MAX1970/MAX1971/MAX1972 19-2297 Rev 1 2/09 Dual, 180 Out-of-Phase, 1.4MHz, 750mA Step- Down Regulator with POR and RSI/PFO General Description Features The MAX1970/MAX1971/MAX1972 dual-output current- Current-Mode, 1.4MHz Fixed-Frequency PWM mode PWM buck regulators operate from 2.6V to 5.5V Operation input and deliver a minimum of 750mA on each output. 180 Out-of-Phase Operation Reduces Input The MAX1970 and MAX1972 operate at a fixed 1.4MHz Capacitor (MAX1971 operates at 700kHz) to reduce output induc- tor and capacitor size and cost. Switching the regula- 1% Output Accuracy Over Load, Line, and tors 180 out-of-phase also reduces the input capacitor Temperature Ranges size and cost. Ceramic capacitors can be used for 750mA Guaranteed Output Current input and output. The output voltages are programmable from 1.2V to V 2.6V to 5.5V Input IN using external feedback resistors, or can be preset to Power-On Reset Delay of 16.6ms (MAX1970) or 1.8V or 3.3V for output 1 and 1.5V or 2.5V for output 2. 175ms (MAX1971 and MAX1972) When one output is higher than 1.2V, the second can be configured down to sub-1V levels. Output accuracy Power-Fail Output (MAX1970 and MAX1972 Only) is better than 1% over variations in load, line, and tem- Power-On Reset Input (MAX1971 Only) perature. Internal soft-start reduces inrush current dur- ing startup. Operation Outside xDSL Band All devices feature power-on reset (POR). The Ultra-Compact Design with Smallest External MAX1971 includes a reset input (RSI), which forces Components POR low for 175ms after RSI goes low. The MAX1970 Outputs Adjustable from 0.8V to V or 1.8V/3.3V IN and MAX1972 include an open-drain power-fail output and 1.5V/2.5V Preset (PFO) that monitors input voltage and goes high when the input falls below 3.94V. For USB-powered xDSL All-Ceramic Capacitor Application modems, this output can be used to detect USB power Soft-Start Reduces Inrush Current failure. A minimum switching frequency of 1.2MHz ensures operation outside the xDSL band. Ordering Information Applications PART TEMP RANGE PIN-PACKAGE xDSL Modems USB-Powered Devices MAX1970EEE -40C to +85C 16 QSOP xDSL Routers Dual LDO Replacement MAX1971EEE -40C to +85C 16 QSOP Copper Gigabit SFP MAX1972EEE -40C to +85C 16 QSOP and GBIC Modules Pin Configuration Typical Operating Circuit V 2.6V TO 5.5V IN TOP VIEW LX1 1 16 PGND POR V IN CC RSI RSI POR V 2 15 LX2 OUT1 CC EN EN LX1 1.8V MAX1971 COMP1 3 14 IN 750mA FB1 COMP1 FB1 4 MAX1970 13 FBSEL1 OUT2 MAX1971 COMP2 LX2 FB2 5 12 FBSEL2 2.5V MAX1972 750mA PF0 (MAX1970/MAX1972) FBSEL1 FB2 COMP2 6 11 V CC RSI (MAX1971) REF 7 10 EN FBSEL2 GND 8 9 POR REF PGND QSOP Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.Dual, 180 Out-of-Phase, 1.4MHz, 750mA Step- Down Regulator with POR and RSI/PFO ABSOLUTE MAXIMUM RATINGS IN, EN, FBSEL1, FBSEL2, PFO, POR, Continuous Power Dissipation (T = +70C) A 16-Pin QSOP (derate 8.3mW/C above +70C)...........667mW RSI, V to GND ...................................................-0.3V to +6V CC COMP1, COMP2, FB1, FB2, Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C REF to GND.............................................-0.3V to (V + 0.3V) CC Lead Temperature (soldering, 10s) .................................+300C LX1, LX2 to PGND .......................................-0.3V to (V + 0.3V) IN PGND to GND .......................................................-0.3V to +0.3V 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 = V = 5V, R = 100k to IN, R = 100k to IN, V = 0, C = 0.1F, FBSEL1 = unconnected, FBSEL2 = IN CC EN POR PFO RSI REF unconnected, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) A A PARAMETER CONDITIONS MIN TYP MAX UNITS IN AND V CC IN Voltage Range 2.6 5.5 V MAX1971 5 10 Switching with no load IN Supply Current mA V = 3.3V IN MAX1970/MAX1972 10 20 MAX1970/MAX1972 1 100 IN Shutdown Current V = 5.5V, V = 0 A IN EN MAX1971 1 60 V rising 2.40 2.55 V Undervoltage CC CC V Lockout Threshold V falling 2.20 2.35 CC REF REF Voltage I = 0, V = 2.6V to 5.5V 1.188 1.200 1.212 V REF IN REF Shutdown Resistance REF to GND, V = 0 10 25 EN REF Soft-Start Current V = 1V 20 25 30 A REF FB1 AND FB2 FBSEL = unconnected, OUT1 = FB1, OUT2 = FB2, FB Regulation Voltage 1.188 1.200 1.212 V V = 1.20V to 1.80V, V = 2.6V to 5.5V COMP IN OUT Voltage Range FBSEL = unconnected 1.2 V V IN V = 2.6V to 5.5V V = 1.2V, FBSEL1= GND 1.782 1.800 1.818 IN COMP1 OUT1 Regulation Voltage V V = 4.5V to 5.5V V = 1.2V, FBSEL1 = V 3.2670 3.3 3.330 IN COMP1 CC V = 1.2V, FBSEL2 = GND 1.485 1.5 1.150 COMP2 OUT2 Regulation Voltage V = 2.6V to 5.5V V IN V = 1.2V, FBSEL2 = V 2.475 2.5 2.525 COMP2 CC Maximum Output Current Guaranteed by design (Note 1) 750 mA FBSEL1 = GND 30 60 120 Measured from FB1 to FB1 Input Resistance k GND FBSEL1 = V 30 60 120 CC FBSEL2 = GND 22.5 45 90 Measured from FB2 to FB2 Input Resistance k GND FBSEL2 = V 22.5 45 90 CC FB Input Bias Current FB1 or FB2, FBSEL = unconnected, V = V = 1.15V 0.01 0.1 A FB1 FB2 2 MAX1970/MAX1971/MAX1972