MAX1858 19-2432 Rev 0 7/02 Dual 180 Out-of-Phase PWM Step-Down Controller with Power Sequencing and POR General Description Features The MAX1858 dual, synchronized, step-down controller Two Independent Output Voltages generates two outputs from input supplies ranging from 180 Out-of-Phase Operation 4.75V to 23V. Each output is adjustable from sub-1V to 18V and supports loads of 10A or higher. Input voltage 90 Out-of-Phase Operation ripple and total RMS input ripple current are reduced by (Using Two MAX1858s) synchronized 180 out-of-phase operation. Foldback Current Limit The switching frequency is adjustable from 100kHz to 4.75V to 23V Input Supply Range 600kHz with an external resistor. Alternatively, the con- troller can be synchronized to an external clock gener- 0 to 18V Output-Voltage Range (Up to 10A) ated to another MAX1858 or a system clock. One >90% Efficiency MAX1858 can be set to generate an in-phase, or 90 Fixed-Frequency Pulse-Width Modulation (PWM) out-of-phase, clock signal for synchronization with addi- tional controllers. This allows two controllers to operate Operation either as an interleaved two- or four-phase system with Adjustable 100kHz to 600kHz Switching each output shifted by 90. The device also features Frequency first-on/last-off power sequencing for compatibility External SYNC Input with DSPs, ASICs, and FPGAs, as well as soft-start and soft-stop to ensure reliable and repeatable power Clock Output for Master/Slave Synchronization sequencing. Power-On/-Off Sequencing with Soft-Start and The MAX1858 eliminates the need for current-sense Soft-Stop resistors by utilizing the low-side MOSFETs on-resistance RST Output with 140ms Minimum Delay as a current-sense element. This protects the DC-DC components from damage during output-overload condi- Lossless Current Limit (No Sense Resistor) tions or when output short-circuit faults without requiring a current-sense resistor. Adjustable foldback current limit reduces power dissipation during short-circuit condition. Ordering Information A power-on reset output signals the system when both outputs reach regulation. PART TEMP RANGE PIN-PACKAGE The MAX1858 is available in a 24-pin QSOP package. MAX1858EEG -40C to +85C 24 QSOP An evaluation kit is available to speed designs. Applications Pin Configuration Network Power Supplies TOP VIEW Telecom Power Supplies COMP2 1 24 EN DSP, ASIC, and FPGA Power Supplies FB2 2 23 DH2 Set-Top Boxes ILIM2 3 22 LX2 Broadband Routers OSC 4 21 BST2 Servers V+ 5 20 DL2 REF 6 19 V L MAX1858 GND 7 18 PGND CKO 8 17 DL1 SYNC 9 16 BST1 Typical Operating Circuit appears at end of data sheet. ILIM1 10 15 LX1 FB1 11 14 DH1 COMP1 12 13 RST 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 MANUAL AVAILABLEDual 180 Out-of-Phase PWM Step-Down Controller with Power Sequencing 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 V to GND Short Circuit..............................................Continuous L 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) BST1 Junction Temperature......................................................+150C 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) L Lead Temperature (soldering, 10s) .................................+300C 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) 4.75 23 V+ Operating Range V V = V+ (Note 2) 4.75 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 R = 60k 0.3 0.6 mA OSC Thermal Shutdown Rising temperature, typical hysteresis = 10C 160 C ILIM = V 75 100 125 L Current-Limit Threshold PGND - LX R = 100k 32 50 62 mV 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 L 4.4 4.55 4.7 V Trip Level 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 3) 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 MAX1858