DS2731 + Rev 1 1/09 Cache-Memory Battery-Backup Management IC General Description Features The DS2731 is a complete power-management solution Lithium Chemistry CCCV Charger for modular backup applications. It is well-suited for 2.5V Adjustable Regulated Charging Up to 1.5A DC and below memory bus voltages, with an input voltage of 12V. The DS2731 includes an internal MOSFET switching Adjustable Charge Voltage from 3.8V to 4.6V power stage for charging a one-cell lithium chemistry bat- External and Internal Thermal Protection tery. It has a fully integrated synchronous buck regulator capable of supplying up to 450mA of cache backup sup- Safety Timer Secondary Termination ply current, and the necessary logic and power devices LED Indicator Outputs for handling the switchover from system power to battery power. The battery charging method of the DS2731 is Detects Power Outage and Switches Between constant current/constant voltage (CCCV). Output voltage Normal Power and Backup Battery can be margined from 3.8V to 4.6V using a resistor- Adjustable High-Efficiency Synchronous Buck divider. Charge is terminated when the charging current Regulator with Skip Mode at Light Loads falls below 5% of full charge current. Switchover to battery backup is initiated by an internal comparator and occurs Low-Power Consumption in Discharge Mode automatically when a sensed-input voltage drops below 2.93V. At light loads, the 2MHz internal synchronous buck regulator operates in burst mode for maximum efficiency. Ordering Information All nonessential functions of the DS2731 are disabled while supplying holdup current to the cache memory, and PIN- TOP PART TEMP RANGE the IC goes into very low-current dormant mode when the PACKAGE MARK battery voltage drops below a user-settable threshold. 28 TSSOP-EP* The DS2731 keeps track of charge status and signals the DS2731E+ -20C to +70C DS2731 (173 mils) user through open-drain I/O pins that can be used to drive LEDs. 28 TSSOP-EP* DS2731E+T&R -20C to +70C DS2731 (173 mils) Applications +Denotes a lead(Pb)-free/RoHS-compliant package. T&R = Tape and reel. RAID Controller Card *EP = Exposed pad. Typical Operating Circuit Pin Configuration TOP VIEW MARGIN 1 28 THM STMR 2 27 RSET DS2731 CTG 3 26 BATT+ AUX 4 25 SNS SWITCH MODE MAIN CBIAS 5 24 CGATE CHARGER POWER (CCCV) VREG 6 23 VIN LITHIUM CIN 7 22 CHG1 BACKUP DS2731 CELL LX 8 21 CHG2 AUXILIARY POWER SGND 9 20 CGND1 POWER MANAGEMENT AGND 10 19 CGND2 REF 11 18 CHARGE LO BATT 12 17 FAULT SWITCHING CACHE DIV 13 16 DONE *EP REGULATOR MEMORY ENS 14 15 ENC TSSOP *EXPOSED PAD 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.Cache-Memory Battery-Backup Management IC ABSOLUTE MAXIMUM RATINGS Voltage Range on CGND1, CGND2, and Continuous Sink Current on VIN, CGND1, SGND Pins Relative to AGND ...........................-0.3V to +0.3V CGND2, SGND, AUX, BATT+ Pins ......................750mA each Voltage Range on VIN, CHG1, CHG2, and Continuous Source Current on CHG1, CGATE Pins Relative to AGND........................-0.3V to +16.0V CHG2, and LX Pins..............................................750mA each Voltage Range on CHARGE, FAULT, and Continuous Sink Current on CHARGE, DONE Pins Relative to AGND .........................-0.3V to +16.0V FAULT, and DONE Pins.........................................20mA each Voltage Range on Any Other Pin Relative Operating Temperature Range ...........................-40C to +85C to AGND ............................................................-0.3V to +6.0V Storage Temperature Range .............................-55C to +125C Soldering Temperature...........................Refer to the IPC/JEDEC J-STD-020 Specification. 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. RECOMMENDED OPERATING CONDITIONS (V = +10.8V to +13.2V, T = -20C to +70C, unless otherwise noted. Typical values are at T = +25C.) IN A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Charger Supply Voltage V (Note 1) 10.8 12.0 13.2 V IN Auxiliary Supply Voltage V (Note 1) 3.0 3.6 V AUX Battery Voltage V Operating as input (Note 1) 2.7 5.0 V BATT+ LED Voltage V IN (Note 1) 0 V (CHARGE, FAULT, DONE Pins) + 0.3 V CBIAS Charger Enable (ENC) (Notes 1, 2) 0 V + 0.3 V CIN Switcher Enable (ENS) (Notes 1, 2) 0 V + 0.3 CHARGER CIRCUIT ELECTRICAL CHARACTERISTICS (V = +10.8V to +13.2V, T = -20C to +70C, unless otherwise noted. Typical values are at T = +25C.) IN A A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V > V (Note 3), IN UVLO-CHG Charger Idle Supply Current I 1 mA IN V = 3.3V AUX I V > V 100 A AUX AUX TRIP V < V , AUX TRIP I 100 150 A Regulator Supply Current BATT+ V > V , ENS disabled BATT+ SLEEP (Note 3) V = V = 0.0V, IN AUX I 10 A SLEEP V < V BATT+ SLEEP C Regulator Voltage V 3.3 V BIAS CBIAS C Regulator Voltage V V - 4.0 V GATE CGATE IN C Capacitance C 2.2 F GATE CGATE C Capacitance C 0.22 F BIAS CBIAS Enable Logic-Low (ENS, ENC) V (Notes 4, 5) 0.4 V IL Enable Logic-High (ENS, ENC) V (Notes 5, 6) 1.6 V IH 2 DS2731