MAX1875/MAX1876 19-2431 Rev 0 7/02 Dual 180 Out-of-Phase PWM Step- Down Controllers with POR General Description Features The MAX1875/MAX1876 dual, synchronized, step-down Two Independent Output Voltages controller generates two outputs from input supplies 180 Out-of-Phase Operation ranging from 4.75V to 23V. Each output is adjustable from sub-1V to 18V and supports loads of 10A or higher. Input 90 Out-of-Phase Operation voltage ripple and total RMS input ripple current are (Using Two MAX1875/MAX1876s) reduced by synchronized 180 out-of-phase operation. Foldback Current Limit The switching frequency is adjustable from 100kHz to 600kHz with an external resistor. Alternatively, the con- 4.75V to 23V Input Supply Range troller can be synchronized to an external clock gener- 0 to 18V Output-Voltage Range (Up to 10A) ated to another MAX1875/MAX1876 or a system clock. One MAX1875/MAX1876 can be set to generate an in- >90% Efficiency phase, or 90 out-of-phase, clock signal for synchro- Fixed-Frequency Pulse-Width Modulation (PWM) nization with additional controllers. This allows two Operation controllers to operate either as an interleaved two- or four-phase system with each output shifted by 90. Adjustable 100kHz to 600kHz Switching These devices also feature soft-start and soft-stop. Frequency The MAX1875/MAX1876 eliminate the need for current- External SYNC Input sense resistors by utilizing the low-side MOSFETs on- resistance as a current-sense element. This protects Clock Output for Master/Slave Synchronization the DC-DC components from damage during output- Soft-Start and Soft-Stop overload conditions or when output short-circuit faults without requiring a current-sense resistor. Adjustable RST Output with 140ms Minimum Delay (MAX1876) foldback current limit reduces power dissipation during Lossless Current Limit (No Sense Resistor) short-circuit conditions. The MAX1876 includes a power-on reset output to signal the system when both Ordering Information outputs reach regulation. The MAX1875/MAX1876 are available in a 24-pin QSOP PART TEMP RANGE PIN-PACKAGE package. An evaluation kit is available to speed designs. MAX1875EEG -40C to +85C 24 QSOP MAX1876EEG -40C to +85C 24 QSOP Applications Network Power Supplies Pin Configuration Telecom Power Supplies TOP VIEW DSP, ASIC, and FPGA Power Supplies COMP2 1 24 EN Set-Top Boxes FB2 2 23 DH2 Broadband Routers ILIM2 3 22 LX2 Servers OSC 4 21 BST2 V+ 5 20 DL2 REF 6 MAX1875/ 19 V L MAX1876 GND 7 18 PGND Typical Operating Circuit appears at end of data sheet. CKO 8 17 DL1 SYNC 9 16 BST1 ILIM1 10 15 LX1 FB1 11 14 DH1 COMP1 12 13 RST (MAX1876 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 PWM Step- Down Controllers with 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) 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 mV L Current-Limit Threshold PGND - LX R = 100k 32 50 62 mV ILIM R = 600k 225 300 375 mV 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 MAX1875/MAX1876