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Analog Devices Inc. LTC3861EUH-1#TRPBF
- Part No.:
- LTC3861EUH-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3861EUH-1#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,961
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Product details
Overview
LTC3861EUH-1#TRPBF from Analog Devices (formerly Linear Technology) is a dual-channel, multiphase synchronous step-down DC/DC voltage mode controller for high-current power delivery. It supports 1–12-phase operation via parallel ICs, delivers ±0.75% reference accuracy at 0.6V, operates from 3V–24V input to 0.6V–(VCC–0.5V) output, and features lossless DCR current sensing with programmable overcurrent protection. It is used in FPGA/DSP core supplies requiring precise current sharing and fast transient response.
For engineers reviewing the LTC3861EUH-1#TRPBF datasheet, LTC3861EUH-1#TRPBF pinout, LTC3861EUH-1#TRPBF application, or LTC3861EUH-1#TRPBF equivalent, key selection criteria include its 250kHz–2.25MHz programmable switching frequency, differential remote sense capability, VCC range of 3V–5.5V, 32-pin 5mm × 5mm QFN package, and support for prebiased load startup with inductor current reversal disabled during soft-start.
Technical Context
The LTC3861EUH-1#TRPBF implements constant-frequency voltage mode control with two independent error amplifiers (COMP1/COMP2), each driving a PWM channel with true op-amp characteristics-low offset (<2mV), high bandwidth (>40MHz unity-gain), and low output impedance. Its differential remote sense amplifier (VSNSP/VSNSN → VSNSOUT) provides accurate load-point regulation by rejecting PCB IR drop.
Current sharing across phases is achieved via an auxiliary loop: master-phase IAVG pin outputs a voltage proportional to average inductor current; slave phases compare their sensed current against this reference and adjust duty cycle accordingly. Overcurrent protection uses 128-cycle latched shutdown with negative OC detection and automatic recovery after 32768 cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 3V to 24V - supports wide-input telecom and industrial rails without external regulators. |
| VOUT Range | 0.6V to (VCC – 0.5V) - enables sub-1V FPGA/DSP core supplies with internal 0.6V reference. |
| 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 (–40°C to 125°C). |
| Current Sensing | Lossless DCR or precision sense resistor - eliminates shunt power loss while maintaining ±1.25mV offset for accurate phase balancing. |
| Package | 32-pin 5mm × 5mm QFN with exposed SGND pad - provides low thermal resistance (θJA = 34°C/W) for high-power density layouts. |
| Operating Temp | –40°C to 125°C junction - qualified for industrial and telecom environments without derating. |
Pinout & Package
Package: 32-lead 5mm × 5mm plastic QFN (UH), exposed pad (Pin 33) is SGND and must be soldered to PCB ground 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. |
| FB1/FB2 (Pins 2, 8) | Error amplifier inverting inputs | Connect to resistor dividers from VSNSOUT or remote VOUT; set regulated output voltage. |
| COMP1/COMP2 (Pins 3, 7) | Error amplifier outputs | Drive external gate drivers; cannot be wired together unless one channel is disabled via FB-to-VCC. |
| VSNSP/VSNSN (Pins 6, 5) | Differential remote sense inputs | VSNSP connects to load-side VOUT; VSNSN connects to load-side SGND - rejects PCB trace resistance. |
| FREQ (Pin 10) | Frequency programming input | Sources 20µA; resistor to SGND sets fSW from 250kHz–2.25MHz; logic level selects preset 600kHz/1MHz when CLKIN is low. |
| RUN1/RUN2 (Pins 24, 17) | Channel enable inputs | ≥2.25V enables channel; ≤2.0V disables it; internal 1.5µA pull-up allows simple open-drain control. |
| PWM1/PWM2 (Pins 25, 16) | Three-state top-gate drive outputs | Direct interface to DrMOS, power blocks, or external gate drivers; high-impedance during shutdown. |
| IAVG (Pin 28) | Average current monitor | Outputs voltage proportional to master-phase average current; tied together across paralleled ICs for current sharing. |
| PGOOD1/PGOOD2 (Pins 27, 14) | Open-drain power-good indicators | Assert low after 30µs delay when output deviates >±10% from target - enables system sequencing and fault reporting. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-channel multiphase control | Supports up to 12-phase operation by daisy-chaining six LTC3861EUH-1#TRPBF controllers - scales current capacity without redesigning control loop compensation. |
