LT1683 Slew Rate Controlled Ultralow Noise Push-Pull DC/DC Controller FEATURES DESCRIPTION n Greatly Reduced Conducted and Radiated EMI The LT 1683 is a switching regulator controller designed to n Low Switching Harmonic Content lower conducted and radiated electromagnetic interference n Independent Control of Output Switch Voltage and (EMI). Ultralow noise and EMI are achieved by controlling Current Slew Rates the voltage and current slew rates of external N-channel n Greatly Reduced Need for External Filters MOSFET switches. Current and voltage slew rates can n Dual N-Channel MOSFET Drivers be independently set to optimize harmonic content of n 20kHz to 250kHz Oscillator Frequency the switching waveforms vs efficiency. The LT1683 can n Easily Synchronized to External Clock reduce high frequency harmonic power by as much as n Regulates Positive and Negative Voltages 40dB with only minor losses in efficiency. n Easier Layout Than with Conventional Switchers The LT1683 utilizes a dual output (push-pull) current mode architecture optimized for low noise topologies. APPLICATIONS The IC includes gate drivers and all necessary oscillator, n Power Supplies for Noise Sensitive Communication control and protection circuitry. Unique error amp circuitry Equipment can regulate both positive and negative voltages. The oscil- n EMI Compliant Offline Power Supplies lator may be synchronized to an external clock for more n Precision Instrumentation Systems accurate placement of switching harmonics. n Isolated Supplies for Industrial Automation Protection features include gate drive lockout for low V , IN n Medical Instruments opposite gate lockout, soft-start, output current limit, n Data Acquisition Systems short-circuit current limiting, gate drive overvoltage clamp L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and DirectSense is a trademark of Linear Technology Corporation. All other trademarks are the and input supply undervoltage lockout. property of their respective owners. TYPICAL APPLICATION Ultralow Noise 48V to 5V DC/DC Converter 48V 510 39F 51k 0.5W 63V MIDCOM 31244 FZT853 10F 1N4148 MBR0530 OPTIONAL 20V MBRS340 22H B 22H A 5V/2A 2N3904 8.2V 5V Output Noise 150F 2100F 68F 11V OS-CON POSCAP (Bandwidth = 100MHz) 20V 17 3 V GCL IN 5pF 10pF 23.2k 200V 14 2 SHDN CAP A 5 976 V5 MBRS340 1 6 GATE A A 10pF SYNC 5pF 1.2nF 200V P-P 200V 200V/DIV 7 18 C CAP B T LT1683 30pF 16.9k 8 19 R GATE B T B Si9422 25k 3.3k 16 4 Si9422 20mV/DIV R VSL CS 25k 3.3k 0.1 15 R 20 CSL PGND 1.5k 7.50k 12 V 9 C FB 5s/DIV 1683 TA01a 0.22F 22nF SS GND NFB 30pF 2.49k 13 11 10 10nF 1683 TA01 1683fd 1LT1683 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Supply Voltage (V ) .................................................20V IN GATE A 1 20 PGND Gate Drive Current .....................................Internal Limit CAP A 2 19 GATE B V5 Current.................................................. Internal Limit GCL 3 18 CAP B SHDN Pin Voltage .....................................................20V CS 4 17 V IN Feedback Pin Voltage (Trans. 10ms) ...................... 10V V5 5 16 R VSL Feedback Pin Current ............................................10mA SYNC 6 15 R CSL Negative Feedback Pin Voltage (Trans. 10ms) ......... 10V C 7 14 SHDN T CS Pin ...........................................................................5V R 8 13 SS T GCL Pin .......................................................................16V FB 9 12 V C SS Pin ...........................................................................3V NFB 10 11 GND Operating Junction Temperature Range G PACKAGE 20-LEAD PLASTIC SSOP (Note 3) ..................................................40C to 125C T = 150C, = 110C/ W JMAX JA Storage Temperature Range ...................65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1683EG PBF LT1683EG TRPBF 1683 20-Lead Plastic SSOP 40C to 125C LT1683IG PBF LT1683IG TRPBF 1683 20-Lead Plastic SSOP 40C to 125C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT1683EG LT1683EG TR 1683 20-Lead Plastic SSOP 40C to 125C LT1683IG LT1683IG TR 1683 20-Lead Plastic SSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: