MAX1858A/MAX1875A/MAX1876A 19-2966 Rev 0 10/03 Dual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR General Description Features The MAX1858A/MAX1875A/MAX1876A dual, synchro- 4.5V to 23V Input Supply Range nized, step-down controllers generate two outputs from 0 to 18V Output Voltage Range (Up to 10A) input supplies ranging from 4.5V to 23V. Each output is adjustable from sub-1V to 18V and supports loads of 10A Adjustable Lossless Foldback Current Limit or higher. Input voltage ripple and total RMS input ripple Adjustable 100kHz to 600kHz Switching current are reduced by synchronized 180 out-of-phase operation. Frequency The switching frequency is adjustable from 100kHz to Optional Synchronization 600kHz with an external resistor. Alternatively, the con- Clock Output for Master/Slave Synchronization troller can be synchronized to an external clock gener- ated by another MAX1858A/MAX1875A/MAX1876A or a 4 x 90 Out-of-Phase Step-Down Converters system clock. One MAX1858A/MAX1875A/MAX1876A (Using Two Controllers, Figure 7) can be set to generate an in-phase, or 90 out-of- Prebias Startup (MAX1875A/MAX1876A) phase, clock signal for synchronization with additional controllers. This allows two controllers to operate either Power Sequencing (MAX1858A) as an interleaved two- or four-phase system with each RST Output with 140ms Minimum Delay output shifted by 90. The MAX1858A/MAX1875A/ (MAX1858A/MAX1876A) MAX1876A feature soft-start. The MAX1858A also fea- tures first-on/last-off power sequencing and soft-stop. Fixed-Frequency Pulse-Width Modulation (PWM) The MAX1858A/MAX1875A/MAX1876A eliminate the Operation need for current-sense resistors by utilizing the low-side MOSFETs on-resistance as a current-sense element. Ordering Information This protects the DC-DC components from damage dur- ing output-overload conditions or output short-circuit PART TEMP RANGE PIN-PACKAGE faults without requiring a current-sense resistor. MAX1858AEEG -40C to +85C 24 QSOP Adjustable foldback current limit reduces power dissipa- MAX1875AEEG -40C to +85C 24 QSOP tion during short-circuit conditions. The MAX1858A/ MAX1876AEEG -40C to +85C 24 QSOP MAX1876A include a power-on reset (POR) output to sig- nal the system when both outputs reach regulation. The MAX1858A/MAX1875A/MAX1876A ensure that the Pin Configuration output voltage does not swing negative when the input power is removed or when EN is driven low. The MAX1875A/MAX1876A also allow prebias startup with- TOP VIEW out discharging the output. COMP2 1 24 EN The MAX1858A/MAX1875A/MAX1876A are available in a FB2 2 23 DH2 24-pin QSOP package. Use the MAX1875 evaluation kit ILIM2 3 22 LX2 or the MAX1858 evaluation kit to evaluate the OSC 4 21 BST2 MAX1858A/MAX1875A/MAX1876A. V+ 5 20 DL2 Applications MAX1858A REF 6 19 V L Network Power Supplies MAX1875A GND 7 18 PGND MAX1876A Telecom Power Supplies CKO 8 17 DL1 DSP, ASIC, and FPGA Power Supplies SYNC 9 16 BST1 Set-Top Boxes ILIM1 10 15 LX1 Broadband Routers FB1 11 14 DH1 Servers COMP1 12 13 RST (N.C.) Desknote Computers () ARE FOR THE MAX1875A ONLY QSOP 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 AVAILABLEDual 180 Out-of-Phase Buck Controllers with Sequencing/Prebias Startup and POR ABSOLUTE MAXIMUM RATINGS V+ to GND..............................................................-0.3V to +25V FB1, FB2, RST, SYNC, EN to GND...........................-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V VL to GND Short Circuit .............................................Continuous V to GND ..................-0.3V to the lower of +6V and (V+ + 0.3V) REF to GND Short Circuit...........................................Continuous L BST1, BST2 to GND ...............................................-0.3V to +30V Continuous Power Dissipation (T = +70C) A LX1 to BST1..............................................................-6V to +0.3V 24-Pin QSOP (derate 9.4mW/C above +70C)...........762mW LX2 to BST2..............................................................-6V to +0.3V Operating Temperature Range ...........................-40C to +85C DH1 to LX1 ..............................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C BST1 DH2 to LX2 ..............................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +150C BST2 DL1, DL2 to PGND........................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C L CKO, REF, OSC, ILIM1, ILIM2, COMP1, COMP2 to GND ..........................-0.3V to (V + 0.3V) L 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, EN = ILIM = V , SYNC = GND, I = 0mA, PGND = GND, C = 0.22F, C = 4.7F (ceramic), R = 60k , L VL REF VL OSC compensation components for COMP are from Figure 1, T = -40C to +85C (Note 1), unless otherwise noted.) A PARAMETER CONDITIONS MIN TYP MAX UNITS GENERAL (Note 2) 4.5 23.0 V+ Operating Range V V = V+ (Note 2) 4.5 5.5 L V+ Operating Supply Current V unloaded, no MOSFETs connected 3.5 6 mA L V + Standby Supply Current EN = LX = FB = 0V 0.3 0.6 mA Thermal Shutdown Rising temperature, typical hysteresis = 10C +160 C ILIM = V 75 100 125 L Current-Limit Threshold PGND - LX mV R = 100k 32 50 62 ILIM R = 600k 225 300 375 ILIM V REGULATOR L Output Voltage 5.5V < V+ < 23V, 1mA < I < 50mA 4.75 5 5.25 V LOAD V Undervoltage Lockout Rising L 4.1 4.2 4.3 V Trip Level V Undervoltage Lockout L (Note 3) 100 mV Hysteresis REFERENCE Output Voltage I = 0A 1.98 2.00 2.02 V REF Reference Load Regulation 0A < I < 50A 0 4 10 mV REF SOFT-START Internal 6-bit DAC for one converter to ramp from 0V to DC-DC Digital Ramp Period 1024 full scale (Note 4) clocks Soft-Start Steps 64 Steps FREQUENCY 0C to +85C 84 100 115 Low End of Range R = 60k kHz OSC -40C to +85C 80 100 120 High End of Range R = 10k 540 600 660 kHz OSC DH Minimum Off-Time R = 10k 250 303 ns OSC 2 MAX1858A/MAX1875A/MAX1876A