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Analog Devices Inc. LTC3811EG#PBF
- Part No.:
- LTC3811EG#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 36-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
LTC3811EG#PBF.pdf
- Description:
- IC REG CTRLR BUCK 36SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,287
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Product details
Overview
LTC3811EG#PBF from Analog Devices (formerly Linear Technology) is a dual-output, multiphase synchronous step-down DC/DC controller optimized for low-voltage core and I/O supplies up to 3.3V. It supports 2-, 4-, or fixed-phase operation with ±0.5% output voltage accuracy, programmable 24mV–85mV current sense threshold, and 250kHz–750kHz adjustable switching frequency. Used in high-current ASIC power delivery with remote differential sensing.
For engineers reviewing the LTC3811EG#PBF datasheet, LTC3811EG#PBF pinout, LTC3811EG#PBF application, or LTC3811EG#PBF equivalent, key selection criteria include its dual-channel PolyPhase® control architecture, 36-lead SSOP wide package with fixed 180° channel phase relationship, DCR or resistor-based current sensing, and support for voltage positioning via external components.
Technical Context
The LTC3811EG#PBF implements peak current mode control with high-bandwidth error amplifiers (8MHz unity-gain bandwidth) and a dedicated high-speed differential remote sense amplifier (1.000 V/V gain, ±6mV offset). Its internal PLL enables synchronization from 175kHz to 900kHz, while MODE/SYNC pin selects forced continuous or discontinuous conduction mode.
This SSOP-packaged variant lacks the PHASEMODE pin and CSOUT output found in QFN versions, fixing channel-to-channel phase at 180° and disabling voltage positioning functionality. It uses separate RUN1/RUN2 enable inputs and independent FB1/FB2 feedback paths for dual-output tracking and sequencing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Dual-output, synchronous buck controller with independent channel control |
| Output Voltage Range | Up to 3.3V; regulated via 0.6V reference with ±0.5% accuracy over temperature |
| Input Voltage Range | 4.5V to 30V - supports wide industrial and telecom input rails |
| Switching Frequency | Programmable 250kHz–750kHz; synchronizable to external clock up to 900kHz |
| Current Sense Range | Adjustable 24mV–85mV threshold - enables precise DCR or discrete resistor sensing |
| Remote Sensing | Differential amplifier with 160kΩ input resistance and 100dB PSRR - rejects PCB trace IR drop |
| Gate Drive Capability | Integrated 1A peak source/sink drivers with 20ns rise/fall times - drives multiple parallel MOSFETs |
| Soft-Start & Tracking | Independent SS/TRACK1 and SS/TRACK2 pins - enable ratiometric or coincident startup sequencing |
Pinout & Package
The LTC3811EG#PBF is housed in a 36-lead plastic SSOP wide package (G package), measuring 10.2mm × 5.3mm × 1.75mm, with exposed thermal pad not present (unlike QFN variants). Pin 1 is located at bottom-left corner when notch faces upward.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1, FB2 | Error amplifier feedback inputs | Connect to resistor divider from output; regulate at 0.6V reference with ±0.5% accuracy |
| COMP1, COMP2 | Error amplifier outputs | High-bandwidth op-amp outputs (8MHz GBW); must not be directly paralleled without disabling slave |
| SENSE1+/–, SENSE2+/– | Current sense differential inputs | Accept 0–3.5V common-mode range; support DCR or shunt-based sensing with programmable 24–85mV threshold |
| RUN1, RUN2 | Channel enable inputs | Logic-level ON/OFF control (VIH = 1.8V, VIL = 0.3V); shutdown reduces IQ to 20μA per channel |
| PGOOD1, PGOOD2 | Open-drain power-good indicators | Assert low when FB deviates >±10%; include 145μs fault delay and 38μs recovery hysteresis |
| MODE/SYNC | Mode select & PLL sync input | Selects CCM/DCM; accepts external clock 175kHz–900kHz for synchronization |
| CLKOUT | Multiphase daisy-chain output | Provides 90° phase-shifted clock signal for cascading additional controllers in 2-/4-phase systems |
| DRVCC | Internal 6V LDO output | Powers bottom gate drivers; supports EXTVCC switchover at 4.5V to reduce losses |
