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Analog Devices Inc. LTC3766IUFD#TRPBF
- Part No.:
- LTC3766IUFD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Supply Controllers, Monitors
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3766IUFD#TRPBF.pdf
- Description:
- IC CONTROLLER SYNCH 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,453
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Product details
Overview
LTC3766IUFD#TRPBF from Analog Devices (formerly Linear Technology) is a secondary-side synchronous forward controller IC designed for isolated active-clamp DC/DC converters. It delivers precise average current limiting (±8% accuracy), direct flux limit protection against transformer saturation, and clean pre-biased load start-up - enabling high-efficiency (94% at 48VIN/15AOUT) battery charger and telecom power systems.
For engineers reviewing the LTC3766IUFD#TRPBF datasheet, LTC3766IUFD#TRPBF pinout, LTC3766IUFD#TRPBF application, or LTC3766IUFD#TRPBF equivalent, key selection criteria include its PolyPhase-capable architecture, dual linear regulator control (VIN-based HV mode & VAUX-based LDO), 28-pin 4mm × 5mm QFN package with exposed thermal pad, and integrated differential remote sensing for ±0.1% output voltage regulation.
Technical Context
The LTC3766IUFD#TRPBF implements secondary-side PWM control with adaptive shoot-through prevention, leading-edge blanking on the SW pin, and volt-second limiting via VSEC to guarantee no transformer saturation during transients. Its error amplifier (gm = 2.7 mS, REA = 5 MΩ) drives ITH for loop compensation, while the FS/SYNC pin supports both resistor-set oscillator (75–500 kHz) and PLL synchronization (100–500 kHz).
It integrates two gate drivers: FG/SG for synchronous rectification and PT+/PT− for pulse-encoded primary-side communication with the LTC3765. The MODE pin selects LV (7.0 V) or HV (8.5 V) VCC regulation, adjusting UVLO thresholds (e.g., VUVLO,RISING = 7.7 V / 4.6 V) and VAUX switchover points accordingly.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VFB Regulated Voltage | 0.600 V ±0.008 V - sets precise 5 V output with ±0.1% load/line regulation via servo loop |
| Average Current Sense Threshold | 0.73 V (CT mode) or 55 mV (RS mode) - enables accurate 15 A output current limit with ripple cancellation |
| Oscillator Frequency Range | 75–500 kHz - configurable via RFS/SYNC; PLL sync supported for multi-phase timing coherence |
| Volt-Second Limit Accuracy | ±4% (5–40 V SW range) - prevents transformer saturation without sacrificing transient response |
| Soft-Start Charge Current | 5 μA - controls ramp rate of output voltage using external SS capacitor |
| Gate Driver Pull-Up/Down RON | FG/SG: 1.5 Ω / 1.0 Ω - ensures fast MOSFET switching with <100 ns delays (RFGD/RSGD-tunable) |
| Operating Junction Temp | –40°C to +125°C - qualified for industrial and telecom environments with θJA = 43°C/W (QFN) |
Pinout & Package
Package: 28-lead (4 mm × 5 mm) plastic QFN with exposed thermal pad (Pin 29 = GND), RoHS-compliant, moisture sensitivity level 3.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SG (Pin 26) | Synchronous MOSFET gate driver output | Drives low-side synchronous rectifier; Kelvin-connected to SW for reverse-current protection |
| FG (Pin 27) | Forward MOSFET gate driver output | Drives high-side forward switch; timing coordinated with PT+ via FGD delay resistor |
| VSEC (Pin 28) | Volt-second integrator input | Terminates PWM on-time when integrated V·t exceeds internal threshold - prevents core saturation |
| MODE (Pin 1) | VCC regulation mode select | GND = LV mode (7.0 V VCC); VCC = HV mode (8.5 V VCC); sets UVLO and VAUX switchover thresholds |
| VS+, VS–, VSOUT (Pins 8–10) | Differential remote sense inputs/output | Enables true Kelvin sensing at load; VSOUT provides unity-gain buffered output for ripple cancellation |
| IS+, IS– (Pins 15, 14) | Current sense differential inputs | Supports resistor-shunt (RS) or current-transformer (CT) sensing; CT mode raises OC threshold to 1.33 V |
| PT+, PT– (Pins 22, 23) | Pulse transformer encoder outputs | Encode PWM + bias power into single pulse train for isolation; in standalone mode, PT+ = standard PWM |
| NDRV (Pin 18) | External pass device drive | Controls base/gate of NPN/MOSFET for HV linear regulator; tie to VCC if using internal VAUX LDO only |
Key Features
| Feature | Design Value |
|---|---|
