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Analog Devices Inc. LTC3861IUH-1#PBF
- Part No.:
- LTC3861IUH-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3861IUH-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:146
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Product details
Overview
LTC3861IUH-1#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, multiphase synchronous step-down DC/DC voltage mode controller designed for high-current power delivery to DSPs, FPGAs, and telecom systems. It supports 3V–24V input, 0.6V–(VCC–0.5V) output, 250kHz–2.25MHz programmable switching frequency, ±0.75% reference accuracy, and lossless DCR current sensing with accurate phase current sharing.
For engineers reviewing the LTC3861IUH-1#PBF datasheet, LTC3861IUH-1#PBF pinout, LTC3861IUH-1#PBF application, or LTC3861IUH-1#PBF equivalent, key selection considerations include its 32-pin 5mm × 5mm QFN package, dual differential remote sense capability, 128-cycle overcurrent fault detection, prebiased load startup support, and compatibility with DrMOS, power blocks, or discrete MOSFET/gate driver topologies.
Technical Context
The LTC3861IUH-1#PBF implements constant-frequency voltage mode control with two independent error amplifiers (COMP1/COMP2), each driving a PWM channel with line feedforward via VINSNS. Its differential remote sense amplifier (VSNSP/VSNSN → VSNSOUT) enables precise load-point regulation by rejecting PCB IR drop.
Current sharing across phases is achieved through inductor DCR sensing (ISNS1P/ISNS1N, ISNS2P/ISNS2N), internal 20µA ILIM biasing for programmable overcurrent thresholds, and IAVG-based master-slave averaging. Phase synchronization up to 12-phase operation is enabled via CLKIN/CLKOUT daisy-chaining and PHSMD-configurable timing relationships.
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 conditions. |
| Operating Temp | –40°C to +125°C junction - qualified for industrial and extended-temperature embedded power applications. |
| Package | 32-pin 5mm × 5mm QFN (UH) - exposes thermal pad (Pin 33 = SGND) for low-θJA thermal management. |
| Current Sensing | Lossless DCR or precision shunt - eliminates sense resistor power loss while maintaining ±1.25mV offset over full temp range. |
Pinout & Package
Package: 32-lead plastic QFN (UH), 5mm × 5mm, exposed thermal pad (Pin 33 = SGND), RoHS-compliant lead-free finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC (Pin 1) | Internal LDO supply input | 3V–5.5V chip supply; requires local 0.1µF–1µF ceramic bypass to SGND. |
| FB1/FB2 (Pins 2, 8) | Error amplifier inverting inputs | Connect to resistor divider from VSNSOUT or remote VOUT; sets regulated output voltage. |
| COMP1/COMP2 (Pins 3, 7) | Error amplifier outputs | Drive external gate drivers; low-impedance op-amp outputs-must not be wired in parallel unless configured as master/slave. |
| 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 errors. |
| FREQ (Pin 10) | Frequency programming node | Sources 20µA; resistor to SGND sets fSW from 250kHz–2.25MHz; logic level selects preset 600kHz/1MHz when CLKIN = low. |
| CLKIN/CLKOUT (Pins 11, 12) | Phase synchronization interface | Accepts 250kHz–2.25MHz external clock; CLKOUT enables daisy-chained multi-controller timing alignment. |
| PHSMD (Pin 13) | Phase relationship control | Voltage-selectable 120°/180°/240° phase offsets between CH1, CH2, and CLKOUT for optimal ripple cancellation. |
| ISNS1P/ISNS1N (Pins 22, 21) | Channel 1 current sense inputs | Accept DCR voltage or shunt resistor differential; enable per-phase current monitoring and balancing. |
| ILIM1/ILIM2 (Pins 23, 18) | Overcurrent threshold set | 20µA current source; resistor to SGND programs OC trip point (e.g., 1.2V = 60mV sense threshold). |
| RUN1/RUN2 (Pins 24, 17) | Channel enable inputs | Logic-high (>2.25V) enables channel; <2V forces shutdown; internal 1.5µA pull-up simplifies sequencing. |
| PWM1/PWM2 (Pins 25, 16) | Three-state gate drive outputs | Directly interface with three-state-compatible gate drivers (e.g., LTC4449); high-Z during fault or soft-start. |
| IAVG (Pin 28) | Average current bus | Master-phase averaged current output; tie together across multiple ICs for accurate inter-phase current sharing. |
| PGOOD1/PGOOD2 (Pins 27, 14) | Open-drain power-good indicators | Assert low after 30µs delay when VOUT deviates >±10% from regulation-supports system-level power sequencing. |
