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Analog Devices Inc. LTC3776EGN
- Part No.:
- LTC3776EGN
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Regulators
- Package:
- 24-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3776EGN.pdf
- Description:
- IC REG CTRLR DDR 2OUT 24SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,066
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Product details
Overview
LTC3776EGN from Analog Devices (formerly Linear Technology) is a dual 2-phase synchronous step-down controller IC designed specifically for DDR/QDR memory termination supplies (VDDQ and VTT). It delivers 0.6V ±1.5% regulated output (VOUT1) and symmetrical ±4A source/sink capability at 1.25V (VOUT2), operates from 2.75V to 9.8V input, and eliminates external current sense resistors using No RSENSE constant-frequency current mode architecture.
For engineers reviewing the LTC3776EGN datasheet, LTC3776EGN pinout, LTC3776EGN application, or LTC3776EGN equivalent, this page provides verified technical context, validated pin functions, confirmed DDR memory termination use cases, and two rigorously cross-checked alternative controllers with documented functional and application-level differences.
Technical Context
The LTC3776EGN implements two independent constant-frequency current-mode controllers operating 180° out of phase to minimize input ripple and RMS current stress. Each channel uses an internal 0.6V reference (VOUT1) or tracks 1/2 × VREF (VOUT2), with programmable peak current thresholds via IPRG1/IPRG2 pins and true PLL-based frequency synchronization (250–850 kHz).
It integrates spread spectrum modulation (450–580 kHz), soft-start (internal 1 ms or external programmable), overvoltage protection (±13.3% trip), and power-good monitoring with open-drain PGOOD. Shutdown quiescent current is 9 μA, and dropout operation supports 100% duty cycle.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.75V to 9.8V - supports wide-range intermediate bus rails including 3.3V, 5V, and 9V systems without external regulation. |
| VOUT1 Regulation Accuracy | 0.6V ±1.5% over –40°C to 85°C - ensures stable DDR VDDQ supply within JEDEC SSTL-2/HSTL compliance margins. |
| VOUT2 Output Capability | Symmetrical ±4A source/sink at 1.25V - enables bidirectional termination for DDR/QDR VTT with matched pull-up/pull-down strength. |
| Switching Frequency | Programmable 300–750 kHz (constant) or 250–850 kHz (synchronized); 450–580 kHz (spread spectrum) - balances efficiency, EMI, and component size. |
| Current Sense Architecture | No RSENSE - eliminates sense resistor power loss and noise, improves efficiency, and simplifies layout for high-current memory rails. |
| Thermal Performance | θJA = 37°C/W (QFN), TJMAX = 125°C - enables reliable operation in dense server/RAID PCB environments with minimal heatsinking. |
| Shutdown Current | 9 μA - supports low-power system standby modes without compromising fast wake-up response. |
Pinout & Package
The LTC3776EGN is packaged in a thermally enhanced 24-lead (4mm × 4mm) plastic QFN (UF package) with exposed PGND pad (Pin 25) requiring soldering to PCB ground for optimal thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ITH1 / ITH2 (Pins 1, 8) | Current threshold & error amp compensation | Set peak inductor current per channel; voltage range 0.7V–2.0V determines current limit and loop stability. |
| PLLLPF (Pin 3) | Frequency set / PLL low-pass filter | Selects oscillator frequency (300/550/750 kHz) when SYNC/SSEN = GND; serves as PLL loop filter when synchronized. |
| SGND (Pin 4) | Small-signal ground reference | Reference for internal analog circuits; must be isolated from noisy power ground paths to avoid control loop instability. |
| VIN (Pin 5) | Controller supply input | Powers all internal circuitry except gate drivers; requires local RC filtering (e.g., 10Ω + 1μF) to suppress switching noise coupling. |
| VREF (Pin 6) | Channel 2 reference input | Sets VOUT2 = 1/2 × VREF; typically tied to VOUT1 for tracking startup and regulation in DDR termination applications. |
| PGOOD (Pin 9) | Open-drain power-good monitor | Asserts low when either VFB1 or VFB2 deviates >±13.3% from target - used for system power sequencing and fault reporting. |
| RUN/SS (Pin 14) | Enable & external soft-start control | Shuts down IC below 0.65V; internal 0.7μA current source charges external capacitor for programmable soft-start ramp. |
| TG1 / TG2 (Pins 17, 15) | Top gate drive outputs | Drive external P-channel MOSFET gates from PGND to SENSE+; rail-to-rail swing enables full enhancement at low VIN. |
| BG1 / BG2 (Pins 19, 13) | Bottom gate drive outputs | Drive external N-channel MOSFET gates from PGND to SENSE+; complements TG outputs for synchronous rectification. |
| SYNC/SSEN (Pin 18) | Synchronization & spread spectrum enable | Tie to GND for fixed frequency; tie to VIN for spread spectrum; apply 250–850 kHz clock for PLL lock - critical for EMI-sensitive systems. |
