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Analog Devices Inc. LT3748IMS#PBF
- Part No.:
- LT3748IMS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width), 12 Leads
- Datasheet:
-
LT3748IMS#PBF.pdf
- Description:
- IC REG CTRLR FLYBACK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,633
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Product details
Overview
LT3748IMS#PBF from Analog Devices is a 100V isolated flyback controller IC designed for primary-side regulation in high-reliability isolated DC/DC converters. It drives an external N-channel MOSFET, operates in boundary mode, supports 5V–100V input, delivers up to ~25W output (e.g., 12V/2A), and eliminates need for opto-isolators or third-winding feedback.
For engineers reviewing the LT3748IMS#PBF datasheet, LT3748IMS#PBF pinout, LT3748IMS#PBF application, or LT3748IMS#PBF equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, automotive-grade thermal performance (–40°C to 125°C), and two confirmed alternative controllers for isolated flyback designs.
Technical Context
The LT3748IMS#PBF implements boundary-mode (critical conduction) control using primary-side flyback waveform sampling to derive isolated output voltage-no opto-isolator or auxiliary winding required. Its internal error amplifier references a 1.223V bandgap and samples at zero-secondary-current crossing to achieve tight load regulation.
It features programmable undervoltage lockout (1.223V threshold with 2.4µA hysteresis sink), 7V internally regulated INTVCC gate driver supply, 1.9A average gate drive capability, and temperature-compensated output regulation via TC/RREF network. Operating frequency varies dynamically with load and transformer magnetizing inductance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 5V to 100V - supports wide-input telecom, industrial, and automotive supplies without external pre-regulation. |
| INTVCC Regulation | 7.0V ±0.2V - powers gate driver and internal circuitry; stable bias enables robust MOSFET switching up to tens of watts. |
| Gate Drive Capability | 1.9A avg source/sink - drives high-Ciss MOSFETs for efficient high-power flyback operation with fast 16ns rise/fall times. |
| SENSE Threshold Range | 15mV to 110mV - sets current limit via external RSENSE; wide range allows precise peak-current control across loads. |
| EN/UVLO Threshold | 1.223V rising, 3.6V INTVCC UVLO - enables clean start-up sequencing and brown-out protection for 12V–72V input rails. |
| Operating Temp Range | –40°C to +125°C junction - qualified per AEC-Q100 Grade I; suitable for under-hood automotive and harsh industrial environments. |
| Package | 16-lead MSOP (12-pin variant) - compact surface-mount footprint with exposed pad for thermal management in space-constrained designs. |
Pinout & Package
LT3748IMS#PBF uses a 16-lead plastic MSOP package with four leads removed (12-pin functional layout), optimized for high-voltage isolation and thermal dissipation in flyback power supplies.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 1) | Main input supply reference | Bypassed locally; supplies startup circuitry and serves as reference for RFB feedback network. |
| EN/UVLO (Pin 3) | Enable and input undervoltage detection | Resistor divider from VIN sets turn-on threshold; sinking 2.4µA provides hysteresis for stable UVLO behavior. |
| INTVCC (Pin 5) | Internally regulated gate driver supply | 7V output powers GATE driver; can be tied to VIN if ≤20V and no third winding used. |
| GATE (Pin 6) | N-channel MOSFET gate driver output | Switches between INTVCC and GND; 1.9A avg drive supports high-power external switches. |
| SENSE (Pin 7) | Primary-side current sense input | Kelvin-connected to RSENSE source; monitors switch current for cycle-by-cycle limiting and boundary detection. |
| GND (Pins 8, 9) | Power and signal ground reference | Dual ground pins reduce noise coupling; SENSE resistor return must connect near these pins. |
| SS (Pin 10) | Soft-start timing node | 5µA current source charges external capacitor; start delayed until VSS reaches ~0.65V. |
| VC (Pin 11) | Error amplifier compensation node | Connect series RC to ground for loop stability; 100pF parallel cap suppresses noise. |
| TC (Pin 12) | Temperature compensation current source | Sources proportional-to-absolute-temperature (PTAT) current into RREF to cancel diode VF drift. |
| RREF (Pin 14) | Reference resistor connection | 6.04kΩ nominal sets output voltage scale; internal 1.223V bandgap reference defines regulation point. |
| RFB (Pin 16) | Feedback resistor connection | Connected to MOSFET drain; ratio RFB/RREF × 1.223V × (1/NPS) determines VOUT, minus diode drop. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side regulation | Eliminates opto-isolator and third winding-reduces BOM cost, improves reliability, avoids aging/nonlinearity issues. |
| Boundary mode operation | Enables small magnetics, inherent load regulation without extra compensation, and no subharmonic oscillation. |
| Programmable soft-start | External capacitor sets controlled ramp-up time, preventing inrush current and transformer saturation at startup. |
| Temperature-compensated output | TC pin current offsets diode forward-voltage drift over temperature, maintaining ±5% regulation across –40°C to 125°C. |
| AEC-Q100 qualified | Validated for automotive applications (Grade I); includes extended temp range, HTOL, and ESD testing per automotive standards. |
Applications
| Telecom Isolated Supply | Automotive High-Voltage DC/DC |
|---|---|
|
Use Scenario: 36V–72V telecom rectified input powering isolated 12V/2A load in central office equipment. IC Role / Device Role / Timing Role: Primary-side flyback controller performing boundary-mode switching, output voltage sensing via drain waveform, and gate drive for external MOSFET. Use Value: Achieves 25W output with <±1.5% line/load regulation-no opto-isolator needed, reducing component count and long-term drift risk. |
Use Scenario: 12V battery-derived input (with boost pre-regulator) powering isolated 5V/1A domain in ADAS ECU. IC Role / Device Role / Timing Role: AEC-Q100 qualified flyback controller delivering stable isolated rail while operating from cold-crank (4.5V) to load-dump (100V) conditions. Use Value: Maintains regulation across –40°C to 125°C ambient; TC compensation ensures <±3% output variation over full temperature range. |
| Industrial Isolated Power | Military/Harsh Environment Supply |
|