| TRACK/SS1/SS2 (Pins 32, 9) | Soft-start and tracking inputs | 2.5µA internal current source charges external capacitor for controlled ramp; also accepts tracking voltage for coordinated multi-rail startup. |
Key Features
| Feature | Design Value |
|---|---|
| Dual differential remote sense | VSNSP/VSNSN amplifier with ±2mV offset and 40MHz unity-gain bandwidth enables <1% load regulation error at point-of-load. |
| Programmable current limit | ILIM pins source 20µA; resistor-to-SGND sets precise overcurrent threshold independent of temperature drift. |
| Prebiased load startup | Inductor current reversal disabled during soft-start-prevents reverse current flow into powered loads like hot-swap backplanes. |
| 128-cycle overcurrent lockout | Requires 128 consecutive fault cycles before shutdown; includes 7-cycle hysteresis to reject transient noise-induced trips. |
| Line feedforward compensation | VINSNS pin modulates PWM comparator ramp in real time-reduces line-step overshoot by >50% vs. standard voltage-mode controllers. |
Applications
| High-Current Distributed Power Systems | DSP, FPGA and ASIC Supplies |
|---|---|
Use Scenario: 48V intermediate bus converted to 1.2V/60A for AI accelerator card with strict ripple and transient response requirements. IC Role / Device Role / Timing Role: Dual-phase controller orchestrating parallel DrMOS stages (e.g., TDA21220), using IAVG bus and PHSMD for interleaved 180° timing to minimize input/output capacitor RMS current. Use Value: Achieves <15mV output deviation under 30A/µs load step (per G05), reducing bulk capacitance by 40% versus single-phase designs. | Use Scenario: Multi-rail power tree for Xilinx Kria KV260 with 1.0V core, 0.85V memory, and 1.8V I/O supplies requiring synchronized startup. IC Role / Device Role / Timing Role: LTC3861IUH-1#PBF controls primary 1.0V rail; TRACK/SS1 drives secondary rails via resistor dividers for ratiometric or coincident tracking per G14/G15. Use Value: Enables <±10mV inter-rail tracking tolerance during startup-critical for avoiding I/O latch-up in mixed-voltage SoCs. |
| Datacom and Telecom Systems | Industrial Power Supplies |
Use Scenario: 12V-to-3.3V/25A conversion in packet processing module with 48V backup battery switchover and EMI constraints. IC Role / Device Role / Timing Role: Configured as 2-phase controller with CLKIN synchronized to system clock; FREQ pin set to 1.2MHz to shrink magnetics and meet CISPR-32 Class B conducted EMI limits. Use Value: 1.2MHz operation reduces inductor size by 65% vs. 300kHz while maintaining >92% peak efficiency (per G08). | Use Scenario: DIN-rail mounted PLC power supply delivering 5V/10A and 24V/3A from 24–48V DC input with extended temperature operation. IC Role / Device Role / Timing Role: LTC3861IUH-1#PBF operates in independent dual-output mode (RUN1/RUN2 separately controlled); CONFIG pin tied to SGND for optimized line feedforward across wide VIN range. Use Value: –40°C to +125°C qualification ensures reliable startup at cold ambient; VINSNS feedforward maintains <0.5% line regulation from 24V to 48V input. |
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 |
|---|---|---|---|
| LTC3860IUH#PBF | Pin-to-pin compatible; lacks dual differential sense amplifiers (single VSNSOUT only); no TRACK/SS2 pin. | Suitable for single-output, single-sense-point applications; cannot support independent dual-rail tracking. | Select LTC3860IUH#PBF only if dual remote sensing and rail tracking are unnecessary-reduces BOM count but sacrifices flexibility. |
| MP2918GL-Z | Monolithic dual-phase controller (integrated MOSFET drivers); fixed 600kHz/1MHz frequencies; no external CLKIN sync or DCR sensing support. | Better suited for cost-sensitive, space-constrained designs where external drivers are undesirable and frequency flexibility is secondary. | Choose MP2918GL-Z for simplified layout and lower component count in non-critical telecom edge nodes; avoid where DCR sensing or >1MHz operation is required. |
Compared with LTC3860IUH#PBF, LTC3861IUH-1#PBF adds dual differential sensing and rail tracking-enabling tighter multi-rail coordination. Versus MP2918GL-Z, it trades integration for design flexibility: external driver support, programmable frequency, and lossless current sensing allow higher efficiency and thermal scalability in high-power systems.
