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Design Note
Reliability Data
LT Journal
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Features
- Senses Output Voltage Directly from Primary Side Winding—No Opto-Isolator Required
- Synchronous Driver for High Efficiency
- Input Voltage Limited Only by External Power Components
- Accurate Output Regulation without User Trims
- Switching Frequency from 50kHz to 250kHz
- Synchronizable
- Load Compensation
- Programmable Undervoltage Lockout
- Available in a Thermally Enhanced 16-Lead TSSOP Package
Typical Application
Description
The LT3825 is an isolated switching regulator controller designed for medium power flyback topologies. A typical application is 10W to 60W with input voltage limited onlyby external power path components. A third transformer winding provides output voltage feedback.
The LT3825 is a current mode controller that regulates output voltage based on sensing secondary voltage via a transformer winding during flyback. This allows for tight output regulation without the use of an opto-isolator,improving dynamic response and reliability. Synchronous rectification increases converter efficiency and improves output cross regulation in multiple output converters.
The LT3825 operates in forced continuous conduction mode which improves cross regulation in multiple winding applications.Switching frequency is user programmable and can be externally synchronized. The part also has load compensation, undervoltage lockout and soft-start circuity.
TSSOP-16
Package Variations and Pricing
| Part Number | Package | Pins | Temp | Price (1-99) |
Price (1k)* |
|---|---|---|---|---|---|
| LT3825EFE#PBF | TSSOP | 16 | E | $4.43 | $3.10 |
| LT3825EFE#TRPBF | TSSOP | 16 | E | $3.16 | |
| LT3825EFE | TSSOP | 16 | E | $8.86 | $6.20 |
| LT3825EFE#TR | TSSOP | 16 | E | $6.32 |
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 |
|---|---|---|---|
| DC1143A | LT3825EFE Demo Board | Synchronous Isolated Flyback, 36V ≤ Vin ≤ 72V, Vout: 3.3V @ 6A | Contact Factory | |
| DC894A-A | LT3825EFE Demo Board I Synchronous Flyback Converter, Vin=36V-72V, Vout=3.3V@12A | $150.00 | |
| DC894B-C | LT3825EFE Demo Board | Isolated, 36V ≤ VIN ≤ 72V, VOUT = 12V @ 5A | $150.00 | |
| DC894C-B | LT3825EFE Isolated Demo Board | Sync Flyback Controller, 36V ≤ VIN ≤ 72V; VOUT = 5V @ 8A | $150.00 | |
| DC894C-C | LT3825EFE Isolated Demo Board | Sync No Opto Flyback Controller, 36V ≤ VIN ≤ 72V; VOUT = 12V @ 5A | $150.00 | |
| DC950A-A | LT3825EFE Demo Board | Isolated Synchronous Flyback, 36V ≤ Vin ≤ 72V, Vout: 5V/2A, 3.3V/3A, 2.5V/3A | $150.00 |