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LINEAR LT3511 Monolithic High Voltage Isolated Flyback Converter User's Manual

Summary

The LT3511 is a high-voltage monolithic switching regulator designed for isolated flyback power conversion, capable of handling inputs from 4.5V to 100V and delivering up to 2.5W of isolated output power. This manual details the product's features, functional specifications, and typical applications, including telecom supplies and industrial power. Ideal for engineers designing compact, highly regulated isolated DC-DC power solutions who require advanced integration like boundary mode operation without external optocouplers or third windings.

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LT3511

查询LT3511供应商

Monolithic High Voltage Isolated Flyback Converter

FEATURES DESCRIPTION n 4.5V to 100V Input Voltage Range

The LT3511 is a high voltage monolithic switching regula-

n Internal 240m A, 150V Power Switch

tor specifically designed for the isolated flyback topology.

n Boundary Mode Operation

No third winding or opto-isolator is required for regula-

n No Transformer Third Winding or

tion as the part senses output voltage directly from the

Opto-Isolator Required for Regulation primary-side flyback waveform. The device integrates a n Improved Primary-Side Winding Feedback

240m A, 150V power switch, high voltage circuitry, and

Load Regulation control into a high voltage 16-lead MSOP package with n VOUT Set with Two External Resistors

four leads removed.

n BIAS Pin for Internal Bias Supply and Power

The LT3511 operates from an input voltage range of 4.5V

Switch Driver

to 100V and delivers up to 2.5W of isolated output power.

n No External Start-Up Resistor

Two external resistors and the transformer turns ratio

n 16-Lead MSOP Package

easily set the output voltage. Off-the-shelf transformers are available for several applications. The high level of APPLICATIONS integration and the use of boundary mode operation results in a simple, clean, tightly regulated application solution to

n Isolated Telecom Power Supplies

UT (V the traditionally tough problem of isolated power delivery.

n Isolated Auxiliary/Housekeeping Power Supplies

L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks

n Isolated Industrial, Automotive and Medical Power

and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5438499, 7471522.

Supplies

TYPICAL APPLICATION

48V to 5V Isolated Flyback Converter Output Load and Line Regulation

VIN 5.25

36V TO 72V 4:1

VIN 0.3A

EN/UVLO 19µH300µH 5.15

169k VOUT

LT3511 VIN = 48V

RFB VIN = 36V

4.95 VIN = 72V

TC SW

VC GND BIAS

3511 TA01a

LOAD CURRENT (m A)

3511 TA01b

Page Summary Contents For LINEAR LT3511 Monolithic High Voltage Isolated Flyback Converter User's Manual