| Differential remote voltage sensing | VSNSP/VSNSN inputs with <2mV offset and 40MHz bandwidth eliminate board-level IR drop errors - maintains ±0.75% regulation at point-of-load. |
| Programmable soft-start & tracking | TRACK/SS1/SS2 pins accept capacitor for controlled ramp or resistor divider for ratiometric/coincident output tracking - simplifies multi-rail power sequencing. |
| Prebiased load startup | Inductor current reversal disabled during soft-start - prevents reverse current flow into precharged outputs, avoiding damage to downstream circuitry. |
| Line feedforward compensation | VINSNS pin modulates PWM ramp in real time with VIN changes - reduces line-step overshoot/undershoot and decouples loop gain from input voltage variation. |
Applications
| High-Current FPGA Core Supply | DSP/ASIC Multi-Rail Sequencing |
|---|---|
Use Scenario: Powering Xilinx Ultrascale+ FPGA core (VCCINT) requiring 60A at 0.85V with <±1% regulation under dynamic load steps. IC Role / Device Role / Timing Role: Dual-phase controller managing two parallel 30A phases with active current sharing via IAVG bus and differential remote sense at BGA balls. Use Value: Achieves <50mV load-step deviation at 20A/µs using 0.47µH inductors and 2.25MHz switching - enabled by high-bandwidth error amplifiers and lossless DCR sensing. | Use Scenario: Generating synchronized 1.2V, 1.8V, and 3.3V rails for TI C66x DSP with strict power-up order and voltage tracking. IC Role / Device Role / Timing Role: LTC3861EUH-1#TRPBF controls primary 1.2V rail; TRACK/SS pins configure secondary rails to ramp proportionally using resistor dividers. Use Value: Eliminates need for external tracking ICs - coincident start-up within 1% voltage matching reduces sequencing complexity and BOM count. |
| Telecom Baseband Processor Supply | Industrial PLC I/O Module Power |
Use Scenario: Delivering 40A at 1.0V to Qualcomm QDM4390 baseband processor in 4G/LTE small cell equipment with 7V–14V input range. IC Role / Device Role / Timing Role: Four-phase configuration using two LTC3861EUH-1#TRPBF ICs; CLKIN synchronized to system clock for EMI reduction. Use Value: 2.25MHz operation allows use of 0.22µH inductors - cuts solution size by 35% versus 500kHz designs while maintaining >92% peak efficiency. | Use Scenario: Providing isolated 5V/3A and 3.3V/2A auxiliary rails in DIN-rail mounted PLC with wide ambient temperature (–40°C to +70°C). IC Role / Device Role / Timing Role: Independent dual-output mode: Channel 1 regulates 5V; Channel 2 regulates 3.3V; RUN1/RUN2 enable sequenced startup per IEC 61000-4-28. Use Value: –40°C to 125°C qualification ensures stable operation without derating; PGOOD outputs interface directly to PLC watchdog timer for fail-safe monitoring. |
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 |
|---|---|---|---|
| ISL95812IRZ-T | Single-chip dual-phase controller with integrated MOSFET drivers; no external gate driver required. Fixed 600kHz/1MHz frequencies only; no DCR sensing support. | Better suited for space-constrained consumer applications where integration outweighs flexibility; lacks remote sense differential amplifier. | Select ISL95812IRZ-T when board area is critical and design uses discrete MOSFETs with driver-less layout; avoid if DCR sensing or >1MHz operation is needed. |
| MP8765GL-Z | Monolithic dual-phase buck converter (integrated power stages); max 20A per phase; 4.5V–18V VIN; no remote sense or IAVG current sharing bus. | Targeted at cost-sensitive embedded systems with moderate current demands; no support for multi-IC paralleling or prebiased startup. | Choose MP8765GL-Z for simplified bring-up in mid-power applications (<40A total); LTC3861EUH-1#TRPBF remains preferred for >60A, telecom-grade reliability, or distributed power architectures. |
Compared with ISL95812IRZ-T and MP8765GL-Z, the LTC3861EUH-1#TRPBF offers superior flexibility in frequency tuning, remote sensing accuracy, and scalable multiphase expansion - making it the only option supporting 12-phase, 120A+ systems with matched current sharing and industrial temperature range.
