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Analog Devices Inc. LTC3866IUF#PBF
- Part No.:
- LTC3866IUF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 24-WFQFN Exposed Pad
- Datasheet:
-
LTC3866IUF#PBF.pdf
- Description:
- IC REG CTRLR BUCK 24QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,929
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Product details
Overview
LTC3866IUF#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 (as low as 0.2 mΩ), supports 4.5 V to 38 V input, delivers 0.6 V to 3.5 V output with ±0.5% accuracy, and operates at 250 kHz to 770 kHz. It is used in high-current DC/DC converters for telecom power systems.
For engineers reviewing the LTC3866IUF#PBF datasheet, LTC3866IUF#PBF pinout, LTC3866IUF#PBF application, or LTC3866IUF#PBF equivalent, key selection criteria include its DCR temperature compensation, differential remote sense amplifier, programmable current limit (10–30 mV), 24-lead QFN package, and support for Burst Mode® operation at light load.
Technical Context
The LTC3866IUF#PBF implements a proprietary dual-sense-input architecture (SNSD+ and SNSA+) that improves signal-to-noise ratio by 14 dB for ultra-low-DCR inductor sensing. Its error amplifier regulates VFB against a precise 0.6 V reference, while ITH voltage sets peak inductor current via current-mode control.
It integrates a high-speed differential remote sense amplifier (gain = 0.999–1.002 V/V, GBW = 3 MHz), programmable oscillator (250–770 kHz), and thermal shutdown. The MODE/PLLIN pin selects between Burst Mode®, pulse-skipping, or continuous conduction-each altering light-load efficiency behavior without changing external components.
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 temperature for CPU/GPU core supplies. |
| Current Sense Threshold | Programmable 10 mV to 30 mV in 5 mV steps via ILIM pin - enables precise overcurrent protection with low-DCR inductors. |
| Switching Frequency | 250 kHz to 770 kHz - adjustable via FREQ pin; allows optimization of size vs. efficiency in high-current designs. |
| DCR Temp Compensation | Enabled via ITEMP pin with NTC thermistor - maintains accurate current limit across –40°C to 125°C junction range. |
| Differential Sense Gain | 0.999–1.002 V/V with 2 mV offset - rejects common-mode noise and enables millivolt-level remote sensing at load. |
| Package | 24-lead (4 mm × 4 mm) QFN with exposed SGND pad - provides low θJA = 47°C/W and robust thermal performance. |
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; connects to RC compensation network for loop stability. |
| VFB (Pin 2) | Feedback input to error amplifier | Compares remote-sensed output voltage (via DIFFOUT divider) to 0.6 V reference. |
| DIFFOUT (Pin 3) | Differential amplifier output | Drives VFB through resistor divider; enables accurate remote sensing without PCB trace IR drop. |
| DIFFN (Pin 4) | Negative input of diffamp | Connected to load ground near output capacitor - critical for rejecting ground noise. |
| DIFFP (Pin 5) | Positive input of diffamp | Connected to output rail near load - forms Kelvin sense pair with DIFFN. |
| SNSD+ (Pin 6) | Primary DCR sense input | Connects to inductor DCR filter (R1C1 matching L/DCR); main path for current sensing. |
| SNS– (Pin 7) | Current comparator negative input | Tied to output node; completes current sense loop with SNSD+/SNSA+. |
| SNSA+ (Pin 8) | Secondary DCR sense input | Filters high-frequency noise; bandwidth set to 5× SNSD+ for SNR enhancement. |
| ILIM (Pin 9) | Current limit threshold programming | DC voltage sets max sense threshold (10–30 mV); enables precise foldback protection. |
| CLKOUT (Pin 10) | Internal clock output | 180° out-of-phase with SW node; used for synchronization or timing diagnostics. |
| PGND (Pin 11) | Power ground return | Return path for VIN, INTVCC, and bottom MOSFET source - must be low-inductance connection. |
| BG (Pin 12) | Bottom gate driver output | Drives NMOS source-to-ground; swings from PGND to INTVCC/EXTVCC. |
| SW (Pin 13) | Switch node | Connects top MOSFET drain, bottom MOSFET source, and inductor - high dV/dt node requiring careful layout. |
| TG (Pin 14) | Top gate driver output | Floating driver referenced to SW; requires bootstrap capacitor (BOOST–SW) for high-side drive. |
| BOOST (Pin 15) | Bootstrap supply input | Connects (+) terminal of bootstrap cap; swings up to VIN + INTVCC during top-FET on-time. |
| INTVCC (Pin 16) | Internal 5.5 V regulator output | Powers internal logic and drivers; decoupled with 4.7 µF ceramic/tantalum to PGND. |
| VIN (Pin 17) | Main input supply | Primary power source for INTVCC regulator; decoupled with 0.1–1 µF capacitor to PGND. |
| EXTVCC (Pin 18) | External bias input | When >4.7 V, bypasses INTVCC LDO - improves efficiency when using external 5 V supply. |
