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Analog Devices Inc. LTC3866EUF#PBF
- Part No.:
- LTC3866EUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3866EUF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:933
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Product details
Overview
LTC3866EUF#PBF from Analog Devices is a single-phase current-mode synchronous step-down switching regulator controller driving all-N-channel MOSFETs. It enables sub-milliohm DCR sensing (down to 0.2 mΩ), supports 4.5V–38V input, delivers 0.6V–3.5V output with ±0.5% accuracy, and operates at programmable 250kHz–770kHz frequency - used in high-current server VRMs and telecom power supplies.
For engineers reviewing the LTC3866EUF#PBF datasheet, LTC3866EUF#PBF pinout, LTC3866EUF#PBF application, or LTC3866EUF#PBF equivalent, key selection considerations include its dual-current-sense architecture for low-DCR inductors, differential remote sensing capability, DCR temperature compensation via ITEMP, and support for Burst Mode®, pulse-skipping, and forced CCM operation.
Technical Context
The LTC3866EUF#PBF implements a proprietary current-mode control architecture with two independent positive sense inputs (SNSD+, SNSA+) that process inductor DCR signals with 14 dB SNR improvement. Its error amplifier regulates VFB against a precision 0.6 V reference, while the ITH pin sets peak inductor current via voltage-controlled current comparator trip threshold.
It integrates a high-speed differential amplifier (AV = 0.999–1.002 V/V, GBW = 3 MHz) for remote voltage sensing, programmable current limit (10–30 mV in 5 mV steps via ILIM), and on-chip gate drivers with 1.1 Ω BG pull-down and 1.5 Ω TG pull-down RDS(ON). Thermal shutdown triggers at junction temperatures exceeding 125°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 38 V - supports wide bus voltages including 5 V, 12 V, 24 V, and 36 V battery or industrial rails. |
| Output Voltage Accuracy | ±0.5 % at 0.6 V reference - ensures tight regulation across load/temperature for CPU/GPU core supplies. |
| Current Sense Threshold | Selectable 10 mV to 30 mV in 5 mV steps - enables precise overcurrent protection with ultra-low-DCR inductors. |
| Switching Frequency | 250 kHz to 770 kHz (programmable via FREQ pin) - balances efficiency, size, and EMI in high-density designs. |
| Differential Amplifier Gain | 0.999–1.002 V/V (±0.1 % gain error) - maintains accurate remote sensing over temperature for <1 % output droop. |
| DCR Temp Compensation | Enabled via ITEMP pin with NTC thermistor - maintains constant current limit despite inductor DCR drift over –40°C to 125°C. |
| Package | 24-lead 4 mm × 4 mm QFN with exposed SGND pad - provides low thermal resistance (θJA = 47°C/W) and compact footprint. |
Pinout & Package
Package: 24-lead (4 mm × 4 mm) plastic QFN with exposed signal ground (SGND) pad (Pin 25), rated for –40°C to 125°C operating junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ITH (Pin 1) | Error amplifier output / current threshold control | Sets peak inductor current by controlling comparator trip point; used for loop compensation and current limiting. |
| VFB (Pin 2) | Feedback input to error amplifier | Receives scaled output voltage (via DIFFOUT/resistive divider) to regulate output against 0.6 V reference. |
| DIFFOUT (Pin 3) | Differential amplifier output | Drives VFB through external resistor divider; enables Kelvin sensing of output voltage at load. |
| DIFFN (Pin 4) | Negative input of diffamp | Connected to load ground plane - critical for accurate remote sensing; must be placed near load return path. |
| DIFFP (Pin 5) | Positive input of diffamp | Connected to output rail near load - completes Kelvin sense pair to reject PCB IR drop errors. |
| SNSD+ (Pin 6) | Main DCR sense positive input | Connects to inductor's DCR network; filter time constant (R×C) must match L/DCR for accurate current sensing. |
| SNS– (Pin 7) | Current comparator negative input | Connected to output node; forms differential pair with SNSD+/SNSA+ for low-noise current measurement. |
| SNSA+ (Pin 8) | Auxiliary DCR sense positive input | Provides second sense path with 5× higher bandwidth (R×C = 1/5 × SNSD+ filter); improves SNR for sub-mΩ DCR. |
| ILIM (Pin 9) | Current limit threshold programming | DC voltage setting max sense threshold (10–30 mV); floating or tied to INTVCC disables limit. |
| CLKOUT (Pin 10) | Internal oscillator clock output | 180° out-of-phase with internal clock; used for synchronization or timing diagnostics. |
| PGND (Pin 11) | Power ground return | Return path for VIN/INTVCC decoupling caps and bottom MOSFET source - must be low-inductance connection. |
| BG (Pin 12) | Bottom gate driver output | Drives NMOS source-follower switch; swings from PGND to INTVCC/EXTVCC - requires low-ESR gate resistor. |
| SW (Pin 13) | Switch node | Connection point for inductor, bottom MOSFET drain, and top MOSFET source; experiences full VIN-to-GND swing. |
| TG (Pin 14) | Top gate driver output | Floating driver referenced to SW; drives top NMOS gate with bootstrapped voltage (up to VIN + INTVCC). |
| BOOST (Pin 15) | Bootstrap capacitor supply | Connects to (+) terminal of bootstrap cap; recharges during BG-on phase to sustain TG drive in high-duty-cycle apps. |
