MAX1536 19-2729 Rev 1 8/05 3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step- Down Regulator with Dynamic Output Voltage Control General Description Features The MAX1536 constant-off-time, pulse-width-modulated Dynamically Selectable Output Voltage from (PWM) step-down DC-to-DC converter is ideal for use in +0.7V to V IN +5.0V and +3.3V to low voltages for notebook and sub- Internal PMOS/NMOS Switches notebook computers. The MAX1536 features an internal 54m /47m On-Resistance at V = +4.5V IN PMOS power switch and internal synchronous rectifica- 63m /53m On-Resistance at V = +3.0V IN tion for high efficiency and reduced component count. No +3.0V to +5.5V Input Voltage Range external Schottky diode is required across the internal synchronous rectifier switch. The internal 54m PMOS 1.4MHz Maximum Switching Frequency power switch and 47m NMOS synchronous-rectifier 2V 0.75% Reference Output switch easily deliver continuous load currents up to 3.6A. Constant-Off-Time PWM Operation The MAX1536 produces dynamically adjustable output voltages for chipsets and graphics processor cores using Selectable Idle Mode/PWM Operation at Light a logic-level control signal. The MAX1536 achieves effi- Loads ciencies as high as 96%. 100% Duty Factor in Dropout The MAX1536 uses a unique current-mode, constant-off- Digital Soft-Start Inrush Current Limiting time, PWM control scheme. It has selectable Idle <1A Typical Shutdown Supply Current TM Mode to maintain high efficiency during light-load <750A Quiescent Supply Current operation, or fixed-PWM mode for low output ripple. The programmable constant-off-time architecture allows a Thermal Shutdown wide range of switching frequencies up to 1.4MHz, opti- 1% V Accuracy Over Line and Load OUT mizing performance trade-offs between efficiency, output External Reference Input switching noise, component size, and cost. The MAX1536 features a digital soft-start to limit surge cur- Power-Good Window Comparator rents during startup, a 100% duty-cycle mode for low- Selectable Power-Good Blanking Time During dropout operation, and a low-power shutdown mode that Output-Voltage Transition disconnects the input from the output and reduces supply current below 1A. The MAX1536 is available in a 28-pin Ordering Information thin QFN package with an exposed backside pad. PART TEMP RANGE PIN-PACKAGE Applications o o MAX1536ETI -40 C to +85 C 28 Thin QFN 5mm x 5mm Chipset/Graphics Cores Notebook Computers o o MAX1536ETI+ -40 C to +85 C 28 Thin QFN 5mm x 5mm with Dual-Supply Voltages DDR Memory Termination +Denotes lead-free package. Active Termination Buses Pin Configuration Minimal Operating Circuit TOP VIEW V IN V OUT 21 20 19 18 17 16 15 +3.0V TO +5.5V +0.7V TO V IN IN LX PGND 22 14 REF PGND 23 13 REFIN FB OD LX 24 12 V CC PGND OD N.C. 25 11 SHDN AGND MAX1536 10 GATE LX 26 MAX1536 REF COMP PGND 27 9 TOFF EXPOSED PADDLE PGOOD N.C. PGND 28 8 REFIN TOFF 1 2 3 4 5 6 7 SKIP THIN QFN A SIGN WILL REPLACE THE FIRST PIN INDICATOR ON LEAD-FREE PACKAGES. Idle Mode is a trademark of Maxim Integrated Products, Inc. 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 AVAILABLE LX LX IN IN IN IN SHDN PGOOD SKIP FBLANK V FB CC COMP AGND3.6A, 1.4MHz, Low-Voltage, Internal-Switch Step- Down Regulator with Dynamic Output Voltage Control ABSOLUTE MAXIMUM RATINGS Continuous Power Dissipation (T = +70C) V , IN, SHDN, SKIP to AGND ................................-0.3V to +6V CC A 28-Pin Thin QFN (derated 20.8mW/C above +70C OD, OD, GATE, PGOOD to AGND...........................-0.3V to +6V 2 COMP, FB, REF to AGND.........................................-0.3V to +6V part mounted on 1in of 1oz copper).........................1667mW Operating Temperature Range ...........................-40C to +85C TOFF, REFIN, FBLANK to AGND .............................-0.3V to +6V IN to V ...............................................................-0.3V to +0.3V Junction Temperature......................................................+150C CC Storage Temperature Range .............................-65C to +150C PGND to AGND.................................................... -0.3V to +0.3V Lead Temperature (soldering, 10s) .................................+300C LX to PGND ................................................ -0.3V to (V + 0.3V) IN LX Current (Note 1).............................................................5.7A REF Short Circuit to AGND.........................................Continuous Note 1: LX has clamp diodes to PGND and IN. Thermal limits dictate the maximum continuous current through these diodes. 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 = V = +3.3V, V = +1.5V, SKIP = AGND, T = 0C to +85C, unless otherwise noted. Typical IN CC SHDN REFIN A values are at T = +25C.) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS PWM CONTROLLER Input Voltage V , V 3.0 5.5 V IN CC Output Adjust Range V V V V OUT REFIN IN T = +25C to +85C -3 0 +3 A V - V = V = +3.0V to FB CC IN Feedback Voltage Accuracy mV V +5.5V, I = 0 REFIN LOAD T = 0C to +85C -4 0 +4 A I = 0 to 3.5A, V = V = +3.0V to +5.5V, LOAD CC IN Feedback Load Regulation 0.3 % SKIP = V CC FB Input Bias Current I V = 1.01 V -50 +50 nA FB FB REFIN Dropout V V = V = +3.0V, I = 3A, FB = AGND 189 330 mV DO CC IN LOAD V = V = +4.5V, I = 0.5A 54 90 CC IN LOAD PMOS Switch On-Resistance R m PMOS V = V = +3.0V, I = 0.5A 63 110 CC IN LOAD V = V = +4.5V, I = 0.5A 47 80 CC IN LOAD NMOS Switch On-Resistance R m NMOS V = V = +3.0V, I = 0.5A 53 90 CC IN LOAD Maximum Output Current I (Note 2) 3.6 A OUT (R M S ) Current-Limit Threshold I (Note 3) 4.0 4.8 5.5 A LIMIT Idle Mode Current Threshold SKIP = AGND 0.21 0.60 1.00 A Zero-Cross Current Threshold SKIP = AGND 200 mA Switching Frequency f (Note 2) 1.4 MHz SW R = 30.1k 0.24 0.30 0.37 TOFF Off-Time t V 0.3 V R = 110k 0.85 1.00 1.15 s OFF FB REFIN TOFF R = 499k 3.8 4.5 5.2 TOFF Extended Off-Time V < 0.3 V 4 t s FB REFIN OFF On-Time t (Note 2) 0.3 s ON Soft-Start Time (Note 3) 3 256 Cycles Quiescent Supply Current I + I SKIP = AGND, V = 1.01 V 350 750 A CC IN FB REFIN 2 MAX1536