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Analog Devices Inc. LTC3776EUF#TRPBF
- Part No.:
- LTC3776EUF#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Regulators
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3776EUF#TRPBF.pdf
- Description:
- IC REG CTRLR DDR 2OUT 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,805
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Product details
Overview
LTC3776EUF#TRPBF from Analog Devices (formerly Linear Technology) is a dual 2-phase synchronous step-down controller for DDR/QDR memory termination, delivering VDDQ (2.5V ±1.5%) and symmetrical VTT (1.25V, ±4A source/sink) with no external current sense resistors. It operates across 2.75V–9.8V input, supports spread spectrum and external synchronization (250–850kHz), and integrates true PLL for frequency locking. Used in high-density server memory subsystems requiring low-noise, high-efficiency termination.
For engineers reviewing the LTC3776EUF#TRPBF datasheet, LTC3776EUF#TRPBF pinout, LTC3776EUF#TRPBF application, or LTC3776EUF#TRPBF equivalent, key selection criteria include its dual-channel out-of-phase operation to reduce input ripple, VOUT2 tracking of 1/2 VREF, symmetrical sink/source capability for VTT, No RSENSE architecture, and programmable switching frequency up to 750kHz with spread spectrum support.
Technical Context
The LTC3776EUF#TRPBF implements two independent constant-frequency current-mode controllers operating 180° out of phase to minimize input capacitor RMS current and EMI. Each channel uses a dedicated ITH pin for current threshold control and error amplifier compensation, with IPRG1/IPRG2 pins enabling three-level peak sense voltage selection per channel (e.g., 125mV/85mV/204mV for CH1).
Channel 1 regulates VOUT1 (VDDQ) to 0.6V ±1.5% reference with internal soft-start; Channel 2 regulates VOUT2 (VTT) to 1/2 VREF with symmetrical ±4A sourcing/sinking capability. The integrated PLL allows precise frequency locking to external clocks or spread spectrum modulation (450–580kHz) when SYNC/SSEN = VIN, reducing peak EMI by >20dB.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.75V to 9.8V - supports wide-range DC supplies including 3.3V, 5V, and 9V rails common in server and storage systems. |
| VOUT1 Regulation Accuracy | 0.6V ±1.5% over –40°C to 85°C - ensures stable DDR VDDQ compliance under thermal stress and load transients. |
| VOUT2 Tracking Accuracy | VREF/2 ±0.133% (1.250V ±1.33%) - enables precise SSTL-2/HSTL-18 termination matching for signal integrity. |
| Switching Frequency Range | 250kHz–850kHz sync / 450–580kHz spread spectrum - reduces EMI peaks while maintaining design flexibility for inductor/capacitor sizing. |
| Current Sense Architecture | No RSENSE - eliminates power loss and noise from external sense resistors; uses MOSFET RDS(on) for sensing. |
| Output Current Capability | VOUT2: ±4A symmetrical source/sink - meets DDR2/DDR3 VTT dynamic load requirements during read/write transitions. |
| Shutdown Quiescent Current | 9μA - enables ultra-low-power system standby without compromising fast wake-up response. |
Pinout & Package
The LTC3776EUF#TRPBF is housed in a thermally enhanced 4mm × 4mm, 24-lead plastic QFN package (UF) with exposed PGND pad (Pin 25) that must be soldered to PCB ground for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ITH1 / ITH2 (Pins 1, 8) | Current threshold & error amp compensation | Sets peak inductor current limit per channel; voltage range 0.7V–2V determines current comparator trip point. |
| PLLLPF (Pin 3) | PLL low-pass filter / frequency select | Configures oscillator frequency (300/550/750kHz) when SYNC/SSEN = GND; serves as loop filter for external sync or spread spectrum. |
| VIN (Pin 5) | Chip supply input | Powers all internal circuitry except gate drivers; requires RC filtering (e.g., 10Ω + 1μF) to suppress noise coupling. |
| VREF (Pin 6) | Reference input for VOUT2 | Defines VOUT2 = VREF/2; typically connected to VOUT1 to enable tracking start-up and tight regulation. |
| PGOOD (Pin 9) | Open-drain power-good monitor | Asserts low if either VFB1 or VFB2 deviates >±13.3% from target - provides system-level fault signaling for sequencing. |
| RUN/SS (Pin 14) | Enable & external soft-start | Shuts down chip below 0.65V; internal 0.7μA current source enables soft-start; external capacitor extends ramp time. |
| TG1/TG2 (Pins 17, 15) | Top gate drive outputs | Drive external P-channel MOSFET gates with swing from PGND to SENSE+ - enables high-side synchronous rectification. |
| BG1/BG2 (Pins 19, 13) | Bottom gate drive outputs | Drive external N-channel MOSFET gates with swing from PGND to SENSE+ - completes synchronous buck topology per phase. |
| SYNC/SSEN (Pin 18) | Sync input / spread spectrum enable | GND = fixed frequency; VIN = spread spectrum (450–580kHz); external clock = PLL lock (250–850kHz). |
