The LT
The LT8309 is a secondary-side synchronous rectifier driver designed to replace the output rectifier diode in a flyback topology. By substituting the diode with an N-channel MOSFET, it eliminates heat constraints associated with high-voltage diodes and improves efficiency. The IC replicates diode behavior by sensing drain-to-source voltage to determine when current becomes negative.
Key features include low minimum on- and off-times for improved noise immunity, a fast 26ns turn-off propagation delay enabling operation in discontinuous conduction mode (DCM) and critical conduction mode (CrCM), and a gate driver with a 0.8Ω pull-down device for fast turn-offs. It supports MOSFETs up to 150V and operates with an input voltage range of 4.5V to 40V.
| Input Voltage Range (VCC) | 4.5 V to 40 V |
|---|---|
| Maximum Junction Temperature | 125°C |
| Turn-Off Propagation Delay | 26 ns (Typical) |
| Gate Driver Pull-Down Resistance | 0.8 Ω |
| Quiescent Current (Not Switching) | 345 µA (Typical) |
The LT8309 allows applications to operate in discontinuous conduction mode (DCM) and critical conduction mode (CrCM).
The part supports up to 150V MOSFETs.