| Direct Flux Limit™ | Hardware-enforced volt-second monitoring eliminates need for conservative duty-cycle limits or complex core modeling |
| Clean pre-biased start-up | Controlled soft-start sequence avoids output voltage overshoot when powering already-charged battery banks |
| True remote differential sensing | Integrated 1.0× gain amplifier with 75 dB CMRR rejects ground noise and compensates for PCB trace IR drop |
| Synchronous MOSFET reverse current limit | SW pin current-sensing detects reverse conduction and shuts down SG within 200 ns to prevent shoot-through |
| Flexible bias generation | Dual-path regulation: VAUX LDO (15 V input → 7/8.5 V VCC) or VIN-based HV linear regulator with external pass device |
Applications
| Isolated Telecom Power Supply | High-Power Battery Charger |
|---|---|
Use Scenario: 36–72 V input telecom rectifier delivering regulated 5 V/15 A to backplane loads with strict efficiency and transient requirements. IC Role / Device Role / Timing Role: Secondary-side PWM controller managing synchronous rectification, flux limiting, and remote sensing across isolation barrier. Use Value: 94% peak efficiency and sub-100 µs load-step response meet GR-1089 Class 5 immunity and NEBS Level 3 thermal specs. | Use Scenario: 48 V battery charging system requiring clean start-up into pre-biased 5 V bus with overvoltage/overcurrent protection. IC Role / Device Role / Timing Role: Precision current-mode controller enforcing constant average current limit and preventing transformer saturation during charge termination. Use Value: Direct Flux Limit guarantees no core reset failure during high-dV/dt transitions; clean start-up avoids damaging Li-ion cell management ICs. |
| Avionics DC/DC Converter | Military Vehicle Power System |
Use Scenario: MIL-STD-704E compliant 28 V input converter generating isolated 5 V for flight control electronics with extended temperature operation. IC Role / Device Role / Timing Role: Robust secondary-side controller with –40°C to +125°C rating, integrated OVP/OCP, and fault-tolerant hand-off from primary-side start-up. Use Value: Self-starting architecture eliminates separate bias supply; exposed-pad QFN ensures reliable thermal performance at 125°C junction temp. | Use Scenario: 24/28 V vehicle platform supplying isolated 5 V to ruggedized communications modules under wide input transients (load dump, cold crank). IC Role / Device Role / Timing Role: Dual-regulator controller supporting VAUX LDO fallback during VIN brownout and HV linear regulator for full-load efficiency. Use Value: VAUX switchover (7.65 V rising / 7.35 V falling) maintains stable VCC during 24 V system dips; UVLO hysteresis prevents chatter during engine cranking. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side forward controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3766EUFD#TRPBF | Same die, –40°C to +125°C grade (E-grade), identical electrical specs and pinout | No functional difference; E-grade has same temp range but lower production test coverage than I-grade | Select when cost-sensitive industrial designs accept E-grade qualification level |
| LTC3766HUFD#TRPBF | Same die, –40°C to +150°C H-grade, higher UVLO thresholds (VUVLO,RISING = 7.9 V), tighter VCC regulation (±0.2 V) | Required for under-hood automotive or high-ambient military deployments where TJ > 125°C occurs | Choose for extended temperature reliability; requires verifying VAUX switchover margins at 150°C |
Compared with LTC3766EUFD#TRPBF, the LTC3766IUFD#TRPBF offers identical functionality with enhanced production screening for industrial reliability, while LTC3766HUFD#TRPBF adds high-temperature operation and tighter regulation - making the I-grade optimal for cost-balanced, thermally demanding telecom and battery systems.
Availability
LTC3766IUFD#TRPBF is available at Aetrix Electronics and suitable for isolated telecom power supplies, high-power battery chargers, avionics DC/DC converters, and military vehicle power systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LTC3766IUFD#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 and maintains full product support, documentation, and manufacturing continuity for all Linear ICs including the LTC3766 series.
The LTC3766 belongs to Linear's high-efficiency isolated power controller family, designed specifically for secondary-side active-clamp forward converters requiring fast transient response, transformer saturation immunity, and simplified bias generation in telecom, industrial, and defense applications.
