............................................-0.3V to +6V REF Short Circuit to GND...........................................Continuous SS, POK1, POK2, SKIP, ILIM, FB to GND ................-0.3V to +6V Continuous Power Dissipation (T = +70C) A STBY, TON, REF, UVP/OVP to GND ........-0.3V to (AV + 0.3V) 28-Pin 5mm x 5mm TQFN (derate 35.7mW/C DD OUT, VTTR to GND ..................................-0.3V to (AV + 0.3V) above +70C).................................................................2.86W DD DL to PGND1..............................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C DD DH to LX....................................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C BST LX to BST..................................................................-6V to +0.3V Storage Temperature Range .............................-65C to +165C LX to GND .................................................................-2V to +30V Lead Temperature (soldering, 10s) .................................+300C VTT to GND...............................................-0.3V to (V + 0.3V) VTTI Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +15V, V = AV = V = STBY = V = V = 5V, V = V = V = 2.5V, UVP/OVP = TP0 = FB = SKIP IN DD DD SHDN BST ILIM OUT REFIN VTTI = GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V = V , T = -40C to +85C, unless otherwise noted. Typical values VTTS VTT A are at T = +25C.) (Note 1) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS MAIN PWM CONTROLLER V 228 IN Input Voltage Range V V , AV 4.5 5.5 DD DD Output Adjust Range V 0.7 5.5 V OUT FB = OUT 0.693 0.7 0.707 Output Voltage Accuracy FB = GND 2.47 2.5 2.53 V (Note 2) FB = V 1.78 1.8 1.82 DD Soft-Start Ramp Time t Rising edge of SHDN to full current limit 1.7 ms SS TON = GND (600kHz) 170 194 219 V = 15V, IN TON = REF (450kHz) 213 243 273 V = 1.5V On-Time t ns ON OUT TON = OPEN (300kHz) 316 352 389 (Note 3) TON = AV (200kHz) 461 516 571 DD Minimum Off-Time t (Note 3) 200 300 450 ns OFF MIN V Quiescent Supply Current I 25 40 A IN IN V Shutdown Supply Current SHDN = GND 1 5 A IN All on (PWM, VTT, and VTTR on) 2.5 5 AV Quiescent Supply Current I mA DD AVDD STBY = GND (only VTTR and PWM on) 1 2 AV + V Shutdown Supply DD DD SHDN = GND 2 10 A Current Rising edge of V 4.05 4.25 4.40 V AV Undervoltage-Lockout IN DD Threshold Hysteresis 50 mV V Quiescent Supply Current I Set V = 0.8V 1 5 A DD VDD FB 2 MAX8550A