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Analog Devices Inc. LTC3861IUHE#TRPBF
- Part No.:
- LTC3861IUHE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 36-WFQFN Exposed Pad
- Datasheet:
-
LTC3861IUHE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 36QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,840
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Product details
Overview
LTC3861IUHE#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, multiphase synchronous step-down voltage mode DC/DC controller supporting up to 12-phase operation via parallel ICs. It delivers accurate current sharing across phases using lossless DCR sensing or precision resistor-based current monitoring, operates from 3V–24V input to 0.6V–(VCC–0.5V) output, and features ±0.75% 0.6V reference accuracy with dual differential remote sense amplifiers - deployed in high-current DSP, FPGA, and telecom power supplies.
For engineers reviewing the LTC3861IUHE#TRPBF datasheet, LTC3861IUHE#TRPBF pinout, LTC3861IUHE#TRPBF application, or LTC3861IUHE#TRPBF equivalent, key selection considerations include its 250kHz–2.25MHz programmable/synchronizable switching frequency, dual independent soft-start/tracking inputs (TRACK/SS1 & TRACK/SS2), integrated line feedforward compensation, prebiased load startup capability, and 36-pin 5mm × 6mm QFN package with exposed thermal pad.
Technical Context
The LTC3861IUHE#TRPBF implements constant-frequency voltage mode control with two independent error amplifiers (COMP1/COMP2), each driving a PWM channel with dedicated FB/VSNSOUT/VSNSP/VSNSN pins for remote differential output sensing. Its architecture supports master-slave current sharing via IAVG averaging and phase synchronization through CLKIN/CLKOUT/PHSMD pins - enabling precise interleaving across 2-, 3-, 4-, 6-, or 12-phase configurations.
It integrates lossless inductor DCR current sensing with ±1.25mV input-referred offset over –40°C to 125°C, programmable overcurrent protection via ILIM1/ILIM2 (20µA-sourced pins), and robust line transient suppression via VINSNS feedforward with CONFIG-selectable gain scaling - all while maintaining stable regulation under prebiased load conditions using controlled inductor current reversal disable during soft-start.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3V to 24V - supports wide-input industrial and telecom rails without external regulators. |
| VOUT Range | 0.6V to (VCC – 0.5V) - enables sub-1V core supplies for modern processors with no level-shifting circuitry. |
| Switching Frequency | 250kHz to 2.25MHz - adjustable via FREQ pin resistor or external CLKIN; allows optimization of size vs. efficiency. |
| Reference Accuracy | ±0.75% at 0.6V - ensures tight output regulation across temperature and line/load variations. |
| Operating Temp | –40°C to 125°C junction - qualified for industrial and extended-temperature embedded systems. |
| Package | 36-pin 5mm × 6mm QFN with exposed SGND pad - provides low thermal resistance (θJA = 43°C/W) and compact layout footprint. |
| Current Sensing | Lossless DCR or precision shunt - eliminates power loss and enables accurate per-phase current balancing in multiphase designs. |
Pinout & Package
The LTC3861IUHE#TRPBF is housed in a 36-lead plastic QFN package (5mm × 6mm) with an exposed signal ground (SGND) pad (Pin 37) that must be soldered to PCB ground for thermal and electrical performance. Pin pitch is 0.5mm; SGND connections are shared across Pins 21, 26, and 37.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB1, FB2 | Error amplifier inverting input | Connects to VSNSOUTx for closed-loop regulation; tying to VCC disables respective channel's error amp and COMP output. |
| COMP1, COMP2 | Error amplifier output | Drives PWM duty cycle; true op-amp output (low impedance); cannot be directly paralleled without master-slave configuration. |
| VSNSP1/VSNSN1, VSNSP2/VSNSN2 | Differential remote sense inputs | VSNSP connects to feedback divider midpoint; VSNSN to load ground - cancels ground path offsets for accurate remote sensing. |
| ISNS1P/ISNS1N, ISNS2P/ISNS2N | Current sense amplifier inputs | Supports DCR or shunt-based sensing; ±1.25mV max input offset ensures precise per-phase current measurement. |
| ILIM1, ILIM2 | Overcurrent threshold set | 20µA current source - resistor to SGND sets OC trip point; enables programmable fault protection per channel. |
| RUN1, RUN2 | Channel enable control | Logic-high (>2.25V) enables channel; <2V forces shutdown - supports independent sequencing and fault isolation. |
| TRACK/SS1, TRACK/SS2 | Soft-start & tracking input | Internal 2.5µA current source charges external capacitor for controlled ramp; also accepts tracking voltage for coordinated multi-rail startup. |
