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Analog Devices Inc. LT3573EMSE#PBF
- Part No.:
- LT3573EMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3573EMSE#PBF.pdf
- Description:
- IC REG FLYBACK 1.25A 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:740
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Product details
Overview
LT3573EMSE#PBF 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 optocoupler 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#PBF datasheet, LT3573EMSE#PBF pinout, LT3573EMSE#PBF application, or LT3573EMSE#PBF equivalent, key selection criteria include its 16-lead MSOP package with exposed thermal pad, programmable current limit via RILIM, soft-start capacitor control, and primary-side feedback architecture eliminating isolation components.
Technical Context
The LT3573EMSE#PBF implements boundary-mode (BCM) current-mode control, detecting zero-current crossing on the secondary side via primary-side flyback waveform sampling - enabling precise output voltage regulation without optocouplers or auxiliary windings. Its internal error amplifier compares a temperature-compensated reference derived from RFB/RREF resistor divider against a 1.23V bandgap.
It integrates a 1.25A/60V NPN switch, programmable soft-start, shutdown/UVLO with hysteresis, compensation pin (VC) for loop stability, and BIAS pin supporting self-powered operation. The exposed pad (Pin 17) is electrically and thermally connected to GND and must be soldered to PCB ground plane.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 40V - supports wide-input industrial and automotive supply rails without external regulators |
| Integrated Power Switch | 1.25A, 60V NPN - eliminates need for external high-voltage transistor in ≤7W isolated designs |
| Switching Frequency Range | 40kHz to 1000kHz - variable-frequency boundary mode enables small magnetics and stable light-load operation |
| RREF Reference Voltage | 1.23V ±2% - precision internal bandgap used with external RFB/RREF to set output voltage |
| Current Limit Accuracy | ±20% over temperature - set by RILIM resistor (e.g., 10kΩ yields 1.25A typical limit) |
| Operating Junction Temp | –40°C to 125°C - qualified for extended industrial and medical environments |
| Package Thermal Resistance | θJA = 50°C/W - requires exposed pad soldering to PCB ground for thermal performance |
Pinout & Package
LT3573EMSE#PBF is housed in a thermally enhanced 16-lead plastic MSOP package with exposed pad (Pin 17), which must be connected to GND for electrical integrity and thermal dissipation. The package footprint complies with JEDEC MO-187AA standard.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 3, 4, 8, 9, 16) | Ground reference | Multiple GND pins reduce ground impedance; exposed pad (Pin 17) is GND and mandatory for thermal management |
| SW (Pin 5) | Switch collector node | High-current switching node; requires short, low-inductance routing to minimize EMI and voltage spikes |
| VIN (Pin 6) | Main input supply | Supplies start-up bias and serves as DCM comparator reference; must be locally bypassed |
| BIAS (Pin 7) | Internal bias supply | Powers switch driver and internal circuitry; can connect to VIN if ≤15V and no third winding used |
| SHDN/UVLO (Pin 8) | Shutdown & undervoltage lockout | Resistor-divider programmable UVLO threshold (1.22V typ); provides hysteresis for clean startup |
| RILIM (Pin 11) | Current limit adjust | Sets peak switch current via resistor to GND; 10kΩ yields 1.25A nominal limit |
| SS (Pin 12) | Soft-start control | Capacitor-connected pin ramps VC voltage to limit inrush; switching starts at ~0.7V |
| VC (Pin 13) | Error amplifier compensation | Connect series RC to GND for loop stability; 100pF parallel cap suppresses noise |
| RFB (Pin 14) | Primary-side feedback input | Samples flyback pulse amplitude; average current ≈200µA during flyback period |
| RREF (Pin 15) | Reference resistor connection | Forms voltage divider with RFB; trimmed for 6.04kΩ nominal value to achieve accurate VOUT |
| TC (Pin 10) | Temperature compensation | Sources positive TC current into RREF to cancel diode VF drift; RTC sets compensation slope |
| TEST (Pin 2) | Factory test only | Must be tied to GND for normal operation; floating or driven causes malfunction |
Key Features
| Feature | Design Value |
|---|---|
| No optocoupler or third winding required | Reduces BOM count, cost, and board area while eliminating opto aging and nonlinearity issues |
| Boundary-mode operation | Enables smaller transformer size, eliminates subharmonic oscillation, and improves load regulation without external compensation |
| Programmable current limit | Adjustable over 200mA–1.85A range via single RILIM resistor - supports flexible power scaling and fault protection |
| Integrated 1.25A/60V NPN switch | Eliminates external high-voltage transistor and associated gate drive complexity in ≤7W applications |
| Temperature-compensated feedback | TC pin injects PTAT current into RREF to offset diode forward voltage drift - maintains <±2% output accuracy over –40°C to 125°C |
| Thermally enhanced MSOP | 16-lead MSOP with exposed pad achieves θJA = 50°C/W - enables high-power density in compact layouts |
Applications
| Industrial Isolated DC/DC | Medical Equipment Power |
|---|---|
Use Scenario: 24V input isolated 5V/1A supply for PLC I/O modules with strict creepage/clearance requirements. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via sampled SW node waveform - replaces optocoupler-based feedback. Use Value: Eliminates optocoupler certification overhead and long-term drift, achieving <±3% output regulation across –40°C to 85°C ambient. |
Use Scenario: 12V-to-±5V isolated dual-rail supply for patient-connected diagnostic sensor front-ends. IC Role / Device Role / Timing Role: Boundary-mode controller delivering galvanically isolated outputs with no third winding - meets IEC 60601-1 creepage standards. Use Value: Reduces transformer complexity and enables compact 15mm × 15mm PCB footprint while maintaining <100mV load regulation error. |
