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Analog Devices Inc. LTC3766EGN#PBF
- Part No.:
- LTC3766EGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Supply Controllers, Monitors
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3766EGN#PBF.pdf
- Description:
- IC CONTROLLER SYNCH 28-SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,095
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Product details
Overview
LTC3766EGN#PBF 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% threshold 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 LTC3766EGN#PBF datasheet, LTC3766EGN#PBF pinout, LTC3766EGN#PBF application, or LTC3766EGN#PBF equivalent, key selection criteria include its PolyPhase®-capable architecture, dual linear regulator control (VIN-based HV mode / VAUX-based bypass), 28-pin SSOP package with Kelvin-sense GND, and compatibility with LTC3765 primary-side controllers in isolated topologies.
Technical Context
The LTC3766EGN#PBF implements secondary-side PWM control using a precision error amplifier (2.7 mS transconductance) and fast average current sensing (47–63 mV RS-mode threshold) to achieve tight output regulation without optocouplers. Its Direct Flux Limit™ circuit monitors volt-second product via VSEC pin with ±4% accuracy across temperature, ensuring no transformer saturation during transients while preserving dynamic response.
It integrates two independent gate drivers (FG/SG with 1.0 Ω pull-down, PT+/PT– with 1.5 Ω pull-down), adaptive dead-time control via SGD/FGD pins, and a differential remote sense amplifier (99–101% gain, 75 dB CMRR) referenced to VS+, VS–, and VSOUT - all operating under dual bias schemes: VIN-regulated HV mode (7.0–7.3 V VCC) or VAUX-powered LDO mode (6.7–7.3 V VCC).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VFB Regulated Voltage | 0.600 V ±1.3%, sets output voltage accuracy via resistor divider on FB pin |
| Average Current Sense Threshold | 55 mV typ. (RS mode), enables accurate constant-current battery charging |
| Direct Flux Limit Accuracy | ±4% over 5–40 VSW, guarantees transformer core reset without sacrificing transient speed |
| Oscillator Frequency Range | 75–500 kHz via RFS/SYNC, supports PLL sync for multi-phase interleaving |
| VCC Operating Range | 5–10 V, supplied either by external HV linear regulator (via NDRV) or internal VAUX LDO |
| Soft-Start Charge Current | 5 μA typ., determines ramp rate of output voltage during startup |
| Overvoltage Threshold | +17% above nominal VOUT, triggers shutdown if FB rises beyond 1.17× reference |
Pinout & Package
The LTC3766EGN#PBF is housed in a 28-lead narrow plastic SSOP (GN package), 5.3 mm × 10.2 mm body, 0.635 mm pitch, exposed pad not present. Thermal resistance θJA = 95°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SG (Pin 1) | Synchronous MOSFET gate driver output | Drives low-side rectifier; supports reverse current limit via SW node monitoring |
| FG (Pin 2) | Forward MOSFET gate driver output | Drives primary-side clamp switch; timing synchronized with PT+ signal |
| VSEC (Pin 3) | Volt-second limit input | Connects RC network to terminate PWM on-time before transformer saturation |
| MODE (Pin 4) | Operating mode selector | GND/VCC selects LV/HV gate drive voltage (7V/8.5V VCC) and corresponding UVLO thresholds |
| PHASE (Pin 5) | PLL phase alignment input | Adjusts internal clock phase relative to FS/SYNC for PolyPhase synchronization |
| FB (Pin 6) | Inverting input of error amplifier | Connects to output divider; regulates VOUT to 0.600 V reference |
| ITH (Pin 7) | Error amplifier output | Hosts compensation network (R/C) between ITH and GND for loop stability |
| RUN (Pin 8) | Enable/disable control with hysteresis | 1.22 V rising threshold initiates soft-start; 1.17 V falling threshold shuts down IC |
| SS (Pin 9) | Soft-start capacitor connection | Capacitor to GND sets output voltage ramp time; 5 μA charge current defines slope |
| IPK (Pin 10) | Inductor ripple cancellation input | Resistor to GND adjusts peak current limit to maintain constant average current |
| VSOUT (Pin 11) | Differential amplifier output | Provides true remote sense output; max sourcing current limits trace impedance design |
| VS+ (Pin 12) | Differential amp non-inverting input | Connects to +VOUT sense point; also used for inductor ripple cancellation |
| VS– (Pin 13) | Differential amp inverting input | Connects to –VOUT sense point; enables Kelvin sensing for <1% load regulation |
| GND (Pin 14) | Signal ground & Kelvin sense return | Must connect to source of synchronous MOSFET for accurate reverse current detection |
| FS/SYNC (Pin 15) | Oscillator set/synchronization input | Sources 20 μA; resistor to GND sets frequency; external clock enables PLL sync |
| REGSD (Pin 16) | Linear regulator shutdown timer | Capacitor to GND limits HV regulator runtime; 1.21 V threshold disables NDRV output |
| IS– (Pin 17) | Negative current sense input | Connects to low-side shunt negative terminal; tied to VCC for CT-mode single-ended sensing |
| IS+ (Pin 18) | Positive current sense input | Connects to low-side shunt positive terminal or CT secondary; enables avg. current limit |
