Datasheet LT3825 (Analog Devices)
| Manufacturer | Analog Devices |
| Description | Isolated No-Opto Synchronous Flyback Controller with Wide Input Supply Range |
| Pages / Page | 32 / 1 — FEATURES. DESCRIPTION. Senses Output Voltage Directly from Primary Side. … |
| File Format / Size | PDF / 390 Kb |
| Document Language | English |
FEATURES. DESCRIPTION. Senses Output Voltage Directly from Primary Side. Winding—No Opto-Isolator Required
Model Line for this Datasheet
Text Version of Document
LT3825 Isolated No-Opto Synchronous Flyback Controller with Wide Input Supply Range
FEATURES DESCRIPTION
n
Senses Output Voltage Directly from Primary Side
The LT®3825 is an isolated switching regulator controller
Winding—No Opto-Isolator Required
designed for medium power flyback topologies. A typical n
Synchronous Driver for High Efficiency
application is 10W to 60W with input voltage limited only n
Input Voltage Limited Only by External
by external power path components. A third transformer
Power Components
winding provides output voltage feedback. n Accurate Output Regulation without User Trims The LT3825 is a current mode controller that regulates n Switching Frequency from 50kHz to 250kHz output voltage based on sensing secondary voltage via a n Synchronizable transformer winding during flyback. This allows for tight n Load Compensation output regulation without the use of an opto-isolator, n Programmable Undervoltage Lockout improving dynamic response and reliability. Synchronous n Available in a Thermally Enhanced 16-Lead rectification increases converter efficiency and improves TSSOP Package output cross regulation in multiple output converters.
APPLICATIONS
The LT3825 operates in forced continuous conduction mode which improves cross regulation in multiple winding n Isolated Medium Power (10W to 60W) Supplies applications. Switching frequency is user programmable n Isolated Telecom, Medical Converters and can be externally synchronized. The part also has load n Instrumentation Power Supplies compensation, undervoltage lockout and soft-start circuity. n Isolated Power over Ethernet Supplies L, LT, LTC, LTM, Burst Mode, SwitcherCAD, Linear Technology and the Linear logo are registered trademarks and No RSENSE, ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 6948466, 5841643.
TYPICAL APPLICATION Efficiency
92 90 36VIN 48VIN 88 72VIN
48V to 3.3V at 12A Isolated Supply
86 84 + V + EFFICIENCY (%) OUT VIN 3.3V 82 36V TO 72V • 470µF 100pF 12A ×4 T1 80 28.7k T1 • 20Ω 47k 20Ω 78 • 47Ω 2 3.01k 3 4 5 6 7 8 9 10 11 12 + LOAD CURRENT (A) 3825 TA01b 47µF SG 402k ×2
Regulation
FB VCC SG PG SENSE+ 3.43 2.2µF SG 0.02Ω 1µF UVLO 3.38 15k LT3825 330Ω 15Ω SENSE– 36VIN 2.2nF 48V PGDLY VC 0.1µF 3.33 IN 72VIN tON SYNC RCMP ENDLY OSC GND SFST CCMP 10nF • • 3.28 12k 100k 2.1k 150k 0.22µF 10k 100k OUTPUT (V) 47pF 0.1µF 3825 TA01a 3.23 3.18 3.13 2 3 4 5 6 7 8 9 10 11 12 LOAD CURRENT (A) 3825 TA01c 3825fe 1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts
FEATURES DESCRIPTION
n
Senses Output Voltage Directly from Primary Side
The LT®3825 is an isolated switching regulator controller
Winding—No Opto-Isolator Required
designed for medium power flyback topologies. A typical n
Synchronous Driver for High Efficiency
application is 10W to 60W with input voltage limited only n
Input Voltage Limited Only by External
by external power path components. A third transformer
Power Components
winding provides output voltage feedback. n Accurate Output Regulation without User Trims The LT3825 is a current mode controller that regulates n Switching Frequency from 50kHz to 250kHz output voltage based on sensing secondary voltage via a n Synchronizable transformer winding during flyback. This allows for tight n Load Compensation output regulation without the use of an opto-isolator, n Programmable Undervoltage Lockout improving dynamic response and reliability. Synchronous n Available in a Thermally Enhanced 16-Lead rectification increases converter efficiency and improves TSSOP Package output cross regulation in multiple output converters.
APPLICATIONS
The LT3825 operates in forced continuous conduction mode which improves cross regulation in multiple winding n Isolated Medium Power (10W to 60W) Supplies applications. Switching frequency is user programmable n Isolated Telecom, Medical Converters and can be externally synchronized. The part also has load n Instrumentation Power Supplies compensation, undervoltage lockout and soft-start circuity. n Isolated Power over Ethernet Supplies L, LT, LTC, LTM, Burst Mode, SwitcherCAD, Linear Technology and the Linear logo are registered trademarks and No RSENSE, ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 6948466, 5841643.
TYPICAL APPLICATION Efficiency
92 90 36VIN 48VIN 88 72VIN
48V to 3.3V at 12A Isolated Supply
86 84 + V + EFFICIENCY (%) OUT VIN 3.3V 82 36V TO 72V • 470µF 100pF 12A ×4 T1 80 28.7k T1 • 20Ω 47k 20Ω 78 • 47Ω 2 3.01k 3 4 5 6 7 8 9 10 11 12 + LOAD CURRENT (A) 3825 TA01b 47µF SG 402k ×2
Regulation
FB VCC SG PG SENSE+ 3.43 2.2µF SG 0.02Ω 1µF UVLO 3.38 15k LT3825 330Ω 15Ω SENSE– 36VIN 2.2nF 48V PGDLY VC 0.1µF 3.33 IN 72VIN tON SYNC RCMP ENDLY OSC GND SFST CCMP 10nF • • 3.28 12k 100k 2.1k 150k 0.22µF 10k 100k OUTPUT (V) 47pF 0.1µF 3825 TA01a 3.23 3.18 3.13 2 3 4 5 6 7 8 9 10 11 12 LOAD CURRENT (A) 3825 TA01c 3825fe 1 Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts
