MAX1864/MAX1865 19-2030 Rev 0 4/01 xDSL/Cable Modem Triple/Quintuple Output Power Supplies General Description Features The MAX1864/MAX1865 power-supply controllers are 4.5V to 28V Input Voltage Range designed to address cost-conscious applications such Master DC-DC Step-Down Converter as cable modem Consumer Premise Equipment (CPE), Preset 3.3V or Adjustable (1.236V to 0.8 V ) IN xDSL CPE, and set-top boxes. Operating off a low-cost, Output Voltage unregulated DC supply (such as a wall adapter output), the MAX1864 generates three positive outputs, and the Fixed-Frequency (100kHz/200kHz) PWM MAX1865 generates four positive outputs and one neg- Controller ative output to provide a cost-effective system power No Current-Sense Resistor supply. Adjustable Current Limit The MAX1864 includes a current-mode synchronous 95% Efficient step-down controller and two positive regulator gain blocks. The MAX1865 has one additional positive gain Two (MAX1864)/Four (MAX1865) Analog block and one negative regulator gain block. The main Gain Blocks synchronous step-down controller generates a Positive Analog Blocks Drive Low-Cost PNP high-current output that is preset to 3.3V or adjustable Pass Transistors to Build Positive Linear from 1.236V to 0.8 V with an external resistive- IN Regulators divider. The 100kHz/200kHz operating frequency allows the use of low-cost aluminum-electrolytic capaci- Negative Analog Block (MAX1865) Drives a tors and low-cost power magnetics. Additionally, the Low-Cost NPN Pass Transistor to Build a MAX1864/MAX1865 step-down controllers sense the Negative Linear Regulator voltage across the low-side MOSFETs on-resistance to Power-Good Indicator efficiently provide the current-limit signal, eliminating Soft-Start Ramp for All Positive Regulators the need for costly current-sense resistors. The MAX1864/MAX1865 generate additional supply Ordering Information rails at low cost. The positive regulator gain blocks use an external PNP pass transistor to generate low-voltage TEMP. PIN- f OSC PART rails directly from the main step-down converter (such RANGE PACKAGE (kHz) as 2.5V or 1.8V from the main 3.3V output) or higher MAX1864TEEE -40C to +85C 16 QSOP 200 voltages using coupled windings from the step-down converter (such as 5V, 12V, or 15V). The MAX1865s MAX1864UEEE -40C to +85C 16 QSOP 100 negative gain block uses an external NPN pass transis- MAX1865TEEP -40C to +85C 20 QSOP 200 tor in conjunction with a coupled winding to generate MAX1865UEEP -40C to +85C 20 QSOP 100 -5V, -12V, or -15V. All output voltages are externally adjustable, providing maximum flexibility. Additionally, the MAX1864/ Pin Configurations MAX1865 feature soft-start for the step-down converter and all the positive linear regulators, and have a power- TOP VIEW good output that monitors all of the output voltages. POK 1 16 IN COMP 2 15 VL Applications OUT 3 14 BST xDSL, Cable, and ISDN Modems FB 4 MAX1864 13 DH Set-Top Boxes B2 5 12 LX FB2 6 11 DL Wireless Local Loop B3 7 10 GND FB3 8 9 ILIM 16 QSOP Pin Configurations continued at end of data sheet. 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 AVAILABLExDSL/Cable Modem Triple/Quintuple Output Power Supplies ABSOLUTE MAXIMUM RATINGS IN, B2, B3, B4 to GND............................................-0.3V to +30V Continuous Power Dissipation (T = +70C) A B5 to OUT...............................................................-20V to +0.3V 16-Pin QSOP (derate 8.3mW/C above +70C)...........666mW VL, POK, FB, FB2, FB3, FB4, FB5 to GND...............-0.3V to +6V 20-Pin QSOP (derate 9.1mW/C above +70C)...........727mW LX to BST..................................................................-6V to +0.3V Operating Temperature Range ...........................-40C to +85C BST to GND............................................................-0.3V to +36V Junction Temperature......................................................+150C DH to LX....................................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +150C BST DL, OUT, COMP, ILIM to GND......................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C L VL Output Current...............................................................50mA VL Short Circuit to GND...................................................100ms 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 = 12V, ILIM = FB = GND, V - V = 5V, T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) IN BST LX A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Operating Input Voltage Range V 4.5 28 V IN (Note 1) V = 0, V = 4V, FB OUT MAX1864 1.0 2 Quiescent Supply Current I V = V = V = 1.5V, mA IN FB2 FB3 FB4 MAX1865 1.4 3 V = -0.1V FB5 VL REGULATOR Output Voltage VL 6V < V < 28V, 0.1mA < I < 20mA 4.75 5.00 5.25 V IN LOAD Power-Supply Rejection PSRR V = 6V to 28V 3 % IN Undervoltage Lockout Trip Level V VL rising, 3% hysteresis (typ) 3.2 3.5 3.8 V UVLO Minimum Bypass Capacitance C 10m < ESR < 500m 1F BYP(MIN) DC-DC CONTROLLER Output Voltage (Preset Mode) V FB = GND 3.272 3.314 3.355 V OUT Typical Output Voltage Range V 1.236 0.8 x V V OUT IN (Adjustable Mode) (Note 2) FB Set Voltage V FB = COMP 1.221 1.236 1.252 V SET (Adjustable Mode) FB Dual Mode Threshold 50 100 150 mV FB Input Leakage Current I V = 1.5V 0.01 100 nA FB FB FB to COMP Transconductance g FB = COMP, I = 5A 70 100 140 S m COMP Current-Sense Amplifier Voltage A V - V = 250mV 4.46 4.9 5.44 V/V LIM IN LX Gain Current-Limit Threshold V V = 5.0V 190 250 310 mV VALLEY ILIM (Internal Mode) Current-Limit Threshold V V = 2.5V 440 530 620 mV VALLEY ILIM (External Mode) Dual Mode is a trademark of Maxim Integrated Products, Inc. 2 MAX1864/MAX1865