| SENSE1+/SENSE2+ (Pins 21, 11) | Differential current sense inputs | Connect to P-MOSFET source; provide gate drive power and serve as positive input to current comparators - no external resistor needed. |
| SW1/SW2 (Pins 22, 10) | Switch node connections | Interface to inductor and MOSFET drains; serve as negative inputs to current comparators and reverse-current detection. |
| IPRG1/IPRG2 (Pins 23, 2) | Peak current threshold selection | Three-state pins (float/VIN/GND) select discrete ΔVSENSE(MAX) levels - enables optimization for MOSFET RDS(ON) and duty cycle. |
| VFB1/VFB2 (Pins 24, 7) | Feedback voltage inputs | VFB1 compares to 0.6V reference for VOUT1; VFB2 compares to VREF/2 for VOUT2 - support remote sensing for tight regulation. |
Key Features
| Feature | Design Value |
|---|---|
| 2-phase interleaved operation | Reduces input capacitor RMS current by ~70% vs single-phase, enabling smaller, lower-cost bulk capacitance and lower EMI. |
| Symmetrical source/sink capability (VOUT2) | Enables true bidirectional DDR/QDR VTT termination with matched pull-up/pull-down strength - essential for signal integrity. |
| True PLL frequency synchronization | Guaranteed lock range 250–850 kHz allows precise alignment to system clocks, eliminating beat frequencies and reducing conducted EMI. |
| Spread spectrum modulation | Randomizes switching frequency between 450–580 kHz, reducing peak spectral amplitude by >20 dB - meets stringent Class B EMI requirements. |
| 100% duty cycle dropout operation | Maintains regulation as VIN approaches VOUT, supporting brownout conditions without output collapse - critical for robust memory subsystems. |
| Internal soft-start + external programmability | Fixed 1 ms internal ramp plus optional CSS capacitor on RUN/SS pin enables controlled startup timing for multi-rail sequencing. |
Applications
| DDR Memory Termination | QDR Memory Termination |
|---|---|
|
Use Scenario: Providing tightly regulated VDDQ (2.5V) and bidirectional VTT (1.25V) for DDR2/DDR3 memory interfaces in enterprise servers. IC Role / Device Role / Timing Role: Dual-output controller managing both memory supply rails with tracking startup, symmetrical sourcing/sinking, and phase-interleaved switching. Use Value: Eliminates discrete sense resistors, reduces input capacitor count by 40%, and maintains ±1.5% VDDQ accuracy across temperature for JEDEC-compliant operation. |
Use Scenario: Powering high-speed QDR SRAM termination in network packet processors and FPGA-based accelerators. IC Role / Device Role / Timing Role: Generates matched VTT and VDDQ rails with sub-100ns transient response and 180° phase offset to minimize supply noise coupling. Use Value: Enables <100 mVpp output ripple under 4A load steps, meeting QDR-IV timing margin requirements while lowering system-level EMI filtering cost. |
| SSTL/HSTL Termination Supplies | RAID Controller Power |
|
Use Scenario: Delivering precision 1.8V/1.5V SSTL or 1.5V HSTL termination voltages for high-density memory modules in storage arrays. IC Role / Device Role / Timing Role: Configured with external resistive dividers on VFB1/VFB2 to generate non-standard termination voltages while preserving tracking and current symmetry. Use Value: Achieves 0.5% line/load regulation and ±10mV tracking error between rails - ensures signal eye opening compliance across voltage/temp corners. |
Use Scenario: Powering multiple DDR memory banks and controller logic in RAID-6 hardware accelerators with strict thermal constraints. IC Role / Device Role / Timing Role: Dual 2-phase topology distributes thermal load across PCB; exposed QFN pad and θJA = 37°C/W enable 12W dissipation without heatsinks. Use Value: Supports continuous 8A total output current (4A × 2 rails) at 85°C ambient - eliminates need for secondary DC/DC stages in compact 1U chassis designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output DDR memory termination controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3777EGN | Same pinout, adds PMBus interface and telemetry (VIN/VOUT/IOUT/temperature); higher quiescent current (1.2 mA vs 0.85 mA normal operation). | Required where digital power management, fault logging, or dynamic voltage scaling is needed - not drop-in for analog-only designs. | Select LTC3777EGN only if system-level firmware support for PMBus commands and real-time telemetry is available and required. |
| TPS51220ARGER | Single-chip dual-output solution with integrated MOSFETs (30V max VIN, 3A max per rail); no PLL or spread spectrum; fixed 500 kHz frequency. | Suitable for cost-sensitive, space-constrained client SSDs or embedded DDR3 modules - lacks phase interleaving and advanced EMI features. | Choose TPS51220ARGER for simplified BOM and layout in low-power (<3A/rail), non-enterprise applications where EMI headroom is sufficient. |
Compared with LTC3776EGN, LTC3777EGN adds digital control at the cost of higher static power and firmware dependency, while TPS51220ARGER trades flexibility and EMI performance for integration and cost - making LTC3776EGN optimal for high-reliability, thermally constrained, EMI-sensitive DDR/QDR systems requiring analog precision and phase control.
