LT1944 Dual Micropower Step-Up DC/DC Converter FEATURES DESCRIPTIO n Low Quiescent Current: The LT 1944 is a dual micropower step-up DC/DC con- 20m A in Active Mode verter in a 10-pin MSOP package. Each converter is <1m A in Shutdown Mode designed with a 350mA current limit and an input voltage n Operates with V as Low as 1.2V range of 1.2V to 15V, making the LT1944 ideal for a wide IN n Low V Switch: 250mV at 300mA variety of applications. Both converters feature a quies- CESAT n Uses Small Surface Mount Components cent current of only 20m A at no load, which further reduces n High Output Voltage: Up to 34V to 0.5m A in shutdown. A current limited, fixed off-time n Tiny 10-Pin MSOP Package control scheme conserves operating current, resulting in high efficiency over a broad range of load current. The 36V U switch allows high voltage outputs up to 34V to be easily APPLICATIO S generated in a simple boost topology without the use of costly transformers. The LT1944s low off-time of 400ns n LCD Bias permits the use of tiny, low profile inductors and capaci- n Handheld Computers tors to minimize footprint and cost in space-conscious n Battery Backup portable applications. n Digital Cameras , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO Dual Output (5V, 30V) Boost Converter 5V Output Efficiency 90 L1 D1 4.7H V IN 5V 85 2.7V 80mA V = 4.2V IN TO 4.2V 810 80 4.7pF 1M V SW1 IN 75 V = 2.7V IN 2 1 SHDN1 FB1 70 C1 C2 LT1944 4.7F 10F 65 4 5 SHDN2 FB2 324k 60 GND PGND PGND SW2 3 7 9 6 55 86.6k 50 0.1 1 10 100 LOAD CURRENT (mA) C3 4.7pF 2M 1944 TA01a 1F L2 D2 10H 30V 8mA C1: TAIYO YUDEN JMK212BJ475 1944 TA01 C2: TAIYO YUDEN JMK316BJ106 C3: TAIYO YUDEN GMK316BJ105 D1, D2: ON SEMI MBR0540 L1: MURATA LQH3C4R7 L2: MURATA LQH3C100 1 EFFICIENCY (%) U ULT1944 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART TOP VIEW V , SHDN1, SHDN2 Voltage ................................... 15V NUMBER IN FB1 1 10 SW1 SHDN1 2 9 PGND SW1, SW2 Voltage .................................................. 36V GND 3 8 V LT1944EMS IN FB1, FB2 Voltage .......................................................V SHDN2 4 7 PGND IN FB2 5 6 SW2 Current into FB1, FB2 Pins ..................................... 1mA MS10 PACKAGE MS10 PART Junction Temperature........................................... 125 C 10-LEAD PLASTIC MSOP MARKING Operating Temperature Range (Note 2) .. 40 C to 85 C T = 125 C, q = 160 C/W JMAX JA Storage Temperature Range ................. 65 C to 150 C LTTR Lead Temperature (Soldering, 10 sec).................. 300 C Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 1.2V, V = 1.2V unless otherwise noted. A IN SHDN PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage 1.2 V Quiescent Current, Each Switcher Not Switching 20 30 m A V = 0V 1 m A SHDN FB Comparator Trip Point l 1.205 1.23 1.255 V FB Comparator Hysteresis 8mV FB Voltage Line Regulation 1.2V < V < 12V 0.05 0.1 %/V IN FB Pin Bias Current (Note 3) V = 1.23V l 30 80 nA FB Switch Off Time V > 1V 400 ns FB V < 0.6V 1.5 m s FB Switch V I = 300mA 250 350 mV CESAT SW Switch Current Limit 250 350 400 mA SHDN Pin Current V = 1.2V 2 3 m A SHDN V = 5V 8 12 m A SHDN SHDN Input Voltage High 0.9 V SHDN Input Voltage Low 0.25 V Switch Leakage Current Switch Off, V = 5V 0.01 5 m A SW Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1944 is guaranteed to meet performance specifications from 0 C to 70 C. Specifications over the 40 C to 85 C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Bias current flows into the FB pin. 2 U WWW