| FREQ, CLKIN, CLKOUT, PHSMD | Multiphase timing interface | FREQ sets frequency; CLKIN synchronizes to external clock; CLKOUT daisy-chains multiple ICs; PHSMD configures CH1–CH2–CLKOUT phase alignment (120°/180°). |
| IAVG | Average current monitor | Outputs voltage proportional to master-phase average current - used for current-sharing loop in parallel configurations; tie to SGND if channels operate independently. |
| PGOOD1, PGOOD2 | Power-good status indicator | Open-drain outputs pulled low when output deviates >±10% from target after 30µs mask timer - enables system-level power sequencing and fault reporting. |
Key Features
| Feature | Design Value |
|---|---|
| Dual differential remote sense amplifiers | Enables accurate output regulation at point-of-load despite PCB trace resistance and ground bounce - critical for sub-1V, high-current rails. |
| Programmable 250kHz–2.25MHz switching frequency | Allows trade-off between component size (higher fSW → smaller L/C) and conduction losses (lower fSW → higher efficiency at heavy loads). |
| Lossless DCR or precision shunt current sensing | Eliminates sense resistor power loss and thermal drift; supports accurate per-phase current matching in 2–12 phase systems. |
| Prebiased load startup with inductor current reversal disable | Ensures safe turn-on into powered systems (e.g., hot-swap, partial power-up) without reverse inductor current causing output collapse or shoot-through. |
| Line feedforward compensation via VINSNS | Directly modulates PWM comparator input in response to VIN changes - reduces line-induced output transients by >50% versus standard voltage-mode control. |
| 128-cycle overcurrent lockout with auto-retry | Prevents destructive latch-up during sustained shorts; resets after 32768 cycles - balances fault protection with system recoverability. |
Applications
| High-Current Distributed Power Systems | DSP, FPGA and ASIC Core Supplies |
|---|---|
Use Scenario: Board-level 60A+ power delivery to multi-core processors in base station radios or AI accelerators. IC Role / Device Role / Timing Role: Dual-phase controller managing two 30A phases with interleaved timing to reduce input/output ripple and EMI. Use Value: Enables use of smaller input capacitors and lower-ripple output filters due to 180° phase shift and synchronized current sharing. | Use Scenario: Generating tightly regulated 0.85V/40A core voltage for Xilinx Versal FPGA with dynamic load steps up to 20A/µs. IC Role / Device Role / Timing Role: Voltage mode controller with dual remote sense and fast error amplifiers delivering <50µs load transient recovery. Use Value: ±0.75% reference accuracy and high-bandwidth error amps maintain <±15mV regulation during rapid load transients. |
| Datacom and Telecom Systems | Industrial Power Supplies |
Use Scenario: 48V-to-12V intermediate bus converter feeding multiple point-of-load regulators in 1RU server switch. IC Role / Device Role / Timing Role: Master controller in 4-phase configuration using CLKOUT daisy-chain to synchronize six LTC3861s across redundant power modules. Use Value: Phase synchronization minimizes input current ripple, reducing bulk capacitor stress and improving system reliability. | Use Scenario: 24V-to-3.3V/20A auxiliary supply for PLC I/O modules operating continuously at 70°C ambient. IC Role / Device Role / Timing Role: Industrial-grade controller with –40°C to 125°C operation, VINSNS feedforward, and robust overcurrent protection. Use Value: Line feedforward and high-temp qualification ensure stable output during brownouts and thermal cycling in harsh factory environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3855IUFD#TRPBF | Single-channel, 4-phase capable; lacks dual independent remote sense amps and TRACK/SS pins; lower max fSW (1MHz). | Suitable for simpler single-output, higher-phase-count systems where independent tracking or dual-rail control is unnecessary. | Select when only one regulated rail is needed and phase count >4 is required - avoids complexity of inter-IC synchronization. |
| MP2960AGQSE-LF-Z | Monolithic dual-phase controller with integrated drivers; fixed 600kHz/1MHz options; no external FREQ programming or CLKIN sync. | Better suited for space-constrained designs where gate driver integration reduces BOM count - but sacrifices frequency flexibility and remote sensing precision. | Choose for cost-sensitive, medium-power applications (<30A/channel) where layout area and component count outweigh programmability needs. |
Compared with LTC3855IUFD#TRPBF and MP2960AGQSE-LF-Z, the LTC3861IUHE#TRPBF uniquely supports dual independent regulated outputs with full remote sensing, programmable frequency up to 2.25MHz, and explicit tracking/soft-start per channel - making it optimal for complex multi-rail, high-accuracy telecom and industrial systems.
