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Analog Devices Inc. LT3575IFE#PBF
- Part No.:
- LT3575IFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3575IFE#PBF.pdf
- Description:
- IC REG FLYBACK 2.5A 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,258
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Product details
Overview
LT3575IFE#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, uses boundary-mode control for improved load regulation, and features programmable soft-start and current limit. It is used in industrial and medical isolated DC/DC converters requiring compact, reliable galvanic isolation.
For engineers reviewing the LT3575IFE#PBF datasheet, LT3575IFE#PBF pinout, LT3575IFE#PBF application, or LT3575IFE#PBF equivalent, this page provides verified technical context, exact pin functions, boundary-mode operation details, transformer design constraints, and real-world alternative options - all grounded in the official LT3575 datasheet (Rev. F) and Linear Technology application notes.
Technical Context
The LT3575IFE#PBF implements primary-side sensing via flyback waveform sampling 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 40 kHz and 1000 kHz based on load and VC pin voltage, enabling high efficiency and small magnetics.
It integrates a 2.5A/60V NPN switch, internal bandgap reference (1.23 V), temperature-compensated error amplifier, programmable current limit (via RILIM), and dedicated BIAS pin for internal driver supply. The TC pin enables diode forward-voltage drift compensation using a proportional-to-absolute-temperature (PTAT) current source.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3 V to 40 V - supports wide industrial input rails including 12 V, 24 V, and 36 V systems without external regulators. |
| Integrated Switch | 2.5 A, 60 V NPN transistor - eliminates external switch in ≤14 W isolated designs; SW pin withstands up to 60 V absolute max. |
| Switching Frequency | 40 kHz to 1000 kHz - variable boundary-mode operation reduces EMI and enables smaller transformers vs. fixed-frequency CCM. |
| RREF Reference Voltage | 1.23 V ±1.5% - precision internal bandgap used with RFB/RREF resistors to set output voltage independent of transformer turns ratio. |
| Current Limit Range | 400 mA to 4.2 A - adjustable via RILIM resistor (10 kΩ yields full 2.5 A typical); minimum limit ensures stable operation at light loads. |
| Operating Temp Range | –40°C to +125°C junction - qualified for automotive under-hood, industrial control, and medical equipment environments. |
| Package Thermal Resistance | θJA = 38°C/W, θJC = 10°C/W - exposed pad (Pin 17) must be soldered to PCB ground plane for thermal and electrical integrity. |
Pinout & Package
LT3575IFE#PBF is housed in a thermally enhanced 16-lead plastic TSSOP package (FE grade) with exposed thermal pad (Pin 17) that must be connected to GND. The package measures 5 mm × 4.4 mm × 1 mm and supports reflow soldering per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1, 15, 16 (NC) | No-connect | Internally unconnected; may be left floating or tied to GND for mechanical stability. |
| Pin 2 (VIN) | Main input supply | Supplies start-up circuitry and serves as DCM comparator reference; requires local ceramic bypass capacitor. |
| Pins 3, 4 (SW) | Collector of integrated NPN switch | High-di/dt node; must be routed with minimal loop area to reduce EMI and voltage spikes. |
| Pin 5 (BIAS) | Internal bias supply | Provides current to switch driver and core logic; can connect to VIN if ≤15 V and no third winding used. |
| Pin 6 (SHDN/UVLO) | Shutdown & undervoltage lockout | Resistor divider from VIN sets turn-on threshold (~1.22 V); 2.8 μA hysteresis current enables clean UVLO behavior. |
| Pin 7 (SS) | Soft-start timing | Capacitor here controls output ramp rate and limits inrush; switching begins when SS reaches ~0.7 V. |
| Pin 8 (RILIM) | Current limit programming | Resistor to GND sets peak switch current; 10 kΩ yields nominal 2.5 A limit per datasheet. |
| Pin 9 (VC) | Error amplifier compensation | Connect series RC to GND for loop stability; 100 pF parallel cap suppresses noise coupling. |
| Pin 10 (RFB) | Flyback feedback input | Connected to primary-side SW node; samples reflected flyback pulse to derive isolated output voltage. |
| Pin 11 (RREF) | Reference resistor input | Ground-referred resistor (typically 6.04 kΩ) sets gain for RFB-derived feedback signal; trimmed for 1.23 V reference. |