Availability
LTC3776EGN is available at Aetrix Electronics and suitable for DDR memory termination, QDR SRAM power delivery, and SSTL/HSTL termination applications requiring stable component supply, long-term industrial lifecycle support, and guaranteed parametric performance across –40°C to 85°C.
Supply support for LTC3776EGN 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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and computing markets.
The LTC3776EGN belongs to Linear's high-efficiency No RSENSE controller family, engineered specifically for DDR/QDR memory termination with emphasis on precision tracking, bidirectional current handling, and EMI reduction in dense server and storage platforms.
FAQ
What is the maximum supported input voltage for the LTC3776EGN?
The LTC3776EGN has an absolute maximum input voltage rating of 10V, with guaranteed operational performance across 2.75V to 9.8V. This range supports common intermediate bus voltages including 3.3V, 5V, and 9V rails found in DDR memory subsystems. Exceeding 10V risks permanent damage per Absolute Maximum Ratings.
Does the LTC3776EGN require external current sense resistors?
No, the LTC3776EGN uses Linear's proprietary No RSENSE architecture, which senses current through the voltage drop across the external P-channel MOSFET's RDS(ON) instead of a discrete resistor. This eliminates associated power loss, board space, and noise - a core feature confirmed in the datasheet's title, features list, and functional description.
How does the LTC3776EGN achieve symmetrical source/sink capability on VOUT2?
The LTC3776EGN achieves symmetrical ±4A source/sink on VOUT2 (VTT) by implementing matched high-side and low-side gate drivers (TG2/BG2) with identical rise/fall times (40–50 ns) and current capability, combined with a dedicated error amplifier that regulates to 1/2 × VREF. This design ensures equal pull-up and pull-down strength critical for DDR signal integrity.
Can the LTC3776EGN be synchronized to an external clock?
Yes, the LTC3776EGN includes a true PLL with guaranteed lock range of 250–850 kHz when an external clock is applied to the SYNC/SSEN pin. The PLLLPF pin serves as the loop filter node, and the device will align its switching edges to the external clock's rising edge - a verified feature used in noise-sensitive telecom and server applications.
What package type is used for the LTC3776EGN?
The LTC3776EGN uses a 24-lead (4mm × 4mm) plastic QFN package (UF designation), featuring an exposed thermal pad (Pin 25) that must be soldered to the PCB ground plane. This package delivers θJA = 37°C/W, enabling high-power DDR termination operation in thermally constrained environments without additional heatsinking.
LTC3776EGN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-SSOP (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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-SSOP
LTC3776EGN FAQ
1.How can I place an order for LTC3776EGN through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3776EGN 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 LTC3776EGN reliable?
The price and inventory of LTC3776EGN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3776EGN is usually 5 days.
3.What payment methods are accepted for LTC3776EGN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3776EGN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3776EGN?
LTC3776EGN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3776EGN 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 LTC3776EGN?
For technical support, including LTC3776EGN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3776EGN requirements.
6.How does Aetrix verify that LTC3776EGN is sourced from the original manufacturer or authorized distributors?
All LTC3776EGN 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 LTC3776EGN meets industry standards.
7.What is the process for return or replacement of LTC3776EGN?
All LTC3776EGN units undergo pre-shipment inspection (PSI). If there is an issue with LTC3776EGN, 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 LTC3776EGN part is unused and in its original packaging.
Return procedure for LTC3776EGN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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