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Analog Devices Inc. LTC3851EUD-1#PBF
- Part No.:
- LTC3851EUD-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3851EUD-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,691
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Product details
Overview
LTC3851EUD-1#PBF 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 topology. It operates from 4V to 38V input, delivers 0.8V–5.5V output with ±1% accuracy, supports phase-lockable 250kHz–750kHz switching, and features PGOOD monitoring, OPTI-LOOP® compensation, and adjustable soft-start/tracking - used in telecom intermediate bus converters requiring tight regulation and thermal robustness.
For engineers reviewing the LTC3851EUD-1#PBF datasheet, LTC3851EUD-1#PBF pinout, LTC3851EUD-1#PBF application, or LTC3851EUD-1#PBF equivalent, this page provides verified package mapping (3mm × 3mm QFN-16), confirmed pin functions including PGOOD and MODE/PLLIN, real-world efficiency curves at 3.3V/15A, and validated alternatives for automotive-grade or extended-temp redesigns.
Technical Context
The LTC3851EUD-1#PBF implements a constant-frequency current-mode control architecture with dual N-channel gate drivers (TG/BG), internal 5V INTVCC LDO, and precision 0.8V reference. Its ITH pin serves as both error amplifier output and current threshold control point, enabling OPTI-LOOP® compensation across wide output capacitance and ESR ranges.
It integrates programmable light-load operation (Burst Mode®, pulse-skipping, or forced CCM) via MODE/PLLIN, output overvoltage protection (±10% trip), current foldback limiting, and ratiometric/coincident tracking via TK/SS. The device replaces ILIM with PGOOD versus LTC3851, confirming its role as a power-good–enhanced variant for safety-critical DC/DC supervision.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports 12V/24V/36V battery and intermediate bus systems without external regulators. |
| Output Voltage Accuracy | ±1% at 0.8V feedback reference - ensures stable 1.2V, 1.8V, 3.3V, or 5V rail regulation under load/temperature variation. |
| Switching Frequency | 250kHz to 750kHz (phase-lockable) - balances MOSFET switching loss vs. inductor/capacitor size in space-constrained designs. |
| PGOOD Threshold | ±10% of VFB (0.72V–0.88V) with 17μs mask timer - enables reliable power sequencing and fault detection in multi-rail systems. |
| Shutdown IQ | 20μA - minimizes standby power in always-on industrial or telecom subsystems. |
| Package | 16-pin 3mm × 3mm QFN with exposed pad - provides θJA = 68°C/W thermal performance for high-current (>10A) applications. |
| Operating Temp | –40°C to +85°C - qualified for commercial/industrial environments without derating. |
Pinout & Package
Package: 16-lead (3mm × 3mm) plastic QFN with exposed thermal pad (Pin 17 = GND). Requires soldering of exposed pad to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 1) | Enable control input | Active-high logic: ≥1.25V enables operation; ≤1.1V forces shutdown with 2μA internal pull-up. |
| TK/SS (Pin 2) | Soft-start and tracking input | 1μA internal current charges external capacitor to ramp VOUT linearly; supports ratiometric tracking of master supply. |
| ITH (Pin 3) | Error amplifier output / current threshold | Controls peak inductor current; sets loop gain and transient response via external compensation network. |
| VFB (Pin 4) | Feedback input | Compares resistive divider voltage against 0.8V reference; determines regulated output voltage setpoint. |
| SENSE– (Pin 5) | Current sense inverting input | Connects to low-side of DCR network or current-sense resistor; common-mode range 0V–5.5V. |
| SENSE+ (Pin 6) | Current sense non-inverting input | Connects to high-side of sensing element; enables accurate current measurement with <1μA bias current. |
| PGOOD (Pin 7) | Open-drain power-good indicator | Pulls low when VFB outside ±10%; requires external pull-up to ≤6V for system-level power sequencing. |
| GND (Pin 8) | Analog/digital ground reference | Kelvin connection point for FB, SENSE, and compensation components; must tie to exposed pad. |
| BG (Pin 9) | Bottom gate driver output | Drives source of low-side N-MOSFET; 1.1Ω pull-down / 2.4Ω pull-up resistance enables fast turn-off. |
| INTVCC (Pin 10) | Internal 5V regulator output | Supplies gate drivers and analog circuitry; requires ≥2.2μF low-ESR ceramic decoupling to GND. |
| VIN (Pin 11) | Main input supply | Accepts 4V–38V; powers INTVCC LDO and high-side driver bootstrap circuit via BOOST path. |
| BOOST (Pin 12) | Floating bootstrap supply | Connects to (+) terminal of bootstrap capacitor; swings from ~VIN to VIN+INTVCC for high-side gate drive. |
| TG (Pin 13) | Top gate driver output | Floating driver referenced to SW node; 1.5Ω pull-down / 2.6Ω pull-up enables efficient N-MOSFET switching. |
| SW (Pin 14) | Switch node connection | Connects to inductor and low-side MOSFET drain; voltage swings from ~–0.3V to VIN during operation. |
| MODE/PLLIN (Pin 15) | Mode selection / external sync input | Selects Burst/Pulse-Skip/CCM; accepts 250–750kHz external clock for synchronization. |
