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Analog Devices Inc. LT3573IMSE#TRPBF
- Part No.:
- LT3573IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3573IMSE#TRPBF.pdf
- Description:
- IC REG FLYBACK 1.25A 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,123
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Product details
Overview
LT3573IMSE#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 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 LT3573IMSE#TRPBF datasheet, LT3573IMSE#TRPBF pinout, LT3573IMSE#TRPBF application, or LT3573IMSE#TRPBF equivalent, key selection considerations include its 16-lead MSOP package with exposed thermal pad, programmable current limit via RILIM, soft-start capacitor interface, and primary-side feedback architecture enabling compact, low-cost isolated DC/DC conversion.
Technical Context
The LT3573IMSE#TRPBF implements boundary-mode (BCM) current-mode control, detecting zero-current crossing on the secondary side via primary-side flyback waveform sampling - eliminating need for optocouplers or auxiliary windings. Its error amplifier derives output voltage information from the SW node during flyback, referenced to a 1.23V internal bandgap.
Regulation relies on RFB/RREF resistor divider and optional TC pin temperature compensation to counter diode forward-voltage drift. The IC integrates oscillator, latch, driver, bias regulator, and DCM comparator, with VC pin providing loop compensation and RILIM setting peak switch current from 200mA to 1.85A.
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 | 1.25A/60V NPN transistor - eliminates external high-voltage switch; SW pin withstands up to 60V absolute max. |
| Switching Frequency | Up to 1000kHz (max), down to 40kHz (min) - variable-frequency BCM enables small magnetics and stable light-load operation. |
| Output Power Capability | Up to 7W with no external power devices - sufficient for isolated 5V/1A or 12V/0.5A supplies using standard off-the-shelf transformers. |
| RREF Reference Voltage | 1.23V ±2% (typ) - precision internal bandgap sets output voltage accuracy when used with RFB/RREF divider. |
| SHDN/UVLO Threshold | 1.22V rising, 1.15–1.29V range - enables programmable undervoltage lockout using resistor divider from VIN. |
| Operating Temp Range | –40°C to +125°C junction - qualified for industrial and extended-temperature embedded systems. |
Pinout & Package
LT3573IMSE#TRPBF is housed in a thermally enhanced 16-lead plastic MSOP package (MSE) with exposed pad (Pin 17) that must be soldered to PCB ground for electrical integrity and thermal performance (θJA = 50°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (Pins 1, 3, 4, 8, 12, 16) | Ground reference and return path | Multiple GND pins reduce impedance; exposed pad (Pin 17) is electrically and thermally connected to GND. |
| SW (Pin 5) | Collector of internal NPN switch | High-di/dt node; requires short, low-inductance routing to transformer primary and snubber components. |
| VIN (Pin 6) | Main input supply connection | Powers startup circuitry and serves as reference for DCM comparator; requires local ceramic bypass capacitor. |
| BIAS (Pin 7) | Internal bias supply for driver and logic | Can be tied to VIN if ≤15V and no third winding used; otherwise supplied from auxiliary winding for efficiency. |
| SHDN/UVLO (Pin 9) | Shutdown and input undervoltage detection | Resistor divider from VIN programs turn-on threshold; provides 2.5µA hysteresis current for clean UVLO behavior. |
| RILIM (Pin 11) | Peak switch current limit programming | 10kΩ to GND sets full 1.25A limit; lower resistance reduces current limit linearly down to 200mA minimum. |
| SS (Pin 13) | Soft-start timing node | Capacitor to GND controls output voltage ramp rate and limits inrush; switching begins at ~0.7V threshold. |
| VC (Pin 14) | Error amplifier compensation | Connect series RC to GND for loop stability; 100pF parallel cap suppresses noise coupling into feedback path. |
| RFB (Pin 15) | Primary-side feedback input | Connected to SW node; samples flyback pulse amplitude to derive isolated output voltage without optocoupler. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side isolated regulation | Eliminates optocoupler and third winding - reduces BOM cost, board area, and long-term reliability risk from opto aging. |
| Boundary-mode operation | Enables zero-current switching each cycle - improves load regulation, allows smaller transformer, avoids subharmonic oscillation. |
| Programmable current limit | RILIM pin accepts resistor to set peak switch current from 200mA to 1.85A - supports flexible power scaling and overcurrent protection tuning. |
| Temperature-compensated feedback | TC pin sources proportional-to-absolute-temperature (PTAT) current into RREF - cancels diode VF drift for stable output over –40°C to +125°C. |
| Thermally enhanced MSOP | 16-lead MSOP with exposed GND pad - achieves θJA = 50°C/W, enabling 7W operation without heatsink in typical layouts. |
Applications
| Industrial Isolated Sensor Supply | Automotive Body Control Module (BCM) Auxiliary Rail |
|---|---|
|
Use Scenario: Providing isolated 5V/0.7A power to analog sensor front-ends in PLC I/O modules operating from 12–24V DC bus. IC Role / Device Role / Timing Role: Primary-side flyback controller regulating output via RFB sampling; handles input transients and wide temperature range. Use Value: Eliminates optocoupler-based feedback, reducing component count by 3–4 parts and improving long-term calibration stability across –40°C to +85°C. |
Use Scenario: Generating isolated 12V/0.4A rail for CAN transceiver and microcontroller in vehicle door module powered from 9–16V battery. IC Role / Device Role / Timing Role: Boundary-mode controller with programmable UVLO (10.5V) and soft-start to meet automotive cold-crank requirements. Use Value: Achieves <±2% output regulation over temperature and line without secondary-side sensing - simplifies compliance with ISO 16750-2. |
| Medical Patient-Monitoring Isolated Bias | Industrial IoT Gateway Isolated Communication Rail |
|
