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Analog Devices Inc. LT3575EFE#PBF
- Part No.:
- LT3575EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3575EFE#PBF.pdf
- Description:
- IC REG FLYBACK 2.5A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,000
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Product details
Overview
LT3575EFE#PBF from Analog Devices (formerly Linear Technology) is a monolithic isolated flyback controller IC with integrated 2.5A/60V NPN power switch, designed for primary-side regulation without optocoupler or third winding. It operates from 3V to 40V input, delivers up to 14W output power, and uses boundary-mode control for improved load regulation in industrial and medical isolated power supplies.
For engineers reviewing the LT3575EFE#PBF datasheet, LT3575EFE#PBF pinout, LT3575EFE#PBF application, or LT3575EFE#PBF equivalent, key selection criteria include its 16-lead TSSOP package with exposed thermal pad, programmable current limit via RILIM, temperature-compensated feedback via TC pin, and boundary-mode operation enabling compact magnetics and stable regulation across –40°C to 125°C.
Technical Context
The LT3575EFE#PBF implements primary-side sensing by sampling the flyback pulse waveform at the SW pin during zero-current detection on the secondary side, eliminating need for optocouplers or auxiliary windings. Its boundary-mode control dynamically adjusts switching frequency between 40kHz and 1MHz based on load, maintaining discontinuous conduction at light loads while improving regulation accuracy.
Internal circuitry includes a dedicated flyback error amplifier referenced to a 1.23V bandgap, a DCM comparator for zero-current detection, and a temperature-compensation current source injected into RREF via the TC pin to offset diode forward-voltage drift. The VC pin provides direct control of peak switch current, and the BIAS pin supplies internal driver bias-configurable from VIN or external winding.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports wide-input industrial and automotive supply rails without external pre-regulation |
| Integrated Switch | 2.5A, 60V NPN - enables self-contained 14W isolated flyback design without external MOSFET |
| Switching Frequency | 40kHz to 1000kHz - variable boundary-mode operation reduces EMI and allows smaller transformer core size |
| RREF Voltage | 1.21V to 1.26V - precision internal reference sets output voltage accuracy with external RFB/RREF divider |
| Operating Temp Range | –40°C to 125°C - qualified for harsh industrial and medical environments with full parameter guarantee |
| Package | 16-Lead TSSOP with exposed GND pad - provides low θJC = 10°C/W thermal resistance for reliable high-power operation |
| SHDN/UVLO Threshold | 1.15V to 1.32V rising - programmable undervoltage lockout prevents erratic startup under brownout conditions |
Pinout & Package
LT3575EFE#PBF is housed in a thermally enhanced 16-lead plastic TSSOP package (FE grade) with an exposed GND pad (Pin 17) that must be soldered to PCB ground for electrical integrity and thermal performance (θJC = 10°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (Pins 3,4) | Collector node of integrated NPN switch | Carries high di/dt switching current; requires short, low-inductance layout to minimize EMI and voltage overshoot |
| BIAS (Pin 5) | Internal bias supply and switch driver source | Can be tied to VIN (if ≤15V) or external winding; bypass capacitor mandatory for stable gate drive |
| SHDN/UVLO (Pin 6) | Shutdown and input undervoltage detection | Resistor divider from VIN sets turn-on threshold; 2.8μA hysteresis current ensures clean UVLO release |
| RILIM (Pin 8) | Programmable switch current limit | 10kΩ to GND sets nominal 3.5A limit; enables overcurrent protection tuning for transformer saturation margin |
| VC (Pin 9) | Error amplifier compensation node | RC network to GND sets loop stability; 100pF parallel cap suppresses noise coupling into control path |
| RFB (Pin 10) | Flyback voltage sampling input | Connects to SW node; average current ≈200μA during flyback period-sets output voltage with RREF and turns ratio |
| RREF (Pin 11) | Reference resistor connection | 6.04kΩ nominal value; receives TC compensation current to cancel diode VF tempco for stable VOUT |
| TC (Pin 12) | Temperature compensation current source | 0.55V/RTC current injected into RREF; cancels negative tempco of output rectifier diode |
| TEST (Pin 13) | Factory test terminal | Must be connected to GND for normal operation; floating or high-impedance state disables device |
| GND (Pins 14,17) | Power and signal ground reference | Exposed pad (Pin 17) is electrically and thermally GND-requires multiple vias to internal ground plane |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side regulation | Eliminates optocoupler and third winding-reduces BOM cost, improves reliability, and simplifies transformer design |
| Boundary-mode control | Enables zero-current switching at every cycle-improves load regulation without external compensation components |
| Programmable soft-start | Capacitor on SS pin controls output ramp rate and limits inrush current-prevents output overshoot during startup |
| Temperature-compensated feedback | TC pin injects proportional-to-absolute-temperature current into RREF-maintains ±1% output accuracy over –40°C to 125°C |
| Thermally enhanced package | Exposed GND pad reduces junction-to-board thermal resistance to 10°C/W-supports continuous 14W operation in compact layouts |
Applications
| Industrial Isolated DC-DC | Automotive Body Control Module |
|---|---|
Use Scenario: 24V vehicle battery powers isolated 5V/1.4A rail for CAN transceiver and microcontroller in body control unit. IC Role / Device Role / Timing Role: LT3575EFE#PBF acts as primary-side regulated flyback controller, generating isolated output without optocoupler while meeting AEC-Q200 ambient temperature requirements. Use Value: Eliminates optocoupler aging and unit-to-unit variation-ensures long-term regulation stability across 15-year automotive service life. | Use Scenario: 12V/24V industrial PLC I/O module requires isolated 3.3V/3A supply for field-side digital inputs with reinforced insulation. IC Role / Device Role / Timing Role: LT3575EFE#PBF implements boundary-mode flyback with Würth 750311422 transformer (5:1) to deliver 3.3V @ 4A with <±1.5% load regulation. Use Value: Programmable RILIM and TC pins enable precise current limiting and temperature compensation-meets IEC 61000-4-5 surge immunity and EN 61000-6-2 emission standards. |
