The LTC1698 is a precision secondary-side forward converter controller that synchronously drives external N-channel MOSFETs. It is designed for use with the LT3781 primary-side synchronous forward converter controller to create a completely isolated power supply. The LT3781 synchronizes the LTC1698 through a small pulse transformer and the LTC1698 drives a feedback optocoupler to close the feedback loop. Output accuracy of ±0.8% and high efficiency over a wide range of load currents are obtained. The LTC1698 provides accurate secondary-side current limit using an external current sense resistor. The input voltage at the MARGIN pin provides ±5% output voltage adjustment. A power good flag and overvoltage input are provided to ensure proper power supply conditions. An auxiliary 3.3V logic supply is included that supplies up to 10mA of output current.
The LTC1698 is a precision secondary‑side synchronous rectifier controller designed to work with the LT3781 primary‑side controller in isolated forward converters. It drives external N‑channel MOSFETs, provides a 3.3 V auxiliary supply, and includes built‑in protection features such as over‑voltage and current‑limit detection.
The document lists absolute maximum ratings, electrical characteristics, pin descriptions, typical performance graphs, and package information for the 16‑lead SSOP and SO versions. It also shows example application schematics and efficiency curves for 3.3 V/15 A and 5 V/30 A converters.
| Supply Voltage (Vpp) | 6 V to 12.6 V |
|---|---|
| Input Voltage Range (MARGIN, Vep, OVPIN, Isysenp) | -0.3 V to 5.3 V |
| Output Voltage Range (Vcomp, lcomp) | -0.3 V to 5.3 V |
| Operating Temperature Range | -40 °C to 85 °C |
| Storage Temperature Range | -65 °C to 150 °C |
| Lead Temperature (Soldering, 10 s) | 300 °C |
| Package Types | 16‑Lead Plastic SSOP, 16‑Lead Plastic SO |
The absolute maximum rating for the input voltage is –0.3 V to 5.3 V.
The LTC1698E operates from –40 °C to 85 °C.