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Analog Devices Inc. LTC3861IUH-1#TRPBF
- Part No.:
- LTC3861IUH-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3861IUH-1#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,798
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Product details
Overview
LTC3861IUH-1#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, multiphase synchronous step-down voltage mode DC/DC controller designed for high-current distributed power systems. It delivers accurate current sharing across phases, supports 250kHz–2.25MHz programmable switching frequency, operates from 3V–24V input to 0.6V–(VCC–0.5V) output, and features lossless DCR current sensing with ±0.75% 0.6V reference accuracy. It is used in FPGA/DSP core supplies requiring tight regulation and fast transient response.
For engineers reviewing the LTC3861IUH-1#TRPBF datasheet, LTC3861IUH-1#TRPBF pinout, LTC3861IUH-1#TRPBF application, or LTC3861IUH-1#TRPBF equivalent, key selection criteria include its dual-phase current-sharing architecture, 32-pin 5mm × 5mm QFN package with exposed SGND pad, VCC range (3V–5.5V), remote differential sense capability, and compatibility with DrMOS/power blocks for telecom and industrial high-density power delivery.
Technical Context
The LTC3861IUH-1#TRPBF implements constant-frequency voltage mode control with two independent error amplifiers (COMP1/COMP2), each driving a PWM channel with precise duty-cycle modulation. Its differential remote sense amplifier (VSNSP/VSNSN → VSNSOUT) enables load-point regulation by rejecting PCB IR drop, while the integrated current sense amplifiers (ISNS1P/N, ISNS2P/N) support both DCR and resistor-based sensing with 18.5× gain and ±1.25mV offset over –40°C to 125°C.
Phase synchronization is managed via CLKIN/CLKOUT daisy-chaining and PHSMD-programmable phase relationships (120°/180°), enabling up to 12-phase operation using six controllers. The chip incorporates a 128-cycle overcurrent counter with hysteresis, programmable soft-start (2.5µA internal current source), and line feedforward compensation through VINSNS to decouple loop gain from VIN variations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3V to 24V - supports wide-input industrial and telecom rails without external pre-regulation. |
| VOUT Range | 0.6V to (VCC – 0.5V) - enables sub-1V FPGA core supplies with direct reference tracking. |
| Switching Frequency | 250kHz to 2.25MHz - adjustable via FREQ pin resistor or external CLKIN; enables optimization of size vs. efficiency. |
| Reference Accuracy | ±0.75% at 0.6V - ensures tight output regulation across temperature and line/load conditions. |
| Current Sense Gain | 18.5× - provides high-sensitivity DCR sensing with minimal PCB layout impact. |
| Operating Temp | –40°C to +125°C junction - qualified for industrial and extended-temperature embedded applications. |
| Package | 32-pin 5mm × 5mm QFN with exposed SGND pad - enables low-thermal-resistance PCB mounting (θJA = 34°C/W). |
Pinout & Package
Package: 32-lead plastic QFN (UH), 5mm × 5mm, exposed SGND pad (Pin 33) requiring solder connection to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (Pin 1) | Chip supply input | 3V–5.5V bias rail; requires local 0.1µF–1µF ceramic bypass to SGND for stable operation. |
| FB1/FB2 (Pins 2, 8) | Error amplifier inverting inputs | Connect to resistor dividers from VSNSOUT or remote VOUT; set regulated output voltage (0.6V reference). |
| COMP1/COMP2 (Pins 3, 7) | Error amplifier outputs | Low-impedance control voltages driving PWM duty cycle; cannot be directly paralleled without master-slave configuration. |
| VSNSP/VSNSN (Pins 6, 5) | Differential sense inputs | Connect to load-side VOUT and sense ground to reject PCB trace resistance and enable true remote sensing. |
| FREQ (Pin 10) | Frequency programming node | Sources 20µA; resistor to SGND sets oscillator frequency from 250kHz–2.25MHz when CLKIN is high/floating. |
| CLKIN/CLKOUT (Pins 11, 12) | Phase synchronization I/O | Enable daisy-chained multiphase operation; CLKIN accepts 250kHz–2.25MHz external clock; CLKOUT drives next controller's CLKIN. |
| ISNS1P/ISNS1N (Pins 22, 21) ISNS2P/ISNS2N (Pins 19, 20) |
Current sense differential inputs | Interface with inductor DCR network or sense resistor; support lossless current monitoring per phase for balancing and protection. |
