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Analog Devices Inc. LTC3731IG#PBF
- Part No.:
- LTC3731IG#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 36-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
LTC3731IG#PBF.pdf
- Description:
- IC REG CTRLR BUCK 36SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,234
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Product details
Overview
LTC3731IG#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 ±1% VREF accuracy over temperature, 120° phase separation per phase, and supports 250kHz–600kHz per-phase switching across desktop/server DC/DC power supplies.
For engineers reviewing the LTC3731IG#PBF datasheet, LTC3731IG#PBF pinout, LTC3731IG#PBF application, or LTC3731IG#PBF equivalent, key selection criteria include phase-matched current sensing (±5% matching), differential remote voltage sensing (IN+/IN−), OPTI-LOOP® compensation, selectable PWM/Burst Mode®/Stage Shedding™ operation, and PLL synchronization for multi-phase scalability.
Technical Context
The LTC3731IG#PBF implements a constant-frequency, current-mode control architecture with three independent phase channels, each featuring dedicated SENSE+ and SENSE− inputs, TG/BG gate drivers, and synchronized 120° phase offset. Its error amplifier (EAIN) compares feedback against a 0.6V internal reference, while ITH serves as the shared compensation node controlling all three current comparators.
Phase-locking is achieved via PLLIN input and PLLFLTR filter pin, enabling frequency locking from 250kHz to 600kHz; the differential amplifier (IN+/IN− → DIFFOUT) provides true remote sensing with 0.995–1.005 gain, <5mV offset, and 50–70dB CMRR - critical for VRM applications where PCB IR drop must be rejected.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | 3-phase synchronous buck controller with external N-MOSFETs |
| Switching Frequency | 250kHz–600kHz per phase, PLL-synchronizable, 120° phase shift |
| Reference Voltage | 0.600V ±1% over –40°C to +85°C operating range |
| Current Sensing | Three independent differential sense pairs (SENSE1±/2±/3±); ±5% max current match at full scale |
| Differential Sensing | IN+/IN− inputs with 0.995–1.005 gain, <5mV offset, 50–70dB CMRR |
| Output Voltage Range | 0.6V–5.5V without diffamp; 0.6V–(VCC–1.2V) with diffamp |
| Protection Features | Short-circuit shutdown timer (defeatable), overvoltage soft latch, undervoltage lockout (UVADJ adjustable), current foldback |
Pinout & Package
Package: 36-lead plastic SSOP (0.209" wide), RoHS-compliant, rated for –40°C to +85°C ambient operation. Exposed thermal pad not present (G-package).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Main supply input | 4.5V–7V logic/driver supply; decoupling critical for gate drive stability |
| RUN/SS | Soft-start & short-circuit timer | Capacitor sets ramp time and latches off after timeout under severe overload |
| ITH | Error amplifier output | Shared compensation node for all three current loops; sets peak inductor current threshold |
| PGOOD | Power-good indicator | Open-drain output asserting low if VOUT deviates >±10% for ≥100µs |
| IN+, IN− | Differential sense inputs | Enable true remote sensing at load terminals; reject PCB trace IR drop |
| SENSE1+ to SENSE3− | Per-phase current sense inputs | Three independent differential pairs for phase-current monitoring and balancing |
| TG1–TG3, BG1–BG3 | Top/bottom gate drivers | Drive external N-MOSFETs; TG outputs are floating, BG referenced to PGND |
| PLLIN, PLLFLTR | Phase-lock interface | Accept external sync signal or set frequency via DC voltage (0–2.4V = 250–600kHz) |
| FCB | Operating mode select | Logic-controlled: float = Burst Mode®, VCC = Stage Shedding™, <0.6V = forced continuous |
| UVADJ | Undervoltage lockout adjust | Set shutdown threshold by resistor divider; trips when <1.2V applied |
Key Features
| Feature | Design Value |
|---|---|
| 3-Phase PolyPhase® Architecture | Reduces RMS input/output capacitor currents by √3×, cutting conduction losses and thermal stress on bulk caps |
| OPTI-LOOP® Compensation | Minimizes required output capacitance by optimizing loop response without external type-II/type-III networks |
| Selectably Optimized Light-Load Efficiency | Burst Mode® (low noise suppression), Stage Shedding™ (constant frequency), or forced continuous - user-selectable via FCB pin |
| True Differential Remote Sensing | IN+/IN− inputs with precision resistors eliminate ground-loop errors and enable accurate regulation at point-of-load in high-current VRMs |
| Phase Scalability to 12 Phases | CLKOUT and PHASMD pins allow daisy-chaining multiple LTC3731 controllers for 6- or 12-phase systems with precise inter-phase alignment |
Applications
| Desktop Server VRM | High-Performance Notebook CPU Power |
|---|---|
Use Scenario: Regulating 1.35V/55A core voltage for dual-socket Xeon server platforms with tight transient response requirements. IC Role / Device Role / Timing Role: 3-phase synchronous buck controller coordinating six external MOSFETs with 120° interleaving and differential remote sensing at CPU socket. Use Value: Achieves <90% efficiency at full load while reducing input ripple current by ~90% versus single-phase design, easing input capacitor selection and thermal management. |
Use Scenario: Delivering stable 1.0V–1.35V core power to mobile Intel Core i7/i9 processors under dynamic load from 0A to 45A. IC Role / Device Role / Timing Role: Primary multiphase controller managing phase shedding and burst mode transitions to maintain regulation during rapid P-state changes. Use Value: Enables <85% light-load efficiency via Stage Shedding™ and eliminates audible coil whine through constant-frequency operation down to 1% load. |
| High-Output Industrial DC/DC Module | GPU Power Delivery System |
Use Scenario: 12V-to-3.3V/60A intermediate bus converter in industrial PLC backplane with strict EMI and thermal constraints. IC Role / Device Role / Timing Role: Fixed-frequency 3-phase controller with PLL synchronization to system clock, minimizing beat frequencies and aiding EMI filtering. Use Value: Phase interleaving reduces input capacitor RMS current by factor of √3, allowing smaller, lower-ESR ceramics and shrinking overall footprint by 35%. |