| SGD (Pin 19) | Synchronous gate delay control | Resistor to GND sets delay from PT+ falling to SG rising; optimizes dead time |
| FGD (Pin 20) | Forward gate delay control | Resistor to GND sets delay from PT+ rising to FG rising; prevents shoot-through |
| NDRV (Pin 21) | External pass device driver | Drives base/gate of NPN/MOSFET for HV linear regulator; tie to VCC if using VAUX only |
| VIN (Pin 22) | HV linear regulator input | Bias supply for HV regulator, standby circuits, and differential amplifier; min. 5 V required |
| SW (Pin 23) | Synchronous MOSFET drain monitor | Kelvin-connected to SW node; enables adaptive blanking, reverse current limit, and VSEC timing |
| VAUX (Pin 24) | Auxiliary LDO input | Enables internal 15 V LDO when >4.7 V (LV) or >7.7 V (HV); bypasses HV regulator to reduce loss |
| PT– (Pin 25) | Pulse transformer driver (inverted) | Transmits encoded PWM + bias power to LTC3765; generates reference clock in standalone mode |
| PT+ (Pin 26) | Pulse transformer driver (non-inverted) | Transmits encoded PWM + bias power to LTC3765; outputs standard PWM in standalone mode |
| PGND (Pin 27) | Gate driver power ground | Connects to source of synchronous MOSFET; separate from signal GND for noise immunity |
| VCC (Pin 28) | Main supply for logic and drivers | Final regulated supply (7.0–7.3 V or 8.1–8.9 V) powering all internal circuitry and gate drivers |
Key Features
| Feature | Design Value |
|---|---|
| Direct Flux Limit™ | Hardware-enforced volt-second limit prevents transformer saturation without compromising transient response |
| True Remote Differential Sensing | VS+, VS–, and VSOUT pins enable Kelvin connections for <0.1% load regulation error |
| Self-Starting Architecture | Eliminates need for separate secondary-side bias supply when paired with LTC3765 |
| Two Independent Linear Regulator Options | Selectable HV mode (VIN → NDRV → VCC) or VAUX LDO mode for optimal efficiency vs. simplicity trade-off |
| PolyPhase® Operation Support | PHASE and FS/SYNC pins allow synchronization of multiple LTC3766 units for interleaved high-power designs |
Applications
| Isolated Telecom Power Supply | High-Power Battery Charger |
|---|---|
Use Scenario: 36–72 V input isolated forward converter delivering 5 V/15 A to telecom shelf management systems. IC Role / Device Role / Timing Role: Secondary-side controller managing synchronous rectification, flux limiting, and remote sensing to maintain tight regulation under dynamic load steps. Use Value: Achieves 94% efficiency at full load and eliminates optocoupler latency for sub-10 µs transient recovery. | Use Scenario: Industrial lithium-ion battery charger requiring constant-current/constant-voltage profiles with pre-biased output capability. IC Role / Device Role / Timing Role: Precision average current limiter and clean start-up controller ensuring safe charging into partially charged batteries. Use Value: Enables reliable CC-CV transition with ±1% current accuracy and zero-output overshoot during hot-plug events. |
| Avionics DC/DC Converter | Military Vehicle Power System |
Use Scenario: 28 V aircraft bus-fed isolated forward converter generating 5 V/10 A for flight control electronics with strict EMI and reliability requirements. IC Role / Device Role / Timing Role: Dual-bias controller (VIN + VAUX) providing fault-tolerant VCC generation and overtemperature/overvoltage protection. Use Value: Supports extended temperature range (–40°C to 125°C) and meets DO-160 lightning surge immunity via robust gate drive timing. | Use Scenario: 24 V/28 V vehicle platform supplying isolated 5 V/12 A to mission-critical communication modules in armored vehicles. IC Role / Device Role / Timing Role: Synchronous forward controller with adaptive dead-time (SGD/FGD) and reverse current limiting for harsh vibration environments. Use Value: Prevents shoot-through failures during engine cranking transients and ensures continuous operation during 12 V brownouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side synchronous forward controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3766IUFD#PBF | Same die, 4 mm × 5 mm QFN package with exposed thermal pad (θJA = 43°C/W) | Better thermal performance for high-density or convection-cooled layouts; requires different PCB footprint | Select when board space or thermal headroom is constrained; verify layout compatibility with UFD land pattern |
| LTC3765 | Primary-side active-clamp forward controller; complementary part, not drop-in replacement | Used on primary side to decode PT+/PT– signals and drive main/clamp MOSFETs; requires LTC3766 on secondary | Required companion IC for complete isolated forward solution; never used alone as LTC3766EGN#PBF substitute |
Compared with LTC3766IUFD#PBF, the LTC3766EGN#PBF offers identical functionality but higher thermal resistance due to SSOP packaging - making it suitable for lower-power or forced-air-cooled designs. Unlike LTC3765, it operates exclusively on the secondary side and cannot replace primary-side control functions.
