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LT8309

Linear
Part Number LT8309
Manufacturer Linear
Description Secondary-Side Synchronous Rectifier Driver
Published Mar 31, 2016
Detailed Description LT8309 Secondary-Side Synchronous Rectifier Driver Features n Works with DCM and BCM/CrCM Conduction Mode Flyback Topo...
Datasheet PDF File LT8309 PDF File

LT8309
LT8309

Overview
LT8309 Secondary-Side Synchronous Rectifier Driver Features n Works with DCM and BCM/CrCM Conduction Mode Flyback Topologies n VCC: 4.
5V to 40V n Supports Up to 150V MOSFETs n 26ns Turn-Off Propagation Delay n Accurate Minimum On and Off Timers for Reliable Operation n Adjustable and Accurate Trip Point: +5mV to –30mV n 1Ω Gate Driver Pull-Down n SOT-23 5-Lead Package Applications n High Output Current Flybacks n High Efficiency Flybacks 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.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Typical Application 40W, 5V Isolated Telecom Supply VIN 36V TO 72V 10µF 15.
4k 412k EN/UVLO VIN LT3748 RFB RREF 5.
33:1 60Ω • 100pF • 147k 6.
04k 10Ω 1µF 2.
2k 30.
9k 0.
1µF TC GATE SS SENSE VC GND INTVCC 12.
1k 15nF 4.
7µF 12mΩ 400µF LT8309 VCC DRAIN GATE INTVCC GND 4.
7µF VOUT + 5V, 8A 6.
2V VOUT– 8309 TA01a EFFICIENCY (%) Efficiency vs Load Current 100 95 90 VIN = 48V WITH LT8309 85 80 VIN = 48V WITH PDS760 DIODE 75 70 65 012345678 LOAD CURRENT (A) 8309 TA01b For ...


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