| INTVCC (Pin 16) | Internal 5.5 V regulator output | Powers internal logic and gate drivers; decoupled with 4.7 µF ceramic/tantalum to PGND. |
| VIN (Pin 17) | Main input supply | Primary power source for INTVCC LDO; decouple with 0.1–1 µF ceramic close to pin and PGND. |
| EXTVCC (Pin 18) | External bias supply input | When >4.7 V applied, bypasses INTVCC LDO for higher efficiency; must be |
| ITEMP (Pin 19) | DCR temperature compensation input | Accepts NTC thermistor voltage to scale current limit vs. temperature - floating disables compensation. |
| PGOOD (Pin 20) | Open-drain power-good indicator | Pulled low when VOUT deviates >±10 % from setpoint after 20 µs debounce; requires external pull-up. |
| MODE/PLLIN (Pin 21) | Mode selection or external sync input | Ground = CCM; INTVCC = pulse-skip; float = Burst Mode®; AC signal = PLL sync to external clock. |
| RUN (Pin 23) | Enable/disable control | Threshold 1.22 V (rising); hysteresis 80 mV; internal 1 µA pull-up; drives full shutdown below 1.14 V. |
| TK/SS (Pin 24) | Soft-start or tracking input | 1.25 µA internal current charges external cap for linear ramp; also accepts external voltage for supply tracking. |
| SGND (Pin 25) | Signal ground reference | Exposed pad; must be soldered to PCB ground plane - serves as reference for feedback, compensation, and sensing. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-path DCR current sensing | Combines SNSD+ and SNSA+ signals to achieve 14 dB SNR improvement - enables stable operation with 0.2 mΩ inductors. |
| Programmable current limit | Five discrete thresholds (10/15/20/25/30 mV) set via ILIM pin voltage - allows precise OCP tuning without changing layout. |
| Differential remote sensing | Integrated 3 MHz GBW amplifier with ±2 mV offset - rejects PCB trace resistance errors for <1 % load regulation at 30 A. |
| Three light-load modes | Burst Mode®, pulse-skipping, and forced CCM selectable via MODE/PLLIN - optimizes efficiency across 1 mA–30 A load range. |
| DCR temperature compensation | ITEMP pin accepts NTC voltage to scale current limit - maintains consistent overcurrent protection from –40°C to 125°C. |
| Robust gate drivers | TG/BG drivers with 1.1–2.6 Ω RDS(ON) and 25 ns transition times - supports fast-switching GaN or low-Qg Si MOSFETs. |
Applications
| Server CPU Core Power Supply | Telecom DC-DC Brick |
|---|---|
|
Use Scenario: High-current, low-voltage VRM for x86 or ARM-based server processors requiring dynamic load steps up to 15 A/µs. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing all-N-channel power stage with sub-mΩ DCR inductor sensing. Use Value: Enables >95 % peak efficiency at 30 A/1.5 V while maintaining <±5 mV output deviation under transient loads via differential remote sensing. |
Use Scenario: 48 V input to 3.3 V/12 V dual-output intermediate bus converter in 19-inch rack-mounted telecom equipment. IC Role / Device Role / Timing Role: Single-phase controller implementing pulse-skipping mode to maintain >88 % efficiency at 10 % load while meeting EN55022 Class B EMI. Use Value: Programmable 250–770 kHz frequency avoids AM radio band; EXTVCC support allows efficient bias from auxiliary 5 V rail. |
| Industrial PLC I/O Power | Medical Imaging Power Module |
|
Use Scenario: DIN-rail mounted programmable logic controller supplying isolated 5 V and 24 V rails to field I/O modules in harsh environments. IC Role / Device Role / Timing Role: Main buck controller with DCR temperature compensation to maintain consistent current limit across –40°C to 70°C ambient. Use Value: ITEMP-driven compensation prevents false OCP trips due to inductor DCR drift; ±0.5 % VREF ensures analog sensor accuracy. |
Use Scenario: Compact, low-noise power supply for CT/MRI detector front-end ASICs requiring ultra-stable 1.2 V at 5 A with <10 µVPP ripple. IC Role / Device Role / Timing Role: Synchronous buck controller operating in forced CCM with external clock sync (via MODE/PLLIN) to eliminate beat frequencies. Use Value: Differential sensing eliminates PCB IR drop errors; Burst Mode® disabled ensures zero low-frequency noise in sensitive analog sections. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2940AGQSE-LF-Z | Fixed 600 kHz frequency; no DCR temperature compensation; integrated MOSFET drivers only (no external FET support) | Targeted at mid-power consumer applications; lacks remote sensing and sub-mΩ DCR capability | Choose MP2940AGQSE-LF-Z only for cost-sensitive, lower-current (<15 A) designs where DCR drift and remote sensing are not required. |
| ISL95836IRZ | Supports 3-phase interleaving; includes SMBus interface; no dual-path DCR sensing; fixed 300/600 kHz options | Designed for laptop CPU VRMs with digital interface requirements; no ITEMP or programmable ILIM | Choose ISL95836IRZ when multi-phase operation, telemetry, or system-level PMBus control are mandatory - not for standalone high-current DCR-sensed designs. |
Compared with MP2940AGQSE-LF-Z and ISL95836IRZ, the LTC3866EUF#PBF uniquely delivers sub-milliohm DCR sensing with temperature compensation, differential remote sensing, and fully programmable frequency/current limit - making it the only option for high-accuracy, high-current industrial and medical buck regulators where layout-induced errors and thermal drift must be eliminated.
