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Features
- Works with DCM and BCM/CrCM Conduction Mode Flyback Topologies
- VCC: 4.5V to 40V
- Supports Up to 150V MOSFETs
- 26ns Turn-Off Propagation Delay
- Accurate Minimum On and Off Timers for Reliable Operation
- Adjustable and Accurate Trip Point: +5mV to –30mV
- 1Ω Gate Driver Pull-Down
- SOT-23 5-Lead Package
Typical Application
Description
The LT®8309 is a secondary-side synchronous rectifier driver that replaces the output rectifier diode in a flyback topology. By replacing the diode with a N-channel MOSFET, applications are no longer restricted by the heat constraints of the output diode. The IC replicates the behavior of a diode by sensing the drain-to-source voltage to determine when the current becomes negative. The LT8309's low minimum on- and off-times help improve noise immunity.
The fast propagation delay of 26ns allows applications to operate in discontinuous conduction mode (DCM) and critical conduction mode (CrCM). The gate driver features a 0.8Ω pull-down device for fast turn-offs. The 40V VCC rating allows the part to be driven from the output voltage or the rectified drain voltage of the MOSFET. A low quiescent current of 400μA maximizes efficiency at low output currents.
SOT-23
Package Variations and Pricing
| Part Number | Package | Pins | Temp | Price (1-99) |
Price (1k)* |
|---|---|---|---|---|---|
| LT8309ES5#PBF | SOT | 5 | E | $2.60 | |
| LT8309ES5#TRMPBF | SOT | 5 | E | $2.60 | $1.84 |
| LT8309ES5#TRPBF | SOT | 5 | E | $2.60 | $1.82 |
| LT8309IS5#PBF | SOT | 5 | I | $2.83 | |
| LT8309IS5#TRMPBF | SOT | 5 | I | $2.83 | $2.00 |
| LT8309IS5#TRPBF | SOT | 5 | I | $2.83 | $1.98 |
| LT8309HS5#TRMPBF | SOT | 5 | H | $3.24 | $2.32 |
| LT8309HS5#TRPBF | SOT | 5 | H | $3.24 | $2.27 |
| LT8309HS5#PBF | SOT | 5 | H | $3.24 | |
| LT8309ES5#TR | SOT | 5 | E | $5.20 | $3.64 |
| LT8309IS5#TR | SOT | 5 | I | $5.66 | $3.96 |
| LT8309HS5#TR | SOT | 5 | H | $6.48 | $4.54 |
| LT8309ES5#TRM | SOT | 5 | E | $5.20 | $3.68 |
| LT8309HS5#TRM | SOT | 5 | H | $6.48 | $4.64 |
| LT8309IS5#TRM | SOT | 5 | I | $5.66 | $4.00 |
| LT8309IS5 | SOT | 5 | I | $5.66 |
Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.
| Part Number | Description | Price | Documentation |
|---|---|---|---|
| DC1961A | LT8309ES5/LT3748EMS Isolated Demo Board | 36V ≤ VIN ≤ 72V; VOUT = 12V @ 5A | $175.00 |