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Analog Devices Inc. LT3574EMS#TRPBF
- Part No.:
- LT3574EMS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT3574EMS#TRPBF.pdf
- Description:
- IC REG FLYBACK 650MA 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,094
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Product details
Overview
LT3574EMS#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic isolated flyback controller IC with integrated 0.65A/60V NPN power switch, designed for primary-side regulation without opto-coupler or third winding. It operates from 3V to 40V input, delivers up to 3W output power, and uses boundary-mode control for improved load regulation in industrial and medical isolated power supplies.
For engineers reviewing the LT3574EMS#TRPBF datasheet, LT3574EMS#TRPBF pinout, LT3574EMS#TRPBF application, or LT3574EMS#TRPBF equivalent, key selection considerations include its 16-lead MSOP package, programmable current limit via RILIM, temperature-compensated feedback via TC pin, soft-start control, and primary-side sensing architecture enabling compact, low-cost isolated DC/DC conversion.
Technical Context
The LT3574EMS#TRPBF implements boundary-mode (BCM) current-mode control, detecting zero-current crossing on the secondary side via primary-side flyback waveform analysis-eliminating need for opto-isolators or auxiliary windings. Its flyback error amplifier samples voltage at the RFB pin during the flyback period, referenced to a 1.23V internal bandgap (RREF).
Regulation relies on precise timing of the DCM comparator (blanking time = 150ns) and sampling window (~350ns minimum off-time), with VC pin controlling peak switch current and TC pin injecting proportional-to-absolute-temperature (PTAT) current into RREF to compensate diode forward-voltage drift. The integrated NPN switch features 150mV typical VCE(SAT) at 0.5A.
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 | 0.65A, 60V NPN transistor - enables self-contained 3W isolated flyback design with no external high-voltage switch required. |
| Switching Frequency | Up to 1000kHz (max), 40kHz (min) - variable-frequency BCM operation improves light-load efficiency and simplifies EMI filtering. |
| RREF Reference Voltage | 1.21V to 1.25V (typ 1.23V) - stable bandgap reference used with RFB/RREF resistor divider to set output voltage accurately. |
| Current Limit Range | 100mA to 1.1A (programmable via RILIM) - allows optimization of transformer size and peak stress for specific output power targets. |
| Operating Temp Range | –40°C to +125°C junction - qualified for harsh industrial and automotive environments with full performance guaranteed. |
| Package | 16-lead MSOP - surface-mount package with exposed pad for thermal management; θJA = 120°C/W. |
Pinout & Package
LT3574EMS#TRPBF is housed in a 16-lead plastic MSOP package (3mm × 4.9mm, 0.5mm pitch) with exposed thermal pad. Pin functions are validated per Linear Technology's official pin configuration diagram (MS package top view).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 3, 4, 8, 10, 16) | Power and signal ground reference | Multiple GND pins reduce ground impedance and improve noise immunity in high-dI/dt flyback switching paths. |
| SW (Pin 5) | Collector of integrated NPN switch | High-slew-rate node carrying primary-side flyback current; requires short, low-inductance PCB routing to minimize EMI and voltage spikes. |
| VIN (Pin 6) | Main input supply connection | Supplies start-up bias and serves as reference for DCM comparator; must be locally bypassed with ≥1µF ceramic capacitor. |
| BIAS (Pin 7) | Internal bias and switch driver supply | Can be connected to VIN (if ≤15V) or third-winding source; requires local 1µF bypass to stabilize gate drive under transient loads. |
| SHDN/UVLO (Pin 8) | Shutdown and undervoltage lockout input | Resistor-divider programmable UVLO threshold (1.22V typ); provides hysteresis (2.5µA pull-down) to prevent oscillation near turn-on point. |
| RILIM (Pin 11) | Current limit adjustment | Ground-referenced resistor sets peak switch current (0.65A at 10kΩ); enables precise magnetic design and overcurrent protection tuning. |
| RFB (Pin 12) | Primary-side feedback input | Connected to SW node; senses reflected flyback voltage to derive isolated output voltage without opto-coupler or third winding. |
| RREF (Pin 13) | Reference resistor connection | Forms voltage divider with RFB to set output; internal 1.23V bandgap reference ensures stable regulation across temperature and line. |
