LT8309 - Secondary-Side Synchronous Rectifier Driver
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.
Packaging
CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.
For complete and up to date package information and drawings, please refer to our packaging page
| Part Number | Package | Code | Temp | Package Drawing |
RoHS |
|---|---|---|---|---|---|
| LT8309ES5#PBF | SOT-23 | S5 | E | 05-08-1635 | Yes |
| LT8309ES5#TRMPBF | SOT-23 | S5 | E | 05-08-1635 | Yes |
| LT8309ES5#TRPBF | SOT-23 | S5 | E | 05-08-1635 | Yes |
| LT8309HS5#PBF | SOT-23 | S5 | H | 05-08-1635 | Yes |
| LT8309HS5#TRMPBF | SOT-23 | S5 | H | 05-08-1635 | Yes |
| LT8309HS5#TRPBF | SOT-23 | S5 | H | 05-08-1635 | Yes |
| LT8309IS5#PBF | SOT-23 | S5 | I | 05-08-1635 | Yes |
| LT8309IS5#TRMPBF | SOT-23 | S5 | I | 05-08-1635 | Yes |
| LT8309IS5#TRPBF | SOT-23 | S5 | I | 05-08-1635 | Yes |
Order Info
- Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
- Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
- Please refer to our general ordering information or the product datasheet for more details
Package Variations and Pricing
| Part Number | Package | Temp | Price (1-99) |
Price (1k)* |
RoHS | |
|---|---|---|---|---|---|---|
| LT8309ES5#PBF | SOT-23 | E | $2.60 | Yes | ||
| LT8309ES5#TRMPBF | SOT-23 | E | $2.60 | $1.84 | Yes | |
| LT8309ES5#TRPBF | SOT-23 | E | $2.60 | $1.82 | Yes | |
| LT8309HS5#PBF | SOT-23 | H | $3.24 | Yes | ||
| LT8309HS5#TRMPBF | SOT-23 | H | $3.24 | $2.32 | Yes | |
| LT8309HS5#TRPBF | SOT-23 | H | $3.24 | $2.27 | Yes | |
| LT8309IS5#PBF | SOT-23 | I | $2.83 | Yes | ||
| LT8309IS5#TRMPBF | SOT-23 | I | $2.83 | $2.00 | Yes | |
| LT8309IS5#TRPBF | SOT-23 | I | $2.83 | $1.98 | Yes | |
| Buy Now • Request Samples | ||||||
Demo Boards
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 | |
| Buy Now | |||
Applications
- High Output Current Flybacks
- High Efficiency Flybacks
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Design Tools
LTspice
LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice
To launch a ready to run LTspice demonstration circuit for this part:
- Step 1: If you have not installed LTspice on this computer, download and install LTspice
- Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
- Step 3: If LTspice does not automatically open after clicking the link above, you can instead run the simulation by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTspice and open the demonstration circuit by selecting 'Open' from the 'File' menu
To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.
Models for the following parts are available in LTspice:
LT8309
Technical Support
- For immediate technical assistance, contact your local sales office or distributor or call 1-800-4-LINEAR (US customers only) or 408-432-1900.
- For less urgent requests, please complete our Technical Support Request Form. Please allow 2-3 business days for reply.