Use Scenario: 12V-to-0.85V/80A GPU core rail in gaming/workstation graphics cards requiring sub-10mV load regulation and fast transient recovery. IC Role / Device Role / Timing Role: Controller with differential sensing (IN+/IN−) and ±5% per-phase current matching to balance thermal loading across parallel inductors/MOSFETs. Use Value: Delivers ±0.5% total output voltage regulation under 50A/µs load steps via fast-response current-mode control and OPTI-LOOP® compensation. |
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 |
|---|---|---|---|
| ISL6322IRZ | Integrated MOSFET drivers only; no external FET support; 4-phase capable; requires external DAC for VID interface | Designed for Intel VRM specifications with integrated PMBus; lacks differential remote sensing | Choose ISL6322IRZ for VID-based CPU power with PMBus telemetry; avoid if differential sensing or discrete FET flexibility is required. |
| MP2940AGQSE | Single-chip 3-phase controller with integrated drivers; supports DCR sensing only; no PLL sync; 400kHz max frequency | Targeted at cost-sensitive notebook applications; lacks UVADJ programmability and stage shedding | Choose MP2940AGQSE for compact, low-BOM-count designs where 600kHz operation and phase scalability are not needed. |
Compared with ISL6322IRZ and MP2940AGQSE, the LTC3731IG#PBF uniquely combines external N-MOSFET flexibility, differential remote sensing, PLL synchronization, and user-selectable light-load modes - making it optimal for high-reliability, thermally constrained, or custom VRM designs requiring precise point-of-load regulation.
Availability
LTC3731IG#PBF is available at Aetrix Electronics and suitable for desktop server VRMs, high-performance notebook CPU power, industrial DC/DC modules, GPU power delivery systems, and telecom base station POL converters requiring stable component supply across extended temperature ranges.
Supply support for LTC3731IG#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 its high-performance power management portfolio with rigorous automotive and industrial qualification standards.
The LTC3731IG#PBF belongs to Linear's PolyPhase® controller family, engineered specifically for high-current, low-voltage DC/DC conversion in computing and communications infrastructure where thermal density, transient response, and layout robustness are critical.
FAQ
What is the operating temperature range for the LTC3731IG#PBF?
The LTC3731IG#PBF is specified for –40°C to +85°C ambient operation, validated across full electrical parameters including ±1% VREF accuracy, ±5% current matching, and stable 250kHz–600kHz PLL operation. This industrial-grade rating ensures reliability in server chassis and embedded computing environments where airflow and thermal gradients are challenging.
How does the LTC3731IG#PBF achieve precise output voltage regulation under high-current loads?
The LTC3731IG#PBF achieves precise regulation using its integrated differential amplifier with IN+ and IN− inputs, which senses voltage directly at the load terminals - rejecting PCB trace resistance errors. Combined with 0.600V ±1% internal reference and OPTI-LOOP® compensation, it maintains ±0.5% total output accuracy even at 55A with 120° phase interleaving reducing output ripple.
Can the LTC3731IG#PBF synchronize to an external clock source?
Yes, the LTC3731IG#PBF supports external synchronization via the PLLIN pin, which accepts TTL/CMOS-compatible clock signals. Its internal phase-locked loop locks the rising edge of TG1 to the PLLIN rising edge, enabling deterministic timing across multiple controllers - essential for scaling to 6- or 12-phase systems without beat-frequency EMI.
What protection features does the LTC3731IG#PBF include for system reliability?
The LTC3731IG#PBF integrates short-circuit shutdown with defeatable timed latch-off, overvoltage soft latch, adjustable undervoltage lockout (via UVADJ), current foldback for MOSFET protection, and thermal shutdown. The RUN/SS pin serves dual role: soft-start ramp and short-circuit timeout - discharging on sustained <70% VOUT to disable drivers after programmable delay.
How does the FCB pin affect light-load efficiency in the LTC3731IG#PBF?
The FCB pin selects among three light-load strategies: floating enables Burst Mode® (lowest IQ, periodic sleep), tying to VCC activates Stage Shedding™ (constant frequency, disables phases below 10% load), and grounding forces continuous conduction. Each mode trades off efficiency, noise, and transient response - allowing optimization for server (Stage Shedding™) vs. audio-sensitive (Burst Mode®) applications.
LTC3731IG#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- PolyPhase®
- Package/Case:
- 36-SSOP (0.209", 5.30mm Width)
- 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:
- 36-SSOP
LTC3731IG#PBF FAQ
1.How can I place an order for LTC3731IG#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3731IG#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 LTC3731IG#PBF reliable?
The price and inventory of LTC3731IG#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3731IG#PBF is usually 5 days.
3.What payment methods are accepted for LTC3731IG#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3731IG#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3731IG#PBF?
LTC3731IG#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3731IG#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 LTC3731IG#PBF?
For technical support, including LTC3731IG#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3731IG#PBF requirements.
6.How does Aetrix verify that LTC3731IG#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3731IG#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 LTC3731IG#PBF meets industry standards.
7.What is the process for return or replacement of LTC3731IG#PBF?
All LTC3731IG#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3731IG#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 LTC3731IG#PBF part is unused and in its original packaging.
Return procedure for LTC3731IG#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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