LTC1759 Smart Battery Charger UFEATURESDESCRIPTIO ■ Single Chip Smart Battery Charger Controller The LTC®1759 Smart Battery Charger is a single chip ■ 100% Compliant (Rev 1.0) SMBus Support charging solution that dramatically simplifies construc- Allows for Operation with or without Host tion of an SBS compliant system. The LTC1759 imple- ■ SMBus Accelerator Improves SMBus Timing ments a Level 2 charger function whereby the charger can ■ Hardware Interrupt and SMBAlert Response be programmed by the battery or by the host. A thermistor Eliminate Interrupt Polling on the battery being charged is monitored for tempera- ■ High Efficiency Synchronous Buck Charger ture, connectivity and battery type information. The SMBus ■ 0.5V Dropout Voltage; Maximum Duty Cycle > 99.5% interface remains alive when the AC power adapter is ■ AC Adapter Current Limit Maximizes Charge Rate* removed and responds to all SMBus activity directed to it, ■ 1% Voltage Accuracy; 5% Current Accuracy including thermistor status (via the ChargerStatus com- ■ Up to 8A Charging Current Capability mand). The charger also provides an interrupt to the host ■ Dual 10-Bit DACs for Charger Voltage and Current whenever a status change is detected (e.g., battery Programming removal, AC adapter connection). ■ User-Selectable Overvoltage and Overcurrent Limits Charging current and voltage are restricted to chemistry ■ High Noise Immunity Thermistor Sensor specific limits for improved system safety and reliability. ■ Small 36-Lead Narrow (0.209") SSOP Package Limits are programmable by two external resistors. Addi- U tionally, the maximum average current from the AC adapter APPLICATIO S is programmable to avoid overloading the adapter when ■ Portable Computers simultaneously supplying load current and charging cur- ■ Portable Instruments rent. When supplying system load current, charging cur- ■ Docking Stations rent is automatically reduced to prevent adapter overload. , LTC and LT are registered trademarks of Linear Technology Corporation. *US Patent Number 5,723,970 UTYPICAL APPLICATIO 15.8k 1k 0.033Ω AC + 10µF ADAPTER 0.1µF LTC1759 35V INPUT V 7 22 DD Al UV 499 DCIN Ω 0.1µF 16 21 VDD DCDIV 0.47µF 4 8 SYSTEM SYNC INFET POWER 5 32 SDB 1 V µF CC 12 9 CHGEN 22µF CLP 33k 25 10 VLIMIT CLN 33k 24 2 ILIMIT TGATE 2.2µF 0.1µF 18 33 DGND 15 BOOSTC µH 0.025Ω 3.83k 17 34 I 0.68µF SET GBIAS + 1µF 28 1 PROG 22µF BOOST SMART 0.33µF 1.5k 27 3 BATTERY VC SW 0.68µF 1k 11 35 COMP1 BGATE 6 30 AGND SPIN 20 29 200Ω RNR SENSE 19 31 200Ω THERM BAT1 VDD 14 23 SDA BAT2 68Ω 15 26 SCL 475k 10k 1k VSET 13 36 INTB 0.047 PGND µF 0.015µF INTB SMBus SCL TO SDA HOST 1759 F01 Figure 1. 4A SMBus Smart Battery Charger 1