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Analog Devices Inc. LTC3851IUD#TRPBF
- Part No.:
- LTC3851IUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3851IUD#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,589
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Product details
Overview
LTC3851IUD#TRPBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous step-down switching regulator controller driving dual N-channel MOSFETs in a constant-frequency current-mode architecture. It operates from 4V to 38V input, delivers 0.8V–5.5V output with ±1% accuracy, supports phase-lockable 250kHz–750kHz switching, and features OPTI-LOOP® compensation for optimized transient response in telecom power supplies.
For engineers reviewing the LTC3851IUD#TRPBF datasheet, LTC3851IUD#TRPBF pinout, LTC3851IUD#TRPBF application, or LTC3851IUD#TRPBF equivalent, key selection criteria include its RSENSE/DCR current sensing flexibility, selectable light-load modes (Burst/Pulse-Skip/CCM), 99% duty cycle capability, integrated 5V INTVCC regulator, and thermal performance in the 3mm × 3mm QFN package.
Technical Context
The LTC3851IUD#TRPBF implements a constant-frequency current-mode control loop with transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and precision 0.8V reference (±1% over –40°C to 125°C). Its ITH pin serves as both current threshold control and compensation node, enabling OPTI-LOOP® optimization across wide output capacitance and ESR ranges.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, 30ns dead-time control, and robust protection including output overvoltage lockout (0.86–0.90V at VFB), current foldback via ILIM-selectable thresholds (30/50/75mV), and dropout recovery with forced top-FET off cycles to recharge the bootstrap capacitor.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide industrial and telecom input rails without external pre-regulation. |
| Output Voltage Accuracy | ±1% - ensures stable regulation under load/line/temp variations for sensitive digital loads. |
| Switching Frequency | 250kHz to 750kHz - adjustable via FREQ/PLLFLTR resistor or synchronizable externally for EMI control. |
| Current Sense Options | RSENSE or DCR - enables high-efficiency, low-loss sensing in high-current applications without sense resistor power loss. |
| Light-Load Modes | Burst Mode®, Pulse-Skipping, Continuous Conduction - selectable via MODE/PLLIN for efficiency vs. noise trade-offs. |
| INTVCC Regulator | 5V ±2% - powers internal circuitry and gate drivers; supports up to 50mA peak load with 0.5–2% load regulation. |
| Duty Cycle Max | 99% - allows ultra-low dropout operation, critical for high-VIN-to-low-VOUT conversion (e.g., 12V→1.2V). |
| Shutdown IQ | 20μA - minimizes system standby power in battery-backed or always-on equipment. |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed pad (Pin 17 = GND, must be soldered to PCB). Thermal resistance θJA = 68°C/W, θJC = 4.2°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 1) | Enable control input | 1.25V threshold with 130mV hysteresis; internal 2μA pull-up enables simple RC soft-start or logic control. |
| TK/SS (Pin 2) | Soft-start/tracking input | 1μA internal charge current ramps output voltage linearly; supports ratiometric tracking of master supply. |
| ITH (Pin 3) | Error amplifier output & current threshold | Directly sets peak inductor current; also serves as compensation node for OPTI-LOOP® stability tuning. |
| VFB (Pin 4) | Feedback input | Connects to resistive divider; regulates output to precise 0.8V reference with ±1% accuracy. |
| SENSE– (Pin 5) | Current sense inverting input | High-impedance (±1μA bias) node for DCR or RSENSE networks; common-mode range 0V–5.5V. |
| SENSE+ (Pin 6) | Current sense non-inverting input | Paired with SENSE–; enables accurate current measurement even with low DCR (<1mΩ) inductors. |
| ILIM (Pin 7) | Current limit select | Tri-level logic: GND=30mV, float=50mV, INTVCC=75mV - sets foldback threshold without external components. |
| GND (Pin 8) | Analog/digital ground | Kelvin connection point for all small-signal and compensation components; tied to exposed pad. |
| BG (Pin 9) | Bottom gate driver output | Drives low-side N-MOSFET gate between GND and INTVCC; 1.1Ω pull-down, 2.4Ω pull-up. |
| INTVCC (Pin 10) | Internal 5V regulator output | Supplies control circuitry and gate drivers; requires ≥2.2μF low-ESR ceramic/tantalum decoupling. |
