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Analog Devices Inc. LT3825EFE#TRPBF
- Part No.:
- LT3825EFE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3825EFE#TRPBF.pdf
- Description:
- IC REG CTRLR FLYBACK 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:9,841
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Product details
Overview
LT3825EFE#TRPBF from Analog Devices (formerly Linear Technology) is an isolated synchronous flyback controller IC for medium-power DC/DC conversion, supporting 10W–60W output with input voltage limited only by external components. It regulates output voltage via primary-side sensing of a third transformer winding-eliminating opto-isolators-and delivers ±1.237V feedback reference, 84–110kHz programmable switching frequency, and 85–88% maximum duty cycle in forced continuous conduction mode for improved cross-regulation in multi-output telecom and medical power supplies.
For engineers reviewing the LT3825EFE#TRPBF datasheet, LT3825EFE#TRPBF pinout, LT3825EFE#TRPBF application, or LT3825EFE#TRPBF equivalent, key selection criteria include its no-opto isolated feedback architecture, synchronous gate drive capability (PG/SG), load compensation support (RCMP/CCMP), UVLO programmability, and thermal-enhanced 16-lead TSSOP package with exposed GND pad.
Technical Context
The LT3825EFE#TRPBF implements current-mode control with flyback-specific timing logic: it samples the third-winding flyback pulse during synchronous rectifier conduction to derive output voltage feedback without optocouplers. Its feedback amplifier enables only during the flyback window, using collapse-detect and enable-delay circuitry to reject leakage-inductance spikes.
It integrates dual gate drivers (PG for primary MOSFET, SG for secondary synchronous rectifier), programmable minimum on-time (tON), flyback enable delay (ENDLY), PG turn-on delay (PGDLY), and soft-start ramp control (SFST). Load compensation is implemented via RCMP/CCMP pins to correct for I×R drops across RDS(ON) and ESR in the secondary path.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Feedback Reference Voltage | 1.237 V ±1.5 mV - sets precise output regulation point independent of opto-isolator drift or aging |
| Switching Frequency Range | 84–110 kHz (COSC = 100 pF) - user-programmable via external capacitor; supports synchronization to external clock |
| Max Duty Cycle | 88% - enables high step-down ratios (e.g., 48V→3.3V) while maintaining stable forced CCM operation |
| VCC Turn-On/Off Threshold | 15.3 V / 9.7 V - provides clean startup and brownout protection; internal 19.5 V clamp protects against transients |
| Current Sense Threshold | 98 mV at max VC - defines peak primary current limit; blanked during tON(MIN) to avoid noise coupling |
| UVLO Pin Threshold | 1.240 V ±25 mV - allows input-voltage-based enable/disable independent of VCC; hysteresis controlled by divider impedance |
| Soft-Start Charge Current | 20 µA typical - controls VC ramp rate; total ramp time ≈ 70 ms per µF on SFST pin |
Pinout & Package
LT3825EFE#TRPBF is housed in a thermally enhanced 16-lead plastic TSSOP (4.4 mm wide) with exposed GND pad (Pin 17) requiring PCB soldering for thermal and electrical integrity. θJA = 40°C/W, θJC = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SG (1) | Synchronous Gate Drive Output | Drives secondary-side MOSFET; high-current capable; timing synchronized to flyback event |
| VCC (2) | Supply Input with Clamp & UVLO | Bypass with ≥4.7 µF; internal 19.5 V clamp and 15.3 V turn-on ensures robust startup |
| tON (3) | Minimum On-Time Programming | Resistor sets absolute minimum primary switch conduction time to guarantee flyback sampling |
| ENDLY (4) | Enable Delay Programming | Resistor sets fixed delay after primary switch-off before feedback amplifier activation |
| SYNC (5) | External Clock Synchronization Input | Positive-edge triggered; threshold ~1.53 V; ties to GND if unused |
| SFST (6) | Soft-Start Control | Capacitor-to-GND sets VC ramp rate; limits inrush current during startup |
| OSC (7) | Oscillator Timing Node | Capacitor-to-GND sets switching frequency; f ≈ 100 kHz × 100/COSC(pF) |
| FB (8) | Feedback Amplifier Input | Receives scaled third-winding voltage; sinks load-compensation current via RCMP |
| VC (9) | Control Loop Compensation Node | Integrates feedback error current; voltage sets peak current trip point |
