LT1612 Synchronous, Step-Down 800kHz PWM DC/DC Converter FEATURES DESCRIPTIO n The LT 1612 is an 800kHz, synchronous step-down DC/ Operates from Input Voltage As Low As 2V n DC converter that operates from an input voltage as low Internal 0.7A Synchronous Switches n as 2V. Internal 0.45W switches deliver output currents up Uses Ceramic Input and Output Capacitors n to 500mA, and the 800kHz switching frequency allows the 620mV Reference Voltage n use of small, low value ceramic input and output capaci- 800kHz Fixed Frequency Switching n tors. Input voltage ranges from 5.5V down to 2V and Programmable Burst Mode Operation n output voltage can be set as low as the 620mV reference. Low Quiescent Current: 160m A TM n The device features Burst Mode operation, keeping 8-Lead MSOP or SO Package efficiency high at light loads. Burst Mode operation can be U defeated by pulling the MODE pin high, enabling constant APPLICATIO S switching throughout the load range for low noise. n Portable Devices No-load quiescent current is 160m A and shutdown current n Lithium-Ion Step-Down Converters is less than 1m A. The device is available in 8-lead SO and n 5V to 3.3V Conversion MSOP packages. n 2-Cell Alkaline Step-Down Converters , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATION Efficiency for LT1612 vs Linear Regulator V = 1.2V OUT 0.1F 90 V IN L1 BOOST V IN 2V 10H V OUT SW SHDN 1.2V 80 V = 2V IN 500mA LT1612 100pF 70 V = 3V IN MODE FB C1 10F V C GND 60 V = 2V (LINEAR) IN R1 R2 215k C2 33.2k 50 232k 1% 68F 1% 3.15V 330pF 40 V = 3V (LINEAR) IN C1: TAIYO-YUDEN JMK325BJ106MN 1612 F01a 30 C2: PANASONIC EEFCDOF680R 10 100 500 L1: SUMIDA CD43-100 LOAD CURRENT (mA) 1612 F01b Figure 1. 2V to 1.2V Converter sn1612 1612fs 1 EFFICIENCY (%) U ULT1612 (Note 1) ABSOLUTE MAXIMUM RATINGS Supply Voltage (V ) ............................................... 5.5V BOOST Pin Voltage ....................................... V + 5.5V IN IN SW Pin Voltage ....................................................... 5.5V Junction Temperature........................................... 125 C FB Pin Voltage ............................................... V + 0.3V Operating Temperature Range (Note 2) ... 40 C to 85 C IN V Pin Voltage ........................................................... 2V Storage Temperature Range ................. 65 C to 150 C C SHDN Pin Voltage ................................................... 5.5V Lead Temperature (Soldering, 10 sec).................. 300 C MODE Pin Voltage .................................................. 5.5V PACKAGE/ORDER INFORMATION ORDER PART ORDER PART TOP VIEW NUMBER NUMBER TOP VIEW V 1 8 SHDN C V 1 8 SHDN C FB MODE 2 7 FB 2 7 MODE LT1612EMS8 LT1612ES8 V 3 6 BOOST V 3 6 BOOST IN IN 5 SW GND 4 GND 4 5 SW MS8 PACKAGE MS8 PART MARKING S8 PART MARKING 8-LEAD PLASTIC MSOP S8 PACKAGE 8-LEAD PLASTIC SO T = 125 C, q = 200 C/ W JMAX JA LTMS T = 125 C, q = 120 C/ W 1612 JMAX JA Consult factory for parts specified with wider operating temperature ranges. The l denotes specifications which apply over the full operating ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are T = 25 C, V = V = 3V A IN SHDN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I Quiescent Current MODE = 5V l 12 mA Q MODE = 0V, Not Switching l 160 220 m A SHDN = 0V l 1 m A V FB Voltage 0.605 0.62 0.635 V FB l 0.60 0.62 0.635 V FB Line Regulation l 0.02 0.15 %/V FB Pin Bias Current (Note 3) l 750 nA g Error Amplifier Transconductance 250 m mhos m Min Input Voltage 2V Max Input Voltage 5.5 V f Oscillator Frequency 700 800 900 kHz OSC l 550 1100 kHz f Line Regulation 1%/V OSC Maximum Duty Cycle 85 90 % l 80 % Shutdown Threshold Minimum Voltage for Active l2V Maximum Voltage for Shutdown l 0.2 V sn1612 1612fs 2 U W U W U WW