My Inquiry
My Account
Analog Devices Inc. LTC3851AEUD#PBF
- Part No.:
- LTC3851AEUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3851AEUD#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:726
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LTC3851AEUD#PBF 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 adjustable output with ±1% accuracy, supports phase-lockable 250kHz–750kHz switching, and enables Burst Mode™, pulse-skipping, or forced continuous conduction-ideal for telecom power supplies requiring high efficiency across wide load ranges.
For engineers reviewing the LTC3851AEUD#PBF datasheet, LTC3851AEUD#PBF pinout, LTC3851AEUD#PBF application, or LTC3851AEUD#PBF equivalent, key selection criteria include its OPTI-LOOP® compensation for wide output capacitor/ESR tolerance, 99% duty cycle capability for ultra-low dropout, RSENSE/DCR current sensing flexibility, and thermally enhanced 3mm × 3mm QFN package with exposed pad for industrial-grade thermal management.
Technical Context
The LTC3851AEUD#PBF implements a constant-frequency current-mode control loop where peak inductor current is set by the ITH voltage, and error amplifier output adjusts ITH to regulate VFB against a precision 0.8V reference. Its transconductance amplifier (gm = 2 mmho, GBW = 3 MHz) provides fast transient response, while OPTI-LOOP® compensation decouples loop stability from output capacitor ESR variations.
Phase-locked loop (PLL) synchronization via MODE/PLLIN enables precise frequency alignment with external clocks up to 750kHz; FREQ/PLLFLTR accepts RC networks to program nominal frequency (e.g., 500kHz at RFREQ = 60kΩ). The IC integrates a 5V INTVCC LDO, anti-shoot-through logic, dropout detection with forced TG off-pulse, and overvoltage protection that disables TG and enables BG during >10% VOUT overshoot.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide-range industrial and telecom DC inputs without pre-regulation. |
| Output Voltage Accuracy | ±1% over –40°C to 125°C - ensures stable regulation under thermal stress in embedded systems. |
| Switching Frequency Range | 250kHz to 750kHz, phase-lockable - balances efficiency (lower f) vs. size (higher f) and enables EMI reduction via synchronization. |
| Current Sense Threshold Options | 30mV / 50mV / 75mV via ILIM pin - allows precise current limit tuning for MOSFET SOA and short-circuit foldback. |
| INTVCC Regulator | 5V ±4%, 50mA peak - powers gate drivers and internal circuitry independently of VIN, enabling robust bootstrap operation. |
| Duty Cycle Capability | Up to 99% - supports ultra-low dropout operation (e.g., 5V→4.95V), critical for post-regulation in distributed power systems. |
| Shutdown Quiescent Current | 20µA - minimizes standby power loss in battery-backed or always-on telecom modules. |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed thermal pad (Pin 17 = GND), rated for –40°C to 125°C junction temperature (θJA = 68°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 1) | Enable control input | 1.22V threshold with 120mV hysteresis; internal 2µA pull-up enables simple RC soft-start or logic-level control. |
| TK/SS (Pin 2) | Soft-start/tracking input | 1µA internal charge current ramps external capacitor; enables monotonic VOUT rise or ratiometric tracking of master supply. |
| ITH (Pin 3) | Error amplifier output & current threshold | Directly sets peak inductor current; gm = 2 mmho and 3 MHz GBW enable fast load transient recovery. |
| VFB (Pin 4) | Feedback input | Compares remote-sensed output voltage to 0.8V reference; ±1% accuracy maintained over full temp range. |
| SENSE– (Pin 5) | Current sense inverting input | Connects to low-side of DCR network or shunt resistor; ±2µA input bias minimizes sensing error. |
| SENSE+ (Pin 6) | Current sense non-inverting input | Accepts high-side DCR or shunt connection; supports both RSENSE and DCR sensing topologies. |
| ILIM (Pin 7) | Current limit select | Tri-level logic: GND = 30mV, float = 50mV, INTVCC = 75mV - configures foldback threshold without external components. |
| GND (Pin 8 + Exposed Pad) | Signal and power ground | Exposed pad must be soldered to PCB ground plane for thermal conduction (θJC = 4.2°C/W) and noise immunity. |
| BG (Pin 9) | Bottom gate driver output | Drives low-side N-MOSFET gate from GND to INTVCC; 1.1Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (Pin 10) | Internal 5V regulator output | Supplies all internal circuitry and gate drivers; requires ≥2.2µF low-ESR ceramic decoupling to GND. |
| VIN (Pin 11) | Main input supply | Accepts 4V–38V; powers INTVCC LDO and provides bootstrap energy via BOOST path. |
| BOOST (Pin 12) | Floating bootstrap supply | Swings from ~VIN+5V down to Schottky drop below INTVCC; charges external bootstrap capacitor during BG on-time. |
