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LT8309 Dataheets PDF



Part Number LT8309
Manufacturers Linear
Logo Linear
Description Secondary-Side Synchronous Rectifier Driver
Datasheet LT8309 DatasheetLT8309 Datasheet (PDF)

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 syn.

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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 more information www.linear.com/LT8309 8309fa 1 LT8309 Absolute Maximum Ratings (Note 1) VCC.............................................................................40V INTVCC GATE.............................................................10V DRAIN...................................................................... 150V Maximum Junction Temperature........................... 125°C Operating Temperature Range (Note 2) LT8309E............................................. –40°C to 125°C LT8309I.............................................. –40°C to 125°C LT8309H............................................. –40°C to 150°C Storage Temperature Range................... –65°C to 150°C Pin Configuration TOP VIEW GATE 1 GND 2 INTVCC 3 5 DRAIN 4 VCC S5 PACKAGE 5-LEAD PLASTIC TSOT-23 θJA = 215°C/W Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT8309ES5#PBF LT8309ES5#TRPBF LTGFZ 5-Lead Plastic TSOT-23 –40°C to 125°C LT8309IS5#PBF LT8309IS5#TRPBF LTGFZ 5-Lead Plastic TSOT-23 –40°C to 125°C LT8309HS5#PBF LT8309HS5#TRPBF LTGFZ 5-Lead Plastic TSOT-23 –40°C to 150°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 8309fa 2 For more information www.linear.com/LT8309 LT8309 E lectrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX Input Voltage Range l 4.5 40 VCC Quiescent Current Comparator Not Switching, INTVCC = 8V 300 345 Turn-On Threshold Turn-Off Threshold RS = 0Ω RS = 0Ω l –69 –57 –45 17 21 25 l 16 28 Drain Voltage Latch Reset Minimum Off-Time RS = 0Ω 1.21 75 95 115 Minimum On-Time 310 360 410 Drain Current Out of Pin l 9.5 10 10.5 INTVCC Linear Regulator INTVCC Quiescent Current INTVCC Voltage Range INTVCC Regulation Voltage INTVCC UVLO Dropout (VCC to INTVCC) Current Limit Not Switching, INTVCC = 8V IINTVCC = –10mA, VIN = 7V 4.5 l 6.8 1 l 30 100 117 10 7 7.2 4.03 1.3 1.6 42 55 Gate Driver Turn-On Propagation Delay (tD(ON)) Turn-Off Propagation Delay (tD(OFF)) tr GATE Driver Output Rise Time tf GATE Driver Output Fall Time Pull-Up Resistance RS = 0Ω, –100mVOD, VDS to VGATE RS = 0Ω, –100mVOD, VDS to VGATE CL = 3300pF CL = 3300pF 31 40 26 36 21 11 2.7 Pull-Down Resistance 0.8 UNITS V µA mV mV mV V ns ns µA µA V V V V mA ns ns ns ns Ω Ω Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT8309E is guaranteed to meet performance s.


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