| IAVG (Pin 28) | Average current monitor | Outputs voltage proportional to master-phase average current; used for inter-IC current sharing in multiphase configurations. |
| PGOOD1/PGOOD2 (Pins 27, 14) | Open-drain power-good indicators | Assert low after 30µs delay when output deviates >±10% from target - enables system-level sequencing and fault reporting. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-phase current sharing | Maintains ≤±3% current imbalance across phases using IAVG bus and per-phase integrators - critical for thermal derating in high-current designs. |
| Lossless DCR sensing | Eliminates sense resistor power loss and board space; supports inductor DCR as current-sense element with 18.5× gain and <±1.25mV offset. |
| Prebiased load startup | Disables inductor current reversal during soft-start - prevents reverse current flow into precharged outputs (e.g., hot-swap systems). |
| Differential remote sensing | VSNS amplifier rejects up to 100mV of ground potential difference between IC and load - improves DC accuracy to ±0.75% over full temp range. |
| Programmable soft-start | Internal 2.5µA current source charges external capacitor on TRACK/SS pins - enables controlled ramp rate and output voltage tracking. |
Applications
| Telecom Server VRMs | FPGA Core Power |
|---|---|
|
Use Scenario: 12V input distributed to multiple 0.85V/60A FPGA core rails in 1U rack servers with strict thermal and transient requirements. IC Role / Device Role / Timing Role: Dual-phase controller managing two parallel 30A phases per rail; synchronizes with system clock via CLKIN for EMI reduction. Use Value: Achieves <1% output deviation under 50A/µs load transients using remote sensing and 2.25MHz operation - eliminates need for post-regulator LDOs. |
Use Scenario: High-density AI accelerator card requiring tightly regulated 0.75V/80A supply with dynamic voltage scaling (DVS) support. IC Role / Device Role / Timing Role: Master-slave configuration of three LTC3861IUH-1#TRPBF units delivering 12-phase operation; uses IAVG bus for real-time current balancing. Use Value: Enables 92% peak efficiency at 80A with 5mm × 5mm footprint per controller - reduces total solution size by 35% vs. single-phase alternatives. |
| Datacom Line Cards | Industrial PLC CPU Supplies |
|
Use Scenario: 48V backplane powering 1.2V/40A DSP clusters in packet processing line cards with -40°C to +85°C ambient requirement. IC Role / Device Role / Timing Role: Two-phase controller interfacing with DrMOS (e.g., TDA21220); uses VINSNS feedforward for immunity to 48V rail ripple. Use Value: Delivers <50mV overshoot during 30A load steps - meets GR-1089 Class B EMI and transient specs without additional filtering. |
Use Scenario: Programmable logic controller with isolated 24V input powering 3.3V/5A and 1.8V/3A auxiliary rails in factory automation environments. IC Role / Device Role / Timing Role: Independent dual-output configuration (RUN1/RUN2 separately controlled); uses TRACK/SS for ratiometric startup of secondary rail. Use Value: Ensures safe power sequencing with <10ms tracking error between rails - prevents latch-up in mixed-voltage SoCs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2950GQ-10-Z | Integrated MOSFET drivers; no external gate driver required; fixed 600kHz/1MHz options only; no differential remote sense. | Better suited for cost-sensitive, medium-current (<30A/channel) applications where layout simplicity outweighs precision sensing needs. | Select MP2950GQ-10-Z when integrating drivers reduces BOM count and thermal management complexity is less critical than ±0.75% regulation. |
| LTC3883IUH-1#TRPBF | Digital PMBus interface; on-chip ADC for telemetry; supports PID loop tuning; same 32-pin QFN but adds I²C pins and EEPROM. | Required for systems needing real-time voltage/current/temperature monitoring, fault logging, or dynamic loop reconfiguration. | Choose LTC3883IUH-1#TRPBF when digital control, telemetry, or field-upgradable compensation is mandatory - not a drop-in replacement. |
Compared with MP2950GQ-10-Z and LTC3883IUH-1#TRPBF, the LTC3861IUH-1#TRPBF offers superior analog precision (differential sensing, ±0.75% ref), wider frequency range (250kHz–2.25MHz), and proven current-sharing stability in >60A multi-phase systems - making it optimal for high-performance analog-controlled power rails.