| TG (Pin 13) | Top gate driver output | Floating driver referenced to SW node; 2.2Ω pull-up and 25ns transition time support high-speed N-MOSFET switching. |
| SW (Pin 14) | Switch node connection | Connects to inductor and MOSFET bridge midpoint; voltage swings from ~–0.3V to VIN, requiring proper layout for EMI control. |
| MODE/PLLIN (Pin 15) | Mode selection & PLL sync input | Selects Burst Mode™ (50k–250kΩ to INTVCC), pulse-skip (float/GND), or forced CCM (tie to INTVCC); accepts 250–750kHz external clock. |
| FREQ/PLLFLTR (Pin 16) | Oscillator programming & PLL filter | RC network sets nominal frequency (250–750kHz); when used with PLL, forms loop filter with external series RC to GND. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance and relaxes ESR constraints-enables use of low-ESR ceramic caps without instability. |
| Tri-Level Adjustable Current Limit | 30mV/50mV/75mV thresholds via single ILIM pin-eliminates need for external DAC or resistor dividers for current foldback tuning. |
| 99% Maximum Duty Cycle | Supports ultra-low dropout operation (e.g., 12V→11.88V), essential for intermediate bus regulation in multi-rail telecom systems. |
| Burst Mode™ Operation | Reduces light-load quiescent current to ~20µA while maintaining tight output regulation-extends battery life in standby modes. |
| DCR or RSENSE Current Sensing | Flexible sensing architecture accommodates cost-sensitive DCR designs or precision shunt-based current limiting. |
| Integrated Overvoltage Protection | Hardware comparator triggers immediate TG off/BG on during >10% VOUT overshoot-prevents damage to downstream FPGAs or ASICs. |
Applications
| Telecom Power Supply | Industrial PLC Power Module |
|---|---|
Use Scenario: 48V intermediate bus conversion to 3.3V/5V for baseband processing units in 5G remote radio heads. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current, high-efficiency DC-DC conversion with strict ripple and transient requirements. Use Value: Phase-lockable 750kHz operation enables synchronized switching across multiple rails to suppress beat frequencies and meet EMI Class B limits. |
Use Scenario: DIN-rail mounted programmable logic controller requiring robust 24V-to-5V/3.3V conversion tolerant of 40V surges and –40°C cold starts. IC Role / Device Role / Timing Role: Main step-down controller with wide VIN range, integrated OV protection, and thermal-enhanced QFN for convection-cooled enclosures. Use Value: 99% duty cycle and 4V–38V input range ensure uninterrupted operation during brownouts and line dips common in factory floor environments. |
| Automotive Infotainment Core Supply | Distributed Data Center PSU |
Use Scenario: 12V battery-derived power for SoC core voltage (1.0V @ 12A) in head-unit applications with strict automotive temperature and reliability requirements. IC Role / Device Role / Timing Role: High-accuracy synchronous controller supporting ratiometric tracking of auxiliary rails and soft-start sequencing per AEC-Q100 guidelines. Use Value: ±1% output accuracy over –40°C to 125°C and TK/SS-controlled monotonic startup prevent SoC latch-up during cold cranking events. |
Use Scenario: Point-of-load (POL) converter in server motherboard VRM delivering 1.8V @ 30A to GPU memory subsystems with dynamic load steps. IC Role / Device Role / Timing Role: Fast-transient current-mode controller with 3 MHz error amplifier GBW and programmable current limit for precise current sharing. Use Value: OPTI-LOOP® compensation maintains stability with low-ESR polymer capacitors, reducing board area and improving transient response to 10A/µs load steps. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8640S | Monolithic 4A buck regulator (integrated MOSFETs); 3V–42V input; Silent Switcher® architecture reduces EMI. | Lower solution size but fixed 4A current limit; lacks tri-level ILIM and DCR sensing flexibility. | Choose LT8640S for space-constrained, low-EMI applications where integrated power stage suffices and current limit adjustability is secondary. |
| MP2918 | 3.5V–36V synchronous controller; 500kHz fixed frequency; no PLL sync or Burst Mode™; supports only RSENSE sensing. | Simpler feature set, lower cost; lacks OPTI-LOOP®, soft-start tracking, and wide frequency range. | Choose MP2918 for cost-sensitive industrial supplies where fixed-frequency operation and basic current-mode control meet requirements. |
Compared with LT8640S and MP2918, the LTC3851AEUD#PBF offers superior design flexibility through its tri-level current limit, DCR/RSENSE sensing choice, OPTI-LOOP® compensation, and phase-lockable frequency-making it optimal for high-reliability, multi-rail telecom and industrial systems demanding precise control and thermal resilience.
