LT3439 Slew Rate Controlled Ultralow Noise1A Isolated DC/DC Transformer Driver UFEATURESDESCRIPTIO ■ Reduced Conducted and Radiated EMI The LT®3439 is a push-pull DC/DC transformer driver that ■ Single Resistor Control of Output Switch Voltage reduces conducted and radiated electromagnetic interfer- and Current Slew Rates ence (EMI). Ultralow noise and EMI are achieved by ■ Cross Conduction Prevention Circuitry controlling the output switch voltage and current slew ■ Two 1A Current Limited Power Switches rates. Slew rates are user adjustable to optimize output ■ Low Minimum Supply Voltage: 2.8V noise versus efficiency. The LT3439 can reduce high ■ Low Shutdown Current: < 20µA frequency harmonic content by as much as 40dB with only ■ 50% Duty Cycle a minor decrease in efficiency. ■ 20kHz to 250kHz Oscillator Frequency The LT3439 includes two 1A current limited power switches ■ Synchronizable to 300kHz to ensure start-up under heavy loads. It also includes an ■ Overcurrent and Overtemperature Protected oscillator that can be synchronized to an external clock for more accurate placement of switcher harmonics. Protec- U tion features include current limiting, undervoltage lock- APPLICATIO S out, thermal shutdown and cross conduction prevention ■ Low Noise Isolated Supplies circuitry. ■ Radio and Telecom Supplies The LT3439 is available in a thermally enhanced 16-pin ■ Distributed Supplies TSSOP with an exposed backside. ■ Medical Instruments ■ Precision Instruments , LTC and LT are registered trademarks of Linear Technology Corporation. ■ Low Noise Filament Supplies UTYPICAL APPLICATIOLow Noise 5V to 5V Push-Pull DC/DC Transformer5V Output Noise OPTIONAL V D1 IN L1 33µH T1 A B VOUT 5V C 5V IN 13 C1 C2 22µF • • 500mA 47µF 47µF 10V VIN B 11 3 6.3V 6.3V SHDN COL A 200µV/DIV • • LT3439 5 14 SYNC COL B 6 CT D2 680pF 7 4 CIN: MURATA GRM235Y5V226Z10 R R C1, C2: TDK C4532X5R0J476M T SL A 16.9k D1, D2: MBR0520 GND PGND 34k L1: TDK SLF6028T-330MR69 20mV/DIV 10 1, 16 T1: COILTRONICS 15835 3439 TA01 5µs/DIV 3439 TA01b sn3439 3439fs 1
