LT3472 Boost and Inverting DC/DC Converter for CCD Bias FEATURES DESCRIPTIO Generates 15V at 20mA, 8V at 50mA The LT 3472 dual channel switching regulator generates from a Li-Ion Cell positive and negative outputs for biasing CCD imagers. Internal Schottky Diodes The device delivers up to 8V at 50mA and 15V at 20mA V Range: 2.2V to 16V from a lithium-ion cell, providing bias for many popular IN Output Voltages Up to 34V CCD imagers. Switching at 1.1MHz, the LT3472 uses tiny, Capacitor-Programmable Soft-Start low profile capacitors and inductors and generates low Sequencing: Positive Output Reaches 88% of Final noise outputs that are easy to filter. Schottky diodes are Value Before Negative Output Begins internal and the output voltages are set with one resistor Requires Only One Resistor to Set Output Voltage per channel, reducing external component count. The Constant Switching Frequency Ensures Low entire solution is less than 1mm profile and occupies just 2 Noise Outputs 50mm . Available in a 10-Lead (3mm 3mm) DFN Package Internal sequencing circuitry disables the negative chan- U nel until the positive channel has reached 88% of its final APPLICATIO S value, ensuring that the sum of the two outputs is always positive. Separate soft-start capacitors for each output CCD Bias allow the ramp of each output to be independently TFT LCD Bias controlled. OLED Bias Rail Generation for Op Amps The LT3472 is available in a low profile (0.75mm) 10-pin , LTC and LT are registered trademarks of Linear Technology Corporation. 3mm 3mm DFN package. TYPICAL APPLICATIO Li-Ion CCD Bias Supply V IN Conversion Efficiency 3V TO 4.2V 2.2F 85 1F 22H47H 80 POS CHANNEL 75 SWP V SWN IN V POS 70 NEG CHANNEL 15V V DN POS 65 20mA 550k 47H FBP LT3472 60 4.7pF V 320k NEG 8V FBN 55 10pF 50mA 50 SHDN SHDN 45 SSP GND SSN 40 2.2F 100nF 100nF 2.2F 0 10 20 30 40 50 LOAD CURRENT (mA) 3472 TA01b 3472 TA01a 3472f 1 EFFICIENCY (%) U ULT3472 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART V , SHDN Voltage ................................................... 16V IN NUMBER SWP 1 10 V SWP, SWN, V Voltage ....................................... 36V POS POS V 2 9 SSP IN DN Voltage ............................................................ 36V LT3472EDD 11 SHDN 3 8 FBP FBP, FBN, SSP, SSN Voltage ................................... 10V SWN 4 7 SSN Maximum Junction Temperature .......................... 125C DN 5 6 FBN DFN PART Operating Temperature Range DD PACKAGE MARKING Extended Commercial......................... 40C to 85C 10-LEAD (3mm 3mm) PLASTIC DFN T = 125C, = 43C/W, = 3C/W Storage Temperature Range ................. 65C to 125C JMAX JA JC EXPOSED PAD IS GND (PIN 11) LBGC MUST BE SOLDERED TO PCB Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 3V, SHDN = 3V unless otherwise noted. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operation Voltage 2.2 V Maximum Operation Voltage 16 V Supply Current SHDN = 3V, Not Switching 2.8 mA SHDN = 0V 0.1 1 A SHDN Voltage High 0.8 V SHDN Voltage Low 0.3 V SHDN Pin Bias Current SHDN = 3V 35 A Positive Feedback Voltage 1.2 1.25 1.3 V Negative Feedback Voltage 5 0 5 mV Positive Feedback Voltage Line Regulation 0.01 %/V Negative Feedback Voltage Line Regulation 0.008 mV/V FBP Current FBP = V 24.5 25 25.3 A FBP FBN Current FBN = V 24.5 25 25.3 A FBN FBP to Start Negative Channel 1.02 1.1 1.18 V Switching Frequency 0.9 1.1 1.4 MHz Maximum Duty Cycle (Both Channels) 88 92 % Positive Channel Switch Current Limit 250 350 mA Negative Channel Switch Current Limit 300 400 mA Positive Channel Switch V I = 200mA 245 mV CESAT SWP Negative Channel Switch V I = 200mA 400 mV CESAT SWN Switch Leakage Current (Both Channels) V = 5V 0.01 5 A SW Schottky DP Forward Drop I = 150mA 700 950 mV DP Schottky DN Forward Drop I = 150mA 750 1000 mV DN Schottky Leakage Current (Both Channels) V = 36V 4 A R Note 1: Absolute Maximum Ratings are those values beyond which the life 0C to 70C. Specifications over the 40C to 85C operating range are of a device may be impaired. assured by design, characterization and correlation with statistical process controls. Note 2: The LT3472E is guaranteed to meet specified performance from 3472f 2 U WWW