| VC (Pin 14) | Error amplifier compensation | Connects to RC network for loop stability; controls peak current limit level and enables boundary-mode timing accuracy. |
| TC (Pin 15) | Temperature compensation input | Drives PTAT current into RREF to cancel diode VF drift; RTC = 20.1kΩ yields ~27.5µA for optimal 5V output tempco cancellation. |
| SS (Pin 16) | Soft-start control | Capacitor-connected node ramps at 7µA; delays startup until ~0.7V reached, limiting inrush current and output overshoot. |
| TEST (Pin 2) | Factory test terminal | Must be tied to GND for normal operation; floating or driven high disables device functionality. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side isolated regulation | Eliminates opto-coupler and third winding-reducing BOM cost, board area, and long-term reliability risks from opto aging and nonlinearity. |
| Boundary-mode control | Enables zero-current switching each cycle, improving load regulation accuracy and allowing smaller magnetics versus CCM designs. |
| Programmable current limit | RILIM pin accepts resistor to set switch current from 100mA to 1.1A-enabling precise transformer sizing and fault robustness tuning. |
| Temperature-compensated feedback | TC pin injects PTAT current into RREF to offset diode VF drift-achieving <±1% output voltage error over –40°C to +125°C. |
| Integrated 60V NPN switch | Reduces external component count and layout complexity while maintaining safe margin below 60V absolute max SW rating. |
Applications
| Industrial Isolated Sensors | Automotive Body Control Modules |
|---|---|
|
Use Scenario: Powering isolated analog front-ends in factory-floor pressure/temperature transmitters with 24V DC input. IC Role / Device Role / Timing Role: Primary-side flyback controller providing 5V/0.35A isolated output with ±1% regulation across –40°C to +85°C ambient. Use Value: Enables single-chip isolation without opto-coupler derating or aging concerns-extending calibration interval and reducing field failure rate. |
Use Scenario: Generating isolated 5V rail for CAN transceiver and microcontroller in vehicle door module with 12V–24V battery input. IC Role / Device Role / Timing Role: Boundary-mode controller delivering 2.5W output with programmable UVLO (12V min) and soft-start for cold-crank immunity. Use Value: Meets AEC-Q200 stress requirements via –40°C to +125°C operation and eliminates opto-coupler qualification burden in automotive supply chain. |
| Medical Patient Monitoring | Industrial PLC I/O Isolation |
|
Use Scenario: Supplying isolated 3.3V/0.7A for ADC and digital isolator in bedside ECG unit requiring 4kV reinforced isolation. IC Role / Device Role / Timing Role: Flyback controller using PA3018NL transformer (4:1) and TC compensation to maintain <±0.5% output accuracy over clinical temperature range. Use Value: Achieves IEC 60601-1 creepage/clearance compliance with simplified transformer design-reducing certification time and cost. |
Use Scenario: Providing isolated 12V/0.25A for analog input channel conditioning in modular PLC backplane with 24V system rail. IC Role / Device Role / Timing Role: Controller operating in BCM with PA3020NL transformer (2:1:0.33) to deliver stable output despite 24V input ripple and load transients. Use Value: Delivers >85% efficiency at full load while meeting EN 61000-4-5 surge immunity via robust RCD clamp integration on SW node. |
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-based flyback controller with primary-side sensing; fixed 66kHz frequency; no TC pin or programmable current limit. | Targets higher-power (>5W) applications with simpler transformer design but lacks temperature compensation for precision outputs. | Choose UCC28911DR when fixed-frequency operation and higher voltage margin outweigh need for tight thermal regulation. |
| MAX17690ATP+T | 65V current-mode flyback controller with integrated 1.2A MOSFET; supports both DCM and CCM; includes comprehensive protection suite (OVP, OTP, OCP). | Offers enhanced safety features for medical/industrial systems but requires external opto-coupler for tight regulation unless using proprietary primary-side algorithm. | Choose MAX17690ATP+T when system-level fault coverage (e.g., output overvoltage lockout) is prioritized over minimal BOM count. |
Compared with UCC28911DR and MAX17690ATP+T, the LT3574EMS#TRPBF uniquely combines boundary-mode operation, built-in temperature compensation, and true opto-free regulation in a 16-pin MSOP-making it optimal for cost-sensitive, thermally demanding isolated supplies under 3W where output accuracy and long-term stability are critical.