Use Scenario: Delivering reinforced-isolation 3.3V/1.5A for ADC reference and isolated SPI interface in Class II patient-connected ECG front-end. IC Role / Device Role / Timing Role: Flyback controller implementing creepage/clearance-compliant design using certified transformer (e.g., PA2362NL) and primary-only feedback. Use Value: Meets IEC 60601-1 4kV AC isolation requirements while avoiding optocoupler CMTI limitations and lifetime derating. |
Use Scenario: Powering isolated RS-485 and Ethernet PHY in smart factory edge gateway operating from 24V PoE-derived supply. IC Role / Device Role / Timing Role: High-efficiency (≥82%) isolated controller supporting 3.3V/5V dual outputs via multi-winding transformer and independent RFB paths. Use Value: Enables compact 2-layer PCB layout with <15mm creepage; RILIM-based current limiting protects against cable fault conditions. |
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 200kHz frequency; no RILIM or TC pin; requires auxiliary winding for bias. | Better suited for universal AC input (85–265VAC); less flexible for low-VIN industrial DC-DC due to higher VDS rating and fixed frequency. | Select UCC28911DR only when designing for offline AC input; LT3573IMSE#TRPBF offers superior low-VIN regulation and programmability for DC-fed isolated supplies. |
| MAX17690ATP+T | 65V/1.2A integrated MOSFET; valley-switching mode; includes comprehensive protection (OVP, OTP, SCP); 20-pin TQFN. | Higher integration (integrated gate driver, robust fault handling); larger package and higher cost; requires more complex compensation. | Choose MAX17690ATP+T when system-level protection and diagnostic capability are critical; LT3573IMSE#TRPBF provides simpler, lower-cost solution for basic isolated DC-DC where external protection suffices. |
Compared with UCC28911DR and MAX17690ATP+T, the LT3573IMSE#TRPBF delivers optimal balance of programmability (RILIM, TC, SS), low-VIN capability (3V min), and minimal external component count - making it ideal for cost-sensitive, DC-input isolated power stages requiring stable regulation without optocouplers.
Availability
LT3573IMSE#TRPBF is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical device power supplies requiring stable component supply, long lifecycle support, and guaranteed traceable sourcing.
Supply support for LT3573IMSE#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 industrial, automotive, communications, and healthcare markets.
The LT3573 product line was developed specifically for primary-side regulated isolated flyback converters - targeting space-constrained, cost-sensitive applications where optocoupler elimination, wide input range, and robust thermal performance are essential.
FAQ
What is the maximum output power achievable with the LT3573IMSE#TRPBF?
The LT3573IMSE#TRPBF can deliver 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 operation within the 3V–40V input range. Real-world output depends on transformer turns ratio, leakage inductance, and thermal management - measured data shows ≥6W sustained at 24VIN/5VOUT with 1A load and 25°C ambient.
Does the LT3573IMSE#TRPBF require an optocoupler for regulation?
No, the LT3573IMSE#TRPBF does not require an optocoupler. It achieves isolated output regulation by sampling the flyback voltage waveform directly at the SW pin during the secondary zero-current period. This primary-side sensing architecture eliminates optocouplers and auxiliary windings, reducing component count, cost, and long-term reliability concerns associated with opto aging and CMTI limitations.
How is output voltage programmed on the LT3573IMSE#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 nominal relationship is VOUT ≈ 1.23V × (RFB/RREF) × (1/NPS) − VF, where NPS is the transformer primary-to-secondary turns ratio and VF is diode forward voltage. Tables in the datasheet provide standard RFB/RREF/RTC values for common outputs (3.3V, 5V, 12V) and ratios (1:1, 2:1, 3:1).
What is the purpose of the TC pin on the LT3573IMSE#TRPBF?
The TC (Temperature Compensation) pin on the LT3573IMSE#TRPBF sources a proportional-to-absolute-temperature (PTAT) current into the RREF node to offset the negative temperature coefficient of the output rectifier diode's forward voltage. Connecting a resistor (e.g., 20.1kΩ) from TC to GND generates ~27.5µA at 25°C, improving output voltage stability over temperature - critical for medical and industrial applications requiring <±2% regulation from –40°C to +125°C.
Can the LT3573IMSE#TRPBF operate with input voltage below 3V?
No, the LT3573IMSE#TRPBF has a specified minimum input voltage of 3V per Absolute Maximum Ratings and Electrical Characteristics tables. Operation below 3V is not guaranteed - startup circuitry, bias generation, and internal regulator functionality are not characterized or supported under that condition. For sub-3V applications, alternative controllers with lower VIN minima (e.g., LT3999) should be evaluated.
LT3573IMSE#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
LT3573IMSE#TRPBF FAQ
1.How can I place an order for LT3573IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3573IMSE#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 LT3573IMSE#TRPBF reliable?
The price and inventory of LT3573IMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3573IMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3573IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3573IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3573IMSE#TRPBF?
LT3573IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3573IMSE#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 LT3573IMSE#TRPBF?
For technical support, including LT3573IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3573IMSE#TRPBF requirements.
6.How does Aetrix verify that LT3573IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3573IMSE#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 LT3573IMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3573IMSE#TRPBF?
All LT3573IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3573IMSE#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 LT3573IMSE#TRPBF part is unused and in its original packaging.
Return procedure for LT3573IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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