Use Scenario: 24V–48V factory automation bus powering isolated 15V sensor interface with reinforced insulation. IC Role / Device Role / Timing Role: Boundary-mode controller enabling compact transformer design and immunity to transformer parameter variation across production lots. Use Value: Delivers consistent output despite ±5% tolerance in RREF/RFB and ±10% transformer turns ratio mismatch. |
Use Scenario: 28V aircraft bus supplying isolated 28V/0.5A payload rail in avionics enclosure with high ambient temperature. IC Role / Device Role / Timing Role: High-junction-temp flyback controller operating up to 125°C junction, with INTVCC dropout <0.7V at 10mA to sustain gate drive under low-VIN stress. Use Value: Enables >90% efficiency at full load with minimal derating-no forced air cooling required in sealed enclosures. |
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 | Fixed-frequency DCM controller; no boundary mode; requires auxiliary winding for VDD; lower max input (85V). | Best for cost-sensitive, lower-power (<10W) designs where transformer size is less critical than BOM simplicity. | Choose UCC28911DR only if auxiliary winding is acceptable and input stays below 85V; not drop-in for LT3748IMS#PBF's primary-side sensing. |
| MAX17690ATP+T | Current-mode flyback controller with integrated 100V MOSFET; fixed 660kHz frequency; no TC compensation pin. | Suitable for ultra-compact, low-component-count designs up to ~15W; lacks temperature compensation for precision outputs. | Select MAX17690ATP+T when board space is constrained and integrated FET suffices; not suitable for >20W or automotive temp-critical apps. |
Compared with UCC28911DR and MAX17690ATP+T, the LT3748IMS#PBF uniquely combines primary-side boundary-mode regulation, 100V input support, AEC-Q100 qualification, and analog temperature compensation-making it the only choice for high-accuracy, high-power, automotive-grade isolated flyback designs requiring no opto-isolator.
Availability
LT3748IMS#PBF is available at Aetrix Electronics and suitable for telecom isolated supplies, automotive high-voltage DC/DC, and industrial embedded power systems requiring stable component supply, long lifecycle support, and AEC-Q100 compliance.
Supply support for LT3748IMS#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 (now part of Analog Devices, Inc., following merger with Maxim Integrated) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3748IMS#PBF belongs to the LT® family of high-voltage power conversion controllers, engineered specifically for isolated flyback topologies demanding primary-side regulation, high efficiency, and automotive-grade reliability.
FAQ
What is the maximum input voltage supported by the LT3748IMS#PBF?
The LT3748IMS#PBF supports an absolute maximum input voltage of 100V on the VIN pin, with guaranteed operation across 5V to 100V. This makes the LT3748IMS#PBF suitable for telecom rectified inputs, automotive load-dump transients, and industrial wide-range supplies without external clamping or pre-regulation.
Does the LT3748IMS#PBF require an opto-isolator or third winding for regulation?
No-the LT3748IMS#PBF performs primary-side regulation by sampling the flyback voltage waveform at the MOSFET drain, eliminating the need for an opto-isolator or auxiliary winding. This reduces component count, improves long-term reliability, and avoids opto aging and nonlinearity issues inherent in traditional isolated flyback designs using the LT3748IMS#PBF.
What is the operating temperature range of the LT3748IMS#PBF?
The LT3748IMS#PBF is rated for a junction temperature range of –40°C to +125°C and is AEC-Q100 qualified for automotive Grade I applications. Its thermal performance is validated across this full range, including stable INTVCC regulation and compensated output voltage tracking-key attributes of the LT3748IMS#PBF in harsh environments.
How does the TC pin function in the LT3748IMS#PBF?
The TC pin of the LT3748IMS#PBF sources a proportional-to-absolute-temperature (PTAT) current into the RREF node to offset the negative temperature coefficient of the output diode's forward voltage. When paired with an external RTC resistor to ground, it enables precise temperature-compensated output regulation-critical for maintaining accuracy in automotive and industrial applications using the LT3748IMS#PBF.
Can the LT3748IMS#PBF drive high-side or synchronous rectifier MOSFETs?
No-the LT3748IMS#PBF is a low-side N-channel MOSFET gate driver only. It cannot directly drive high-side switches or synchronous rectifiers. Its GATE pin outputs a ground-referenced signal swinging between INTVCC and GND. For secondary-side synchronous rectification, an external driver or dedicated SR controller (e.g., LTC3900) must be used alongside the LT3748IMS#PBF.
LT3748IMS#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width), 12 Leads
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Flyback
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 5V ~ 100V
- Frequency - Switching:
- -
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Soft Start
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP
LT3748IMS#PBF FAQ
1.How can I place an order for LT3748IMS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3748IMS#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 LT3748IMS#PBF reliable?
The price and inventory of LT3748IMS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3748IMS#PBF is usually 5 days.
3.What payment methods are accepted for LT3748IMS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3748IMS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3748IMS#PBF?
LT3748IMS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3748IMS#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 LT3748IMS#PBF?
For technical support, including LT3748IMS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3748IMS#PBF requirements.
6.How does Aetrix verify that LT3748IMS#PBF is sourced from the original manufacturer or authorized distributors?
All LT3748IMS#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 LT3748IMS#PBF meets industry standards.
7.What is the process for return or replacement of LT3748IMS#PBF?
All LT3748IMS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3748IMS#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 LT3748IMS#PBF part is unused and in its original packaging.
Return procedure for LT3748IMS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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