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Analog Devices Inc. LTC3851EUD#TRPBF
- Part No.:
- LTC3851EUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3851EUD#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:5,356
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Product details
Overview
LTC3851EUD#TRPBF from Analog Devices (formerly Linear Technology) is a high-performance synchronous step-down switching regulator controller driving dual N-channel MOSFETs in constant-frequency current-mode operation up to 750 kHz. It features ±1% output voltage accuracy, 0.8 V reference, 4 V–38 V input range, and adjustable current limit via ILIM pin - enabling robust DC/DC conversion for telecom power supplies and industrial distributed systems.
For engineers reviewing the LTC3851EUD#TRPBF datasheet, LTC3851EUD#TRPBF pinout, LTC3851EUD#TRPBF application, or LTC3851EUD#TRPBF equivalent, key selection criteria include phase-lockable frequency tuning (250–750 kHz), OPTI-LOOP® compensation for wide output capacitor/ESR compatibility, selectable light-load modes (Burst/Pulse-Skip/CCM), and 3mm × 3mm QFN thermal performance with exposed pad grounding.
Technical Context
The LTC3851EUD#TRPBF implements a constant-frequency current-mode control architecture with slope compensation, where peak inductor current is set by the ITH voltage and regulated against feedback at VFB. Its transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) enables stable loop response across diverse output capacitance and ESR values.
It integrates dual gate drivers (TG/BG) with matched 25 ns rise/fall times, anti-shoot-through logic, and dropout detection that forces periodic top-FET off-time to recharge the bootstrap capacitor. The MODE/PLLIN pin serves dual function: selecting light-load operating mode and accepting external clock synchronization for deterministic timing in multi-rail systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4 V to 38 V - supports wide-input industrial and telecom rails without pre-regulation. |
| Output Voltage Accuracy | ±1% over temperature - ensures precise regulation for sensitive digital loads like FPGAs and ASICs. |
| Switching Frequency | 250 kHz to 750 kHz (phase-lockable) - balances efficiency vs. magnetics size; programmable via resistor on FREQ/PLLFLTR. |
| Reference Voltage | 0.8 V ±0.8% - low-voltage reference enables accurate scaling down to 0.8 V output with minimal divider loss. |
| Quiescent Current | 20 μA in shutdown - minimizes standby power in battery-backed or always-on systems. |
| Current Sense Threshold | 30 mV / 50 mV / 75 mV (ILIM-selectable) - provides three discrete current-limit settings for design flexibility and fault margining. |
| Driver On-Resistance | TG: 2.6 Ω (pull-up), 1.5 Ω (pull-down); BG: 2.4 Ω / 1.1 Ω - ensures fast, low-loss MOSFET switching with <30 ns dead-time control. |
| Thermal Resistance | θJA = 68°C/W (QFN), θJC = 4.2°C/W - enables high-power density designs with PCB copper thermal spreading via exposed pad. |
Pinout & Package
Package: 16-lead (3 mm × 3 mm) plastic QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 1) | Enable control input | Logic-high (>1.25 V) enables operation; internal 2 μA pull-up allows simple RC soft-start; <1.1 V forces shutdown with INTVCC disable. |
| TK/SS (Pin 2) | Soft-start/tracking input | Internal 1 μA current charges external capacitor to ramp VOUT linearly; also accepts external voltage for supply tracking. |
| ITH (Pin 3) | Error amplifier output & current threshold | Voltage sets peak inductor current; also serves as compensation node for OPTI-LOOP® network. |
| FB (Pin 4) | Feedback input | Compares resistive-divider output against 0.8 V reference; high-impedance input (<50 nA bias) minimizes divider error. |
| SENSE– (Pin 5) | Current sense inverting input | Connects to low-side of DCR network or current-sense resistor; common-mode range 0–5.5 V supports high-side sensing. |
| SENSE+ (Pin 6) | Current sense non-inverting input | Connects to high-side of DCR/resistor; matched input impedance enables accurate differential sensing with minimal offset. |
| ILIM (Pin 7) | Current limit select | Tri-level logic: GND = 30 mV, float = 50 mV, INTVCC = 75 mV - configures foldback threshold without external components. |
| GND (Pin 8) | Analog/digital ground | Kelvin connection point for all small-signal references, compensation, and CIN/CVCC return paths. |
| BG (Pin 9) | Bottom gate driver output | Drives source-follower N-MOSFET gate between GND and INTVCC; low RDS(on) ensures fast turn-off and reverse-current prevention. |
| INTVCC (Pin 10) | Internal 5 V LDO output | Powers internal circuitry and gate drivers; requires ≥2.2 μF low-ESR ceramic/tantalum decoupling to GND. |
