LT1308A/LT1308B High Current, Micropower Single Cell, 600kHz DC/DC Converters FEATURESDESCRIPTION n 5V at 1A from a Single Li-Ion Cell The LT®1308A/LT1308B are micropower, fi xed frequency n 5V at 800mA in SEPIC Mode from Four NiCd Cells step-up DC/DC converters that operate over a 1V to 10V n Fixed Frequency Operation: 600kHz input voltage range. They are improved versions of the n Boost Converter Outputs up to 34V LT1308 and are recommended for use in new designs. n Starts into Heavy Loads The LT1308A features automatic shifting to power sav- n Automatic Burst Mode™ Operation at ing Burst Mode operation at light loads and consumes Light Load (LT1308A) just 140μA at no load. The LT1308B features continuous n Continuous Switching at Light Loads (LT1308B) switching at light loads and operates at a quiescent cur- n Low V rent of 2.5mA. Both devices consume less than 1μA in CESAT Switch: 300mV at 2A n Pin-for-Pin Upgrade Compatible with LT1308 shutdown. n Lower Quiescent Current in Shutdown: 1μA (Max) Low-battery detector accuracy is signifi cantly tighter than n Improved Accuracy Low-Battery Detector the LT1308. The 200mV reference is specifi ed at ± 2% Reference: 200mV ± 2% at room and ±3% over temperature. The shutdown pin n
Available in 8-Lead SO and 14-Lead TSSOP Packages enables the device when it is tied to a 1V or higher source and does not need to be tied to VIN as on the LT1308. An internal V APPLICATIONS C clamp results in improved transient response and the switch voltage rating has been increased to 36V, n GSM/CDMA Phones enabling higher output voltage applications. n Digital Cameras The LT1308A/LT1308B are available in the 8-lead SO and n LCD Bias Supplies the 14-lead TSSOP packages. n Answer-Back Pagers n GPS Receivers L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective n Battery Backup Supplies owners. n Handheld Computers TYPICAL APPLICATIONConverter Effi ciency L1 4.7μH D1 95 5V V V IN = 3.6V IN = 4.2V 1A 90 VIN SW + 85 C1 LBI LBO R1* 47μF 80 V LT1308B 309k IN = 2.5V Li-Ion + VIN = 1.5V SHUTDOWN SHDN 75 FB C2 CELL 220μF VC GND 70 R2 EFFICIENCY (%) 47k 100k 65 100pF 60 55 C1: AVX TAJC476M010 L1: MURATA LQH6C4R7 50 C2: AVX TPSD227M006 *R1: 887k FOR VOUT = 12V 1 10 100 1000 1308A/B F01a D1: IR 10BQ015 LOAD CURRENT (mA) Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter 1308A/B F01b 1308abfb 1
