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Analog Devices Inc. LT1425IS#TRPBF
- Part No.:
- LT1425IS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1425IS#TRPBF.pdf
- Description:
- IC REG FLYBACK 135MA 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,935
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Product details
Overview
LT1425IS#TRPBF from Analog Devices is a monolithic isolated flyback switching regulator IC designed for primary-side sensing in transformer-isolated DC/DC converters. It integrates a 1.6A/35V N-channel power switch, current-mode control, 285kHz oscillator, and flyback error amplifier - eliminating need for optoisolators or third-winding feedback. Delivers up to 6W output power with ±5% output voltage accuracy across 20mA–200mA load range in medical and telecom isolated supplies.
For engineers reviewing the LT1425IS#TRPBF datasheet, LT1425IS#TRPBF pinout, LT1425IS#TRPBF application, or LT1425IS#TRPBF equivalent, key selection criteria include primary-side regulation capability, shutdown current (15µA), RREF-referred transconductance (400–1600 µmho), load compensation support via ROCOMP/RCCOMP, and SOIC-16 package compatibility with industrial temperature range (–40°C to 125°C).
Technical Context
The LT1425IS#TRPBF implements a proprietary flyback error amplifier that samples the primary-side VSW flyback pulse waveform to infer isolated output voltage - avoiding optoisolators or auxiliary windings. Its control loop uses RREF-referred transconductance (400–1600 µmho) and clamped VC node (1.9V max) to set current-mode trip point via integrated current comparator.
It supports discontinuous conduction mode (DCM) regulation down to light loads using minimum enable time (180ns) and collapse-detect logic, while optional load compensation adjusts target voltage based on average switch current via ROCOMP resistor and RCCOMP capacitor - correcting for secondary ESR, diode VF, and transformer turns ratio nonidealities.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Breakdown Voltage | 35V - enables use with ≤20V input and flyback spikes up to 35V without external clamp |
| Switch Current Limit | 1.2A (–40°C to 125°C, 50% duty) - sets maximum deliverable power and short-circuit protection threshold |
| Operating Frequency | 285kHz typical - determines transformer size, EMI profile, and minimum output capacitor requirements |
| Quiescent Supply Current | 7mA - defines no-load power loss and thermal budget in always-on isolated supplies |
| Shutdown Supply Current | 15µA - enables ultra-low-power standby mode for energy-sensitive applications |
| Reference Current (RREF) | 396–420µA - establishes precision of resistor-programmed output voltage (VOUT ∝ RFB/RREF) |
| Feedback Amplifier Clamp | 1.9V - limits VC pin voltage to prevent overdrive and ensure stable loop compensation |
Pinout & Package
LT1425IS#TRPBF is housed in a 16-pin narrow SOIC (S package) with exposed substrate ground connections at pins 1, 8, 9, and 16. Thermal resistance θJA = 75°C/W; maximum junction temperature = 145°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (1,8,9,16) | Substrate ground | Die substrate connection; must tie directly to low-impedance ground plane to minimize noise coupling into analog blocks |
| RFB (3) | Flyback feedback input | Senses VSW flyback pulse amplitude; current ≈400µA sets output voltage scaling with RREF |
| VC (4) | Control voltage output | Integrator node for loop compensation; connects to external capacitor to ground for stability |
| RREF (5) | Reference resistor input | Ground-referred resistor (≈3.0kΩ) sets reference current; defines gain of feedback path |
| SYNC (6) | External clock sync input | Accepts 10–90% duty cycle logic signal; synchronizes internal 285kHz oscillator to avoid beat frequencies |
| SGND (7) | Signal ground | Reference for internal bandgap and feedback amplifier; must be isolated from PGND currents |
| PGND (10) | Power ground | Emiter of internal switch; carries high di/dt currents - requires dedicated low-inductance ground path |
| VSW (11) | Switch collector node | High-voltage, high-current switching node; trace length must be minimized to reduce EMI and ringing |
| VIN (12) | Input supply | 3V–20V operation; includes undervoltage lockout at 2.8V to prevent erratic startup |
| RCCOMP (13) | Load compensation filter | Connects 0.1µF ceramic capacitor to ground; filters ROCOMP-derived compensation current |
| ROCOMP (14) | Load compensation resistor | Adjusts target output voltage vs load current to compensate for secondary impedance (ESR, VF, turns ratio) |
| SHDN (15) | Shutdown control | Logic-low (<0.9V) disables switching and reduces supply current to 15µA |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side output voltage sensing | Eliminates optoisolator and third winding - reduces BOM count, cost, and board area in isolated flyback designs |
| Discontinuous mode regulation | Maintains ±5% output accuracy down to 20mA load without external circuitry - simplifies light-load behavior |
| Resistor-programmable output | VOUT determined by RFB/RREF ratio and transformer turns ratio - enables precise, trim-free voltage setting |
| Optional load compensation | ROCOMP/RCCOMP network corrects for output impedance effects (diode VF, secondary ESR, transformer leakage) |
| 285kHz fixed-frequency operation | Enables predictable EMI filtering and consistent transformer design across production units |
| 15µA shutdown current | Supports low-power standby in battery-backed or energy-harvesting isolated systems |
Applications
| Medical Isolated Power | Ethernet PHY Isolation |
|---|---|
Use Scenario: Providing isolated –9V bias for Ethernet magnetics and PHY interface ICs in industrial switches. IC Role / Device Role / Timing Role: Primary-side regulated flyback controller generating isolated negative rail without optocoupler feedback. Use Value: Achieves ±5% output accuracy at 20–200mA load with no user trims - meets IEEE 802.3af timing and voltage tolerance requirements. |
Use Scenario: Generating isolated ±5V rails for patient-connected diagnostic equipment requiring reinforced insulation. IC Role / Device Role / Timing Role: Monolithic flyback regulator delivering 6W isolated output with creepage/clearance compliance via transformer barrier. Use Value: Eliminates optoisolator aging and unit-to-unit variation - ensures long-term calibration stability in Class II medical devices. |
