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Analog Devices Inc. LTC3731CUH#PBF
- Part No.:
- LTC3731CUH#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 32-WFQFN Exposed Pad
- Datasheet:
-
LTC3731CUH#PBF.pdf
- Description:
- IC REG CTRLR BUCK 32QFN
- Quantity:
- Payment:
- Shipping:
Inventory:298
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Product details
Overview
LTC3731CUH#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 output voltage, and 250kHz–600kHz per-phase switching frequency-optimized for high-current DC/DC power supplies in desktop/server applications.
For engineers reviewing the LTC3731CUH#PBF datasheet, LTC3731CUH#PBF pinout, LTC3731CUH#PBF application, or LTC3731CUH#PBF equivalent, key selection criteria include its PolyPhase® architecture, differential remote sensing capability, OPTI-LOOP® compensation, Stage Shedding™/Burst Mode® light-load optimization, and 32-pin 5mm × 5mm QFN thermal performance (θJA = 34°C/W).
Technical Context
The LTC3731CUH#PBF implements a constant-frequency, current-mode control loop with three independent PWM channels operating at 120° phase separation. Each channel uses an internal transconductance error amplifier (gm = 4–7 mmho), ITH-based current threshold modulation, and dedicated SENSE+/- inputs for per-phase current sensing with ±5% matching across phases.
It integrates a PLL-based synchronization system (PLLIN/PLLFLTR) enabling frequency locking from 250kHz to 600kHz, plus a precision differential amplifier (AV = 0.995–1.005 V/V, CMRR = 50–70 dB) for true remote sensing of both VOUT+ and VOUT−. The UH package ties PHASMD and PGOOD functions to a single pin, supporting 6- or 12-phase expansion via CLKOUT.
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 with external clock |
| Output Voltage Range | 0.6V–5.5V without diffamp; 0.6V–(VCC–1.2V) with diffamp |
| VREF Accuracy | ±1% over temperature (0°C to 70°C for C-grade) |
| Current Sensing | Differential SENSE+/- inputs per phase; max threshold 60–90mV with ±5% matching |
| Thermal Performance | θJA = 34°C/W (UH QFN); exposed pad = SGND, requires PCB soldering |
| Protection Features | Short-circuit shutdown timer, overvoltage soft latch, adjustable UVLO (1.13–1.23V), current foldback |
Pinout & Package
Package: 32-lead (5mm × 5mm) plastic QFN (UH), exposed pad = SGND, must be soldered to PCB for thermal and signal integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BOOST1–BOOST3 | Floating top-gate supply | Drives TG1–TG3 via bootstrapped capacitors; swing = VCC to VCC + VIN |
| TG1–TG3 | Top N-MOSFET gate drivers | High-current floating outputs; voltage swing referenced to SWx nodes |
| BG1–BG3 | Bottom N-MOSFET gate drivers | Ground-referenced outputs; swing = 0V to VCC |
| SENSE1±–SENSE3± | Per-phase current sense inputs | Differential inputs to current comparators; set trip threshold with RSENSE |
| IN+, IN− | Differential remote sense inputs | Connect to load terminals for true VOUT regulation; reject ground noise |
| DIFFOUT | Differential amplifier output | Feeds EAIN; enables precise feedback with external resistor divider |
| ITH | Error amplifier output / compensation node | Controls all three current thresholds; used for OPTI-LOOP® compensation |
| PLLIN / PLLFLTR | PLL synchronization interface | Accepts external clock (PLLIN); PLLFLTR sets oscillator frequency (0–2.4V = 250–600kHz) |
| PHASMD/PGOOD | Phase shift select / power-good indicator | In UH package: logic level selects CLKOUT phase (30°/60°); open-drain PGOOD with 100µs fault delay |
| RUN/SS | Soft-start / run enable / short-circuit timer | Capacitor sets ramp time and short-circuit timeout; discharges under severe overload |
| UVADJ | Adjustable undervoltage lockout input | Threshold = 1.13–1.23V; holds RUN/SS low until UVADJ > 1.2V |
| VCC | Main supply and gate drive power | 4.5V–7V; powers logic and high-current drivers; requires local 0.1µF decoupling to PGND |
