EVALUATION KIT AVAILABLE MAX8550/MAX8551 Integrated DDR Power-Supply Solutions for Desktops, Notebooks, and Graphic Cards General Description Features The MAX8550/MAX8551 integrate a synchronous-buck Buck Controller PWM controller to generate V , a sourcing and sinking DDQ Quick-PWM with 100ns Load-Step Response LDO linear regulator to generate V , and a 10mA refer- TT Up to 95% Efficiency ence output buffer to generate V . The buck controller TTR 2V to 28V Input Voltage Range drives two external N-channel MOSFETs to generate out- 1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable Output put voltages down to 0.7V from a 2V to 28V input with out- Up to 600kHz Selectable Switching Frequency put currents up to 15A. The LDO can sink or source up to 1.5A continuous and 3A peak current. Both the LDO out- Programmable Current Limit with Foldback Capability put and the 10mA reference buffer output can be made to track the REFIN voltage. These features make the 1.7ms Digital Soft-Start and Independent Shutdown MAX8550/MAX8551 ideally suited for DDR memory appli- cations in desktops, notebooks, and graphic cards. Overvoltage/Undervoltage-Protection Option Power-Good Window Comparator The PWM controller in the MAX8550/MAX8551 utilizes Maxims proprietary Quick-PWM architecture with pro- LDO Section grammable switching frequencies of up to 600kHz. This Fully Integrated VTT and VTTR Capability control scheme handles wide input/output voltage ratios VTT has 3A Sourcing/Sinking Capability with ease and provides 100ns response to load tran- VTT and VTTR Outputs Track V / 2 REFIN sients while maintaining high efficiency and a relatively All-Ceramic Output-Capacitor Designs constant switching frequency. The MAX8550 offers fully 1.0V to 2.8V Input Voltage Range programmable UVP/OVP and skip-mode options ideal in portable applications. Skip mode allows for improved Power-Good Window Comparator efficiency at lighter loads. The MAX8551, which is tar- Ordering Information geted towards desktop and graphic-card applications, does not offer the pulse-skip feature. PART TEMP RANGE PIN-PACKAGE The VTT and VTTR outputs track to within 1% of V / 2. REFIN MAX8550ETI -40 C to +85C 28 5mm 5mm TQFN The high bandwidth of this LDO regulator allows excel- MAX8550ETI+ -40 C to +85C 28 5mm 5mm TQFN lent transient response without the need for bulk capac- MAX8551ETI -40 C to +85C 28 5mm 5mm TQFN itors, thus reducing cost and size. MAX8551ETI+ -40 C to +85C 28 5mm 5mm TQFN The buck controller and LDO regulators are provided with independent current limits. Adjustable lossless foldback +Denotes a lead(Pb)-free/RoHS-compliant package. current limit for the buck regulator is achieved by monitor- Pin Configuration ing the drain-to-source voltage drop of the low-side MOS- FET. Additionally, overvoltage and undervoltage protection mechanisms are built in. Once the overcurrent TOP VIEW condition is removed, the regulator is allowed to enter soft-start again. This helps minimize power dissipation + during a short-circuit condition. The MAX8550/MAX8551 TON 1 21 DL allow flexible sequencing and standby power manage- OVP/UVP 2 20 BST (N.C. FOR ment using the SHDNA, SHDNB, and STBY inputs. MAX8551) 3 19 LX REF Both the MAX8550 and MAX8551 are available in a MAX8550 ILIM 4 18 DH small 5mm 5mm, 28-pin thin QFN package. MAX8551 POK1 5 17 VIN Applications POK2 6 16 OUT DDR I and DDR II Memory Power Supplies STBY 7 15 FB Desktop Computers Notebooks and Desknotes Graphic Cards Game Consoles 5mm x 5mm Thin QFN RAID Typical Operating Circuit appears at end of data sheet. Networking Quick-PWM is a trademark of Maxim Integrated Products, Inc. For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maximintegrated.com. 19-3173 Rev 3 4/13 SS 8 28 SHDNB VTTS 9 27 SHDNA VTTR 10 26 AV DD SKIP PGND2 11 25 (TP1 FOR MAX8551) VTT 12 24 GND VTTI 13 23 PGND1 REFIN 22 14 V DDMAX8550/MAX8551 Integrated DDR Power-Supply Solutions 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 to GND .......................................-0.3V to +0.3V DD, DD SHDNA, SHDNB, 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 = V = V = V = 5V, V = V = V = 2.5V, UVP/OVP = STBY = FB = SKIP IN DD DD SHDNA SHDNB 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 SHDNA to full current limit 1.7 ms SS TON = GND (600kHz) 170 194 219 V = 15V, IN TON = REF (450kHz) 213 243 273 On-Time t V = 1.5V 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 SHDNA = SHDNB = GND 1 5 A IN All on (PWM, VTT, and VTTR on) 2.5 5 SHDNA = GND (only VTT and VTTR on) 2 4 AV Quiescent Supply Current I mA DD AVDD STBY = AV (only VTTR and PWM on) 1 2 DD SHDNB = GND (only PWM on) 0.5 1 AV + V Shutdown Supply DD DD SHDNA = SHDNB = GND 2 10 A Current Rising edge of V 4.1 4.25 4.4 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 Maxim Integrated