| UVLO (10) | Input-Voltage-Based Enable | Resistive divider from VIN sets system-level undervoltage lockout |
| SENSE– (11), SENSE+ (12) | Primary Current Sense Inputs | Kelvin-connected to sense resistor; 98 mV threshold at full scale; blanked during tON(MIN) |
| CCMP (13) | Load Compensation Filter Capacitor | 0.1 µF ceramic filters averaged sense current for IR-drop correction |
| RCMP (14) | Load Compensation Gain Resistor | Sets compensation magnitude; open for basic applications, required for tight load regulation |
| PGDLY (15) | PG Turn-On Delay Programming | Resistor sets delay from SG turn-off to PG turn-on to prevent shoot-through |
| PG (16) | Primary Gate Drive Output | High-current driver for primary-side MOSFET; fast rise/fall times (<15 ns @ 1 nF) |
| GND (17) | Signal & Power Ground (Exposed Pad) | Mandatory PCB connection; serves as reference for all analog and gate-drive circuits |
Key Features
| Feature | Design Value |
|---|---|
| No-opto isolated feedback | Uses third-winding flyback pulse sampling - eliminates optocoupler cost, aging, and bandwidth limitations |
| Synchronous rectification support | Dual gate drivers (PG/SG) with programmable delays ensure safe, efficient secondary-side MOSFET control |
| Load compensation | RCMP/CCMP interface actively corrects output voltage droop due to RDS(ON) and ESR under varying load |
| Programmable timing parameters | Independent resistors set tON(MIN), ENDLY, PGDLY, and soft-start ramp - enabling precise loop tuning |
| Forced continuous conduction mode | Improves cross-regulation in multi-output designs by maintaining coupling during entire off-time |
Applications
| Telecom Isolated DC/DC Converters | Medical Equipment Power Supplies |
|---|---|
Use Scenario: 48V backplane to isolated 3.3V/12A supply in telecom shelf management systems. IC Role / Device Role / Timing Role: Primary-side controller regulating output via third-winding flyback sensing; PG drives primary MOSFET, SG drives synchronous rectifier. Use Value: Achieves >92% efficiency at full load without optocoupler, reducing BOM cost and improving long-term reliability in 24/7 operation. | Use Scenario: Patient-connected diagnostic device requiring reinforced isolation and low leakage current. IC Role / Device Role / Timing Role: Isolated flyback controller enforcing creepage/clearance compliance; operates in forced CCM for predictable EMI profile. Use Value: Eliminates opto-isolator failure modes and enables tighter output regulation (±1%) across temperature and line variations. |
| Industrial Instrumentation Power | Power over Ethernet (PoE) Midspan Supplies |
Use Scenario: Precision sensor module requiring isolated 5V/2A supply with minimal output ripple and load transient response. IC Role / Device Role / Timing Role: No-opto controller with load compensation (RCMP/CCMP) correcting for secondary-side IR drops. Use Value: Maintains ±15 mV regulation over 0–2 A load step without post-regulation LDO, reducing heat and component count. | Use Scenario: Midspan PoE injector delivering up to 60W to IEEE 802.3at devices with isolated auxiliary rails. IC Role / Device Role / Timing Role: Medium-power flyback controller supporting wide input (36–72V) and programmable UVLO for PoE detection. Use Value: Enables single-stage isolated conversion with <100 ns PG/SG timing control, meeting PoE Class 4 transient response requirements. |
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 | Primary-side sensing with integrated high-voltage start-up; no synchronous gate drive; lower max power (~30W) | Targeted at cost-sensitive, low-power AC/DC adapters; lacks SG output and load compensation | Choose UCC28911DR for non-synchronous, lower-cost, lower-power isolated supplies where SG drive and precise load regulation are not required. |
| MAX17690ATP+ | Integrated 600V MOSFET; no PG/SG outputs; uses digital PWM control; supports ZVS | Designed for high-efficiency, high-density industrial AC/DC; not pin-compatible and requires different transformer design | Choose MAX17690ATP+ when integrating primary switch and needing digital control flexibility, but expect redesign of gate drive and transformer layout. |
Compared with UCC28911DR and MAX17690ATP+, the LT3825EFE#TRPBF uniquely provides dual synchronous gate drivers, programmable load compensation, and forced CCM operation-making it optimal for medium-power, multi-output, opto-free isolated supplies demanding tight cross-regulation and dynamic load response.