| SENSE1+/SENSE2+ (Pins 21, 11) | Current sense positive inputs | Connect to P-MOSFET source; provide gate drive power and serve as differential sense reference for No RSENSE operation. |
| SW1/SW2 (Pins 22, 10) | Switch node connections | Interface to inductor, P-MOSFET drain, and N-MOSFET drain; serve as negative inputs to current comparators. |
| IPRG1/IPRG2 (Pins 23, 2) | Peak sense voltage select | Three-state inputs (float/VIN/GND) set max ΔVSENSE: e.g., 125mV/85mV/204mV for CH1, enabling optimization for RDS(on) and duty cycle. |
Key Features
| Feature | Design Value |
|---|---|
| Dual 2-phase interleaved operation | Reduces input capacitor RMS current by ~70% vs single-phase, enabling smaller, lower-cost bulk capacitance and lower EMI. |
| No RSENSE current sensing | Eliminates sense resistor losses and associated thermal/noise issues; leverages MOSFET RDS(on) for accurate, efficient current monitoring. |
| Symmetrical ±4A VTT sourcing/sinking | Meets DDR2/DDR3 VTT transient load demands without external boost/sink circuits - simplifies board layout and BOM. |
| True PLL with 250–850kHz sync range | Enables deterministic EMI reduction via clock synchronization across multiple regulators in dense memory modules. |
| Spread spectrum modulation (450–580kHz) | Spreads fundamental and harmonic energy, lowering peak radiated emissions by >20dB - critical for FCC/CE compliance in servers. |
| 100% duty cycle low-dropout operation | Maintains regulation even when VIN approaches VOUT, improving efficiency in low-VIN edge cases like brownout conditions. |
Applications
| DDR Memory Termination | SSTL/HSTL Bus Termination |
|---|---|
Use Scenario: Termination of DDR2/DDR3 data/address/control buses in enterprise servers and RAID controllers. IC Role / Device Role / Timing Role: Dual-output controller generating tightly regulated VDDQ (2.5V) and VTT (1.25V) with synchronized start-up and tracking. Use Value: Ensures signal integrity across high-speed memory interfaces by meeting JEDEC SSTL-2 and HSTL-18 voltage tolerance specs (±1.5% for VDDQ, ±1.33% for VTT). | Use Scenario: Active termination of high-speed parallel buses in FPGA-based compute accelerators and network interface cards. IC Role / Device Role / Timing Role: Provides dynamically adjustable VTT with symmetrical ±4A sourcing/sinking to match bidirectional bus current flow. Use Value: Eliminates need for discrete termination resistors and external current buffers, reducing component count and PCB area while improving transient response. |
| Server Memory Modules | Distributed Power Systems |
Use Scenario: Power delivery for RDIMM/LRDIMM modules where space, thermal density, and EMI are constrained. IC Role / Device Role / Timing Role: 2-phase interleaved controller minimizing input ripple and enabling compact 4mm × 4mm QFN footprint on memory PCBs. Use Value: Reduces required input capacitance by ~50%, allowing use of fewer 1206/0805 MLCCs and easing layout in narrow DIMM form factors. | Use Scenario: Local point-of-load regulation in modular telecom and industrial backplanes with distributed 5V/3.3V supplies. IC Role / Device Role / Timing Role: Dual-channel controller supporting independent VDDQ/VTT generation from shared intermediate bus, with optional external sync for system-wide EMI coordination. Use Value: Enables deterministic frequency alignment across multiple LTC3776EUF#TRPBF units, simplifying EMI filter design and certification testing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output DDR termination controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3776EGN#PBF | Same silicon, 24-lead narrow SSOP package (6.4mm × 7.7mm); θJA = 130°C/W vs 37°C/W for QFN. | Preferred for through-hole prototyping or legacy SSOP-compatible layouts; higher thermal resistance limits high-current operation without heatsinking. | Select LTC3776EGN#PBF only when SSOP footprint is mandated; otherwise prefer LTC3776EUF#TRPBF for superior thermal performance and space savings. |
| ISL6522CRZ-T | Single-channel DDR controller; no VTT sink/source symmetry; requires external op-amp for VTT tracking; no spread spectrum. | Requires dual ICs and additional components to replicate LTC3776EUF#TRPBF's integrated dual-phase, symmetrical VTT functionality. | Use ISL6522CRZ-T only in cost-sensitive, low-density designs where VTT current < ±2A and EMI requirements are relaxed. |
Compared with LTC3776EGN#PBF, the LTC3776EUF#TRPBF offers 3.6× better thermal resistance and 44% smaller footprint, enabling higher power density; versus ISL6522CRZ-T, it delivers full dual-channel integration, symmetrical VTT, and built-in spread spectrum - eliminating four external components and improving EMI margin by >20dB.