Availability
LTC3866EUF#PBF is available at Aetrix Electronics and suitable for server CPU power delivery, telecom DC-DC bricks, and industrial PLC I/O power systems requiring stable component supply, long-term lifecycle support, and guaranteed parametric performance across –40°C to 125°C.
Supply support for LTC3866EUF#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) is a global leader in high-performance analog, mixed-signal, and power management ICs, serving precision instrumentation, communications, and industrial markets.
The LTC3866 belongs to Linear's high-efficiency synchronous controller product line, designed specifically for high-current, low-voltage DC-DC conversion where DCR-based current sensing, remote voltage sensing, and thermal stability are critical.
FAQ
What is the minimum inductor DCR supported by the LTC3866EUF#PBF?
The LTC3866EUF#PBF supports inductor DCR as low as 0.2 mΩ with careful PCB layout and proper filtering on SNSD+ and SNSA+ pins. Its dual-path sensing architecture provides 14 dB SNR improvement over conventional methods, enabling stable regulation and accurate current limiting even at sub-milliohm levels - a capability confirmed in the datasheet's Typical Performance Characteristics (Figure G12).
How does the LTC3866EUF#PBF implement DCR temperature compensation?
The LTC3866EUF#PBF uses the ITEMP pin to accept a voltage from an NTC thermistor placed near the output inductor. This voltage scales the current sense threshold dynamically to counteract DCR increase with temperature. When ITEMP is left floating or tied to INTVCC, compensation is disabled - full functionality requires external NTC network per the Applications Information section.
Can the LTC3866EUF#PBF operate without an external bootstrap diode?
No - the LTC3866EUF#PBF requires an external bootstrap diode between INTVCC and BOOST to recharge the bootstrap capacitor during BG-on periods. The datasheet specifies this in the "INTVCC/EXTVCC Power" section and shows it explicitly in the Typical Application schematic (TA01a). Omitting it risks insufficient TG drive voltage during high-duty-cycle operation.
What are the voltage limits on the EXTVCC pin of the LTC3866EUF#PBF?
The EXTVCC pin of the LTC3866EUF#PBF must be held between 4.5 V and 4.7 V (typical switchover threshold) and never exceed 6 V absolute maximum. Additionally, VIN must always remain greater than VEXTVCC to prevent backfeeding - violating either condition risks permanent damage, as specified in the Absolute Maximum Ratings table.
Does the LTC3866EUF#PBF support synchronization to an external clock?
Yes - the MODE/PLLIN pin of the LTC3866EUF#PBF accepts an external clock signal to force continuous conduction mode and synchronize the internal oscillator. When driven with a clean square wave, the internal clock locks to the external frequency with 180° phase alignment relative to CLKOUT, enabling multi-phase interleaving or EMI reduction in dense layouts.
LTC3866EUF#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 38V
- Frequency - Switching:
- 250kHz ~ 770kHz
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-QFN (4x4)
LTC3866EUF#PBF FAQ
1.How can I place an order for LTC3866EUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3866EUF#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 LTC3866EUF#PBF reliable?
The price and inventory of LTC3866EUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3866EUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3866EUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3866EUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3866EUF#PBF?
LTC3866EUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3866EUF#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 LTC3866EUF#PBF?
For technical support, including LTC3866EUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3866EUF#PBF requirements.
6.How does Aetrix verify that LTC3866EUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3866EUF#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 LTC3866EUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3866EUF#PBF?
All LTC3866EUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3866EUF#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 LTC3866EUF#PBF part is unused and in its original packaging.
Return procedure for LTC3866EUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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