MAX1973/MAX1974 19-2547 Rev 0 7/02 Smallest 1A, 1.4MHz Step-Down Regulators General Description Features The MAX1973/MAX1974 are constant-frequency 2 Tiny Circuit Footprint of 0.19in 1.4MHz pulse-width-modulated (PWM) current-mode Ultra-Low Circuit Height of 1.8mm step-down regulators. The output voltage can be set as low as 0.75V using an external voltage-divider, or it can 4.7F Ceramic Input and Output Capacitors be set to preset outputs of 1V, 1.5V (MAX1974), 1.8V, 2.6V to 5.5V Input Voltage or 2.5V (MAX1973) without requiring external resistors. The MAX1973 also includes a voltage-margining fea- 1A Output Current ture that offsets the output voltage up or down 4% to 1% Accurate facilitate board-level production testing. A fixed 1.4MHz operating frequency ensures operation Built-In 4% Logic-Controlled Voltage Margining outside the DSL frequency band, provides fast transient (MAX1973) response, and allows the use of small external compo- Preset 1V, 1.5V, 1.8V, 2.5V, or 0.75V to V IN nents. Only 4.7F input and output ceramic capacitors Adjustable Output are needed for 1A applications. Forced PWM operation ensures a constant switching frequency over all load Fixed-Frequency PWM Current-Mode Operation conditions. 1.4MHz Switching Frequency, Operate Outside Output voltage accuracy is 1% over load, line, and DSL Band temperature operating ranges. The MAX1973 features 100% Duty-Cycle Dropout Capability voltage margining the MAX1974 provides a POK out- put to indicate when the output has reached 90% of its Small External Components nominal regulation voltage. Both devices are available in small 10-pin MAX packages. Applications Ordering Information Network Equipment PART TEMP RANGE PIN-PACKAGE Cellular Base Stations MAX1973EUB -40C to +85C 10 MAX DSL and Wireless Modems/Routers MAX1974EUB -40C to +85C 10 MAX Optical Modules Central-Office DSL and Telecom Pin Configurations DSP/ASIC Core and IO supplies TOP VIEW Selector Guide appears at end of data sheet. FBSEL 1 10 CTL1 Typical Operating Circuit COMP 2 9 IN MAX1973 FB 3 8 LX SS 4 7 PGND OUTPUT INPUT 1.25V TO V IN GND 5 6 CTL2 2.6V TO 5.5V 1A IN LX MAX COMP FB FBSEL 1 10 ON FBSEL MAX1973 CTL1 VOLTAGE SS COMP 2 9 IN MARGINING CTL2 MAX1974 ON/OFF FB 3 8 LX GND PGND SS 4 7 PGND GND 5 6 POK MAX1974 OUTPUT DOWN TO 0.75V MAX 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.Smallest 1A, 1.4MHz Step-Down Regulators ABSOLUTE MAXIMUM RATINGS IN, POK, CTL1, CTL2, FBSEL, ON to GND ..............-0.3V to +6V Continuous Power Dissipation (T = +70C) A COMP, FB, SS to GND ................................-0.3V to (V + 0.3V) 10-Pin MAX (derate 5.6mW/C above +70C) .......... 444mW IN PGND to GND .......................................................-0.3V to +0.3V Operating Temperature Range ...........................-40C to +85C LX Current (Note 1)...............................................-2.4A to +2.4A Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Note 1: LX has internal clamp diodes to IN and PGND. Applications that forward bias these diodes should take care not to exceed the IC package power dissipation limit. 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, FB = OUT, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) IN CTL A A PARAMETER CONDITIONS MIN TYP MAX UNITS IN IN Voltage Range 2.6 5.5 V IN Undervoltage Lockout Rising and falling, hysteresis is 25mV (typ) 2.2 2.35 2.5 V Threshold Supply Current Switching with no load 4.0 7.5 mA Supply Current in Dropout V set for 3.6V 3 5 mA OUT Shutdown Supply Current V = 5.5V 0.1 10 A IN FB MAX1973 1.25 V IN Output Voltage Range V MAX1974 0.75 V IN FBSEL not connected 1.2375 1.25 1.2625 MAX1973 FBSEL = GND 1.7820 1.8 1.8180 FBSEL = IN 2.4750 2.5 2.5250 FB Regulation Voltage V FBSEL not connected 0.7425 0.75 0.7575 MAX1974 FBSEL = GND 0.99 1.00 1.01 FBSEL = IN 1.485 1.500 1.515 FB Regulation Voltage MAX1973, CTL1 = GND, CTL2 = IN +3 +4 +5 % Positive Voltage Margining FB Regulation Voltage MAX1973, CTL1 = IN, CTL2 = GND -3 -4 -5 % Negative Voltage Margining FB Input Resistance to GND in 10 30 70 k Preset Output Modes FB Input Bias Current FBSEL not connected -0.1 0.01 +0.1 A SS (REFERENCE OUTPUT) MAX1974 0.75 SS Voltage V MAX1973 1.25 2 MAX1973/MAX1974