Datasheet LT8311 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Synchronous Rectifier Controller with Opto-Coupler Driver for Forward Converters |
| Pages / Page | 48 / 1 — FEATURES. DESCRIPTION. Wide Input Supply Range: 3.7V to 30V. Preactive … |
| File Format / Size | PDF / 744 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Wide Input Supply Range: 3.7V to 30V. Preactive Mode:. No Pulse Transformer Required
Model Line for this Datasheet
Text Version of Document
LT8311 Synchronous Rectifier Controller with Opto-Coupler Driver for Forward Converters
FEATURES DESCRIPTION
n
Wide Input Supply Range: 3.7V to 30V
The LT®8311 is used on the secondary side of a forward n
Preactive Mode:
converter to provide synchronous MOSFET control and n
No Pulse Transformer Required
output voltage feedback through an opto-coupler. The n
DCM Operation at Light Load
LT8311’s unique preactive mode allows control of the n
SYNC Mode:
secondary-side MOSFETs without requiring a traditional n
FCM or DCM Operation at Light Load
pulse transformer for primary- to secondary-side com- n
Achieves Highest Efficiency
munication. In preactive mode, the output inductor current n
1.5% Feedback Voltage Reference
operates in discontinuous conduction mode (DCM) at n
10mA Opto-Coupler Driver
light load. If forced continuous mode (FCM) operation is n
Output Power Good Indicator
desired at light load, the LT8311 can, alternatively, be used n Integrated Soft-Start Function in SYNC mode, where a pulse transformer is required to send synchronous control signals from the primary-side
APPLICATIONS
IC to the LT8311. n Offline and HV Car Battery Isolated Power Supplies The LT8311 offers a full featured opto-coupler controller, n 48V Isolated Power Supplies incorporating a 1.5% reference, a transconductance error n Industrial, Automotive and Military Systems amplifier and a 10mA opto-driver. Power good monitoring L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear and output soft-start/overshoot control are also included. Technology Corporation. All other trademarks are the property of their respective owners. The LT8311 is available in a 16-lead FE package with pins removed for high voltage spacing requirements.
TYPICAL APPLICATION 18V to 72V, 12V/8A Active Clamp Isolated Forward Converter
V 4:4 6.8µH IN VOUT 18V to 12V 4.7µF + 72V 68pF × 3 100k • • 20k V 470µF IN 22µF UVLO_VSEC 2.2µF 100V 100nF × 2 2.2nF 2k 5.9k 100nF FSW 100k OVLO AOUT FG FB 2k 1.82k 11.3k LT3753 10k CSW LT8311 1.78k CSP IVSEC 240kHz OUT CG VIN VOUT RT 71.5k 2k 1.78k 100k SYNC 31.6k ISENSEP CSN S PGOOD OUT OC 6mΩ 1.5k OPTO TAO ISENSEN INTVCC COMP TAS 4.7µF SYNC PMODE 49.9k TOS INTV 15nF CC SS TIMER GND 2.2µF TBLNK COMP 4.7µF 100Ω GND SS1 SS2 FB 100k 2.94k 124k 10pF 1µF 0.47µF 1µF 34k 1µF 100k 8311 TA01 1k 2.2nF 8311f For more information www.linear.com/LT8311 1 Document Outline Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation FUNDAMENTALS OF FORWARD CONVERTER OPERATION IN CCM LT8311 SYNCHRONOUS CONTROL SCHEMES PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL OPTO-COUPLER CONTROL Applications Information VIN BIAS SUPPLY INTVCC BIAS SUPPLY LT8311 OPTO CONTROL FUNDAMENTALS LT8311 SYNCHRONOUS CONTROL FUNDAMENTALS PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL Typical Applications Package Description Typical Application Related Parts
FEATURES DESCRIPTION
n
Wide Input Supply Range: 3.7V to 30V
The LT®8311 is used on the secondary side of a forward n
Preactive Mode:
converter to provide synchronous MOSFET control and n
No Pulse Transformer Required
output voltage feedback through an opto-coupler. The n
DCM Operation at Light Load
LT8311’s unique preactive mode allows control of the n
SYNC Mode:
secondary-side MOSFETs without requiring a traditional n
FCM or DCM Operation at Light Load
pulse transformer for primary- to secondary-side com- n
Achieves Highest Efficiency
munication. In preactive mode, the output inductor current n
1.5% Feedback Voltage Reference
operates in discontinuous conduction mode (DCM) at n
10mA Opto-Coupler Driver
light load. If forced continuous mode (FCM) operation is n
Output Power Good Indicator
desired at light load, the LT8311 can, alternatively, be used n Integrated Soft-Start Function in SYNC mode, where a pulse transformer is required to send synchronous control signals from the primary-side
APPLICATIONS
IC to the LT8311. n Offline and HV Car Battery Isolated Power Supplies The LT8311 offers a full featured opto-coupler controller, n 48V Isolated Power Supplies incorporating a 1.5% reference, a transconductance error n Industrial, Automotive and Military Systems amplifier and a 10mA opto-driver. Power good monitoring L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear and output soft-start/overshoot control are also included. Technology Corporation. All other trademarks are the property of their respective owners. The LT8311 is available in a 16-lead FE package with pins removed for high voltage spacing requirements.
TYPICAL APPLICATION 18V to 72V, 12V/8A Active Clamp Isolated Forward Converter
V 4:4 6.8µH IN VOUT 18V to 12V 4.7µF + 72V 68pF × 3 100k • • 20k V 470µF IN 22µF UVLO_VSEC 2.2µF 100V 100nF × 2 2.2nF 2k 5.9k 100nF FSW 100k OVLO AOUT FG FB 2k 1.82k 11.3k LT3753 10k CSW LT8311 1.78k CSP IVSEC 240kHz OUT CG VIN VOUT RT 71.5k 2k 1.78k 100k SYNC 31.6k ISENSEP CSN S PGOOD OUT OC 6mΩ 1.5k OPTO TAO ISENSEN INTVCC COMP TAS 4.7µF SYNC PMODE 49.9k TOS INTV 15nF CC SS TIMER GND 2.2µF TBLNK COMP 4.7µF 100Ω GND SS1 SS2 FB 100k 2.94k 124k 10pF 1µF 0.47µF 1µF 34k 1µF 100k 8311 TA01 1k 2.2nF 8311f For more information www.linear.com/LT8311 1 Document Outline Related Parts Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation FUNDAMENTALS OF FORWARD CONVERTER OPERATION IN CCM LT8311 SYNCHRONOUS CONTROL SCHEMES PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL OPTO-COUPLER CONTROL Applications Information VIN BIAS SUPPLY INTVCC BIAS SUPPLY LT8311 OPTO CONTROL FUNDAMENTALS LT8311 SYNCHRONOUS CONTROL FUNDAMENTALS PREACTIVE MODE SYNCHRONOUS CONTROL SYNC MODE SYNCHRONOUS CONTROL Typical Applications Package Description Typical Application Related Parts