| Telecom Line Card Supply | Industrial IoT Sensor Isolation |
Use Scenario: Powering isolated RS-485 transceivers and ADC front-ends in telecom line cards with 48V backplane input. IC Role / Device Role / Timing Role: High-efficiency flyback controller operating from wide-input 3–20V range with synchronized frequency option. Use Value: 285kHz switching enables compact transformer design; SYNC pin allows EMI spreading across multiple converters on same board. |
Use Scenario: Providing galvanically isolated 5V-to-–9V conversion for wireless sensor nodes in hazardous environments. IC Role / Device Role / Timing Role: Low-quiescent-current (7mA) flyback IC supporting battery backup during mains failure. Use Value: 15µA shutdown mode extends battery life; SOIC-16 package supports automated assembly in high-volume sensor modules. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated flyback regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28711DR | Fixed-frequency quasi-resonant controller; requires external MOSFET; no integrated switch; 30V max VDS | Lacks primary-side sensing - needs optocoupler or auxiliary winding; higher BOM count and layout complexity | Choose when higher efficiency at light load is critical and external FET selection is preferred |
| MAX17690ATP+T | Integrated 100V/1.2A switch; supports 4.5–40V input; no load compensation; 600kHz switching | Higher input voltage range but lacks ROCOMP-based secondary impedance correction - less accurate under variable load | Choose for wider VIN range and higher frequency; avoid where ±5% load regulation is mandatory |
Compared with UCC28711DR and MAX17690ATP+T, the LT1425IS#TRPBF uniquely combines integrated 35V switch, primary-side sensing, and programmable load compensation - enabling simpler, more accurate isolated flyback designs within its 3–20V input and 6W power envelope.
Availability
LT1425IS#TRPBF is available at Aetrix Electronics and suitable for medical instrumentation, Ethernet isolation, and telecom line card supplies requiring stable component supply, industrial temperature operation (–40°C to 125°C), and lead-free RoHS-compliant packaging.
Supply support for LT1425IS#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, Inc. (ADI) is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and power management.
The LT1425IS#TRPBF belongs to ADI's isolated power controller product line, engineered specifically for primary-side regulated flyback converters in safety-critical and space-constrained applications where optoisolator elimination is essential.
FAQ
What is the maximum output power achievable with the LT1425IS#TRPBF?
The LT1425IS#TRPBF delivers up to 6W of output power without external power devices. This limit arises from the integrated 1.6A/35V switch, thermal constraints of the SOIC-16 package (θJA = 75°C/W), and 285kHz switching frequency. Exceeding 6W requires external MOSFETs and careful thermal design - which the LT1425IS#TRPBF does not support.
Does the LT1425IS#TRPBF require an optoisolator or third winding for feedback?
No. The LT1425IS#TRPBF uses primary-side sensing of the VSW flyback pulse waveform to infer isolated output voltage - eliminating both optoisolators and auxiliary transformer windings. This is implemented via its proprietary flyback error amplifier and RFB/RREF resistor network, as confirmed in the device's block diagram and Applications Information section.
How does the load compensation function work in the LT1425IS#TRPBF?
The LT1425IS#TRPBF implements load compensation by measuring average switch current and injecting a corrective current into the RFB node via the ROCOMP resistor. This offsets voltage drop caused by secondary ESR, diode forward voltage, and transformer leakage - improving load regulation. The RCCOMP capacitor filters this signal, and the data sheet specifies ∆VRCCOMP/∆ISW = 0.45Ω for design calculations.
What is the operating temperature range for the LT1425IS#TRPBF?
The LT1425IS#TRPBF is rated for operation from –40°C to 125°C ambient temperature. This "I-grade" specification is explicitly stated in the Order Information table and Absolute Maximum Ratings section of the datasheet, distinguishing it from the "C-grade" LT1425CS#TRPBF (0°C to 125°C).
Can the LT1425IS#TRPBF be synchronized to an external clock?
Yes. The LT1425IS#TRPBF features a dedicated SYNC pin (Pin 6) that accepts logic-level signals with 10–90% duty cycle to synchronize its internal 285kHz oscillator. The datasheet specifies minimum SYNC amplitude of 1.5V and synchronization range of 320–450kHz - enabling EMI reduction in multi-converter systems.
LT1425IS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm 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):
- 2.8V
- Voltage - Input (Max):
- 20V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 135mA (Switch)
- Frequency - Switching:
- 285kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 100°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1425IS#TRPBF FAQ
1.How can I place an order for LT1425IS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1425IS#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 LT1425IS#TRPBF reliable?
The price and inventory of LT1425IS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1425IS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1425IS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1425IS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1425IS#TRPBF?
LT1425IS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1425IS#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 LT1425IS#TRPBF?
For technical support, including LT1425IS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1425IS#TRPBF requirements.
6.How does Aetrix verify that LT1425IS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1425IS#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 LT1425IS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1425IS#TRPBF?
All LT1425IS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1425IS#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 LT1425IS#TRPBF part is unused and in its original packaging.
Return procedure for LT1425IS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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