MAX8543/MAX8544 19-3155 Rev 0 5/04 Step-Down Controllers with Prebias Startup, Lossless Sensing, Synchronization, and OVP General Description Features The MAX8543/MAX8544 current-mode, constant-fre- Prebias Startup/Monotonic quency PWM buck controllers operate from a 3V to 1% Output Accuracy 13.2V input supply and generate adjustable 0.8V to 0.9 x V output voltages at loads up to 25A. They feature IN Ceramic, Polymer, or Electrolytic Capacitors adjustable switching frequency and synchronization for 200kHz to 1MHz Adjustable Frequency noise-sensitive applications. The MAX8543/MAX8544 can start with (or without) a pre- 160kHz to 1.2MHz Synchronization existing bias on the output, without discharging the out- Lossless, Foldback Current Limit put. This feature simplifies tracking supply designs for core and I/O applications and redundant supply designs. Overvoltage Protection The MAX8543/MAX8544 use the DC resistance of the Enable (On/Off) output inductor as the current-sense element for loss- Adjustable Soft-Start less, low-cost current sensing. The current-sense threshold can be set to four discrete levels to accom- MAX8544 modate inductors with different DC resistance values. Latch-Off/Autorecovery The MAX8544 features a power-OK monitor and two Power-OK Monitor MAX8544 controllers that can operate at 180 out-of- Out-of-Phase Clock Output phase for dual-output applications. Applications Ordering Information Base Stations PART TEMP RANGE PIN-PACKAGE Networks and Telecom MAX8543EEE -40C to +85C 16 QSOP Storage MAX8544EEP -40C to +85C 20 QSOP Servers Pin Configurations appear at end of data sheet. Typical Operating Circuit INPUT 3V TO 13.2V V = 3V IN TO 5.5V IN ON VL OFF EN FSYNC BST OPTIONAL SS SYNCHRONIZATION OUTPUT DH 0.8V TO 0.9 x V IN MAX8543 UP TO 25A LX COMP DL ILIM CS+ GND PGND CS- POK (MAX8544) FB 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.Step-Down Controllers with Prebias Startup, Lossless Sensing, Synchronization, and OVP ABSOLUTE MAXIMUM RATINGS IN, EN, CS+, CS- to GND .......................................-0.3V to +14V Continuous Power Dissipation (T = +70C) A BST, DH to LX ..........................................................-0.3V to +6V 16-Pin QSOP (derate 8.3mW/C above +70C) .......666.7mW BST to GND............................................................-0.3V to +20V 20-Pin QSOP (derate 9.1mW/C above +70C) .......727.3mW DL, COMP, ILIM2, SS, SYNCO, Operating Temperature Range ...........................-40C to +85C FSYNC to GND .......................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C VL VL, FB, POK, ILIM1, ILIM, MODE to GND................-0.3V to +6V Storage Temperature Range .............................-65C to +150C PGND to GND .......................................................-0.3V to +0.3V Lead Temperature (soldering, 10s) .................................+300C 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 = 13.2V, V - V = 5V, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) IN BST LX A A PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Input Voltage Range VL connected to IN for V < 5.5V 3.0 13.2 V IN Quiescent Supply Current V = 0.9V, no switching 2 3 mA FB EN = GND, MODE = GND, IN not connected to VL 10 Shutdown Supply Current A EN = GND, VL = IN, MODE = GND 20 VL Undervoltage-Lockout Trip Level V rising, typical hysteresis is 80mV 2.52 2.7 2.88 V VL Output Voltage Adjust Range (V ) (Note 1) 0.8 V OUT VL Output Voltage 5.5V < V < 13.2V, 1mA < I < 75mA 4.5 5 5.5 V IN VL VL Output Current 75 mA VOLTAGE REFERENCE SS Shutdown Resistance From SS to GND, V = 0V 20 100 EN SS Soft-Start Current V = 0.625V 14 24 34 A REF Soft-Start Ramp Time Output from 0% to 100%, C = 0.01F to 1F 33 ms/F REF ERROR AMPLIFIER FB Regulation Voltage 0.792 0.8 0.808 V Transconductance 70 110 160 S COMP Shutdown Resistance From COMP to GND, V = 0V 20 100 EN FB Input Leakage Current V = 0.9V 5 100 nA FB FB Input Common-Mode Range -0.1 +0.9 V CURRENT-SENSE AMPLIFIER V = 0V 8.8 11 13.2 ILIM1 V = (1/3)V 4.8 6 7.2 ILIM1 VL Voltage Gain V = 0 to 13V V / V OUT V = (2/3)V 3.2 4 4.8 ILIM1 VL V = V 2.4 3 3.6 ILIM1 VL CURRENT LIMIT ILIM2 Output Current (MAX8544 Only) R = 50k to 200k 4.5 5 5.5 A ILIM2 ILIM1 Input Current V = 0V or V -1 +1 A ILIM1 VL 2 MAX8543/MAX8544