| PGND | Power ground | Direct connection point for bottom MOSFET sources and CIN (–) terminal |
| SGND | Signal ground | Must be routed separately to PGND; exposed pad = SGND in UH package |
Key Features
| Feature | Design Value |
|---|---|
| PolyPhase® 3-phase architecture | 120° phase interleaving reduces input/output RMS current by ~58%, improving capacitor lifetime and thermal design |
| Differential remote sensing (IN+/IN−) | Rejects PCB IR drop and ground noise; enables accurate regulation at point-of-load in VRM systems |
| Stage Shedding™ and Burst Mode® | Automatically disables 2/3 phases below ~10% load (shedding) or enters burst cycles at ultra-light loads for peak efficiency |
| OPTI-LOOP® compensation | Minimizes required output capacitance by optimizing loop stability with minimal external components |
| Programmable phase synchronization | PLLIN/PLLFLTR allows daisy-chaining up to 12-phase systems using CLKOUT and PHASMD-selectable timing |
| Robust protection suite | Includes short-circuit shutdown timer, overvoltage soft latch, current foldback, and thermal shutdown (TJMAX = 125°C) |
Applications
| Server VRM Power Delivery | Desktop CPU Core Supply |
|---|---|
Use Scenario: High-current, low-voltage core supply for dual-socket Xeon platforms requiring tight regulation under dynamic load steps. IC Role / Device Role / Timing Role: 3-phase synchronous buck controller managing 55A+ output with differential remote sensing at CPU socket. Use Value: ±5% phase current matching minimizes thermal stress on individual inductors/MOSFETs; 120° interleaving cuts input ripple current by >90% vs single-phase. |
Use Scenario: Main 12V-to-1.2V conversion for high-performance gaming desktop CPUs with transient response demands. IC Role / Device Role / Timing Role: Primary multiphase controller delivering fast load-step response (<10µs) via high-bandwidth error amplifier and low-latency current sensing. Use Value: OPTI-LOOP® compensation enables stable operation with <1000µF total COUT; Burst Mode® maintains >85% efficiency at 1A load. |
| Notebook GPU Power Rail | Industrial FPGA Core Supply |
Use Scenario: Compact, thermally constrained GPU core supply in thin-and-light notebooks requiring high power density. IC Role / Device Role / Timing Role: 3-phase controller operating at 600kHz per phase to shrink magnetics while maintaining efficiency. Use Value: 5mm × 5mm QFN package with θJA = 34°C/W enables direct heatsink mounting; Stage Shedding™ eliminates switching loss at idle. |
Use Scenario: Reliable, long-lifetime core supply for Xilinx/Intel FPGAs in industrial PLCs where thermal derating and voltage accuracy are critical. IC Role / Device Role / Timing Role: Controller with ±1% VREF accuracy and differential sensing ensures stable 0.85V core rail despite board-level voltage drops. Use Value: Adjustable UVLO (via UVADJ) and programmable short-circuit timeout prevent false trips in noisy factory environments. |
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-T | 4-phase controller; supports Intel VR12.5; no integrated differential amplifier; requires external DAC for remote sense | Targeted at Intel CPU VRMs with strict VID protocol compliance; less flexible for custom FPGA/GPU rails | Choose ISL6322IRZ-T only when Intel VR12.5 compliance and 4-phase scaling are mandatory |
| MP2940AGQKT-Z | 3-phase controller with integrated MOSFET drivers only; no PLL sync; fixed 500kHz frequency; lower VREF accuracy (±1.5%) | Suitable for cost-sensitive embedded systems; lacks differential sensing and phase extension capability | Choose MP2940AGQKT-Z for simplified BOM in non-VRM applications where remote sensing and PLL sync are unnecessary |
Compared with ISL6322IRZ-T and MP2940AGQKT-Z, the LTC3731CUH#PBF uniquely combines differential remote sensing, PLL-based multi-phase synchronization, and Stage Shedding™/Burst Mode®-enabling superior accuracy, scalability, and light-load efficiency in custom high-current DC/DC designs.
