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Analog Devices Inc. LTC3731IUH#PBF
- Part No.:
- LTC3731IUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3731IUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,250
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Product details
Overview
LTC3731IUH#PBF from Analog Devices (formerly Linear Technology) is a 3-phase, synchronous buck switching regulator controller driving external N-channel MOSFETs in fixed-frequency current-mode operation. It delivers up to 55A output at 1.35V with ±5% phase current matching, 0.6V–5.5V adjustable VOUT, and 250kHz–600kHz per-phase switching frequency. Used in high-current DC/DC power supplies for desktop/server CPUs and VRMs.
For engineers reviewing the LTC3731IUH#PBF datasheet, LTC3731IUH#PBF pinout, LTC3731IUH#PBF application, or LTC3731IUH#PBF equivalent, key selection criteria include its 3-phase PolyPhase® architecture, differential remote sensing capability, Stage Shedding™/Burst Mode® light-load optimization, OPTI-LOOP® compensation, and support for up to 12-phase expansion via CLKOUT and PLLIN synchronization.
Technical Context
The LTC3731IUH#PBF implements a constant-frequency, peak-current-mode control loop with three independent channels, each featuring dedicated SENSE+/- inputs, TG/BG drivers, and 120° phase interleaving. Its error amplifier (EAIN) compares feedback against a ±1% over temperature 0.6V reference, while ITH serves as the shared compensation node controlling all three current comparators.
It integrates a precision differential amplifier (IN+/IN− → DIFFOUT) for true remote sensing, a phase-locked loop (PLLIN/PLLFLTR) for frequency synchronization or voltage-controlled tuning, and configurable protection including short-circuit shutdown timer (via RUN/SS), overvoltage soft latch, and adjustable undervoltage lockout (UVADJ).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VOUT Range | 0.6V to 5.5V without diffamp; 0.6V to (VCC – 1.2V) with diffamp - enables precise regulation across standard CPU/core voltages. |
| Switching Frequency | 250kHz to 600kHz per phase - balances efficiency, thermal design, and transient response; PLL-synchronizable. |
| Current Matching | ±5% output current matching between phases - reduces thermal imbalance and allows smaller inductors/MOSFETs. |
| VREF Accuracy | ±1% over –40°C to +85°C - ensures stable output voltage under industrial temperature conditions. |
| Differential Sensing Gain | 0.995–1.005 V/V with 50–70dB CMRR - rejects PCB trace IR drops and ground noise for accurate point-of-load regulation. |
| Driver Output Capability | TG/BG rise/fall times ≤90ns into 3300pF - supports fast-switching GaN/SiC or low-Qg MOSFETs without excessive gate drive loss. |
| Protection Features | Adjustable UVLO (UVADJ), timed short-circuit shutdown (RUN/SS), overvoltage soft latch, current foldback - enables robust system-level fault handling. |
Pinout & Package
The LTC3731IUH#PBF is housed in a 32-lead, 5mm × 5mm plastic QFN package with exposed die attach pad (Pin 33) soldered to SGND. Thermal resistance θJA = 34°C/W enables high-power density layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TG1–TG3 | Top gate drivers | Floating high-side N-MOSFET gate outputs; require bootstrap capacitors tied to BOOSTn/SWn nodes. |
| BG1–BG3 | Bottom gate drivers | Ground-referenced low-side N-MOSFET gate outputs; swing from PGND to VCC. |
| SENSE1±–SENSE3± | Per-phase current sense inputs | Differential inputs to current comparators; set trip threshold via RSENSE and ITH voltage. |
| IN+, IN− | Differential remote sense inputs | Connect directly to load terminals; enable true point-of-load regulation despite PCB IR drop. |
| DIFFOUT | Differential amplifier output | Drives EAIN to close feedback loop; provides unity-gain buffered remote sense signal. |
| RUN/SS | Soft-start & short-circuit timer | Capacitor sets ramp time to full load; also discharges during output fault to trigger timed shutdown. |
| PLLIN / PLLFLTR | Phase-lock & frequency control | PLLIN accepts external sync clock; PLLFLTR sets oscillator frequency (250–600kHz) or accepts DC voltage for tuning. |
| PHASMD/PGOOD | Phase shift select / Power good indicator | In UH package, shared pin: logic low = 30° CLKOUT phase shift; logic high = 60°; also functions as open-drain PGOOD output. |