Availability
LTC3861IUHE#TRPBF is available at Aetrix Electronics and suitable for high-current distributed power systems, DSP/FPGA core supplies, and industrial embedded power conversion requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3861IUHE#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 its high-performance analog and power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3861IUHE#TRPBF belongs to Linear's PolyPhase® controller family, designed specifically for scalable, high-efficiency multiphase DC/DC conversion in datacom, telecom, and computing infrastructure where current sharing accuracy and transient response are critical.
FAQ
What is the maximum number of phases supported by the LTC3861IUHE#TRPBF?
The LTC3861IUHE#TRPBF itself is a dual-phase controller, but up to six LTC3861IUHE#TRPBF ICs can be operated in parallel to achieve 1-, 2-, 3-, 4-, 6-, or 12-phase operation. Phase alignment is managed via CLKIN/CLKOUT daisy-chaining and PHSMD pin configuration - enabling precise interleaving without external timing components.
Does the LTC3861IUHE#TRPBF support prebiased load startup?
Yes, the LTC3861IUHE#TRPBF safely powers prebiased loads by disabling inductor current reversal during soft-start. This prevents reverse current flow that could collapse the output or damage downstream circuitry - a key requirement in hot-swap and modular power system designs where rails may already be energized.
How does the LTC3861IUHE#TRPBF implement current sharing across multiple phases?
The LTC3861IUHE#TRPBF uses an auxiliary current sharing loop: the master phase's IAVG pin outputs a voltage proportional to its average inductor current. Each slave phase compares its own current sense signal to this IAVG reference and adjusts its COMP voltage accordingly - dynamically equalizing per-phase currents with <±3% mismatch across temperature and load.
What is the function of the CONFIG pin on the LTC3861IUHE#TRPBF?
The CONFIG pin on the LTC3861IUHE#TRPBF selects the gain of the line feedforward multiplier to maintain consistent modulator response across varying input voltages and switching frequencies. It is internally pulled to SGND and can be tied to VCC or left floating to configure feedforward strength - optimizing line transient suppression without loop compensation changes.
Can the LTC3861IUHE#TRPBF operate with both DCR and shunt-based current sensing simultaneously?
No - the LTC3861IUHE#TRPBF supports either lossless DCR sensing or precision shunt sensing per channel, but not both simultaneously. The ISNS1P/ISNS1N and ISNS2P/ISNS2N inputs are dedicated to one method per channel; mixing methods would require external signal conditioning not supported by the internal current sense amplifier architecture.
LTC3861IUHE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 36-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- PWM Signal
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 2
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 3V ~ 5.5V
- Frequency - Switching:
- 250kHz ~ 3MHz
- Duty Cycle (Max):
- 91.5%
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Phase Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-QFN (5x6)
LTC3861IUHE#TRPBF FAQ
1.How can I place an order for LTC3861IUHE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3861IUHE#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 LTC3861IUHE#TRPBF reliable?
The price and inventory of LTC3861IUHE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3861IUHE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3861IUHE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3861IUHE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3861IUHE#TRPBF?
LTC3861IUHE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3861IUHE#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 LTC3861IUHE#TRPBF?
For technical support, including LTC3861IUHE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3861IUHE#TRPBF requirements.
6.How does Aetrix verify that LTC3861IUHE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3861IUHE#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 LTC3861IUHE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3861IUHE#TRPBF?
All LTC3861IUHE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3861IUHE#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 LTC3861IUHE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3861IUHE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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