MAX8545/MAX8546/MAX8548 19-2795 Rev 2 6/07 Low-Cost, Wide Input Range, Step-Down Controllers with Foldback Current Limit General Description Features The MAX8545/MAX8546/MAX8548 are voltage-mode 2.7V to 28V Input Range pulse-width-modulated (PWM), step-down DC-DC con- Foldback Short-Circuit Protection trollers ideal for a variety of cost-sensitive applications. No Additional Bias Supply Needed They drive low-cost n-channel MOSFETs for both the high-side switch and synchronous rectifier, and require 0.8V to 0.83 x V Output IN no external current-sense resistor. These devices can Up to 95% Efficiency supply output voltages as low as 0.8V. Low-Cost External Components The MAX8545/MAX8546/MAX8548 have a wide 2.7V to 28V input range, and do not need any additional bias No Current-Sense Resistor voltage. The output voltage can be precisely regulated All n-Channel MOSFET Design from 0.8V to 0.83 x V . These devices can provide effi- IN Adaptive Gate Drivers Eliminate Shoot-Through ciency up to 95%. Lossless short-circuit and current-limit protection is provided by monitoring the R of the DS(ON) Lossless Overcurrent and Short-Circuit low-side MOSFET. The MAX8545 and MAX8548 have a Protection current-limit threshold of 320mV, while the MAX8546 has 300kHz Switching Frequency a current-limit threshold of 165mV. All devices feature (MAX8545/MAX8546) foldback-current capability to minimize power dissipation under short-circuit condition. Pulling the COMP/EN pin 100kHz Switching Frequency (MAX8548) low with an open-collector or low-capacitance, open- Pin-Compatible with the MAX1967 drain device can shut down all devices. Thermal Shutdown The MAX8545/MAX8546 operate at 300kHz and the MAX8548 operates at 100kHz. The MAX8545/MAX8546/ Selector Guide MAX8548 are compatible with low-cost aluminum elec- trolytic capacitors. Input undervoltage lockout prevents SWITCHING CURRENT-LIMIT proper operation under power-sag operations to prevent PART FREQUENCY THRESHOLD external MOSFETs from overheating. Internal soft-start is (kHz) (mV) included to reduce inrush current. These devices are MAX8545 300 -320 offered in space-saving 10-pin MAX packages. MAX8546 300 -165 Applications MAX8548 100 -320 Set-Top Boxes Notebook Docking Station Supplies Graphic Card and Video Typical Operating Circuit Supplies Cable Modems and INPUT Routers Desktops and Desknotes 2.7V TO 28V Networking Power PCI Express Power Supplies Supplies V VL CC Telecom Power Supplies OUTPUT V BST IN 0.8V TO Ordering Information DH 0.9 x V IN UP TO 6A PIN- LX PKG MAX8545 PART TEMP RANGE PACKAGE MAX8546 CODE DL MAX8548 10 MAX MAX8545EUB -40C to +85C U10-2 GND COMP/ 10 MAX MAX8545EUB+ -40C to +85C U10-2 EN OFF FB 10 MAX MAX8546EUB -40C to +85C U10-2 ON 10 MAX MAX8546EUB+ -40C to +85C U10-2 10 MAX MAX8548EUB -40C to +85C U10-2 MAX8548EUB+ -40C to +85C 10 MAX U10-2 OPTIONAL +Denotes a lead-free package. Pin Configuration appears at end of data sheet. MAX is a registered trademark of Maxim Integrated Products, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com.Low-Cost, Wide Input Range, Step-Down Controllers with Foldback Current Limit ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND unless otherwise noted.) LX to GND ................................................................-1V to +30V V to GND ............................................................-0.3V to +30V Input Current (any pin) .....................................................50mA IN V to GND .............................-0.3V, lower of 6V or (VL + 0.3V) Continuous Power Dissipation (T = +70C) CC A FB to GND ................................................................-0.3V to +6V 10-Pin MAX (derate 5.6mW/C above +70C) ..........444mW BST to GND............................................................-0.3V to +36V Operating Temperature Range ...........................-40C to +85C VL, DL, COMP to GND ..............................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C CC BST to LX..................................................................-0.3V to +6V Storage Temperature Range .............................-65C to +150C DH to LX....................................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C BST VL Short to GND ......................................................................5s 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 = V = V = 5V, T = -40C to +85C, unless otherwise noted. Typical values are at T = +25C.) IN L CC A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V = VL, V separate from V 4.9 28.0 CC IN CC V Operating Range V V IN IN V = VL = V 2.7 5.5 IN CC V Undervoltage Lockout IN Rising and falling edge, hysteresis = 2% 2.35 2.50 2.66 V (UVLO) Trip Level 0.7 V Operating Supply Current V = 0.88V (no switching) 1.2 mA IN FB 5.5V < V < 28V, V = VL, IN CC VL Output Voltage 4.7 5 5.3 V 1mA < I < 25mA LOAD Rising temperature, typical Thermal Shutdown +160 C hysteresis = 10C (Note 1) OSCILLATOR MAX8545, MAX8546 250 300 360 Frequency f kHz OSC MAX8548 80 100 120 DH output, MAX8545, MAX8546 5 Minimum Duty Cycle DC % MIN MAX8548 10 DH output, MAX8545, MAX8546 83 86 Maximum Duty Cycle DC % MAX MAX8548 90 95 SOFT-START MAX8545, MAX8546 6.6 Digital Ramp Period ms 10.2 MAX8548 MAX8545, MAX8546 V / 64 OUT Soft-Start Levels V V / 32 MAX8548 OUT 2 MAX8545/MAX8546/MAX8548