| VIN (Pin 11) | Main input supply | Accepts 4–38 V input; powers INTVCC LDO and supplies energy to boost capacitor during high-duty-cycle operation. |
| BOOST (Pin 12) | Bootstrap supply node | Connects to (+) terminal of bootstrap capacitor; swings from ~INTVCC − 0.4 V to VIN + INTVCC - enables floating top-gate drive. |
| TG (Pin 13) | Top gate driver output | Drives high-side N-MOSFET gate referenced to SW node; integrated level shifter eliminates need for external charge pump. |
| SW (Pin 14) | Switch node | Connects to inductor and MOSFET sources; voltage swings from ~−0.4 V (Schottky drop) to VIN - critical for layout EMI control. |
| FREQ/PLLFLTR (Pin 16) | Oscillator programming & PLL filter | Resistor-to-GND sets nominal frequency; when used with external clock on MODE/PLLIN, forms PLL loop filter with RC network. |
| MODE/PLLIN (Pin 15) | Mode selection & sync input | Selects Burst/Pulse-Skip/CCM via resistor/GND/INTVCC; accepts 250–750 kHz external clock for deterministic multi-phase synchronization. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® compensation | Minimizes required output capacitance and relaxes ESR constraints - simplifies design for polymer or low-ESR ceramic outputs. |
| Adjustable current foldback limiting | Three ILIM-selectable thresholds (30/50/75 mV) provide scalable short-circuit protection without external sensing resistors. |
| 99% maximum duty cycle | Enables ultra-low dropout operation - supports VOUT close to VIN (e.g., 5 V → 4.95 V) without requiring linear post-regulation. |
| Output overvoltage protection (OVP) | Detects >10% VOUT overshoot and forces bottom-FET on to clamp - prevents damage to downstream 3.3 V or 1.8 V ICs. |
| Thermally enhanced QFN package | 3 mm × 3 mm footprint with exposed GND pad delivers θJA = 68°C/W - enables >15 A continuous output with proper PCB copper area. |
| Low shutdown IQ (20 μA) | Reduces system standby power - critical for always-on IoT gateways and remote sensors with battery backup. |
Applications
| Telecom Power Supply | Industrial PLC Power Rail |
|---|---|
|
Use Scenario: Generating isolated 3.3 V/5 V rails from 48 V backplane in telecom line cards. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating intermediate bus voltage with tight transient response. Use Value: Phase-lockable 500 kHz operation avoids beat frequencies with other system clocks; ±1% accuracy maintains compliance with PICMG 3.0 spec. |
Use Scenario: Providing 12 V/15 A main power rail for programmable logic controllers in factory automation cabinets. IC Role / Device Role / Timing Role: High-efficiency step-down controller driving discrete N-MOSFETs with DCR current sensing. Use Value: 99% duty cycle supports brownout operation down to 12.5 V input; ILIM-selectable foldback protects against motor stall faults. |
| Automotive Infotainment Core Supply | Distributed DC Power System |
|
Use Scenario: Regulating 1.2 V core voltage for SoC in automotive head units with 12 V battery input. IC Role / Device Role / Timing Role: Precision buck controller with soft-start and tracking for coordinated power sequencing. Use Value: TK/SS pin enables ratiometric tracking with master 5 V rail; 0.8 V reference ensures accurate low-VOUT regulation. |
Use Scenario: Local point-of-load conversion in server rack power distribution units feeding multiple compute modules. IC Role / Device Role / Timing Role: Synchronized buck controller operating in forced CCM mode for low-noise, ripple-sensitive loads. Use Value: MODE/PLLIN pin locks switching to system clock - eliminates beat interference in adjacent ADC or RF 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 |
|---|---|---|---|
| LT8610EMSE#TRPBF | Integrated power stage (42 V, 3.5 A), fixed 2 MHz frequency, no external MOSFET drive. | Lower BOM count for <5 A designs; lacks ILIM-selectable current limit and phase-lock capability. | Choose LT8610EMSE#TRPBF for compact, low-component-count solutions below 3.5 A; LTC3851EUD#TRPBF retains flexibility for higher-current discrete FETs. |
| TPS546D24RSAR | 40 V, 60 A digital multiphase controller with PMBus interface; requires external drivers and MOSFETs. | Supports telemetry, dynamic voltage scaling, and multi-phase interleaving - not available in LTC3851EUD#TRPBF. | Choose TPS546D24RSAR for programmable, telemetry-enabled high-current systems; LTC3851EUD#TRPBF offers analog simplicity and lower latency control. |
Compared with LT8610EMSE#TRPBF and TPS546D24RSAR, the LTC3851EUD#TRPBF occupies a unique niche: analog-controlled, externally driven, phase-lockable buck controller optimized for 5–20 A industrial/telecom rails where design flexibility, thermal manageability in QFN, and deterministic timing matter more than integration or digital configurability.