Availability
LTC3861EUH-1#TRPBF is available at Aetrix Electronics and suitable for high-current FPGA core supplies, telecom baseband processor power, and industrial PLC I/O modules requiring stable component supply, long-term lifecycle assurance, and guaranteed industrial temperature performance.
Supply support for LTC3861EUH-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 LTC3861EUH-1#TRPBF.
The LTC3861EUH-1#TRPBF belongs to Linear's PolyPhase® controller family, designed specifically for high-efficiency, high-current distributed power systems in datacom, telecom, and industrial computing where precise current sharing and fast transient response are mandatory.
FAQ
What is the maximum number of LTC3861EUH-1#TRPBF controllers that can be paralleled for multiphase operation?
Up to six LTC3861EUH-1#TRPBF controllers can operate in parallel to achieve 1-, 2-, 3-, 4-, 6-, or 12-phase configurations. This scalability is enabled by the CLKOUT and PHSMD pins, which coordinate phase alignment and current sharing across all devices. The IAVG pin must be connected together across all paralleled ICs to maintain accurate current balance.
Does the LTC3861EUH-1#TRPBF support prebiased load startup, and how is it implemented?
Yes, the LTC3861EUH-1#TRPBF safely powers prebiased loads by disabling inductor current reversal during soft-start. This behavior is inherent to the controller's architecture and requires no external components or configuration. It prevents reverse current flow into an already charged output capacitor, protecting downstream circuitry and ensuring reliable startup in systems with backup supplies or hot-swap conditions.
What are the absolute maximum ratings for the VSNSP and VSNSN pins on the LTC3861EUH-1#TRPBF?
The absolute maximum rating for both VSNSP and VSNSN pins on the LTC3861EUH-1#TRPBF is –0.3V to (VCC + 0.1V). Exceeding this range may cause permanent damage. These pins are designed for differential sensing across the output capacitor, with typical common-mode range from –0.3V to VCC – 0.5V and input-referred offset under ±2mV over temperature.
Can the LTC3861EUH-1#TRPBF be synchronized to an external clock, and what is the supported frequency range?
Yes, the LTC3861EUH-1#TRPBF supports external clock synchronization via the CLKIN pin over a range of 250kHz to 2.25MHz. The rising edge of CLKIN aligns with the rising edge of PWM1 in closed-loop operation. When CLKIN is active, the FREQ pin becomes a logic select for internal presets; when CLKIN is high or floating, FREQ sets frequency via an external resistor to SGND.
How does the LTC3861EUH-1#TRPBF implement current sharing between phases, and what is the role of the IAVG pin?
The LTC3861EUH-1#TRPBF implements current sharing using a master-slave architecture where the master phase's IAVG pin outputs a voltage proportional to its average inductor current. Slave phases compare their sensed current against this reference and adjust duty cycle via integrator summation with COMP. In multi-IC systems, all IAVG pins must be tied together; for independent operation, IAVG is grounded. Typical IAVG capacitance is 100pF.
LTC3861EUH-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)
LTC3861EUH-1#TRPBF FAQ
1.How can I place an order for LTC3861EUH-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3861EUH-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 LTC3861EUH-1#TRPBF reliable?
The price and inventory of LTC3861EUH-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 LTC3861EUH-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3861EUH-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3861EUH-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3861EUH-1#TRPBF?
LTC3861EUH-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3861EUH-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 LTC3861EUH-1#TRPBF?
For technical support, including LTC3861EUH-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3861EUH-1#TRPBF requirements.
6.How does Aetrix verify that LTC3861EUH-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3861EUH-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 LTC3861EUH-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3861EUH-1#TRPBF?
All LTC3861EUH-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3861EUH-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 LTC3861EUH-1#TRPBF part is unused and in its original packaging.
Return procedure for LTC3861EUH-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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