Key Features
| Feature | Design Value |
|---|---|
| PolyPhase® 3-phase interleaving | 120° phase separation reduces input/output RMS current by √3, cutting capacitor size and ESR losses by ~75% vs single-phase. |
| Stage Shedding™ mode | Disables two phases below ~10% load, eliminating their gate charge and switching losses while maintaining fixed-frequency operation. |
| Burst Mode® operation | Reduces light-load quiescent current to <100µA by gating entire switching cycles, minimizing switching loss at ultra-low loads. |
| OPTI-LOOP® compensation | Minimizes required output capacitance (COUT) by optimizing loop stability across wide load/transient ranges without external type-II/III networks. |
| Differential remote sensing | IN+/IN− inputs reject common-mode noise and board-level voltage drops, enabling ±0.5% total output regulation accuracy in VRM applications. |
| Configurable protection suite | Independent UVLO (UVADJ), programmable short-circuit timeout (RUN/SS), overvoltage soft latch, and current foldback ensure safe startup and fault recovery. |
Applications
| Desktop & Server VRMs | High-Performance Notebook CPUs |
|---|---|
Use Scenario: Regulating core voltage for multi-core Intel/AMD processors in ATX PSUs and motherboard VRMs. IC Role / Device Role / Timing Role: 3-phase synchronous buck controller managing up to 55A load with phase-interleaved timing to reduce input ripple and improve transient response. Use Value: ±5% current matching ensures balanced thermal loading across MOSFETs and inductors, enabling compact 4-layer PCB designs with minimal heatsinking. |
Use Scenario: Providing tightly regulated 1.0–1.35V core supply for mobile CPUs under dynamic DVFS load profiles. IC Role / Device Role / Timing Role: Current-mode controller using Burst Mode® and Stage Shedding™ to maintain >85% efficiency from 10mA to 45A load range. Use Value: Differential sensing compensates for voltage drop across flex cables and connectors, ensuring ±1% output accuracy at the CPU socket. |
| High-Output DC/DC Power Supplies | Multi-Phase Industrial Power Modules |
Use Scenario: Generating 12V-to-1.2V/60A intermediate bus conversion in telecom rectifiers and base station power systems. IC Role / Device Role / Timing Role: Primary controller coordinating three external MOSFET stages with synchronized CLKOUT output for seamless 6- or 12-phase expansion. Use Value: PLLIN synchronization allows multiple LTC3731IUH#PBF units to operate coherently, reducing input EMI and enabling modular, scalable power architectures. |
Use Scenario: Building field-upgradeable 3–12 phase power modules for FPGA/ASIC acceleration cards requiring <1% output tolerance. IC Role / Device Role / Timing Role: Phase-locked controller providing deterministic timing alignment across distributed power stages via PLLIN and PHASMD configuration. Use Value: Shared ITH node and unified compensation simplify multi-phase loop tuning; exposed SGND pad ensures low-inductance grounding for <10mV noise floor. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-phase synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2940AGQ-PR | Integrated 3-phase controller with embedded gate drivers and PMBus interface; no external diffamp; max fSW = 1MHz. | Targets digital power management systems requiring telemetry and dynamic margining; lacks analog PLL sync and Stage Shedding™. | Select MP2940AGQ-PR when PMBus monitoring, telemetry, or higher switching frequency (>600kHz) is required - not for analog-synchronized legacy VRMs. |
| ISL95836IRZ | Intel VR12.5-compliant 3-phase controller; supports DVID, PROCHOT#, and SVID; fixed 0.6V ref; no user-configurable UVLO. | Designed specifically for Intel CPU platforms with strict VID protocol compliance; no standalone analog diffamp or CLKOUT expansion. | Select ISL95836IRZ only for Intel-based notebooks/desktops requiring native SVID handshake - not for generic high-current DC/DC or non-Intel applications. |
Compared with MP2940AGQ-PR and ISL95836IRZ, the LTC3731IUH#PBF offers superior analog flexibility - including user-programmable UVLO, standalone differential sensing, PLLIN/CLKOUT for multi-chip synchronization, and dual light-load modes - making it ideal for custom high-efficiency, thermally constrained, or non-standard platform designs where digital interface or vendor lock-in is undesirable.
