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Analog Devices Inc. LT3573EMSE#TRPBF
- Part No.:
- LT3573EMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3573EMSE#TRPBF.pdf
- Description:
- IC REG FLYBACK 1.25A 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:9,364
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Product details
Overview
LT3573EMSE#TRPBF from Analog Devices (formerly Linear Technology) is a monolithic isolated flyback controller IC with integrated 1.25A/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 7W output power, and uses boundary-mode control for improved load regulation in industrial and medical isolated power supplies.
For engineers reviewing the LT3573EMSE#TRPBF datasheet, LT3573EMSE#TRPBF pinout, LT3573EMSE#TRPBF application, or LT3573EMSE#TRPBF equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative parts with documented differences, and supply support for high-reliability embedded power designs.
Technical Context
The LT3573EMSE#TRPBF implements boundary-mode current-mode control to sample the isolated output voltage directly from the primary-side flyback waveform at zero-secondary-current instants-eliminating need for opto-isolators or auxiliary windings. Its internal error amplifier references a 1.23V bandgap and derives feedback via RFB/RREF resistor network across the transformer primary.
It integrates a 60V NPN switch, programmable current limit (via RILIM), soft-start (SS), temperature-compensated reference (TC→RREF), and thermal shutdown. The VC pin sets peak switch current, while SHDN/UVLO enables input-voltage-dependent enable/disable with 1.22V threshold and 2.5µA hysteresis current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports wide-input industrial rails including 12V, 24V, and 36V systems without external regulators. |
| Integrated Switch | 1.25A, 60V NPN - eliminates external transistor; SW pin withstands up to 60V, enabling safe operation with ≤50V reflected flyback voltage. |
| Switching Frequency | Up to 1000kHz (max), down to 40kHz (min) - variable-frequency boundary mode enables small magnetics and avoids subharmonic oscillation. |
| RREF Reference Voltage | 1.23V ±2% - precise internal bandgap used with RFB/RREF resistors to set output voltage; line regulation <0.03%/V ensures stability across input range. |
| Operating Temp Range | –40°C to +125°C - qualified for automotive under-hood, industrial control, and medical equipment environments. |
| Package Thermal Resistance | θJA = 50°C/W - exposed pad (Pin 17) must be soldered to PCB ground plane for thermal management and EMI reduction. |
| Quiescent Current | ≤1mA (typical) - enables low-power standby modes; drops to 0µA below UVLO threshold (~0.7V). |
Pinout & Package
LT3573EMSE#TRPBF is housed in a thermally enhanced 16-lead MSOP package (3mm × 4mm) with exposed pad (Pin 17) electrically and thermally connected to GND. The exposed pad must be soldered to a PCB ground plane using multiple vias for reliable thermal dissipation and noise immunity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 3, 4, 8, 12, 16) | Ground reference and return path | Multiple GND pins reduce impedance; all must connect to low-impedance PCB ground plane, especially for switching current return. |
| SW (Pin 5) | Collector of integrated NPN switch | High-di/dt node; requires shortest possible trace to transformer primary and snubber components to minimize EMI and voltage spikes. |
| VIN (Pin 6) | Main input supply connection | Supplies start-up bias and DCM comparator reference; must be locally bypassed with ≥1µF ceramic capacitor near pin. |
| BIAS (Pin 7) | Internal bias and driver supply | Provides current to switch driver and internal logic; can be tied to VIN if VIN ≤15V and no third winding is used. |
| SHDN/UVLO (Pin 9) | Enable/disable and undervoltage lockout | Resistor divider from VIN sets turn-on threshold (1.22V typ); 2.5µA hysteresis current enables clean UVLO behavior without external hysteresis circuitry. |
| RILIM (Pin 11) | Peak switch current limit setting | Connect resistor to GND: 10kΩ sets full 1.25A limit; lower resistance reduces current limit linearly per datasheet curve. |
| SS (Pin 13) | Soft-start timing node | Capacitor to GND controls output ramp rate and inrush current; switching begins when SS reaches ~0.7V. |
| VC (Pin 14) | Error amplifier compensation | Connect series RC to GND for loop stability; 100pF parallel cap suppresses noise; voltage sets peak switch current. |
| RFB (Pin 15) | Flyback feedback input | Connected to transformer primary; forms voltage divider with RREF to derive output voltage information from flyback pulse amplitude. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side isolated regulation | Eliminates opto-coupler and third winding-reduces BOM cost, improves long-term reliability, and avoids opto aging/nonlinearity issues. |
| Boundary-mode operation | Enables zero-current switching on secondary side, improving load regulation without external compensation and allowing smaller transformers vs CCM. |
| Programmable current limit | RILIM pin allows precise adjustment of peak switch current from 200mA to 1.85A-supports flexible power scaling and overcurrent protection tuning. |
| Temperature-compensated reference | TC pin sources proportional-to-absolute-temperature (PTAT) current into RREF to cancel diode forward-voltage drift-improves output voltage stability over –40°C to +125°C. |
| Thermally enhanced MSOP | Exposed pad (Pin 17) reduces θJA to 50°C/W-enables 7W operation without heatsink in standard PCB layouts with adequate copper area. |
Applications
| Industrial Isolated DC/DC | Medical Equipment Power |
|---|---|
Use Scenario: 24V bus-powered PLC I/O module requiring isolated 5V/1A output with <±1% regulation over temperature and load. IC Role / Device Role / Timing Role: Primary-side flyback controller managing boundary-mode switching, output voltage sampling, and current limiting without secondary-side feedback components. Use Value: Enables compact, low-cost isolation with no opto-coupler drift or aging-critical for long-life industrial deployments where field recalibration is impractical. |
Use Scenario: Patient-connected diagnostic device needing reinforced isolation between 12V battery input and 3.3V/500mA isolated logic supply per IEC 60601-1. IC Role / Device Role / Timing Role: Regulates isolated output using primary-side flyback sensing, meeting creepage/clearance requirements while eliminating opto-isolator failure modes. Use Value: Reduces risk of single-point failure in safety-critical paths; boundary-mode operation ensures stable regulation even during rapid load transients typical in sensor readout circuits. |
