LT1944-1 Dual Micropower Step-Up DC/DC Converter FEATURES DESCRIPTIO n Low Quiescent Current: The LT 1944-1 is a dual micropower step-up DC/DC 20m A in Active Mode converter in a 10-pin MSOP package. One converter is <1m A in Shutdown Mode designed with a 100mA current limit and a 400ns off-time n Operates with V as Low as 1.2V the other with a 175mA current limit and a 1.5m s off-time. IN n Low V Switches: 85mV at 70mA The 1.5m s off-time converter is ideal for generating an CESAT n Uses Small Surface Mount Components output voltage that is close to the input voltage (i.e. a Li- n High Output Voltage: Up to 34V Ion to 5V converter, or a two-cell to 3.3V converter). With n Tiny 10-Pin MSOP Package an input voltage range of 1.2V to 15V, the LT1944-1 is ideal for a wide variety of applications. Both converters feature U a quiescent current of only 20m A at no load, which further APPLICATIO S reduces to 0.5m A in shutdown. A current limited, fixed off- time control scheme conserves operating current, result- n Small TFT LCD Panels ing in high efficiency over a broad range of load current. n Handheld Computers Tiny, low profile inductors and capacitors can be used to n Battery Backup minimize footprint and cost in space-conscious portable n Digital Cameras applications. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO Triple Output Power Supply (5V, 15V, 10V) for LCD Displays L1 5V Output Efficiency D1 22H V IN 5V 90 2.7V 40mA TO 4.2V 86 85 4.7pF 1M V SW2 IN V = 4.2V 80 IN 4 5 SHDN2 FB2 75 C1 C2 V = 2.7V IN LT1944-1 4.7F 4.7F 2 1 70 SHDN1 FB1 324k 65 GND PGND PGND SW1 3 7 9 10 60 178k 55 50 C3 4.7pF 0.1 1 10 100 2M 1F L2 LOAD CURRENT (mA) D2 22H 1944-1 TA01a 15V 2.5mA D3 C1, C2: TAIYO YUDEN JMK212BJ475 C4 C3, C4: TAIYO YUDEN EMK212BJ105 5V 1F C5: TAIYO YUDEN EMK107BJ104 C5 D1, D2, D3, D4: CENTRAL SEMI CMDSH3 D4 0.1F 10V L1, L2: MURATA LQH3C220 1944-1 TA01 1mA 1 EFFICIENCY (%) U ULT1944-1 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 LT1944-1EMS 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 LTTU 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, Switcher 1 (Note 4) V > 1V 400 ns FB V < 0.6V 1.5 m s FB Switch Off Time, Switcher 2 (Note 4) V > 1V 1.5 m s FB V < 0.6V 1.5 m s FB Switch V I = 70mA 85 120 mV CESAT SW Switch Current Limit, Switcher 1 65 100 125 mA Switch Current Limit, Switcher 2 130 175 225 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 temperature range are assured by design, characterization and correlation of a device may be impaired. with statistical process controls. Note 2: The LT1944-1E is guaranteed to meet performance specifications Note 3: Bias current flows into the FB pin. from 0 C to 70 C. Specifications over the 40 C to 85 C operating Note 4: See Figure 1 for Switcher 1 and Switcher 2 locations. 2 U WWW