Availability
LTC3851AEUD#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLC modules, automotive infotainment systems, and distributed data center PSUs requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.
Supply support for LTC3851AEUD#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 its legacy of high-performance analog and power management ICs with rigorous automotive, industrial, and aerospace qualification standards.
The LTC3851A product line was designed for high-efficiency, wide-input synchronous buck controllers targeting telecom, industrial, and automotive applications where precision regulation, thermal robustness, and flexible current sensing are critical.
FAQ
What is the maximum operating junction temperature for the LTC3851AEUD#PBF?
The LTC3851AEUD#PBF is rated for –40°C to 125°C junction temperature. Its 3mm × 3mm QFN package features an exposed thermal pad (Pin 17 = GND) with θJA = 68°C/W and θJC = 4.2°C/W, enabling reliable operation in thermally constrained telecom and industrial environments when properly soldered to a PCB ground plane.
How does the ILIM pin configure current limit thresholds on the LTC3851AEUD#PBF?
The ILIM pin on the LTC3851AEUD#PBF provides tri-level current limit selection: grounding sets 30mV, floating sets 50mV, and tying to INTVCC sets 75mV maximum sense voltage. This directly programs the current comparator's foldback threshold without external components-critical for matching MOSFET safe operating area and optimizing short-circuit protection.
Can the LTC3851AEUD#PBF synchronize to an external clock, and what is the supported frequency range?
Yes, the LTC3851AEUD#PBF supports external clock synchronization via the MODE/PLLIN pin, accepting input frequencies from 250kHz to 750kHz. When synchronized, the IC operates in forced continuous conduction mode and locks its internal oscillator phase to the external source-enabling EMI reduction in multi-rail systems and deterministic switching timing.
What is the purpose of the TK/SS pin on the LTC3851AEUD#PBF, and how is it used for soft-start?
The TK/SS pin on the LTC3851AEUD#PBF controls output voltage ramp rate during startup. An internal 1µA current charges an external capacitor to ground, generating a linear voltage ramp. As TK/SS rises from 0V to 0.8V, the feedback regulation point follows it-ensuring monotonic VOUT rise and preventing inrush current. It also supports ratiometric tracking of master supplies.
Does the LTC3851AEUD#PBF support both RSENSE and DCR current sensing, and how is the selection made?
Yes, the LTC3851AEUD#PBF supports both RSENSE and DCR current sensing via the SENSE+ and SENSE– pins. No configuration pins or registers are needed-the topology is selected by external circuitry: connect a shunt resistor between SENSE+ and SENSE– for RSENSE; connect a DCR network (RC filter) between SENSE+ and SW, with SENSE– to GND. Both methods are validated in the datasheet's typical applications.
LTC3851AEUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-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):
- 4V ~ 38V
- Frequency - Switching:
- 235kHz ~ 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)
LTC3851AEUD#PBF FAQ
1.How can I place an order for LTC3851AEUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AEUD#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 LTC3851AEUD#PBF reliable?
The price and inventory of LTC3851AEUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AEUD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851AEUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AEUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AEUD#PBF?
LTC3851AEUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AEUD#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 LTC3851AEUD#PBF?
For technical support, including LTC3851AEUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AEUD#PBF requirements.
6.How does Aetrix verify that LTC3851AEUD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AEUD#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 LTC3851AEUD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851AEUD#PBF?
All LTC3851AEUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AEUD#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 LTC3851AEUD#PBF part is unused and in its original packaging.
Return procedure for LTC3851AEUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LTC3851AEUD#PBF Tags
-
UCC28C45DR
Texas Instruments
-
UCC28C40DR
Texas Instruments
-
UCC28C43DR
Texas Instruments
-
ZXSC410E6TA
Diodes Incorporated
-
LM3524DMX/NOPB
Texas Instruments
-
LM3489MMX/NOPB
Texas Instruments
-
MIC2102YML-TR
Microchip Technology
-
LM5148RGYR
Texas Instruments
-
TL598CDR
Texas Instruments
-
LM5155DSSR
Texas Instruments
-
LM25085MYX/NOPB
Texas Instruments
-
UCC2813DTR-0
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