FAQ
What is the primary function of the LTC3766IUFD#TRPBF in an isolated power supply?
The LTC3766IUFD#TRPBF serves as a secondary-side synchronous forward controller that manages PWM timing, current limiting, volt-second protection, and remote sensing for isolated active-clamp DC/DC converters. It works with the LTC3765 primary-side controller to enable high-efficiency, fast-transient, self-starting power supplies - eliminating the need for separate bias regulators and ensuring robust operation in telecom and battery charger systems. The LTC3766IUFD#TRPBF integrates all critical control functions on the secondary side for precision output regulation.
How does the Direct Flux Limit™ feature protect the transformer in the LTC3766IUFD#TRPBF?
The Direct Flux Limit™ in the LTC3766IUFD#TRPBF monitors the volt-second product applied to the main power transformer via the VSEC pin. When the integrated V·t exceeds an internal threshold (±4% accuracy over 5–40 V SW range), the PWM on-time is immediately terminated - preventing core saturation without compromising transient response. This hardware-based protection replaces conservative duty-cycle limits and eliminates reliance on transformer parameter tolerances. The LTC3766IUFD#TRPBF thus guarantees safe operation even under worst-case startup, overload, or asymmetry conditions.
Can the LTC3766IUFD#TRPBF operate without the LTC3765 primary-side controller?
Yes - the LTC3766IUFD#TRPBF supports standalone operation when the MODE pin is pulled to GND through a 100 kΩ (LV) or 50 kΩ (HV) resistor. In this mode, PT+ outputs a standard PWM signal for direct primary MOSFET drive, PT− generates a reference clock, and FGD is ignored (dead time set adaptively). However, full isolated functionality - including pulse-encoded communication, self-starting architecture, and active clamp control - requires the LTC3765. The LTC3766IUFD#TRPBF retains all secondary-side features (remote sensing, current limit, flux protection) in standalone mode.
What are the key differences between the LTC3766IUFD#TRPBF and LTC3766HUFD#TRPBF?
The LTC3766IUFD#TRPBF is rated for –40°C to +125°C operation with standard UVLO (7.7 V rising) and VCC regulation (8.5 V HV mode), while the LTC3766HUFD#TRPBF extends the junction temperature range to +150°C and tightens VCC regulation accuracy (±0.2 V vs ±0.4 V) with higher UVLO (7.9 V rising). Both share identical pinout, package, and core functionality. The LTC3766IUFD#TRPBF targets industrial telecom and battery systems; the H-grade is required for under-hood automotive or high-ambient military use where sustained 150°C operation is mandated.
How does the LTC3766IUFD#TRPBF handle start-up into a pre-biased output?
The LTC3766IUFD#TRPBF implements clean pre-biased start-up by disabling synchronous rectification until the output voltage reaches regulation, then gradually enabling duty cycle with controlled soft-start ramp (via SS capacitor). Its precision current limit and adaptive blanking prevent inrush current and output overshoot. During hand-off from primary-side start-up (e.g., with LTC3765), the LTC3766IUFD#TRPBF begins regulating only after detecting adequate VCC and RUN pin voltage - ensuring seamless transition without voltage disturbance. This behavior makes the LTC3766IUFD#TRPBF ideal for battery charger applications where the output bus may be pre-charged.
LTC3766IUFD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Direct Flux Limit™, PolyPhase®
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Applications:
- Synchronous Forward Controller
- Voltage - Input:
- 5V ~ 32V
- Voltage - Supply:
- 5V ~ 10V
- Current - Supply:
- 5 mA
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3766IUFD#TRPBF FAQ
1.How can I place an order for LTC3766IUFD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3766IUFD#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 LTC3766IUFD#TRPBF reliable?
The price and inventory of LTC3766IUFD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3766IUFD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3766IUFD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3766IUFD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3766IUFD#TRPBF?
LTC3766IUFD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3766IUFD#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 LTC3766IUFD#TRPBF?
For technical support, including LTC3766IUFD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3766IUFD#TRPBF requirements.
6.How does Aetrix verify that LTC3766IUFD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3766IUFD#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 LTC3766IUFD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3766IUFD#TRPBF?
All LTC3766IUFD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3766IUFD#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 LTC3766IUFD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3766IUFD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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