MAX1955/MAX1956 19-2623 Rev 0 1/03 1.6V to 5.5V Input, 0.5% Accurate, Dual 180 Out-of-Phase Step-Down Controllers General Description Features The MAX1955/MAX1956 are dual-output, fixed-frequency, Operates from a 1.6V to 5.5V Supply (MAX1956) voltage-mode, pulse-width modulated (PWM) step-down 0.5% Output Accuracy controllers with 0.5% output accuracy. Each controller 0.8V to 0.9V Output Range IN switches at a constant 600kHz and is 180 out-of-phase with the other controller, reducing input ripple current Up to 25A per Phase Output Current and the number of input capacitors. On-Chip Boost Regulator Provides 5V Gate Drive An on-chip bias supply generates a 5V gate drive to Up to 93% Efficiency deliver up to 25A output current per phase with low-cost N-channel MOSFETs at up to 93% efficiency. Lossless 180 Out-of-Phase Operation adjustable current limit eliminates expensive current- 4% Voltage Margining sense resistors and improves efficiency. Foldback current Lossless, Foldback Current Limit limit reduces power dissipation during short-circuit conditions and handles transient overloads better than Selectable Voltage Sequencing controllers using hiccup-mode short-circuit protection. Synchronizable to External Clock Output voltage margining shifts output voltage by Digital Soft-Start and Soft-Stop 4% from the nominal value to simplify system test. Outputs also can be powered up and down in select- Small 28-Pin, 5mm 5mm Thin QFN Package able sequences to meet core and logic supply-rail requirements. Ordering Information The MAX1955/MAX1956 are available in a 28-lead thin PART TEMP RANGE PIN-PACKAGE QFN package with exposed pad. MAX1955 ETI -40C to +85C 28 Thin QFN-EP* Applications MAX1956 ETI -40C to +85C 28 Thin QFN-EP* Base Stations *EP = Exposed pad. Telecom and Network Equipment Servers Pin Configuration appears at end of data sheet. DSP, ASIC, P, and FPGA Supplies Typical Operating Circuit INPUT 1.6V TO 5.5V VDD IN V DD LXB BST2 OUTPUT 2 0.8V TO 0.9V IN BST1 DH2 UP TO 25A OUTPUT 1 DH1 0.8V TO 0.9V IN LX2 LX1 UP TO 25A MAX1956 DL2 DL1 FB2 PGND COMP2 FB1 COMP1 REF SEQ GND SYNCHRONIZATION ILIM1 CLOCK VDD SYNC ILIM2 EN AV DD ON/OFF VOLTAGE MARGINING 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 AVAILABLE1.6V to 5.5V Input, 0.5% Accurate, Dual 180 Out-of-Phase Step-Down Controllers ABSOLUTE MAXIMUM RATINGS IN, AVDD, SYNC, EN, ILIM , FB , SEQ to GND.......-0.3V to +6V PGND to GND or VDD to AVDD............................-0.3V to +0.3V COMP , REF to GND..............................-0.3V to (V + 0.3V) REF Short-Circuit to GND...........................................Continuous AVDD LXB to GND ..............................................-0.3V to (V + 0.3V) I ...................................................................................250mA VDD VDD DL to GND ...............................(V - 0.3V) to (V + 0.3V) Continuous Power Dissipation* (T = +70C) PGND VDD A BST to GND ..........................................................-0.3V to +12V 28-Lead Thin QFN DH1 to LX1 ...............................................-0.3V to (BST1 + 0.3V) (derate 20.8mW/C above +70C)................................1667mW DH2 to LX2 ...............................................-0.3V to (BST2 + 0.3V) Operating Temperature Range ...........................-40C to +85C LX1 to BST1..............................................................-6V to +0.3V Junction Temperature......................................................+150C LX2 to BST2..............................................................-6V to +0.3V Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering 10s) ..................................+300C *Exposed pad soldered to PC board. 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 = V = 3.3V V = V = 5V V = V = 0 C = 0.22F SEQ = SYNC = GND T = 0C to +85C, unless other- IN EN VDD AVDD PGND GND REF A wise noted. Typical values are at T = +25C.) A PARAMETER CONDITIONS MIN TYP MAX UNITS MAX1955 2.25 5.50 IN Input Voltage Range V MAX1956 (Note 1) 1.6 5.5 MAX1955, hysteresis = 35mV 1.9 2.2 IN Input Voltage UVLO Rise or fall V MAX1956, hysteresis = 30mV 1.30 1.58 FB Regulation Voltage 0.796 0.8 0.804 V FB Regulation Voltage with Percentage change from nominal regulation voltage 3 4 5 % Positive Voltage Margining FB Regulation Voltage with Percentage change from nominal regulation voltage -5 -4 -3 % Negative Voltage Margining Line Regulation Error Note 2 0.1 0.3 % Feedback Input Bias -0.2 +0.2 A Feedback Transconductance 1 2 3 mS COMP Source Current 100 150 A COMP Sink Current 100 150 A COMP Pulldown Resistance In shutdown 100 Output Soft-Start Time 4.27 ms Step-Down Switching Frequency SYNC = GND (Note 3) 540 600 660 kHz SYNC Frequency Range 2 times step-down switching frequency 1080 1320 kHz Maximum Duty Cycle Measured at DH 90 93 97 % Minimum Duty Cycle Measured at DH 7 10 % 2 MAX1955/MAX1956