Availability
LT3574EMS#TRPBF is available at Aetrix Electronics and suitable for industrial sensors, automotive body electronics, and medical monitoring equipment requiring stable component supply, extended temperature operation, and certified isolated power conversion.
Supply support for LT3574EMS#TRPBF 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-branded power ICs.
The LT3574EMS#TRPBF belongs to Linear's isolated power controller family, engineered specifically for opto-coupler-free flyback converters in space-constrained, thermally aggressive environments where reliability and regulation accuracy are paramount.
FAQ
What is the maximum output power achievable with the LT3574EMS#TRPBF?
The LT3574EMS#TRPBF delivers up to 3W of isolated output power without an external power switch. This limit is determined by the 0.65A/60V integrated NPN switch, boundary-mode efficiency, and thermal dissipation in the 16-lead MSOP package. Output power varies with input voltage and transformer turns ratio-e.g., 2.5W at 30V input with 3:1 ratio, dropping to 2W at 20V input. Exceeding 3W requires external switch augmentation.
Does the LT3574EMS#TRPBF require an opto-coupler or third winding for regulation?
No, the LT3574EMS#TRPBF does not require an opto-coupler or third winding. It achieves isolated output voltage regulation by directly sensing the primary-side flyback waveform at the SW pin and reconstructing output voltage via the RFB/RREF resistor divider and internal 1.23V bandgap reference-enabling fully primary-side controlled flyback operation.
How is output voltage set on the LT3574EMS#TRPBF?
Output voltage on the LT3574EMS#TRPBF 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, multiplied by the internal 1.23V reference and transformer turns ratio, determines VOUT. For example, a 5V output with 3:1 turns ratio uses RFB = 80.6kΩ and RREF = 6.04kΩ per Table 3 in the datasheet.
What is the purpose of the TC pin on the LT3574EMS#TRPBF?
The TC pin on the LT3574EMS#TRPBF sources a proportional-to-absolute-temperature (PTAT) current into the RREF node to compensate for the negative temperature coefficient of the output rectifier diode's forward voltage drop. Connecting a resistor (e.g., 20.1kΩ) from TC to GND injects ~27.5µA, counteracting VF drift and maintaining output voltage accuracy within ±0.5% over –40°C to +125°C.
Can the LT3574EMS#TRPBF operate with input voltages below 3V?
No, the LT3574EMS#TRPBF has a specified minimum input voltage of 3V per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 3V violates the device's operational specification and may result in failure to start, unstable regulation, or undefined behavior. For sub-3V inputs, alternative controllers with lower UVLO thresholds must be selected.
LT3574EMS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 650mA
- Frequency - Switching:
- 40kHz ~ 1MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP
LT3574EMS#TRPBF FAQ
1.How can I place an order for LT3574EMS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3574EMS#TRPBF 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 LT3574EMS#TRPBF reliable?
The price and inventory of LT3574EMS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3574EMS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3574EMS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3574EMS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3574EMS#TRPBF?
LT3574EMS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3574EMS#TRPBF 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 LT3574EMS#TRPBF?
For technical support, including LT3574EMS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3574EMS#TRPBF requirements.
6.How does Aetrix verify that LT3574EMS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3574EMS#TRPBF 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 LT3574EMS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3574EMS#TRPBF?
All LT3574EMS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3574EMS#TRPBF, 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 LT3574EMS#TRPBF part is unused and in its original packaging.
Return procedure for LT3574EMS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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