Availability
LTC3861IUH-1#TRPBF is available at Aetrix Electronics and suitable for telecom server VRMs, FPGA core power supplies, and industrial PLC CPU supplies requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature grade (–40°C to +125°C).
Supply support for LTC3861IUH-1#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 full product support, datasheets, and application engineering for legacy Linear parts including the LTC3861 series.
The LTC3861-1 family was designed specifically for high-current, multiphase synchronous buck conversion in datacom, telecom, and industrial systems where precision current sharing, remote sensing, and wide-frequency programmability are essential.
FAQ
What is the maximum number of phases supported by LTC3861IUH-1#TRPBF?
The LTC3861IUH-1#TRPBF supports up to 12-phase operation by daisy-chaining up to six controllers via CLKIN/CLKOUT and configuring PHSMD pins. Each LTC3861IUH-1#TRPBF provides two phases, and phase alignment is programmable (120° or 180°) to minimize input/output capacitor RMS current. This scalability enables >100A solutions without custom ASICs.
Does LTC3861IUH-1#TRPBF support prebiased output startup?
Yes, the LTC3861IUH-1#TRPBF disables inductor current reversal during soft-start to safely power prebiased loads. When TRACK/SS pins are used for soft-start, the controller actively prevents negative inductor current, avoiding reverse current flow into an already charged output capacitor - critical for hot-swap and redundant power systems.
How does the differential remote sense amplifier improve regulation accuracy in LTC3861IUH-1#TRPBF?
The LTC3861IUH-1#TRPBF's differential remote sense amplifier (VSNSP/VSNSN → VSNSOUT) measures the true load voltage by rejecting PCB trace resistance between the IC and output capacitor. With ±2mV input offset and 1.007V/V gain, it enables ±0.75% output accuracy even with 100mV ground shift - eliminating errors that would otherwise degrade regulation in high-current, multi-layer PCBs.
Can LTC3861IUH-1#TRPBF operate with both DCR and resistor-based current sensing?
Yes, the LTC3861IUH-1#TRPBF supports both methods: DCR sensing connects ISNS1P/N and ISNS2P/N across an RC network parallel to the inductor; resistor sensing places a discrete shunt between ISNSxP and ISNSxN. Both use the same 18.5× gain path and share identical overcurrent thresholds, allowing design flexibility without sacrificing protection integrity.
What is the function of the IAVG pin on LTC3861IUH-1#TRPBF?
The IAVG pin on LTC3861IUH-1#TRPBF outputs a voltage proportional to the instantaneous average current of the master phase in multiphase configurations. When multiple LTC3861IUH-1#TRPBF units are paralleled, their IAVG pins are tied together to form a shared current reference bus - enabling real-time per-phase current balancing via internal integrators without external circuitry.
LTC3861IUH-1#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 32-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:
- 32-QFN (5x5)
LTC3861IUH-1#TRPBF FAQ
1.How can I place an order for LTC3861IUH-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3861IUH-1#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 LTC3861IUH-1#TRPBF reliable?
The price and inventory of LTC3861IUH-1#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3861IUH-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3861IUH-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3861IUH-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3861IUH-1#TRPBF?
LTC3861IUH-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3861IUH-1#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 LTC3861IUH-1#TRPBF?
For technical support, including LTC3861IUH-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3861IUH-1#TRPBF requirements.
6.How does Aetrix verify that LTC3861IUH-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3861IUH-1#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 LTC3861IUH-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3861IUH-1#TRPBF?
All LTC3861IUH-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3861IUH-1#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 LTC3861IUH-1#TRPBF part is unused and in its original packaging.
Return procedure for LTC3861IUH-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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