LT1949 600kHz, 1A Switch PWM DC/DC Converter FEATURES DESCRIPTIO n 1A, 0.5W , 30V Internal Switch The LT 1949 is a fixed frequency step-up DC/DC con- n Operates with V as Low as 1.5V verter with a 1A, 0.5W internal switch. Capable of gener- IN n 600kHz Fixed Frequency Operation ating 10V at 175mA from a 3.3V input, the LT1949 is ideal n Low-Battery Detector Stays Active in Shutdown for generating bias voltages for large screen LCD panels. n Low V Switch: 410mV at 800mA Constant frequency 600kHz operation results in a low CESAT n Pin-for-Pin Compatible with the LT1317B noise output that is easy to filter and the 30V switch rating n Small 8-Lead MSOP and SO Packages allows output voltage up to 28V using a single inductor. An external compensation pin gives the user flexibility in U optimizing loop compensation, allowing small low ESR APPLICATIO S ceramic capacitors to be used at the output. The 8-lead n MSOP and SO packages ensure a low profile overall LCD Bias Supplies n solution. GPS Receivers n Battery Backup The LT1949 includes a low-battery detector that stays n Portable Electronic Equipment alive when the device goes into shutdown. Quiescent n Diagnostic Medical Instrumentation current in shutdown is 25m A, while operating current is 4.5mA. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO V IN 90 3.3V L1 V = 10V D1 OUT 10H 80 + V SW C1 IN 3.6V 3V IN 4.2V IN IN 22F 70 R1 LT1949 V 1M OUT 60 FB 10V SHUTDOWN SHDN 175mA V GND C 50 C2 R2 10F 68k 40 140k CERAMIC 330pF 30 20 1949 F01 C1: AVX TAJA226M006R 5 10 50 100 300 C2: TAIYO YUDEN LMK325BJ106MN LOAD CURRENT (mA) D1: MBRM120LT3 L1: SUMIDA CDRH62B-100 1949 F02 Figure 1. 3.3V to 10V/175mA DC/DC Converter Figure 2. 3.3V to 10V Converter Efficiency 1 EFFICIENCY (%) U ULT1949 ABSOLUTE AXI U RATI GS (Note 1) V , LBO Voltage..................................................... 12V Junction Temperature.......................................... 125 C IN SW Voltage ............................................... 0.4V to 30V Operating Temperature Range (Note 2) FB Voltage .................................................... V + 0.3V LT1949EMS8.......................................40 C to 85 C IN V Voltage ................................................................ 2V LT1949ES8/LT1949IS8 .......................40 C to 85 C C LBI Voltage ............................................ 0V V 1V Storage Temperature ........................... 65 C to 150 C LBI SHDN Voltage ........................................................... 6V Lead Temperature (Soldering, 10sec).................. 300 C UUW PACKAGE/ORDER I FOR ATIO ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW V 1 8 LBO C V 1 8 LBO C LT1949ES8 LT1949EMS8 FB 2 7 LBI 7 LBI FB 2 SHDN 3 6 V IN SHDN V LT1949IS8 3 6 IN GND 4 5 SW GND SW 4 5 MS8 PACKAGE MS8 PART MARKING S8 PART MARKING 8-LEAD PLASTIC MSOP S8 PACKAGE T = 125 C, q = 120 C/W JMAX JA 8-LEAD PLASTIC SO 1949E LTJC T = 125 C, q = 120 C/W JMAX JA 1949I Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 2V, V = 2V unless otherwise noted. A IN SHDN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Quiescent Current l 4.5 7.5 mA Q V = 0V l 25 40 m A SHDN V Feedback Voltage 1.22 1.24 1.26 V FB l 1.20 1.24 1.26 V I FB Pin Bias Current (Note 3) l 12 80 nA B Input Voltage Range l 1.7 12 V g Error Amp Transconductance D I = 5m A l 70 140 240 m mhos m A Error Amp Voltage Gain 700 V/V V Maximum Duty Cycle l 80 85 % Switch Current Limit (Note 4) V = 2.5V, Duty Cycle = 30% 1 1.13 1.5 A IN V = 2.5V, Duty Cycle = 30% l 0.95 1.5 A IN f Switching Frequency l 500 600 750 kHz OSC Shutdown Pin Current V = V l 0.015 0.1 m A SHDN IN V = 0V l 2.3 7 m A SHDN LBI Threshold Voltage 190 200 210 mV l 180 200 220 mV LBO Output Low I = 10m A l 0.15 0.25 V SINK LBO Leakage Current V = 250mV, V = 5V l 0.02 0.1 m A LBI LBO LBI Input Bias Current (Note 5) V = 150mV l 560 nA LBI Low-Battery Detector Gain 1MW Pull-Up 2000 V/V Switch Leakage Current V = 5V l 0.01 3 m A SW 2 U WWW