| Automotive Body Control | Test & Measurement Isolation |
Use Scenario: 12V–36V automotive body control unit requiring isolated 5V/700mA supply for CAN transceiver and microcontroller, operating from –40°C to +125°C. IC Role / Device Role / Timing Role: Integrated NPN flyback controller delivering regulated output across wide input range and extreme temperature, with UVLO hysteresis preventing brownout oscillation. Use Value: Eliminates external high-voltage transistor and opto-isolator-reducing component count, board space, and qualification effort for AEC-Q100 Grade 1 compliance. |
Use Scenario: Bench power supply with isolated analog front-end requiring 15V/400mA output referenced to floating ground, with <0.5% load regulation. IC Role / Device Role / Timing Role: Boundary-mode flyback controller providing precise primary-side regulation and programmable soft-start to prevent inrush into sensitive measurement circuitry. Use Value: Delivers lab-grade regulation stability without secondary-side feedback components-avoiding layout sensitivity and enabling repeatable calibration across production units. |
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 regulation; no integrated switch; requires external HV MOSFET. | Supports higher input voltages (up to 85VAC rectified); lacks integrated NPN, so needs external gate driver and HV FET; no TC pin for diode temp compensation. | Choose UCC28911DR when >60V input capability or higher efficiency at light loads (with valley-switching) is required; not drop-in due to external switch and different feedback architecture. |
| MAX17690ATP+T | 65V integrated MOSFET flyback controller; includes active X-cap discharge; no RILIM pin-fixed current limit; different soft-start implementation. | Designed for AC/DC adapters; includes safety features like X-cap discharge; lacks TC pin and programmable current limit; operates in quasi-resonant mode instead of boundary mode. | Choose MAX17690ATP+T for certified AC/DC adapter designs requiring integrated safety functions; not suitable for precision DC/DC where TC compensation or adjustable current limit is needed. |
Compared with LT3573EMSE#TRPBF, UCC28911DR offers higher voltage headroom but requires external components and lacks temperature compensation, while MAX17690ATP+T adds safety features but sacrifices design flexibility in current limiting and thermal regulation-making LT3573EMSE#TRPBF optimal for compact, high-precision isolated DC/DC where primary-side accuracy and thermal stability are critical.
Availability
LT3573EMSE#TRPBF is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, and automotive body electronics requiring stable component supply, long-lifecycle support, and guaranteed performance across –40°C to +125°C.
Supply support for LT3573EMSE#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, industrial, automotive, and healthcare markets.
The LT3573 belongs to Linear's isolated power controller product line, engineered specifically for opto-free, transformer-coupled flyback converters where size, reliability, and temperature-stable regulation are prioritized over ultra-high efficiency or universal AC input.
FAQ
What is the maximum output power achievable with LT3573EMSE#TRPBF?
The LT3573EMSE#TRPBF can deliver up to 7W output power with no external power devices, as confirmed in the datasheet's Typical Application section. This assumes proper transformer selection (e.g., PA2454NL for 5V/1A), boundary-mode operation, and thermal management via the exposed pad. Output power varies with input voltage, turns ratio, and layout-e.g., 6W at 30V input with 3:1 ratio, dropping to 5W at 20V.
Does LT3573EMSE#TRPBF require an opto-coupler or third winding for regulation?
No-LT3573EMSE#TRPBF achieves isolated output regulation by sampling the primary-side flyback waveform at zero-secondary-current instants, eliminating the need for an opto-coupler or auxiliary winding. This is explicitly stated in the DESCRIPTION and FEATURES sections of the datasheet and validated in the TYPICAL APPLICATION schematic (3573 TA01).
How is output voltage set on LT3573EMSE#TRPBF?
Output voltage 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 bandgap and adjusted for transformer turns ratio and diode drop, determines VOUT. Standard values (e.g., RREF = 6.04kΩ, RFB = 27.4kΩ for 5V with 1:1 turns) are provided in Table 1 of the datasheet.
What is the function of the TC pin on LT3573EMSE#TRPBF?
The TC pin on LT3573EMSE#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. A resistor from TC to GND (e.g., 20.1kΩ) sets the compensation current (27.5µA typ), improving output voltage stability over temperature-confirmed in Electrical Characteristics and OPERATION sections.
Can LT3573EMSE#TRPBF operate with input voltage below 3V?
No-LT3573EMSE#TRPBF has a specified minimum input voltage of 3V, as listed in Absolute Maximum Ratings and Electrical Characteristics. Operation below 3V is not characterized or guaranteed; startup circuitry requires sufficient VIN to bias internal regulators, and the 1.22V SHDN/UVLO threshold implies functional operation only above ~3V with margin.
LT3573EMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- 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:
- 1.25A
- 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-EP
LT3573EMSE#TRPBF FAQ
1.How can I place an order for LT3573EMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3573EMSE#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 LT3573EMSE#TRPBF reliable?
The price and inventory of LT3573EMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3573EMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3573EMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3573EMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3573EMSE#TRPBF?
LT3573EMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3573EMSE#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 LT3573EMSE#TRPBF?
For technical support, including LT3573EMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3573EMSE#TRPBF requirements.
6.How does Aetrix verify that LT3573EMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3573EMSE#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 LT3573EMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3573EMSE#TRPBF?
All LT3573EMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3573EMSE#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 LT3573EMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3573EMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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