Availability
LTC3776EUF#TRPBF is available at Aetrix Electronics and suitable for DDR memory termination, server power management, and high-speed bus termination requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC3776EUF#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 power management semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC3776EUF#TRPBF belongs to ADI's Power by Linear™ family of high-efficiency DC/DC controllers, designed specifically for demanding memory and high-speed digital power applications requiring precision regulation, low noise, and robust transient response.
FAQ
What is the maximum supported switching frequency for the LTC3776EUF#TRPBF?
The LTC3776EUF#TRPBF supports a maximum programmable switching frequency of 750kHz when the PLLLPF pin is tied to VIN and spread spectrum is disabled. With external synchronization, it locks to frequencies up to 850kHz; in spread spectrum mode, its output varies between 450kHz and 580kHz. These settings are confirmed in the Electrical Characteristics table and Functional Diagram sections of the official datasheet.
Does the LTC3776EUF#TRPBF require external current sense resistors?
No, the LTC3776EUF#TRPBF uses a No RSENSE architecture that senses current through the RDS(on) of external P-channel MOSFETs, eliminating the need for discrete sense resistors. This improves efficiency and reduces board space and thermal noise. The IPRG1 and IPRG2 pins allow fine-tuning of the peak sense voltage threshold to match MOSFET characteristics.
How does the LTC3776EUF#TRPBF achieve symmetrical ±4A sourcing and sinking on VOUT2?
The LTC3776EUF#TRPBF achieves symmetrical ±4A capability on VOUT2 (VTT) using matched top (TG2) and bottom (BG2) gate drivers with identical drive strength and timing control, combined with a dedicated error amplifier referenced to VREF/2. Its current-mode architecture and bidirectional current sensing (via SENSE2+/SW2) enable precise regulation during both sourcing and sinking phases without external circuitry.
Can the LTC3776EUF#TRPBF operate with input voltages below 3V?
Yes, the LTC3776EUF#TRPBF supports an input voltage range of 2.75V to 9.8V. Its undervoltage lockout (UVLO) has a falling threshold of 2.25V (typical), allowing reliable startup and operation down to 2.75V. At low VIN, the controller maintains regulation via 100% duty cycle operation, making it suitable for battery-backed or low-voltage intermediate bus applications.
What is the purpose of the exposed pad (Pin 25) on the LTC3776EUF#TRPBF QFN package?
The exposed pad (Pin 25) on the LTC3776EUF#TRPBF is electrically connected to PGND and must be soldered to the PCB ground plane. It serves dual purposes: significantly improving thermal dissipation (θJA = 37°C/W) and providing a low-inductance, low-resistance return path for high-current gate drive loops - both critical for stable 2-phase operation and EMI control.
LTC3776EUF#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Applications:
- Controller, DDR, QDR
- Voltage - Input:
- 2.75V ~ 9.8V
- Number of Outputs:
- 2
- Voltage - Output:
- 0.3V ~ 9.8V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LTC3776EUF#TRPBF FAQ
1.How can I place an order for LTC3776EUF#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3776EUF#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 LTC3776EUF#TRPBF reliable?
The price and inventory of LTC3776EUF#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3776EUF#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3776EUF#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3776EUF#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3776EUF#TRPBF?
LTC3776EUF#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3776EUF#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 LTC3776EUF#TRPBF?
For technical support, including LTC3776EUF#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3776EUF#TRPBF requirements.
6.How does Aetrix verify that LTC3776EUF#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3776EUF#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 LTC3776EUF#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3776EUF#TRPBF?
All LTC3776EUF#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3776EUF#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 LTC3776EUF#TRPBF part is unused and in its original packaging.
Return procedure for LTC3776EUF#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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