Availability
LTC3731CUH#PBF is available at Aetrix Electronics and suitable for server VRM power delivery, desktop CPU core supplies, and industrial FPGA core rails requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LTC3731CUH#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 the LTC portfolio.
The LTC3731CUH#PBF belongs to Linear's high-performance PolyPhase® controller family, designed specifically for high-current, low-voltage DC/DC conversion in computing and communications infrastructure where thermal efficiency, transient response, and layout robustness are critical.
FAQ
What is the operating temperature range for the LTC3731CUH#PBF?
The LTC3731CUH#PBF is rated for 0°C to 70°C ambient operation (C-grade). Its junction temperature must not exceed 125°C, and with θJA = 34°C/W, it supports high-power density layouts when the exposed SGND pad is properly soldered to the PCB thermal plane. Derating curves in the datasheet define safe power limits across this range.
How does the LTC3731CUH#PBF implement remote voltage sensing?
The LTC3731CUH#PBF uses dedicated IN+ and IN− pins connected directly to the load's positive and negative terminals, feeding a precision unity-gain differential amplifier (AV = 0.995–1.005 V/V, CMRR ≥ 50 dB). Its DIFFOUT pin drives the EAIN feedback node, enabling true point-of-load regulation that rejects PCB trace resistance and ground noise-critical for VRM accuracy.
Can the LTC3731CUH#PBF be synchronized to an external clock source?
Yes-the LTC3731CUH#PBF supports full PLL-based synchronization via the PLLIN pin, which accepts an external clock signal. The internal phase detector locks the rising edge of TG1 to the PLLIN rising edge. The PLLFLTR pin serves as both the PLL filter node and a DC voltage input (0–2.4V) to set frequency from 250kHz to 600kHz without external clocking.
What are the key differences between Burst Mode® and Stage Shedding™ operation on the LTC3731CUH#PBF?
Burst Mode® (FCB floating) pulses the output in bursts at light loads to minimize switching loss, yielding highest efficiency but introducing low-frequency output ripple. Stage Shedding™ (FCB = VCC) disables two phases entirely below ~10% load, maintaining constant 250kHz–600kHz frequency with lower noise-ideal for noise-sensitive applications where efficiency trade-offs are acceptable.
Is the PHASMD pin functional in the LTC3731CUH#PBF package?
In the LTC3731CUH#PBF (32-pin QFN), the PHASMD and PGOOD functions share a single pin per the datasheet. Driving this pin low yields 30° CLKOUT phase shift; driving it high yields 60°. This dual-function pin enables compact 6- or 12-phase system expansion while conserving package real estate-unlike the SSOP version where PHASMD is separate.
LTC3731CUH#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:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-QFN (5x5)
LTC3731CUH#PBF FAQ
1.How can I place an order for LTC3731CUH#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3731CUH#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 LTC3731CUH#PBF reliable?
The price and inventory of LTC3731CUH#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3731CUH#PBF is usually 5 days.
3.What payment methods are accepted for LTC3731CUH#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3731CUH#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3731CUH#PBF?
LTC3731CUH#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3731CUH#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 LTC3731CUH#PBF?
For technical support, including LTC3731CUH#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3731CUH#PBF requirements.
6.How does Aetrix verify that LTC3731CUH#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3731CUH#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 LTC3731CUH#PBF meets industry standards.
7.What is the process for return or replacement of LTC3731CUH#PBF?
All LTC3731CUH#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3731CUH#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 LTC3731CUH#PBF part is unused and in its original packaging.
Return procedure for LTC3731CUH#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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