Availability
LTC3851EUD#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLCs, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and consistent parametric performance across temperature.
Supply support for LTC3851EUD#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving precision instrumentation, communications, and industrial markets.
The LTC3851EUD#TRPBF belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding DC/DC conversion in telecom, industrial, and automotive applications where reliability, thermal performance, and flexible light-load operation are critical.
FAQ
What is the maximum input voltage rating for the LTC3851EUD#TRPBF?
The LTC3851EUD#TRPBF has an absolute maximum input voltage (VIN) rating of 40 V, with recommended continuous operation from 4 V to 38 V. Exceeding 40 V risks permanent damage per Absolute Maximum Ratings. The device's internal 5 V LDO (INTVCC) derives power from VIN, so maintaining VIN within spec ensures stable gate drive and control logic operation.
How does the ILIM pin affect current limiting on the LTC3851EUD#TRPBF?
The ILIM pin on the LTC3851EUD#TRPBF selects one of three maximum current sense thresholds: 30 mV (ILIM = GND), 50 mV (ILIM = float), or 75 mV (ILIM = INTVCC). This directly sets the peak inductor current limit before foldback initiates, enabling scalable short-circuit protection without recalculating sense resistors or DCR networks for different output current requirements.
Can the LTC3851EUD#TRPBF synchronize to an external clock, and what is the supported frequency range?
Yes, the LTC3851EUD#TRPBF can synchronize its internal oscillator to an external clock applied to the MODE/PLLIN pin, supporting input frequencies from 250 kHz to 750 kHz. When synchronized, it operates in forced continuous conduction mode. The FREQ/PLLFLTR pin must be configured with an RC network to serve as the PLL loop filter for stable lock.
What thermal considerations apply to the LTC3851EUD#TRPBF in its 3 mm × 3 mm QFN package?
The LTC3851EUD#TRPBF in the UD package has θJA = 68°C/W and θJC = 4.2°C/W. Effective thermal design requires soldering the exposed pad (Pin 17) to a minimum 100 mm² PCB copper area connected to system ground. Without proper pad thermal connection, junction temperature rise exceeds limits under >10 A load, risking thermal shutdown or long-term reliability degradation.
Does the LTC3851EUD#TRPBF support output voltage tracking during startup?
Yes, the LTC3851EUD#TRPBF supports ratiometric or coincident tracking via the TK/SS pin. By connecting an external resistor divider from a master supply to TK/SS, the controller ramps its output voltage proportionally to the master rail - ensuring safe power sequencing for multi-rail FPGAs or processors without requiring external supervisors.
LTC3851EUD#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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC3851EUD#TRPBF FAQ
1.How can I place an order for LTC3851EUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851EUD#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 LTC3851EUD#TRPBF reliable?
The price and inventory of LTC3851EUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851EUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851EUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851EUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851EUD#TRPBF?
LTC3851EUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851EUD#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 LTC3851EUD#TRPBF?
For technical support, including LTC3851EUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851EUD#TRPBF requirements.
6.How does Aetrix verify that LTC3851EUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851EUD#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 LTC3851EUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851EUD#TRPBF?
All LTC3851EUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851EUD#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 LTC3851EUD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851EUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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