MAX8576MAX8579 19-3289 Rev 1 6/05 3V to 28V Input, Low-Cost, Hysteretic Synchronous Step-Down Controllers General Description Features The MAX8576MAX8579 synchronous PWM buck con- 3V to 28V Supply Voltage Range trollers use a hysteretic voltage-mode control algorithm 1.2% Accurate Over Temperature to achieve a fast transient response without requiring loop compensation. The MAX8576/MAX8577 contain an Adjustable Output Voltage Down to 0.6V internal LDO regulator allowing the controllers to func- 200kHz to 500kHz Switching Frequency tion from only one 3V to 28V input supply. The Adjustable Temperature-Compensated Hiccup MAX8578/MAX8579 do not contain the internal LDO and require a separate supply to power the IC when the Current Limit input supply is higher than 5.5V. The MAX8576 Lossless Peak Current Sensing MAX8579 output voltages are adjustable from 0.6V to Monotonic Startup into Prebias Output 0.9 x V at loads up to 15A. IN (MAX8576/MAX8578) Nominal switching frequency is programmable over the 200kHz to 500kHz range. High-side MOSFET sensing is Startup Overvoltage Protection used for adjustable hiccup current-limit and short-cir- (MAX8577/MAX8579) cuit protection. The MAX8576/MAX8578 can start up Enable/Shutdown into a precharged output without pulling the output volt- age down. The MAX8577/MAX8579 have startup output Adjustable Soft-Start overvoltage protection (OVP), and will pull down a precharged output. Ordering Information Applications PART TEMP RANGE PIN-PACKAGE Motherboard Power Supplies MAX8576EUB -40C to +85C 10 MAX AGP and PCI-Express Power Supplies MAX8577EUB -40C to +85C 10 MAX Graphic-Card Power Supplies MAX8578EUB -40C to +85C 10 MAX Set-Top Boxes MAX8579EUB -40C to +85C 10 MAX Point-of-Load Power Supplies Typical Operating Circuit INPUT UP TO 28V FB OCSET SS IN MAX8576 VL DH MAX8577 OUTPUT 0.6V TO 0.9 x V IN GND LX DL BST MAX is a registered trademark of Maxim Integrated Products, Inc. Pin Configurations appear at end of data sheet. 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 AVAILABLE3V to 28V Input, Low-Cost, Hysteretic Synchronous Step-Down Controllers ABSOLUTE MAXIMUM RATINGS IN to GND (MAX8576/MAX8577) ...........................-0.3V to +30V EN to GND (MAX8578/MAX8679EUB).....................-0.3V to +6V VL to GND (MAX8576/MAX8577).............................-0.3V to +6V OCSET to GND (MAX8576/MAX8677) ........-0.3V to (V + 0.3)V IN IN to VL (MAX8576/MAX8577) ...............................-0.3V to +30V OCSET to GND (MAX8578/MAX8679) ...................-0.3V to +30V V to GND (MAX8578/MAX8579) ..........................-0.3V to +6V OCSET to LX (MAX8576/MAX8677) ............-0.6V to (V + 0.3)V CC IN SS to GND (MAX8576/MAX8577) ...............-0.3V to (V + 0.3)V OCSET to LX (MAX8578/MAX8679).......................-0.6V to +30V VL SS to GND (MAX8578/MAX8579)...............-0.3V to (V + 0.3)V DH and DL Continuous Current ............................250mA RMS CC DL to GND (MAX8576/MAX8577) ...............-0.3V to (V + 0.3)V Continuous Power Dissipation (T = +70C) VL A DL to GND (MAX8578/MAX8579) ..............-0.3V to (V + 0.3)V 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW CC BST to GND............................................................-0.3V to +36V Operating Temperature Range ...........................-40C to +85C BST to LX..................................................................-0.3V to +6V Junction Temperature......................................................+150C LX to GND .....................-1V (-2.5V for <50ns Transient) to +30V Storage Temperature Range .............................-65C to +150C DH to LX..................................................-0.3V to +(V + 0.3)V Lead Temperature (soldering, 10s) ................................+300C BST FB to GND ................................................................-0.3V to +6V 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 (MAX8576/MAX8577 only), 4.7F capacitor from VL (MAX8576/MAX8577 only) or V (MAX8578/MAX8579 only) to GND IN CC V = V = 5V (MAX8578/MAX8579 only) 0.01F capacitor from SS to GND V = 0.65V V = 5V V = V = 0V V = CC EN FB BST LX GND OCSET 11.5V DH = unconnected DL = unconnected T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) A A PARAMETER CONDITIONS MIN TYP MAX UNITS SUPPLY VOLTAGES MAX8576/MAX8577 5.5 28.0 IN Supply Voltage V IN = VL (MAX8576/MAX8577) 3.0 5.5 V Input Voltage MAX8576/MAX8577 3.0 5.5 V CC VL Output Voltage I = 10mA (MAX8576/MAX8577) 4.75 5.0 5.25 V VL VL Maximum Output Current MAX8576/MAX8577 20 mA Rising 2.75 2.8 2.90 V VL or V Undervoltage Lockout CC Falling 2.4 2.45 2.5 (UVLO) Hysteresis 350 mV V = 12V 0.6 2 IN No switching, V = 0.65V FB V = V = 5V 1.1 3 IN VL (MAX8576/MAX8577) V = V = 3.3V 0.6 2 Supply Current mA IN VL V = 5V 0.6 2 V = 0V or V = 0.65V, no CC EN FB switching (MAX8578/MAX8579) V = 3.3V 0.6 2 CC REGULATOR Output Regulation Accuracy V peak 0.593 0.6 0.607 V FB Output Regulation Hysteresis (Note 1) 12.5 20 28.0 mV FB falling to DL falling 50 FB Propagation Delay ns FB rising to DH falling 70 Overvoltage-Protection (OVP) 0.70 0.75 0.80 V Threshold T = +85C60 A High-Side Current-Sense A Program Current (Note 2) T = +25C 42.5 50 57.5 A 2 MAX8576MAX8579