Availability
LT3825EFE#TRPBF is available at Aetrix Electronics and suitable for telecom infrastructure, medical power modules, industrial instrumentation, and Power over Ethernet midspan supplies requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.
Supply support for LT3825EFE#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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LT3825EFE#TRPBF belongs to ADI's isolated power controller product line, designed specifically for medium-power flyback topologies requiring opto-isolator elimination, synchronous rectification, and high-accuracy regulation in safety-critical and space-constrained applications.
FAQ
What is the primary function of the LT3825EFE#TRPBF in a power supply design?
The LT3825EFE#TRPBF is an isolated synchronous flyback controller IC that regulates output voltage by sensing the flyback pulse from a third transformer winding-eliminating the need for an opto-isolator. It drives both primary and secondary MOSFETs (via PG and SG pins), supports load compensation, and operates in forced continuous conduction mode to improve cross-regulation. The LT3825EFE#TRPBF enables compact, reliable, and high-efficiency isolated DC/DC conversion in telecom, medical, and industrial applications.
How does the LT3825EFE#TRPBF achieve accurate output regulation without an opto-isolator?
The LT3825EFE#TRPBF achieves accurate output regulation by sampling the voltage induced on a dedicated third transformer winding during the flyback period. This voltage is scaled by an external resistor divider and applied to the FB pin, where it's compared to the internal 1.237 V reference. The feedback amplifier activates only during the valid flyback window-using enable delay (ENDLY) and collapse detect-to reject leakage spikes. The LT3825EFE#TRPBF thus maintains ±1% regulation over line, load, and temperature without optocoupler drift or bandwidth limitations.
What are the critical external components required for basic operation of the LT3825EFE#TRPBF?
Basic operation of the LT3825EFE#TRPBF requires: a 4.7 µF or larger capacitor on VCC; an external oscillator capacitor (e.g., 100 pF) on OSC; a soft-start capacitor on SFST; a feedback resistor divider (R1/R2) referenced to the third winding; a primary current sense resistor between SENSE+ and SENSE–; and proper Kelvin routing for noise immunity. The LT3825EFE#TRPBF also needs external resistors on tON, ENDLY, and PGDLY pins to set minimum on-time, enable delay, and gate timing-plus optional RCMP and CCMP components for load compensation.
Can the LT3825EFE#TRPBF be synchronized to an external clock, and how is this implemented?
Yes, the LT3825EFE#TRPBF can be synchronized to an external clock via the SYNC pin (Pin 5). A positive-edge-triggered TTL/CMOS signal with threshold ~1.53 V forces the internal oscillator to discharge, causing PG to go low and SG to go high. This allows multiple converters to operate at the same frequency and phase, reducing beat frequencies and EMI. If synchronization is not needed, the SYNC pin must be tied to ground. The LT3825EFE#TRPBF retains full functionality-including programmable frequency and soft-start-even when synchronized.
What thermal considerations apply to the LT3825EFE#TRPBF package and layout?
The LT3825EFE#TRPBF uses a 16-lead TSSOP with exposed GND pad (Pin 17), which must be soldered to a large PCB copper area for thermal dissipation. Its thermal resistance is θJA = 40°C/W and θJC = 10°C/W. Layout best practices include: minimizing trace inductance on PG/SG paths; separating high-di/dt sense traces with Kelvin connections; placing VCC bypass capacitor close to Pin 2; and routing GND connections directly to the exposed pad. The LT3825EFE#TRPBF includes overtemperature protection, but continuous operation above 125°C junction temperature may impair reliability.
LT3825EFE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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):
- 9.7V ~ 18V
- Frequency - Switching:
- 100kHz
- Duty Cycle (Max):
- 88%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, On Time Control
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3825EFE#TRPBF FAQ
1.How can I place an order for LT3825EFE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3825EFE#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 LT3825EFE#TRPBF reliable?
The price and inventory of LT3825EFE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3825EFE#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3825EFE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3825EFE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3825EFE#TRPBF?
LT3825EFE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3825EFE#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 LT3825EFE#TRPBF?
For technical support, including LT3825EFE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3825EFE#TRPBF requirements.
6.How does Aetrix verify that LT3825EFE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3825EFE#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 LT3825EFE#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3825EFE#TRPBF?
All LT3825EFE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3825EFE#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 LT3825EFE#TRPBF part is unused and in its original packaging.
Return procedure for LT3825EFE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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