| ITEMP (Pin 19) | DCR temperature compensation input | Accepts NTC thermistor voltage; disables compensation if floated or tied to INTVCC. |
| PGOOD (Pin 20) | Open-drain power-good indicator | Pulls low when VOUT deviates >±10% after 20 µs mask timer - enables system sequencing. |
| MODE/PLLIN (Pin 21) | Mode select / external sync input | Ground = CCM; INTVCC = pulse-skip; float = Burst Mode®; AC signal = PLL sync. |
| FREQ (Pin 22) | Oscillator frequency control | 10 µA sink; resistor to GND sets frequency (250–770 kHz);也可 driven by voltage. |
| RUN (Pin 23) | Enable/disable control | 1.22 V turn-on threshold; internal 1 µA pull-up; supports controlled soft-start sequencing. |
| TK/SS (Pin 24) | Tracking/soft-start input | 1.25 µA internal charge current; enables voltage ramp or tracking of another supply rail. |
| SGND (Pin 25) | Signal ground reference | Exposed pad - must be soldered to PCB ground plane; reference for feedback, compensation, and sense circuits. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-path DCR sensing (SNSD+/SNSA+) | 14 dB SNR improvement enables reliable operation with 0.2 mΩ inductors - reduces conduction loss and thermal stress. |
| Programmable current limit (10–30 mV) | Five-step selection via ILIM pin eliminates need for precision shunts - simplifies BOM and layout for high-current designs. |
| Differential remote sense amplifier | 0.999–1.002 V/V gain, 2 mV offset, and 90 dB PSRR reject PCB noise - ensures <±0.5% output regulation under dynamic load. |
| DCR temperature compensation | ITEMP pin accepts NTC thermistor to maintain constant current limit across –40°C to 125°C - prevents thermal runaway in sealed enclosures. |
| Three light-load modes | Burst Mode®, pulse-skipping, and CCM selectable via MODE/PLLIN - maximizes efficiency from 1 mA to full load without external circuitry. |
| Integrated dropout recovery | Forces periodic top-FET off-time when VIN ≈ VOUT - ensures bootstrap capacitor recharge during low-VIN operation. |
Applications
| Computer Systems | Telecom Systems |
|---|---|
Use Scenario: Point-of-load (POL) conversion for FPGA, ASIC, or CPU core voltage rails requiring <1% output tolerance and fast transient response. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing 1.5 V/30 A output with differential remote sensing and DCR current monitoring. Use Value: Enables use of low-DCR planar inductors to achieve >95% efficiency at 30 A while maintaining ±0.5% regulation under load steps. | Use Scenario: Intermediate bus converter (IBC) in 48 V telecom rectifier modules powering downstream 12 V or 5 V distribution rails. IC Role / Device Role / Timing Role: High-input-voltage synchronous controller supporting 4.5 V–38 V input, with programmable frequency for EMI compliance. Use Value: Delivers stable 12 V output from variable 48 V input with minimal external components and no current-sense resistor losses. |
| Industrial Instruments | DC Power Distribution Systems |
Use Scenario: Precision analog supply in medical imaging equipment where low noise, high PSRR, and thermal stability are critical. IC Role / Device Role / Timing Role: Regulates isolated 3.3 V analog rail using differential sensing and DCR temp compensation to avoid drift over ambient changes. Use Value: Maintains <±0.5% output accuracy from –40°C to 85°C ambient without calibration - reduces system-level test overhead. | Use Scenario: Redundant 24 V DC-DC module in distributed power architecture for factory automation controllers. IC Role / Device Role / Timing Role: Controller with PGOOD sequencing, RUN enable, and EXTVCC option for efficient multi-rail power management. Use Value: Supports hot-swap capability via controlled soft-start (TK/SS) and fault signaling (PGOOD), enabling seamless module replacement. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3855IUFD#PBF | Single-phase, 4.5 V–38 V input, but lacks DCR temperature compensation and dual-sense architecture. | Not suitable for ultra-low-DCR (<0.5 mΩ) or wide-temperature industrial deployments. | Select only if DCR temp compensation and sub-milliohm sensing are not required. |
| MP2918GL-Z | Supports 4.5 V–32 V input and 0.6 V–5.5 V output, but uses single-sense input and fixed 600 kHz frequency. | Cannot match LTC3866IUF#PBF's 14 dB SNR advantage or programmable current limit steps. | Consider for cost-sensitive, lower-performance telecom POL where layout noise is minimal. |
Compared with LTC3855IUFD#PBF and MP2918GL-Z, the LTC3866IUF#PBF uniquely delivers sub-milliohm DCR sensing with temperature compensation and differential remote sensing - essential for high-efficiency, high-reliability 30 A+ point-of-load designs where thermal drift and PCB noise must be minimized.
