MAX1878 19-2248 Rev 2 5/11 Dual-Output Step-Down and LCD Step-Up Power Supply for PDAs General Description Features The MAX1878 dual power supply contains a step-down Evaluation Kit Available to Speed Designs and step-up DC-DC converter in a small 12-pin TQFN Two Output Voltages package for use in PDAs. The step-down DC-DC convert- Main Output: 1.25V to V IN er delivers over 500mA to an output as low as 1.25V for LCD Output: Up to 28V logic power. The step-up DC-DC converter delivers over 2.0V to 5.5V Input Range 15mA and an output as high as 28V for a liquid crystal dis- play (LCD). With an input voltage from 2.0V to 5.5V the Low 19A Quiescent Supply Current MAX1878 is intended for use in systems powered by a 1A Shutdown Supply Current 2-cell alkaline or 1-cell lithium-ion (Li+) battery. High Switching Frequency for Small External Fast switching frequency allows the use of small inductors Components and capacitors, and the low 19A typical quiescent cur- rent allows high efficiency when the system is in standby Small 0.75mm High 4mm x 4mm 12-Pin TQFN mode. Each output can be independently enabled. Package The MAX1878 is available in a small 0.75mm high 4mm x 4mm 12-pin TQFN package and requires no external FETs. The MAX1878 evaluation kit is available to speed designs. Ordering Information Applications Personal Digital Assistants (PDA) PIN- TOP PART TEMP RANGE PACKAGE MARK Organizers/Translators MAX1878ETC+ -40C to +85C 12- TQFN- E P * AAGC MP3 Players +Denotes a lead(Pb)-free/RoHS-compliant package. GPS Receivers *EP = Exposed pad. Pin Configuration Typical Operating Circuit TOP VIEW 10H INPUT 2.0V TO 5.5V 98 7 LCD OUTPUT IN LXLCD UP TO 28V 0.1F FBLCD ONLCD 10 6 FBLCD AIN1 AIN2 11 5 FB PGNDLCD MAX1878 10H MAIN OUTPUT MAX1878 LX 1.25V TO V IN AIN2 PGND 12 4 EP* FB + ON OFF ON MAIN ON OFF LCD ONLCD 12 3 PGND AGND PGNDLCD TQFN 4mm x 4mm *CONNECT EP TO AGND. 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. EVALUATION KIT AVAILABLE IN LXLCD LX AGND AIN1 ONDual-Output Step-Down and LCD Step-Up Power Supply for PDAs ABSOLUTE MAXIMUM RATINGS FB, FBLCD, AIN1, AIN2, ON, ONLCD to AGND ......-0.3V to +6V Continuous Power Dissipation (T = +70C) A AIN2 to AIN1..........................................................-0.3V to +0.3V 12-Pin TQFN (derate 24.4mW/C above +70C) ...........1.95W AIN1, AIN2 to IN....................................................-0.3V to +0.3V Operating Temperature Range ...........................-40C to +85C IN to PGND...............................................................-0.3V to +6V Junction Temperature......................................................+150C LX to PGND .................................................-0.3V to (V + 0.3V) Storage Temperature Range .............................-65C to +150C IN LXLCD to PGNDLCD..............................................-0.3V to +30V Lead Temperature (soldering, 10s) .................................+300C PGND, PGNDLCD to AGND..................................-0.3V to +0.3V Soldering Temperature (reflow) .......................................+260C LX Current.........................................................................800mA LXLCD Current..................................................................500mA 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. PACKAGE THERMAL CHARACTERISTICS (Note 1) TQFN Junction-to-Ambient Thermal Resistance ( )...............41C/W JA Junction-to-Case Thermal Resistance ( )......................6C/W JC Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four- layer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial. ELECTRICAL CHARACTERISTICS (V = V = 2.5V, circuit of Figure 1, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) IN AIN A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS GENERAL Input Voltage Range V , V 2.0 5.5 V IN AIN V rising 1.92 2.0 IN Undervoltage Lockout Threshold V V UVLO V falling 1.7 1.82 IN Undervoltage Lockout Hysteresis 100 mV V = V = 1.30V, V = 0V, FB FBLCD ONLCD 19 30 I + AIN1 step-down converter only Quiescent Current A I AIN2 V = V = 1.30V 24 38 FB FBLCD Shutdown Quiescent Current V = V = 0V 0 1 A ON ONLCD MAIN OUTPUT (Step-Down Converter) Output Voltage Adjustment Range V 1.25 V V MAIN IN T = +25C to +85C 1.225 1.250 1.275 A FB Regulation Voltage V V = V = 2V V FB IN AIN T = 0C to +85C 1.220 1.280 A FB Input Bias Current I V = V = 2V 10 50 nA FB IN AIN V = V = 2.5V 250 500 Main Output Current IN AIN I V = 1.8V mA MAIN MAIN (Note 2) V = V = 2.0V 200 350 IN AIN I = 150mA, V = V = 2V to 3V, LOAD IN AIN Line Regulation 1% FB = GND Load Regulation V = V = 2.5V, I = 10mA to 150mA 1 % IN AIN LOAD V = V = 2V, I = 150mA, IN AIN LOAD 150 V = 0.8V FB Dropout Voltage mV V = V = 3V, I = 150mA, IN AIN LOAD 100 V = 0.8V FB 2 MAX1878