| INTVCC | Analog/digital core supply | Electrically isolated from DRVCC; requires RC decoupling to suppress gate noise coupling |
| SGND | Signal ground reference | Separate from PGND; connects to INTVCC and FB divider grounds to minimize noise injection |
| PGND | Power ground return | Return path for bottom FET sources and DRVCC capacitor; electrically isolated from SGND |
| VIN | Main input supply rail | 4.5V–30V input; powers internal bias circuitry and provides bootstrap energy via DRVCC |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent control loops | Enables asymmetric output configurations (e.g., 2V/1.5V) with separate soft-start, tracking, and enable |
| High-accuracy remote sensing | Differential amplifier rejects up to 5.5V common-mode offset and provides 100dB PSRR for stable regulation under load transients |
| Flexible current sensing | RNG1/RNG2 pins allow linear programming of sense threshold from 24mV to 85mV - supports both DCR and precision shunts |
| Low minimum on-time | 65ns tON(MIN) enables high VIN-to-low VOUT conversion (e.g., 12V→1.2V at 500kHz) without pulse skipping |
| Thermal protection | 165°C junction shutdown with 25°C hysteresis prevents latch-up during overload or poor heatsinking |
| Robust gate drive | 1A peak source/sink capability with <30ns deadtime control ensures clean FET switching and minimizes shoot-through risk |
Applications
| Network Servers | High-Current ASIC Supplies |
|---|---|
Use Scenario: Dual-rail power delivery for CPU core (VDD) and I/O (VDDQ) in 1U rack servers with tight thermal constraints. IC Role / Device Role / Timing Role: LTC3811EG#PBF acts as master controller managing two synchronized 2-phase buck stages, each delivering up to 30A with remote sense compensation. Use Value: ±0.5% output accuracy and differential sensing maintain voltage stability across PCB voltage drops, ensuring reliable operation under dynamic 20A/μs load steps. | Use Scenario: Powering multi-die FPGA or ASIC with strict voltage tolerance (±3%) and sequencing requirements. IC Role / Device Role / Timing Role: LTC3811EG#PBF provides independent soft-start and tracking via SS/TRACK pins to coordinate ramp-up of core (1.0V) and auxiliary (2.5V) rails. Use Value: Ratiometric tracking ensures secondary rail follows primary within 1% during startup, preventing latch-up or I/O contention during configuration. |
| Low-Voltage Power Distribution | Industrial Embedded Computing |
Use Scenario: Distributed 1.8V/3.3V power for memory subsystems in storage arrays with long PCB traces. IC Role / Device Role / Timing Role: LTC3811EG#PBF employs DIFF/IN+ and DIFF/IN− inputs to measure voltage directly at DRAM module terminals, rejecting trace IR loss. Use Value: High PSRR (100dB) and low offset (±6mV) ensure <10mV regulation error at point-of-load despite 150mΩ trace resistance. | Use Scenario: Power management in fanless edge AI accelerators operating from 12V automotive or PoE-derived input. IC Role / Device Role / Timing Role: LTC3811EG#PBF operates in forced CCM mode (via MODE/SYNC tie-high) to eliminate audible noise and ensure predictable EMI behavior. Use Value: Fixed-frequency operation (250–750kHz) allows precise EMI filter design, while thermal shutdown (165°C) protects against enclosure overheating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output multiphase buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3873EG#PBF | Single-output, 2-phase controller; no second FB/COMP channel or independent RUN pins | Suitable only for single-rail systems; lacks dual-tracking capability and independent enable | Select when only one output rail is needed and board space is constrained |
| MP8770GQ-Z | Monolithic dual buck (integrated FETs); max 12V input; no DCR sensing or differential remote sense | Lower BOM count but limited to ≤12V input and ≤15A per channel; no voltage positioning | Choose for cost-sensitive, medium-current applications where integration outweighs flexibility |
Compared with LTC3873EG#PBF and MP8770GQ-Z, the LTC3811EG#PBF uniquely delivers independent dual-loop control with full remote sensing, programmable current thresholds, and robust 30V input capability - making it optimal for high-reliability, multi-rail server and ASIC power systems.
