MAX1637 19-1321 Rev 2 8/05 Miniature, Low-Voltage, Precision Step-Down Controller General Description Features The MAX1637 synchronous, buck, switch-mode power- 2% DC Accuracy supply controller generates the CPU supply voltage in 0.1% (typ) DC Load Regulation battery-powered systems. The MAX1637 is a stripped- down version of the MAX1636 in a smaller 16-pin QSOP Adjustable Switching Frequency to 350kHz package. The MAX1637 is intended to be powered sep- Idle Mode Pulse-Skipping Operation arately from the battery by an external bias supply (typi- cally the +5V system supply) in applications where the 1.10V to 5.5V Adjustable Output Voltage battery exceeds 5.5V. The MAX1637 achieves excellent 3.15V Minimum IC Supply Voltage (at V pin) CC DC and AC output voltage accuracy. This device can operate from a low input voltage (3.15V) and delivers the Internal Digital Soft-Start excellent load-transient response needed by upcoming 1.1V 2% Reference Output generations of dynamic-clock CPUs. Using synchronous rectification, the MAX1637 achieves 1A Total Shutdown Current up to 95% efficiency. Efficiency is greater than 80% over Output Overvoltage Crowbar Protection a 1000:1 load-current range, which extends battery life in system-suspend or standby mode. Excellent dynamic Output Undervoltage Shutdown (foldback) response corrects output load transients caused by the Tiny 16-Pin QSOP Package latest dynamic-clock CPUs within five 300kHz clock cycles. Powerful 1A on-board gate driv-ers ensure fast Ordering Information external N-channel MOSFET switching. PART TEMP RANGE PIN-PACKAGE The MAX1637 features a logic-controlled and synchro- MAX1637EEE 40C to +85C 16 QSOP nizable, fixed-frequency, pulse-width-modulation (PWM) operating mode. This reduces noise and RF interference MAX1637EEE+ 40C to +85C 16 QSOP in sensitive mobile-communications and pen-entry appli- +Denotes lead-free package. cations. Asserting the SKIP pin enables fixed-frequency mode, for lowest noise under all load conditions. For a Typical Operating Circuit stand-alone device that includes a +5V VL linear regula- tor and low-dropout capabilities, refer to the MAX1636 V V BIAS BATT data sheet. Applications V V CC GG Notebook Computers Subnotebook Computers SHDN Handy-Terminals, PDAs MAX1637 Pin Configuration DH BST TOP VIEW CSH 1 16 SKIP LX OUTPUT CSL 2 15 LX DL CC FB 3 14 DH PGND CC 4 MAX1637 13 BST REF REF 5 12 PGND SKIP CSH SHDN 6 11 DL CSL SYNC SYNC 7 10 V GG GND FB GND 8 9 V CC QSOP A SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES. Idle Mode is a trademark of Maxim Integrated Products. 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 AVAILABLEMiniature, Low-Voltage, Precision Step-Down Controller ABSOLUTE MAXIMUM RATINGS GND to PGND .............................................................+2V to -2V REF Short-Circuit to GND ..............................................Indefinite LX, BST to GND......................................................-0.3V to +36V Operating Temperature Range ...........................-40C to +85C BST, DH to LX...........................................................-0.3V to +6V Continuous Power Dissipation (T = +70C) A V , V , CSL, CSH, SHDN to GND.......................-0.3V to +6V QSOP (derate 8.3mW/C above +70C)......................667mW CC GG DL to GND..................................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +160C GG REF, SKIP, SYNC, CC to GND ...................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C CC REF Output Current.............................................................20mA 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 (Circuit of Figure 1, V = V = 5V, SYNC = V , I = 0mA, T = 0C to +85C, unless otherwise noted. Typical values are at CC GG CC REF A T = +25C.) A PARAMETER CONDITIONS MIN TYP MAX UNITS SMPS CONTROLLER Input Voltage Range V , V 3.15 5.5 V CC GG FB tied to V , 0mV < (CSH - CSL) < 80mV, OUT Output Voltage 1.080 1.100 1.120 V includes line and load regulation V = 5V V 5.5 CC REF Output Adjustment Range V V = 3.3V V 3.6 CC REF CSH > CSL 80 100 120 Current-Limit Threshold mV CSH < CSL -145 -100 -55 V = V = 5V 1.5 2.5 CC GG Power Consumption Output not switching mW V = V = 3.3V 1 1.75 CC GG Shutdown Supply Current SHDN = GND, V = V 0.5 3 A CC GG FB Input Current V = V -50 50 nA FB REF Soft-Start Ramp Time 512 clocks SHDN to full current limit, four levels Idle-Mode Switchover Threshold CSH - CSL 20 30 40 mV AC Load Regulation CSH - CSL = 0mV to CSH - CSL = 100mV 2 % INTERNAL REFERENCE V Undervoltage Lockout Threshold Rising edge, hysteresis = 15mV 2.80 3.05 V CC V Undervoltage Lockout Threshold Rising edge, hysteresis = 15mV 2.80 3.05 V GG REF Output Voltage REF load = 0A 1.080 1.100 1.120 V REF Load Regulation REF load = 0A to 50A 10 mV REF Line Regulation V = 3.15V to 5.5V 3 mV CC OSCILLATOR SYNC = V 270 300 330 CC Oscillator Frequency kHz SYNC = GND 170 200 230 SYNC = V 89 92 CC Maximum Duty Factor % SYNC = GND 93 96 SYNC Input Pulse Width High 200 ns SYNC Input Pulse Width Low 200 ns SYNC Input Rise/Fall Time (Note 1) 200 ns SYNC Input Frequency Range 240 340 kHz 2 MAX1637