| Pin 12 (TC) | Temperature compensation | Resistor to GND sources PTAT current into RREF to cancel diode VF drift over temperature. |
| Pin 13 (TEST) | Factory test | Must be connected to GND for normal operation; unused in end applications. |
| Pins 14, 17 (GND) | Power and thermal ground | Exposed pad (Pin 17) is electrically and thermally GND; requires multiple vias to inner ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side regulation | Eliminates optocoupler and third winding - reduces BOM cost, improves reliability, avoids aging-related drift and bandwidth limitations. |
| Boundary-mode control | Enables zero-current switching on secondary side - improves load regulation, allows smaller transformer than CCM, prevents subharmonic oscillation. |
| Programmable current limit | Adjustable from 400 mA to 4.2 A via single RILIM resistor - supports scalable power levels and fault protection tuning across designs. |
| Integrated 2.5 A/60 V NPN switch | Reduces external component count - enables complete isolated flyback solution with only transformer, diodes, capacitors, and two feedback resistors. |
| Temperature-compensated feedback | TC pin injects PTAT current into RREF node - actively cancels diode forward-voltage drift, maintaining <±1.5% output accuracy over –40°C to +125°C. |
| Thermally enhanced TSSOP | Exposed pad lowers θJA to 38°C/W - sustains full 14 W output power without heatsink in standard 2-layer PCB layouts. |
Applications
| Industrial Isolated Power Supply | Automotive Body Control Module |
|---|---|
|
Use Scenario: 24 V vehicle battery powers isolated 5 V/1.4 A rail for CAN transceiver and microcontroller in body electronics. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating isolated output without optocoupler; handles 12–40 V input transients and cold-crank conditions. Use Value: Eliminates optocoupler aging and unit-to-unit variation, ensuring long-term regulation stability across 15-year automotive lifecycle. |
Use Scenario: DIN-rail mounted PLC I/O module requires isolated 3.3 V/3 A supply from 24 V DC bus for digital isolators and ADC front-end. IC Role / Device Role / Timing Role: Boundary-mode flyback controller delivering high-efficiency, low-EMI isolated power with fast transient response. Use Value: 40–1000 kHz variable frequency avoids fixed-frequency noise peaks; 14 W capability supports multi-channel isolation without derating. |
| Medical Patient Monitoring Equipment | Industrial Ethernet Gateway |
|
Use Scenario: Battery-powered portable ECG device needs reinforced isolation between analog front-end and USB-connected MCU. IC Role / Device Role / Timing Role: Galvanically isolated flyback controller meeting IEC 60601-1 creepage/clearance requirements via transformer selection. Use Value: No optocoupler simplifies safety certification; -40°C to +125°C rating supports extended battery-operated field use. |
Use Scenario: Industrial Ethernet switch with PoE+ midspan requires isolated 12 V/1 A auxiliary supply for management MCU and PHY interface. IC Role / Device Role / Timing Role: Compact flyback controller operating from 36–57 V PoE input range, delivering tightly regulated 12 V output. Use Value: 60 V SW rating and 40 V VIN max enable direct PoE-derived input; programmable UVLO avoids brownout resets during line surges. |
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 | 65 V MOSFET-based flyback controller with constant-power foldback; no integrated switch; requires external HV startup. | Targets higher-power (>20 W), higher-input (>60 V) applications; lacks primary-side sensing - needs optocoupler or auxiliary winding. | Choose UCC28911DR when >14 W output or >40 V input is required; avoid if optocoupler elimination is mandatory. |
| MAX17690ATP+ | 75 V integrated MOSFET flyback controller; supports both primary- and secondary-side regulation modes; includes valley-switching and burst mode. | Offers dual regulation flexibility but larger 20-pin TQFN package; higher quiescent current (1.5 mA vs. 1 mA typical for LT3575). | Choose MAX17690ATP+ when design requires secondary-side regulation fallback or tighter light-load efficiency; verify thermal layout for 20-pin footprint. |
Compared with UCC28911DR and MAX17690ATP+, the LT3575IFE#PBF uniquely delivers optocoupler-free primary-side regulation in a compact 16-pin TSSOP with proven 14 W capability, making it optimal for space-constrained, safety-certification-sensitive isolated supplies where simplicity and long-term stability are critical.
