6.5V to 100V input — wide-bus forward controller
The LT3752EFE#PBF is a current-mode PWM controller for isolated forward converters, accepting a supply rail from 6.5V up to 100V. That 100V ceiling covers 48V telecom buses with margin for transients, 72V railway batteries, and 24V industrial rails without an external pre-regulator. Switching frequency is programmable from 100kHz to 500kHz, letting the designer trade transformer size against core loss. The 95% maximum duty cycle supports high step-down ratios — useful when a 100V input must produce a 3.3V or 5V output without an intermediate bus.
Synchronous rectifier drive and isolation capability
The controller includes a synchronous rectifier driver output, which eliminates the Schottky catch diode in the secondary — improves efficiency by 3-5% in a typical 50W forward converter. The output configuration is positive, isolation capable, meaning the controller drives a primary-side transistor while the secondary-side synchronous rectifier can be referenced to the isolated output ground. Control features include Enable, Frequency Control, and Soft Start. The soft-start pin ramps the duty cycle on power-up, preventing output overshoot and inrush current through the transformer. Frequency control allows synchronization to an external clock via the Clock Sync input.
38-TSSOP-EP — thermal and footprint considerations
Housed in a 38-lead TSSOP with exposed pad, the package measures 4.40mm wide with 0.173" (4.40mm) body length. The 125°C ceiling is the absolute junction limit — actual case temperature will be lower depending on the copper area and airflow. The sibling LT3752HFE#PBF extends this to 150°C for higher ambient applications.