LT1533 Ultralow Noise 1A Switching Regulator FEATURES DESCRIPTION n Greatly Reduced Conducted and Radiated EMI The LT 1533 is a new class of switching regulator designed (<100V in Typical Application) to reduce conducted and radiated electromagnetic interfer- P-P n Low Switching Harmonic Content ence (EMI). Ultralow noise and EMI are achieved by providing n Independent Control of Switch Voltage and user control of the output switch slew rates. Voltage and Current Slew Rates current slew rates can be independently programmed to n Two 1A Current Limited Power Switches optimize switcher harmonic content versus efficiency. The n Regulates Positive and Negative Voltages LT1533 can reduce high frequency harmonic power by as n 20kHz to 250kHz Oscillator Frequency much as 40dB with only minor losses in efficiency. n Easily Synchronized to External Clock The LT1533 utilizes a dual output switch current mode n Wide Input Voltage Range: 2.7V to 23V architecture optimized for low noise topologies. The IC n Low Shutdown Current: 12A Typical includes two 1A power switches along with all necessary n Easier Layout than with Conventional Switchers oscillator, control and protection circuitry. Unique error amp n Outputs Can Be Forced to 50% Duty Cycle for circuitry can regulate both positive and negative voltages. Unregulated Applications The internal oscillator may be synchronized to an external U clock for more accurate placement of switching harmonics. APPLICATIONS Protection features include cycle by cycle current limit pro- tection, undervoltage lockout and thermal shutdown. n Precision Instrumentation Systems n Isolated Supplies for Industrial Automation Low minimum supply voltage and low supply current during n Medical Instruments shutdown make the LT1533 well suited for portable applica- n Wireless Communications tions. The part may also be forced into a 50% duty cycle mode n Single Board Data Acquisition Systems for unregulated applications. The LT1533 is available in the 16-pin narrow SO package. , LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATION Low Noise 5V to 12V Forward Push-Pull DC/DC Converter 5V L2 L1 1N4148 300H 33H B A 12V Output Noise (BW = 100MHz) T1 14 + 12V 33F V 150mA IN 11 2 SHDN COL A C1 + + C2 1N4148 3 47F 33F DUTY 15 COL B 16V 20V 4 820pF Note 1 SYNC A 16 <100V P-P 5 100V/DIV PGND C T LT1533 15k 13 16.9k 6 R VSL R T B 15k 12 2mV/DIV R CSL 21.5k, 1% 15k 10 7 1533 TA01 V FB C GND NFB C1: SANYO OS-CON 2.49k 9 8 0.015F 1000pF C2: AVX TPS TANTALUM 1% L1: COILTRONICS CTX300-2 2s/DIV 1533 TA02 L2: COILCRAFT DT1608C-333 T1: COILTRONICS CTX02-13834 NOTE 1: 25nH TRACE INDUCTANCE OR COILCRAFT B07T 1 U ULT1533 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) TOP VIEW ORDER PART Input Voltage (V ) .................................................. 30V IN NUMBER Switch Voltage (COL A, COL B) ............................... 30V NC 1 16 PGND SHDN Pin Voltage .................................................... 30V COL A 2 15 COL B DUTY 3 14 V LT1533CS Feedback Pin Current............................................ 10mA IN SYNC 4 13 R VSL LT1533IS Negative Feedback Pin Current ............................ 10mA C 5 12 R T CSL Storage Temperature Range ................. 65C to 150C R 6 11 SHDN T Maximum Junction Temperature ......................... 125C FB 7 10 V C Operating Junction Temperature Range NFB 8 9 GND LT1533C ............................................... 0C to 100C LT1533I ............................................ 40C to 100C S PACKAGE 16-LEAD NARROW PLASTIC SO Lead Temperature (Soldering, 10 sec).................. 300C T = 125C, = 100C/ W JMAX JA Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS V = 5V, V = 0.9V, V = V . COL A, COL B, SHDN, NFB, DUTY pins open, unless otherwise noted. IN C FB REF SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Supply and Protection V Recommended Operating Range l 2.7 23 V IN V Minimum Input Voltage l 2.55 2.7 V IN(MIN) I Supply Current 2.7V V 23V, R , R , R = 17k l 12 18 mA VIN IN VSL CSL T I Shutdown Supply Current 2.7V V 23V, V = 0V l 12 30 A VIN(OFF) IN SHDN V Shutdown Threshold 2.7V V 23V l 0.4 0.8 1.2 V SHDN IN I Shutdown Input Current 2 A SHDN Error Amplifiers V Reference Voltage Measured at Feedback Pin 1.235 1.250 1.265 V REF l 1.215 1.250 1.275 V I Feedback Input Current V = V l 250 900 nA FB FB REF FB Reference Voltage Line Regulation 2.7V V 23V l 0.003 0.03 %/V REG IN V Negative Feedback Reference Voltage Measured at Negative Feedback Pin with l 2.550 2.500 2.420 V NFR Feedback Pin Open I Negative Feedback Input Current V = V l 37 25 A NFR NFB NFR NFB Negative Feedback Reference Voltage 2.7V V 23V l 0.002 0.05 %/V REG IN Line Regulation 2 U W U W U WW