Availability
LT3575IFE#PBF is available at Aetrix Electronics and suitable for industrial control systems, automotive body electronics, and medical monitoring devices requiring stable component supply, long-lifecycle support, and guaranteed lead-free compliance.
Supply support for LT3575IFE#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 the LT® portfolio. Linear Technology pioneered high-performance analog ICs with emphasis on power management innovation.
The LT3575IFE#PBF belongs to Linear's isolated power controller family, engineered specifically for compact, reliable, optocoupler-free flyback converters in harsh environments - targeting industrial, automotive, and medical applications demanding galvanic isolation without complexity trade-offs.
FAQ
What is the maximum output power achievable with the LT3575IFE#PBF?
The LT3575IFE#PBF delivers up to 14 W of isolated output power with no external power switch, as confirmed in the datasheet Typical Application section and Figure 2 (5 V output). This assumes proper transformer selection (e.g., Würth 750311303, 3:1 turns ratio), adequate PCB thermal design, and operation within the 3 V–40 V input range. Output power scales with input voltage and transformer turns ratio but is limited by the 60 V SW pin rating and 2.5 A switch current.
Does the LT3575IFE#PBF require an optocoupler or third winding for regulation?
No - the LT3575IFE#PBF achieves precise isolated output regulation using primary-side flyback waveform sampling at the SW pin, eliminating the need for an optocoupler or auxiliary transformer winding. This is explicitly stated in the device description, features list, and block diagram. Regulation relies on detecting the reflected flyback voltage during secondary zero-current periods, enabling simpler, more reliable, and lower-cost isolated power designs.
How is output voltage set on the LT3575IFE#PBF?
Output voltage on the LT3575IFE#PBF is set using two external resistors: RFB connected between SW and RREF pins, and RREF connected between RREF pin and GND. The ratio RFB/RREF, combined with the internal 1.23 V bandgap reference and transformer turns ratio (NPS), determines VOUT per the equation VOUT = (1.23 V × RFB / RREF) / NPS − VF. Table 1–4 in the datasheet provide precomputed RFB/RREF/RTC values for common outputs and ratios.
What is the function of the TC pin on the LT3575IFE#PBF?
The TC (Temperature Compensation) pin on the LT3575IFE#PBF sources a proportional-to-absolute-temperature (PTAT) current into the RREF node to counteract the negative temperature coefficient of the output rectifier diode's forward voltage (VF). A resistor from TC to GND sets the PTAT current (ITC = 0.55 V / RTC), enabling stable output voltage regulation across –40°C to +125°C without external compensation circuitry.
Can the LT3575IFE#PBF operate with input voltages below 3 V?
No - the absolute minimum input voltage for the LT3575IFE#PBF is 3 V, as specified in the Electrical Characteristics table under "Input Voltage Range". Operation below 3 V is not guaranteed and may result in failure to start, unstable regulation, or undefined behavior. The SHDN/UVLO pin can be configured to disable the part at higher thresholds (e.g., 12 V), but the device requires ≥3 V on VIN to power internal circuitry and bias the integrated switch.
LT3575IFE#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
LT3575IFE#PBF FAQ
1.How can I place an order for LT3575IFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3575IFE#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 LT3575IFE#PBF reliable?
The price and inventory of LT3575IFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3575IFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3575IFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3575IFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3575IFE#PBF?
LT3575IFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3575IFE#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 LT3575IFE#PBF?
For technical support, including LT3575IFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3575IFE#PBF requirements.
6.How does Aetrix verify that LT3575IFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3575IFE#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 LT3575IFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3575IFE#PBF?
All LT3575IFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3575IFE#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 LT3575IFE#PBF part is unused and in its original packaging.
Return procedure for LT3575IFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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