Availability
LTC3766EGN#PBF 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 and long-term industrial lifecycle support.
Supply support for LTC3766EGN#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for all Linear power products.
The LTC3766EGN#PBF belongs to Linear's high-efficiency isolated controller family, engineered specifically for secondary-side synchronous forward converters in telecom, industrial, and defense applications where fast transient response and transformer protection are critical.
FAQ
What is the primary function of the LTC3766EGN#PBF in an isolated power supply?
The LTC3766EGN#PBF 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. When paired with the LTC3765 primary-side controller, the LTC3766EGN#PBF enables full secondary-side regulation without optocouplers - delivering fast transient response and eliminating primary-side feedback latency. Its Direct Flux Limit™ and clean pre-biased start-up make it especially suited for high-reliability battery charging and telecom systems.
How does the LTC3766EGN#PBF implement transformer saturation protection?
The LTC3766EGN#PBF implements transformer saturation protection via its Direct Flux Limit™ circuit, which continuously monitors the volt-second product applied to the main power transformer using the VSEC pin. A resistor-capacitor network connected between SW and VSEC sets the maximum allowable volt-seconds; when the integrated VSEC voltage exceeds the internal threshold (±4% accuracy), the PWM on-time is immediately terminated. This hardware-based protection operates independently of loop bandwidth, guaranteeing no saturation even during large load transients - unlike software-based or duty-cycle-limited approaches.
Can the LTC3766EGN#PBF operate without the LTC3765 primary-side controller?
Yes, the LTC3766EGN#PBF supports standalone operation in non-isolated configurations. By connecting a 100 kΩ resistor from the MODE pin to GND, the IC enters low-voltage standalone mode: PT+ outputs a standard PWM signal usable directly to drive a primary-side MOSFET, while PT– generates a reference clock. However, in this mode, FGD functionality is disabled and adaptive dead-time control relies solely on SW node transitions. For isolated applications - the intended use case - the LTC3766EGN#PBF must be used with the LTC3765 to encode PWM and bias power onto the pulse transformer.
What are the two VCC bias generation methods supported by the LTC3766EGN#PBF?
The LTC3766EGN#PBF supports two independent VCC bias generation methods: (1) High-voltage linear regulator mode, where VIN supplies bias to an external NPN/MOSFET pass device driven by NDRV, producing 7.0–7.3 V (LV) or 8.1–8.9 V (HV) VCC; and (2) Internal VAUX LDO mode, where VAUX >4.7 V (LV) or >7.7 V (HV) activates a 15 V internal regulator that powers VCC directly. The MODE pin selects between LV/HV output levels and automatically adjusts UVLO thresholds. Using VAUX bypass reduces power loss but requires sufficient auxiliary voltage; the HV regulator provides greater flexibility with higher input ranges.
Does the LTC3766EGN#PBF provide reverse current protection for the synchronous rectifier?
Yes, the LTC3766EGN#PBF provides dedicated synchronous MOSFET reverse current protection. It monitors the SW node voltage while SG is high: when SW falls below a threshold (66–79 mV in LV mode, 140–156 mV in HV mode), the IC detects reverse conduction and rapidly turns off SG. This protection is implemented via internal circuitry referenced to the Kelvin-connected GND pin, ensuring accuracy independent of PCB trace resistance. A series resistor between SW and the synchronous MOSFET drain allows fine-tuning of the reverse current trip point - enabling optimization for specific MOSFET RDS(on) and system-level fault tolerance requirements.
LTC3766EGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Direct Flux Limit™, PolyPhase®
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- 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-SSOP
LTC3766EGN#PBF FAQ
1.How can I place an order for LTC3766EGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3766EGN#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 LTC3766EGN#PBF reliable?
The price and inventory of LTC3766EGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3766EGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC3766EGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3766EGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3766EGN#PBF?
LTC3766EGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3766EGN#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 LTC3766EGN#PBF?
For technical support, including LTC3766EGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3766EGN#PBF requirements.
6.How does Aetrix verify that LTC3766EGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3766EGN#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 LTC3766EGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC3766EGN#PBF?
All LTC3766EGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3766EGN#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 LTC3766EGN#PBF part is unused and in its original packaging.
Return procedure for LTC3766EGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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