Page 1 LT3511 查询LT3511供应商 Monolithic High Voltage Isolated Flyback Converter FEATURES DESCRIPTION n 4.5V to 100V Input Voltage Range The LT3511 is a high voltage monolithic switching regula- n Internal 240m ...
Page 2 LT3511 查询LT3511供应商 PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS (Note 1) SW (Note 4) ............................................................150V TOP VIEW EN/UVLO SW VIN, EN/UVLO .......................
Page 3 UT (V SW IT CH CE SA VO LT AG (m V) LT3511 查询LT3511供应商 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are a...
Page 4 AX IM UM RE QU EN CY (k Hz EN /U VL PI CU RR EN (µ A) LT3511 查询LT3511供应商 TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted. EN/UVLO Pin (Hysteresis) Current EN/UVLO Pin Current EN/...
Page 5 LT3511 查询LT3511供应商 PIN FUNCTIONS EN/UVLO (Pin 1): Enable/Undervoltage Lockout. The EN/ VC (Pin 10): Compensation Pin for Internal Error Amplifier. UVLO pin is used to start up the LT3511. Pull the pin...
Page 6 LT3511 查询LT3511供应商 BLOCK DIAGRAM VIN T1 VOUT RFB SWVIN CURRENT FLYBACK Q3 Q2 ERROR ONE CURRENT A2 TC AMP SHOT COMPARATOR R5 gm V1 VIN RREF DRIVER BIAS BIAS MASTER LATCH C4 A4 RSENSE 0.02Ω GND INTERNAL...
Page 7 LT3511 查询LT3511供应商 OPERATION The LT3511 is a current mode switching regulator IC de- controls the current level just as it does in normal current signed specifically for the isolated flyback topology....
Page 8 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION PSUEDO DC THEORY the effect of nonzero secondary output impedance (ESR). Boundary control mode minimizes the effect of this im- In the Block Diagram, RREF (...
Page 9 LT3511 查询LT3511供应商 OU TP UT OW ER (W OU TP UT OW ER (W APPLICATIONS INFORMATION similar to a nonisolated buck-boost. The duty cycle will One design example would be a 5V output converter with affect t...
Page 10 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION TRANSFORMER DESIGN CONSIDERATIONS Linear Technology has worked with several leading mag- netic component manufacturers to produce pre-designed Successful ap...
Page 11 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION Turns Ratio Saturation Current Note that when using an RFB/RREF resistor ratio to set The current in the transformer windings should not ex- output voltage,...
Page 12 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION VSW VSW <150V <150V VLEAKAGE t OFF > 400ns t OFF > 400ns TIME TIME t SP < 150ns t SP < 150ns without Clamp with Clamp Figure 5. Maximum Vo...
Page 13 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION Table 2 and 3 show some recommended diodes and Zener pulse. The smaller flyback pulse results in a higher regulated diodes. output voltage. The inductive di...
Page 14 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION Selecting RFB and RREF Resistor Values VIN The following section provides an equation for setting R1 RFB and RREF values. The equation should only serve EN/...
Page 15 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION BIAS Pin Considerations improves overall system efficiency. Design the third wind- ing to output a voltage between 3.3V and 12V. For a typi- The BIAS pin po...
Page 16 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION 150V 72V 40V Step 3: Determine primary inductance, switching frequency and saturation current. NPS 2.45 Primary inductance for the transformer must be set a...
Page 17 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION VOUT •IOUT •2 Step 5: Choose an output capacitor. IPEAK VIN •D The output capacitor choice should minimize output voltage ripple and balance the trade-off b...
Page 18 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION Choose a diode that is fast and has sufficient reverse Step 9: Adjust RFB based on output voltage. voltage breakdown: Power up the application with applicat...
Page 19 LT3511 查询LT3511供应商 APPLICATIONS INFORMATION Step 11: Calculate new value for RTC. Step 15: Ensure minimum load. RFB 1.85m V °C Check minimum load requirement at maximum input RTC(NEW) ∆VOUT voltage. T...
Page 20 LT3511 查询LT3511供应商 TYPICAL APPLICATIONS 48V to 5V Isolated Flyback Converter VIN 4:1:1 D1 36V TO 72V 1M VIN T1 C4 EN/UVLO 19µH 300µH 22µF 43.2k VOUT 169k RFB LT3511 RREF C1: TAIYO YUDEN HMK316B7105KL-...
Page 21 LT3511 查询LT3511供应商 TYPICAL APPLICATIONS 24V to 5V Isolated Flyback Converter VIN D1 20V TO 30V 5V VIN Z1 0.25A EN/UVLO 300µH 22µF R2 80.6k VOUT 249k LT3511 RFB C1: MURATA GRM31CR71H475KA12B C3: TAIYO ...
Page 22 LT3511 查询LT3511供应商 TYPICAL APPLICATIONS 12V to ±70V Isolated Flyback Converter VIN D1 VOUT1 1:5:5 8V TO 20V 70V 2.2µF VIN Z1 EN/UVLO 80µH 562k VOUT1 RFB VOUT2 LT3511 4m A 0.47µF VOUT2 TC SW VC GND BIA...
Page 23 LT3511 查询LT3511供应商 PACKAGE DESCRIPTION MS Package Varitation: MS16 (12) 16-Lead Plastic MSOP with 4 Pins Removed (Reference LTC DWG # 05-08-1847 Rev A) (.159 ± .004) (NOTE 3) 0.280 ± 0.076 (.011 ± .00...
Page 24 LT3511 查询LT3511供应商 TYPICAL APPLICATION 48V to ±15V Isolated Flyback Converter VIN D1 VOUT1 2:1:1 36V TO 72V 15V 1µF VIN EN/UVLO 350µH 4.7µF R2 VOUT1 RFB VOUT2 LT3511 RREF 50m A TC SW VOUT2 VC GND BIAS...

Manual Details

Brand Linear
Pages 24
File Size 1.77 MB
Published May 25, 2026
157 views

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Frequently Asked Questions

What is the input voltage range for the LT3511 converter?

The device operates from an input voltage range of 4.5V to 100V.

Does the LT3511 require external isolation components?

No, boundary mode operation allows it to sense output voltage directly, eliminating the need for a third winding or opto-isolator.

What type of applications is the LT3511 suitable for?

It is ideal for isolated telecom power supplies, auxiliary/housekeeping power, and industrial/automotive power delivery.

Where can the LT3511 be mounted for high reliability?

The device comes in a 16-Lead MSOP package with integrated components to simplify assembly.