| Medical Patient Monitoring | Test & Measurement Equipment |
Use Scenario: Portable ECG monitor requires 5V/2A isolated power from USB-C PD input (5–20V) with >4kV reinforced isolation for patient safety. IC Role / Device Role / Timing Role: LT3575EFE#PBF regulates output using PA2369NL transformer (5:1), leveraging primary-side sensing to meet IEC 60601-1 creepage/clearance requirements. Use Value: No optocoupler reduces component count and failure modes-simplifies ISO 13485 design validation and reduces time-to-certification. | Use Scenario: Bench power supply auxiliary rail generates ±12V isolated outputs from 24V input for op-amp biasing and ADC reference circuits. IC Role / Device Role / Timing Role: LT3575EFE#PBF controls dual-output flyback with center-tapped secondary, using RFB/RREF to set precise 12V and –12V with independent TC compensation. Use Value: Boundary-mode operation minimizes transformer size and audible noise-critical for low-noise lab-grade instrumentation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28911DR | 65V MOSFET, 120kHz fixed-frequency, no TC pin, lower max output power (10W) | Lacks temperature compensation and programmable current limit-less suitable for wide-temp medical designs | Prefer LT3575EFE#PBF when ±1% output stability over temperature is required or >12W output needed |
| MAX17690ATP+T | 65V MOSFET, 1MHz max frequency, integrated current sense, no RILIM pin | Uses internal current sense instead of RILIM resistor-reduces external parts but limits overcurrent tuning flexibility | Choose LT3575EFE#PBF for designs requiring adjustable current limit and proven transformer compatibility with Würth/Pulse parts |
Compared with UCC28911DR and MAX17690ATP+T, the LT3575EFE#PBF offers unique temperature-compensated feedback via TC pin, boundary-mode operation for superior load regulation, and validated support for off-the-shelf transformers-making it optimal for high-reliability, wide-temperature industrial and medical isolated supplies.
Availability
LT3575EFE#PBF is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical patient monitoring systems requiring stable component supply with guaranteed long-term availability.
Supply support for LT3575EFE#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for all Linear ICs including the LT3575 series.
The LT3575 product line was designed specifically for isolated flyback power conversion with primary-side regulation-targeting applications where optocoupler elimination, small magnetics, and wide-temperature operation are critical.
FAQ
What is the maximum output power achievable with LT3575EFE#PBF?
The LT3575EFE#PBF delivers up to 14W output power with no external power switch, as confirmed in the datasheet's Typical Applications section. This assumes proper transformer selection (e.g., Würth 750311422 for 3.3V/4A), adequate PCB thermal design with the exposed pad fully soldered, and operation within the 3V–40V input range. Power is limited by internal switch SOA and thermal dissipation-not by control loop bandwidth.
Does LT3575EFE#PBF require an optocoupler for regulation?
No, the LT3575EFE#PBF does not require an optocoupler. It achieves isolated output regulation by sampling the flyback pulse waveform directly at the SW pin during secondary zero-current detection-a method confirmed in the DEVICE DESCRIPTION and OPERATION sections. This eliminates optocoupler-related aging, nonlinearity, and dynamic response limitations.
How is output voltage set on LT3575EFE#PBF?
The output voltage of LT3575EFE#PBF is set using two external resistors-RFB connected to the SW node and RREF tied to ground-with the ratio RFB/RREF determining VOUT per the equation VOUT = (VBG × RFB/RREF × NPS) – VF, where VBG = 1.23V, NPS is transformer turns ratio, and VF is diode forward drop. Table 1–4 in the datasheet provide standard resistor values for common VOUT and NPS combinations.
What is the function of the TC pin on LT3575EFE#PBF?
The TC pin on LT3575EFE#PBF sources a temperature-proportional current (0.55V/RTC) into the RREF node to compensate for the negative temperature coefficient of the output rectifier diode's forward voltage. This ensures stable output voltage across –40°C to 125°C, as verified in the ERROR AMPLIFIER-TEMPERATURE COMPENSATION section and Typical Performance Characteristics (Figure G03).
Can LT3575EFE#PBF operate with input voltage below 3V?
No, LT3575EFE#PBF has a minimum specified input voltage of 3V per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 3V is not characterized or guaranteed-the internal bias regulator and switch driver cannot maintain functionality, and startup may fail. For sub-3V applications, alternative controllers such as LT3999 or discrete solutions are required.
LT3575EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive or Negative, Isolation Capable
- Topology:
- Flyback
- Output Type:
- -
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 2.5A
- Frequency - Switching:
- 40kHz ~ 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3575EFE#PBF FAQ
1.How can I place an order for LT3575EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3575EFE#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3575EFE#PBF reliable?
The price and inventory of LT3575EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3575EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3575EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3575EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3575EFE#PBF?
LT3575EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3575EFE#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3575EFE#PBF?
For technical support, including LT3575EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3575EFE#PBF requirements.
6.How does Aetrix verify that LT3575EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3575EFE#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3575EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3575EFE#PBF?
All LT3575EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3575EFE#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3575EFE#PBF part is unused and in its original packaging.
Return procedure for LT3575EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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