MAX796/MAX797/MAX799 19-0221 Rev 4 9/05 Step-Down Controllers with Synchronous Rectifier for CPU Power General Description Features The MAX796/MAX797/MAX799 high-performance, step- 96% Efficiency down DC-DC converters with single or dual outputs 4.5V to 30V Input Range provide main CPU power in battery-powered systems. 2.5V to 6V Adjustable Output These buck controllers achieve 96% efficiency by using synchronous rectification and Maxims proprietary Idle Preset 3.3V and 5V Outputs (at up to 10A) Mode control scheme to extend battery life at full-load Multiple Regulated Outputs (up to 10A) and no-load outputs. Excellent dynamic +5V Linear-Regulator Output response corrects output transients caused by the latest dynamic-clock CPUs within five 300kHz clock cycles. Precision 2.505V Reference Output Unique bootstrap circuitry drives inexpensive N-channel Automatic Bootstrap Circuit MOSFETs, reducing system cost and eliminating the 150kHz/300kHz Fixed-Frequency PWM Operation crowbar switching currents found in some PMOS/NMOS switch designs. Programmable Soft-Start The MAX796/MAX799 are specially equipped with a sec- 375A Typ Quiescent Current (V = 12V, V = 5V) IN OUT ondary feedback input (SECFB) for transformer-based 1A Typ Shutdown Current dual-output applications. This secondary feedback path improves cross-regulation of positive (MAX796) or nega- tive (MAX799) auxiliary outputs. The MAX797 has a logic-controlled and synchronizable Ordering Information fixed-frequency pulse-width-modulating (PWM) operating mode, which reduces noise and RF interference in sensi- PART TEMP RANGE PIN-PACKAGE tive mobile-communications and pen-entry applications. MAX796CPE 0C to +70C 16 Plastic DIP The SKIP override input allows automatic switchover to MAX796CSE 0C to +70C 16 Narrow SO idle-mode operation (for high-efficiency pulse skipping) at MAX796C/D 0C to +70C Dice* light loads, or forces fixed-frequency mode for lowest noise MAX796EPE -40C to +85C 16 Plastic DIP at all loads. MAX796ESE -40C to +85C 16 Narrow SO The MAX796/MAX797/MAX799 are all available in 16- MAX796MJE -55C to +125C 16 CERDIP pin DIP and narrow SO packages. See the table below to compare these three converters. Ordering Information continued at end of data sheet. *Contact factory for dice specifications. PART MAIN OUTPUT SPECIAL FEATURE Regulates positive secondary MAX796 3.3V/5V or adj voltage (such as +12V) Pin Configuration MAX797 3.3V/5V or adj Logic-controlled low-noise mode Regulates negative secondary MAX799 3.3V/5V or adj TOP VIEW voltage (such as -5V) SS DH 1 16 Applications LX (SECFB) SKIP 2 15 BST REF 3 Notebook and Subnotebook Computers 14 GND 4 MAX796 DL 13 PDAs and Mobile Communicators MAX797 5 PGND SYNC 12 MAX799 Cellular Phones VL SHDN 6 11 V+ FB 7 10 CSH 8 9 CSL Idle Mode is a trademark of Maxim Integrated Products. DIP/SO ( ) ARE FOR MAX796/ MAX799. U 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 AVAILABLEStep-Down Controllers with Synchronous Rectifier for CPU Power ABSOLUTE MAXIMUM RATINGS V+ to GND.................................................................-0.3V, +36V VL Output Current...............................................................50mA GND to PGND........................................................................2V Continuous Power Dissipation (T = +70C) A VL to GND ...................................................................-0.3V, +7V SO (derate 8.70mW/C above +70C)........................696mW BST to GND...............................................................-0.3V, +36V Plastic DIP (derate 10.53mW/C above +70C) .........842mW DH to LX...........................................................-0.3V, BST + 0.3V CERDIP (derate 10.00mW/C above +70C)..............800mW LX to BST.....................................................................-7V, +0.3V Operating Temperature Ranges SHDN to GND............................................................-0.3V, +36V MAX79 C ......................................................0C to +70C SYNC, SS, REF, FB, SECFB, SKIP, DL to GND..-0.3V, VL + 0.3V MAX79 E ....................................................-40C to +85C CSH, CSL to GND .......................................................-0.3V, +7V MAX79 MJE .................................................-55C to +125C VL Short Circuit to GND..............................................Momentary Storage Temperature Range .............................-65C to +160C REF Short Circuit to GND...........................................Continuous Lead Temperature (soldering, 10s) .....................................+300 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+ = 15V, GND = PGND = 0V, I = I = 0A, T = 0C to +70C for MAX79 C, T = 0C to +85C for MAX79 E, VL REF A A T = -55C to +125C for MAX79 M, unless otherwise noted.) A PARAMETER CONDITIONS MIN TYP MAX UNITS +3.3V AND +5V STEP-DOWN CONTROLLERS MAX79 C 4.5 30 Input Supply Range V MAX79 E/M 5.0 30 0mV < (CSH-CSL) < 80mV, FB = VL, 6V < V+ < 30V, 5V Output Voltage (CSL) 4.85 5.10 5.25 V includes line and load regulation 0mV < (CSH-CSL) < 80mV, FB = 0V, 4.5V < V+ < 30V, 3.3V Output Voltage (CSL) 3.20 3.35 3.46 V includes line and load regulation Nominal Adjustable Output External resistor divider REF 6 V Voltage Range Feedback Voltage (CSH-CSL) = 0V 2.43 2.505 2.57 V 0mV < (CSH-CSL) < 80mV 2.5 Load Regulation % 25mV < (CSH-CSL) < 80mV 1.5 Line Regulation 6V < V+ < 30V 0.04 0.06 %/V CSH-CSL, positive 80 100 120 Current-Limit Voltage mV CSH-CSL, negative -50 -100 -160 SS Source Current 2.5 4.0 6.5 A SS Fault Sink Current 2.0 mA FLYBACK/PWM CONTROLLER Falling edge, hysteresis = 15mV (MAX796) 2.45 2.505 2.55 SECFB Regulation Setpoint V Falling edge, hysteresis = 20mV (MAX799) -0.05 0 0.05 INTERNAL REGULATOR AND REFERENCE VL Output Voltage SHDN = 2V, 0mA < I < 25mA, 5.5V < V+ < 30V 4.7 5.3 V VL VL Fault Lockout Voltage Rising edge, hysteresis = 15mV 3.8 4.1 V VL/CSL Switchover Voltage Rising edge, hysteresis = 25mV 4.2 4.7 V 2 MAX796/MAX797/MAX799