Availability
LTC3731IUH#PBF is available at Aetrix Electronics and suitable for desktop/server VRMs, high-performance notebook CPU power delivery, and high-output industrial DC/DC power supplies requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC3731IUH#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 technical and manufacturing continuity for all Linear power products, including rigorous qualification and long-term product roadmaps.
The LTC3731IUH#PBF belongs to Linear's PolyPhase® controller family, designed specifically for high-current, low-voltage DC/DC conversion in computing and communications infrastructure where thermal density, transient response, and phase current balance are critical.
FAQ
What is the operating temperature range of the LTC3731IUH#PBF?
The LTC3731IUH#PBF is rated for an industrial operating ambient temperature range of –40°C to +85°C. This is confirmed in the "ORDER INFORMATION" table, where the "I" grade suffix denotes the –40°C to +85°C range, and the "UH" package specifies θJA = 34°C/W for reliable thermal performance under sustained 55A loads.
Does the LTC3731IUH#PBF support remote voltage sensing, and how is it implemented?
Yes, the LTC3731IUH#PBF supports true differential remote sensing via dedicated IN+ and IN– pins connected to the load terminals. These feed a precision unity-gain differential amplifier (AV = 0.995–1.005 V/V, CMRR ≥50dB) whose output (DIFFOUT) drives the EAIN error amplifier input - enabling accurate regulation despite PCB trace resistance and ground noise.
How does the LTC3731IUH#PBF manage light-load efficiency?
The LTC3731IUH#PBF offers three selectable light-load modes via the FCB pin: Burst Mode® (FCB floating) for lowest IQ, Stage Shedding™ (FCB = VCC) for fixed-frequency low-noise operation, and Forced Continuous (FCB < 0.6V). Each mode dynamically adjusts switching behavior to minimize gate charge, conduction, and switching losses across the 10mA–55A load range.
Can multiple LTC3731IUH#PBF controllers be synchronized for more than 3 phases?
Yes. The LTC3731IUH#PBF supports up to 12-phase operation via its CLKOUT output and PLLIN input. CLKOUT provides a phase-aligned clock signal; PLLIN accepts that or another external clock to synchronize the internal oscillator. PHASMD pin configures 30° or 60° offset between TG1 and CLKOUT, enabling deterministic interleaving across multiple controllers.
What is the function of the PHASMD/PGOOD pin in the UH package?
In the LTC3731IUH#PBF (UH package), PHASMD and PGOOD share a single pin. When used as PHASMD, it selects 30° (logic low) or 60° (logic high) phase offset between TG1 and CLKOUT. When used as PGOOD, it functions as an open-drain output pulled low if VOUT deviates >±10% for >100µs. The two functions are mutually exclusive and configured by external circuitry.
LTC3731IUH#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:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 3
- Output Phases:
- 3
- Voltage - Supply (Vcc/Vdd):
- 3.8V ~ 7V
- Frequency - Switching:
- 225kHz ~ 680kHz
- Duty Cycle (Max):
- 98.5%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Phase Control, Power Good, Soft Start
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3731IUH#PBF FAQ
1.How can I place an order for LTC3731IUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3731IUH#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 LTC3731IUH#PBF reliable?
The price and inventory of LTC3731IUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3731IUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3731IUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3731IUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3731IUH#PBF?
LTC3731IUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3731IUH#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 LTC3731IUH#PBF?
For technical support, including LTC3731IUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3731IUH#PBF requirements.
6.How does Aetrix verify that LTC3731IUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3731IUH#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 LTC3731IUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3731IUH#PBF?
All LTC3731IUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3731IUH#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 LTC3731IUH#PBF part is unused and in its original packaging.
Return procedure for LTC3731IUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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