Availability
LTC3866IUF#PBF is available at Aetrix Electronics and suitable for computer systems, telecom infrastructure, and industrial instrumentation requiring stable component supply, long-term lifecycle support, and guaranteed –40°C to 125°C operation.
Supply support for LTC3866IUF#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.
The LTC3866IUF#PBF belongs to the LTC® high-current synchronous controller product line, designed specifically for high-efficiency, low-DCR, and thermally robust DC/DC conversion in demanding computing and communications applications.
FAQ
What is the minimum inductor DCR supported by the LTC3866IUF#PBF?
The LTC3866IUF#PBF supports inductor DCR as low as 0.2 mΩ with proper PCB layout and filtering. Its dual-sense architecture (SNSD+ and SNSA+) enhances signal-to-noise ratio by 14 dB, enabling stable current-mode control even with sub-milliohm sensing elements - critical for minimizing conduction loss in high-current applications.
How does the LTC3866IUF#PBF implement DCR temperature compensation?
The LTC3866IUF#PBF implements DCR temperature compensation via the ITEMP pin, which accepts a voltage from an NTC thermistor placed near the output inductor. This voltage adjusts the current sense threshold dynamically to counteract DCR drift over temperature - ensuring consistent current limiting from –40°C to 125°C without software or external calibration.
Can the LTC3866IUF#PBF operate without an external current-sense resistor?
Yes - the LTC3866IUF#PBF is designed exclusively for DCR-based current sensing and does not require an external sense resistor. It uses the inductor's inherent DCR (0.2–1 mΩ typical) as the current-sense element, eliminating resistor power loss and board space while enabling higher efficiency in high-current designs.
What are the key differences between Burst Mode®, pulse-skipping, and CCM operation on the LTC3866IUF#PBF?
The LTC3866IUF#PBF selects light-load operation mode via MODE/PLLIN: grounded = continuous conduction mode (CCM); tied to INTVCC = pulse-skipping; floating = Burst Mode®. Burst Mode® delivers highest light-load efficiency (<30 µA IQ) by gating entire switching cycles; pulse-skipping reduces switching frequency; CCM maintains fixed frequency for lowest output ripple.
Is the LTC3866IUF#PBF pin-compatible with other members of the LTC38xx family?
No - the LTC3866IUF#PBF has a unique 24-pin QFN pinout optimized for dual DCR sensing and differential remote sensing. It is not pin-compatible with LTC3855, LTC3880, or LTC3883. Layout reuse requires verification of all signal routing, especially SNSD+/SNSA+, DIFFP/DIFFN, and ITEMP connections.
LTC3866IUF#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)
LTC3866IUF#PBF FAQ
1.How can I place an order for LTC3866IUF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3866IUF#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 LTC3866IUF#PBF reliable?
The price and inventory of LTC3866IUF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3866IUF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3866IUF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3866IUF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3866IUF#PBF?
LTC3866IUF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3866IUF#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 LTC3866IUF#PBF?
For technical support, including LTC3866IUF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3866IUF#PBF requirements.
6.How does Aetrix verify that LTC3866IUF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3866IUF#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 LTC3866IUF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3866IUF#PBF?
All LTC3866IUF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3866IUF#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 LTC3866IUF#PBF part is unused and in its original packaging.
Return procedure for LTC3866IUF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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