LT3575 Isolated Flyback Converter without an Opto-Coupler FEATURESDESCRIPTION n 3V to 40V Input Voltage Range The LT®3575 is a monolithic switching regulator specifi c- n 2.5A, 60V Integrated NPN Power Switch ally designed for the isolated fl yback topology. No third n Boundary Mode Operation winding or optoisolator is required for regulation. The n No Transformer Third Winding or part senses the isolated output voltage directly from the Optoisolator Required for Regulation primary side fl yback waveform. A 2.5A, 60V NPN power n Improved Primary-Side Winding Feedback switch is integrated along with all control logic into a Load Regulation 16-lead TSSOP package. n VOUT Set with Two External Resistors The LT3575 operates with input supply voltages from n BIAS Pin for Internal Bias Supply and Power 3V to 40V, and can deliver output power up to 14W with NPN Driver no external power switch.The LT3575 utilizes boundary n Programmable Soft-Start mode operation to provide a small magnetic solution with n Programmable Power Switch Current Limit improved load regulation. n Thermally Enhanced 16-Lead TSSOP The output voltage is easily set with two external resistors APPLICATIONS and the transformer turns ratio. Off the shelf transformers are available for many applications. n Industrial, Automotive and Medical Isolated L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks Power Supplies and No RSENSE and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION5V Isolated Flyback Converter V Load Regulation IN 12V TO 24V 1 3:1 10μF 357k 0.22μF 1k V + V OUT IN = 24V VIN 5V, 1.4A SHDN/UVLO 24μH 2.6μH 47μF 51.1k 0 V – OUT VIN = 12V 80.6k RFB LT3575 TAGE ERROR (%) RREF TC –1 6.04k RILIM OUTPUT VOL SS SW VC GND TEST BIAS –2 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 28.7k 10k 11.5k IOUT (A) 10nF 4.7nF 4.7μF 3575 TA01b 3575 TA01 3575f 1