Availability
LTC3861IUH-1#PBF is available at Aetrix Electronics and suitable for high-current distributed power systems, DSP/FPGA core supplies, and datacom/telecom DC/DC converters requiring stable component supply, long-term lifecycle assurance, and industrial temperature grade performance.
Supply support for LTC3861IUH-1#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.
The LTC3861IUH-1#PBF belongs to Linear's PolyPhase® controller family, engineered specifically for high-efficiency, high-current, multiphase buck conversion in infrastructure and computing applications demanding precise current sharing and fast transient response.
FAQ
What is the maximum supported switching frequency for the LTC3861IUH-1#PBF?
The LTC3861IUH-1#PBF supports a programmable switching frequency range from 250kHz to 2.25MHz. This is achieved either by connecting a resistor from the FREQ pin to SGND (with CLKIN floating or high), or by synchronizing to an external clock signal applied to CLKIN within that same frequency band. The upper limit of 2.25MHz enables compact magnetics and fast transient response in space-constrained applications.
Does the LTC3861IUH-1#PBF support prebiased load startup?
Yes, the LTC3861IUH-1#PBF safely powers prebiased loads by disabling inductor current reversal during soft-start. This prevents reverse current flow into an already-powered output rail-a critical requirement in hot-swap and redundant power architectures. The behavior is inherent to the controller's architecture and requires no external configuration beyond standard soft-start capacitor setup on TRACK/SS1 or TRACK/SS2.
How does current sharing work across multiple LTC3861IUH-1#PBF controllers?
Current sharing across multiple LTC3861IUH-1#PBF controllers is implemented via the IAVG pin. In master-slave configuration, the master IC's IAVG pin outputs a voltage proportional to its average inductor current. All slave IAVG pins are tied together, and each phase compares its sensed current against this shared average using internal integrators. The resulting correction is summed with the COMP voltage to adjust duty cycle-ensuring balanced current distribution across up to 12 phases.
Can the LTC3861IUH-1#PBF operate with only one phase active?
Yes, the LTC3861IUH-1#PBF can operate in single-phase mode. Either RUN1 or RUN2 can be held low to disable one channel while the other remains fully functional. When only one channel is active, the unused COMP pin must be left unconnected or pulled to VCC (not grounded) to three-state it. The remaining channel retains full functionality-including remote sensing, programmable frequency, and overcurrent protection-as documented in the LTC3861IUH-1#PBF datasheet.
What is the purpose of the CONFIG pin on the LTC3861IUH-1#PBF?
The CONFIG pin on the LTC3861IUH-1#PBF configures the line feedforward multiplier to maintain consistent modulator gain across varying input voltages and switching frequencies. It can be tied to VCC, SGND, or left floating (internally pulled to SGND) to select among three feedforward scaling options. Proper CONFIG pin selection ensures optimal line transient response and stable loop gain-especially important in wide-VIN applications like 24V–48V industrial supplies.
LTC3861IUH-1#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 32-WFQFN Exposed Pad
- Packaging:
- Tube
- 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#PBF FAQ
1.How can I place an order for LTC3861IUH-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3861IUH-1#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 LTC3861IUH-1#PBF reliable?
The price and inventory of LTC3861IUH-1#PBF 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#PBF is usually 5 days.
3.What payment methods are accepted for LTC3861IUH-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3861IUH-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3861IUH-1#PBF?
LTC3861IUH-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3861IUH-1#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 LTC3861IUH-1#PBF?
For technical support, including LTC3861IUH-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3861IUH-1#PBF requirements.
6.How does Aetrix verify that LTC3861IUH-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3861IUH-1#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 LTC3861IUH-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3861IUH-1#PBF?
All LTC3861IUH-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3861IUH-1#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 LTC3861IUH-1#PBF part is unused and in its original packaging.
Return procedure for LTC3861IUH-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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