| VIN (Pin 11) | Main input supply | Accepts 4V–38V; powers INTVCC LDO and provides source for bootstrap charging via BOOST. |
| BOOST (Pin 12) | Bootstrap supply | Floating rail for top gate driver; swings from ~VIN + INTVCC down to Schottky drop below GND. |
| TG (Pin 13) | Top gate driver output | Drives high-side N-MOSFET gate referenced to SW node; 1.5Ω pull-down, 2.6Ω pull-up. |
| SW (Pin 14) | Switch node | Connects to inductor; voltage swings from ~0V (Schottky drop) to VIN during operation. |
| FREQ/PLLFLTR (Pin 16) | Oscillator programming / PLL filter | Resistor-to-GND sets frequency; with external clock on MODE/PLLIN, forms PLL loop filter. |
| MODE/PLLIN (Pin 15) | Mode select / sync input | Selects Burst/Pulse-Skip/CCM or accepts external clock (250–750kHz) for synchronization. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by enabling stable loop response across wide COUT/ESR ranges - reduces BOM cost and board area. |
| Tri-Level Current Limit (ILIM) | Hardware-selectable 30/50/75mV thresholds eliminate need for external current-sense resistor trimming or calibration. |
| 99% Maximum Duty Cycle | Enables high-step-down ratios (e.g., 24V→1.8V) without requiring pre-regulators - simplifies multi-rail power architecture. |
| Integrated 5V INTVCC Regulator | Eliminates external bias supply; supports full gate drive strength and internal logic without auxiliary winding or LDO. |
| Output Overvoltage Protection | Active clamp at >10% overvoltage (0.86–0.90V at VFB) prevents damage to downstream ICs during transients or feedback faults. |
| Thermally Enhanced QFN | 3mm × 3mm footprint with exposed GND pad achieves θJA = 68°C/W - enables high-power density designs without heatsinks. |
Applications
| Telecom Power Supply | Industrial PLC Module |
|---|---|
Use Scenario: Point-of-load (POL) converter in 48V telecom shelf supplying 3.3V/15A to FPGA and ASIC cores. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current, high-efficiency DC-DC conversion with tight transient response. Use Value: OPTI-LOOP® compensation maintains stability with low-ESR polymer capacitors; 250kHz–750kHz programmability meets EMI compliance requirements. | Use Scenario: 24V input to 5V/10A isolated auxiliary supply in programmable logic controller backplane. IC Role / Device Role / Timing Role: Non-isolated buck controller delivering clean, regulated 5V for microcontroller, I/O drivers, and communication interfaces. Use Value: RSENSE/DCR sensing flexibility accommodates either cost-sensitive (resistor) or high-efficiency (DCR) implementations; 99% duty cycle supports brownout operation. |
| Automotive Infotainment System | Distributed DC Power System |
Use Scenario: 12V vehicle battery to 1.2V/8A core supply for SoC in head-unit display processor. IC Role / Device Role / Timing Role: High-accuracy, high-reliability buck controller operating across –40°C to 125°C ambient with automotive-grade qualification. Use Value: ±1% output accuracy and robust UVLO (3.25V) ensure reliable startup and operation during cold-crank and load-dump events. | Use Scenario: Centralized 48V bus powering multiple 12V intermediate distribution points in data center rack. IC Role / Device Role / Timing Role: High-efficiency, synchronized buck controller enabling phase interleaving and EMI reduction across parallel modules. Use Value: PLL synchronization via MODE/PLLIN pin allows precise clock alignment across multiple LTC3851IUD#TRPBF units - reducing system-level ripple and noise. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3851-1IUD#TRPBF | Includes power-good (PGOOD) output; lacks adjustable current limit (fixed ILIM). | Suitable where system monitoring requires PGOOD assertion but current limit adjustment is unnecessary. | Choose when status signaling is prioritized over fine-grained overcurrent tuning. |
| MP2918GL-Z | Monolithic 6A buck converter (integrated MOSFETs); lower max VIN (36V); no DCR sensing support. | Targeted at space-constrained, medium-current applications where integration outweighs flexibility. | Prefer for compact, lower-power designs where external FETs and DCR sensing are not required. |
Compared with LTC3851-1IUD#TRPBF, the LTC3851IUD#TRPBF offers adjustable current limiting via ILIM pin but no PGOOD signal; compared with MP2918GL-Z, it provides higher current scalability, wider input range, and DCR sensing-making it suitable for high-performance, discrete-FET power stages.