Availability
LTC3811EG#PBF is available at Aetrix Electronics and suitable for network servers, high-current ASIC supplies, and low-voltage power distribution requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across –40°C to +85°C.
Supply support for LTC3811EG#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 product support, documentation, and manufacturing continuity for all Linear-branded power ICs including the LTC3811 series.
The LTC3811EG#PBF belongs to Linear's high-performance PolyPhase® controller family, designed specifically for high-efficiency, low-voltage, high-current DC/DC conversion in computing, networking, and industrial infrastructure equipment.
FAQ
What is the maximum input voltage rating for the LTC3811EG#PBF?
The LTC3811EG#PBF has an absolute maximum input voltage rating of 30V on the VIN pin. Continuous operation is specified from 4.5V to 30V. Exceeding 30V may cause permanent damage. The device includes internal protection against overvoltage on BOOST1/BOOST2 (up to 37V) and SW1/SW2 (up to 30V), but VIN remains the primary system input limit. Always observe derating guidelines for reliability in high-temperature environments.
Does the LTC3811EG#PBF support differential remote sensing?
Yes, the LTC3811EG#PBF supports differential remote sensing via dedicated DIFF/IN+ and DIFF/IN− pins. These connect to opposite terminals of the output capacitor at the load, enabling rejection of PCB trace IR drop. The integrated differential amplifier provides 1.000 V/V gain, ±6mV offset, and 100dB PSRR. The DIFF/OUT pin feeds into FB1 or FB2 through an external resistor divider, completing the remote-sense loop for precise point-of-load regulation.
Can the LTC3811EG#PBF be used in single-output, 4-phase configurations?
Yes, the LTC3811EG#PBF supports single-output, 4-phase operation using CLKOUT daisy-chaining. In this configuration, one LTC3811EG#PBF acts as master (driving CLKOUT), while a second unit synchronizes its switching via MODE/SYNC tied to CLKOUT. The fixed 180° channel phase in the SSOP package enables natural 2-phase per controller, totaling 4 phases. External phase interleaving logic is not required, and the PLL ensures tight frequency and phase alignment across controllers.
What is the purpose of the RNG1 and RNG2 pins on the LTC3811EG#PBF?
The RNG1 and RNG2 pins on the LTC3811EG#PBF program the peak current sense voltage threshold for each channel independently. Connecting RNGx to SGND sets 24mV, to INTVCC sets 50mV, or to a voltage between 0.6V and 2V linearly scales the threshold up to 85mV. This allows optimization for DCR sensing (lower thresholds) or shunt resistors (higher thresholds), directly affecting current limit accuracy and light-load efficiency. The LTC3811EG#PBF uses these pins to configure sensing sensitivity without external op-amps or DACs.
How does the LTC3811EG#PBF handle power-good signaling?
The LTC3811EG#PBF provides open-drain PGOOD1 and PGOOD2 outputs that pull low when the respective FB pin voltage deviates beyond ±10% of nominal (e.g., 0.6V ±60mV). Each includes a 145μs fault detection delay and 38μs recovery delay to suppress transient glitches. The comparator hysteresis is 12mV, and leakage is <1.0μA at 6V. These signals interface directly with FPGA or processor reset controllers, enabling safe system power sequencing and fault isolation in dual-rail applications.
LTC3811EG#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 36-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 30V
- Frequency - Switching:
- 250kHz ~ 750kHz
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Phase Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-SSOP
LTC3811EG#PBF FAQ
1.How can I place an order for LTC3811EG#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3811EG#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 LTC3811EG#PBF reliable?
The price and inventory of LTC3811EG#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3811EG#PBF is usually 5 days.
3.What payment methods are accepted for LTC3811EG#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3811EG#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3811EG#PBF?
LTC3811EG#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3811EG#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 LTC3811EG#PBF?
For technical support, including LTC3811EG#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3811EG#PBF requirements.
6.How does Aetrix verify that LTC3811EG#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3811EG#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 LTC3811EG#PBF meets industry standards.
7.What is the process for return or replacement of LTC3811EG#PBF?
All LTC3811EG#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3811EG#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 LTC3811EG#PBF part is unused and in its original packaging.
Return procedure for LTC3811EG#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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