| Automotive Body Control | Test & Measurement Isolation |
Use Scenario: 12V/24V battery-fed 3.3V isolated supply for CAN transceiver and microcontroller in junction box ECUs. IC Role / Device Role / Timing Role: Flyback controller with UVLO hysteresis (1.22V rising, 1.18V falling) ensuring robust cold-crank operation down to 3.5V battery. Use Value: Maintains regulation during engine cranking transients and supports AEC-Q200-compliant magnetic selection (e.g., PA2454NL). |
Use Scenario: 40V max input isolated 12V/0.5A supply for benchtop oscilloscope analog front-end channel isolation. IC Role / Device Role / Timing Role: Precision primary-side regulator using RFB/RREF + TC network to hold output within ±0.5% over 0–50°C calibration range. Use Value: Enables traceable, drift-free voltage references without optocoupler gain variation - critical for metrology-grade accuracy. |
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 | 700V integrated MOSFET; fixed 50kHz frequency; no RILIM or TC pin; requires optocoupler for tight regulation | Better suited for universal AC input (85–265VAC); lacks primary-side precision feedback for DC-DC | Select UCC28911DR only when AC input is required and optocoupler-based regulation is acceptable |
| MAX17690ATP+T | 65V integrated MOSFET; valley-switching mode; no TC pin; supports synchronous rectification | Higher efficiency at medium loads; no built-in temperature compensation for diode VF drift | Choose MAX17690ATP+T when >85% efficiency is prioritized over ±1% tempco and transformer simplicity |
Compared with UCC28911DR and MAX17690ATP+T, the LT3573EMSE#PBF uniquely combines primary-side sensing, temperature-compensated feedback, and programmable boundary-mode control - making it optimal for DC-input, space-constrained, high-accuracy isolated supplies where optocoupler elimination is mandatory.
Availability
LT3573EMSE#PBF is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, and automotive body electronics requiring stable component supply with guaranteed long-term availability and full RoHS compliance.
Supply support for LT3573EMSE#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 LT3573 family.
The LT3573 product line was engineered specifically for isolated flyback power conversion in space- and cost-sensitive applications - emphasizing primary-side regulation, minimal external components, and robust operation across industrial temperature ranges.
FAQ
What is the maximum output power achievable with the LT3573EMSE#PBF?
The LT3573EMSE#PBF delivers up to 7W of isolated output power with no external power devices. This assumes optimal transformer selection (e.g., PA2454NL for 5V/1A), proper snubber design, and input voltage within 3V–40V range. At 24V input and 5V/1A output, typical efficiency exceeds 82%, and power capability scales with turns ratio and thermal management - verified in Linear Technology's typical application circuits.
Does the LT3573EMSE#PBF require an optocoupler for regulation?
No, the LT3573EMSE#PBF does not require an optocoupler. It senses the isolated output voltage directly from the primary-side flyback waveform using internal sampling circuitry. This eliminates optocoupler-related issues such as aging, unit-to-unit variation, and limited bandwidth - confirmed in the device's block diagram and OPERATION section of the official datasheet.
How is output voltage programmed on the LT3573EMSE#PBF?
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) yield 5V with 1:1 transformer - per Table 1 in the LT3573 datasheet.
What is the purpose of the TC pin on the LT3573EMSE#PBF?
The TC (Temperature Compensation) pin on the LT3573EMSE#PBF sources a positive-temperature-coefficient current into the RREF node to counteract the negative temperature coefficient of the output rectifier diode's forward voltage. A resistor (RTC) from TC to GND sets this current; for example, 28kΩ yields optimal compensation for common Schottky diodes - detailed in the ERROR AMPLIFIER-TEMPERATURE COMPENSATION section.
Can the LT3573EMSE#PBF operate with a 1:1 transformer?
Yes, the LT3573EMSE#PBF supports 1:1 transformers and includes validated resistor values for this configuration - e.g., RREF = 6.04kΩ and RFB = 27.4kΩ for 5V output (Table 1). However, maximum input voltage must satisfy N < (50V – VIN(MAX)) / (VOUT + VF) to avoid SW pin overvoltage; at VIN = 40V and VOUT = 5V, a 1:1 ratio remains within safe 60V SW rating.
LT3573EMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm 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:
- 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#PBF FAQ
1.How can I place an order for LT3573EMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3573EMSE#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 LT3573EMSE#PBF reliable?
The price and inventory of LT3573EMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3573EMSE#PBF is usually 5 days.
3.What payment methods are accepted for LT3573EMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3573EMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3573EMSE#PBF?
LT3573EMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3573EMSE#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 LT3573EMSE#PBF?
For technical support, including LT3573EMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3573EMSE#PBF requirements.
6.How does Aetrix verify that LT3573EMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3573EMSE#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 LT3573EMSE#PBF meets industry standards.
7.What is the process for return or replacement of LT3573EMSE#PBF?
All LT3573EMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3573EMSE#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 LT3573EMSE#PBF part is unused and in its original packaging.
Return procedure for LT3573EMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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