Availability
LTC3851IUD#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLC modules, and automotive infotainment systems requiring stable component supply across extended temperature ranges.
Supply support for LTC3851IUD#TRPBF 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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LTC3851 product line delivers high-efficiency, flexible synchronous buck controllers for demanding industrial, telecom, and automotive power systems where precision, reliability, and thermal performance are critical.
FAQ
What is the maximum input voltage rating for the LTC3851IUD#TRPBF?
The LTC3851IUD#TRPBF has an absolute maximum input voltage (VIN) rating of 40V. Its operational input range is specified from 4V to 38V, making it suitable for 24V and 48V industrial and telecom systems. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
How does the ILIM pin configure current limiting on the LTC3851IUD#TRPBF?
The ILIM pin on the LTC3851IUD#TRPBF selects one of three maximum current sense thresholds: 30mV (ILIM = GND), 50mV (ILIM = float), or 75mV (ILIM = INTVCC). This tri-level configuration directly sets the foldback threshold for short-circuit protection without external resistors or calibration.
Can the LTC3851IUD#TRPBF synchronize to an external clock, and how is it configured?
Yes, the LTC3851IUD#TRPBF can synchronize to an external clock applied to the MODE/PLLIN pin (250kHz–750kHz range). When used, the FREQ/PLLFLTR pin must be connected to GND via an RC network to serve as the PLL loop filter; the device then operates in forced continuous mode with locked phase.
What package type and thermal characteristics apply to the LTC3851IUD#TRPBF?
The LTC3851IUD#TRPBF uses a 16-lead 3mm × 3mm plastic QFN package with exposed GND pad (Pin 17). Its thermal resistance is θJA = 68°C/W and θJC = 4.2°C/W. The exposed pad must be soldered to PCB for proper thermal and electrical performance.
Does the LTC3851IUD#TRPBF support DCR current sensing, and what design considerations apply?
Yes, the LTC3851IUD#TRPBF supports DCR current sensing via SENSE+ and SENSE– pins. To implement it, an RC network matching the L/DCR time constant must be placed near the inductor; R2 scales the sensed voltage. The high-impedance inputs (±1μA bias) enable accurate low-voltage sensing without loading the DCR network.
LTC3851IUD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- 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):
- 4V ~ 38V
- Frequency - Switching:
- 250kHz ~ 750kHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC3851IUD#TRPBF FAQ
1.How can I place an order for LTC3851IUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851IUD#TRPBF 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 LTC3851IUD#TRPBF reliable?
The price and inventory of LTC3851IUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851IUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851IUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851IUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851IUD#TRPBF?
LTC3851IUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851IUD#TRPBF 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 LTC3851IUD#TRPBF?
For technical support, including LTC3851IUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851IUD#TRPBF requirements.
6.How does Aetrix verify that LTC3851IUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851IUD#TRPBF 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 LTC3851IUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851IUD#TRPBF?
All LTC3851IUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851IUD#TRPBF, 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 LTC3851IUD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851IUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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