| FREQ/PLLFLTR (Pin 16) | Oscillator programming / PLL filter | Resistor-to-GND sets frequency; RC network configures PLL loop filter when synchronized. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by optimizing loop stability across wide COUT/ESR ranges - reduces BOM cost and board area. |
| Three Light-Load Modes | Selectable Burst Mode® (highest efficiency), pulse-skipping (low ripple), or forced CCM (lowest noise) - enables optimal trade-off per application requirement. |
| Output Overvoltage Protection | Hardware-based ±10% OV lockout disables top MOSFET and activates bottom MOSFET - prevents damage to downstream 3.3V/1.8V ICs during transients. |
| Adjustable Soft-Start & Tracking | Single external capacitor on TK/SS enables monotonic VOUT ramp; resistor divider allows precise ratiometric startup with master supply. |
| DCR or RSENSE Sensing | Supports lossless inductor DCR sensing or precision shunt resistor - eliminates sense resistor power loss in high-current (>10A) designs. |
Applications
| Telecom Intermediate Bus Converter | Industrial PLC Power Supply |
|---|---|
Use Scenario: 48V backplane to 12V/5V intermediate bus conversion in carrier-grade line cards with strict thermal limits. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing up to 15A load with phase-locked 500kHz switching to reduce EMI in dense backplane layouts. Use Value: 95% peak efficiency at 5A (VIN=12V, VOUT=3.3V) and 68°C/W thermal resistance enable convection-cooled operation without heatsinks. |
Use Scenario: DIN-rail mounted programmable logic controller requiring isolated 24V input to regulated 3.3V/1.2V rails for FPGA and I/O interfaces. IC Role / Device Role / Timing Role: High-reliability step-down controller with PGOOD sequencing and –40°C to +85°C operation for uncontrolled cabinet environments. Use Value: ±1% output accuracy and 17μs PGOOD mask ensure deterministic power-up of safety-critical logic without brownout resets. |
| Automotive Infotainment Core Supply | Distributed Data Center DC/DC Module |
Use Scenario: 12V vehicle battery to 1.2V core supply for SoC in head-unit systems with aggressive EMI requirements. IC Role / Device Role / Timing Role: Synchronous buck controller with Burst Mode® operation to maintain >85% efficiency at 100mA standby load while minimizing audible noise. Use Value: 20μA shutdown IQ and selectable light-load modes extend battery runtime during key-off states without compromising transient response. |
Use Scenario: 12V server motherboard VRM supplying 0.8V–3.3V to ASICs, memory, and PCIe switches with dynamic load steps. IC Role / Device Role / Timing Role: High-bandwidth current-mode controller with OPTI-LOOP® enabling <10μs transient recovery for 50A/μs load steps. Use Value: 99% duty cycle capability and 90ns minimum on-time support ultra-low dropout and high VIN/VOUT ratios in compact 3mm × 3mm footprint. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3851EMSE-1#PBF | Identical functionality but in 16-lead MSOP package (θJA = 35–40°C/W); no exposed thermal pad. | Better suited for prototyping or low-power (<8A) designs where thermal density is lower. | Select when board layout favors MSOP footprint or thermal management uses copper pour instead of exposed pad soldering. |
| MP2491DD-LF-Z | Monolithic 3A buck converter (integrated MOSFETs); fixed 500kHz frequency; no PGOOD or tracking capability. | Targeted at cost-sensitive, low-current applications where external FETs and advanced sequencing are unnecessary. | Choose only for sub-3A loads where integration outweighs flexibility - not a functional replacement for LTC3851EUD-1#PBF's 15A+ capability. |
Compared with LTC3851EMSE-1#PBF, the LTC3851EUD-1#PBF offers superior thermal performance (68°C/W vs. 35–40°C/W) and higher current scalability due to QFN exposed pad; versus MP2491DD-LF-Z, it provides full external FET control, PGOOD, and multi-mode light-load optimization essential for high-reliability 10A+ systems.
Availability
LTC3851EUD-1#PBF is available at Aetrix Electronics and suitable for telecom intermediate bus converters, industrial PLC power supplies, and automotive infotainment core supplies requiring stable component supply, long-term lifecycle support, and guaranteed commercial temperature grade.
Supply support for LTC3851EUD-1#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 semiconductors with deep expertise in precision power conversion.
The LTC3851-1 family was designed specifically for high-efficiency, high-current synchronous buck regulation in demanding infrastructure applications - emphasizing thermal resilience, light-load efficiency, and robust fault protection.
FAQ
What is the maximum output current supported by the LTC3851EUD-1#PBF?
The LTC3851EUD-1#PBF itself does not limit output current; it drives external N-channel MOSFETs. In typical 15A applications (e.g., VIN=12V, VOUT=3.3V), thermal design using the 3mm × 3mm QFN package and proper PCB layout enables sustained 15A operation. Peak current depends on selected FETs, inductor, and thermal management - the controller's current sense threshold is adjustable up to 65mV.
Does the LTC3851EUD-1#PBF support DCR current sensing?
Yes, the LTC3851EUD-1#PBF fully supports DCR current sensing via SENSE+ and SENSE– pins. Its high-impedance inputs (<1μA bias) and wide common-mode range (0V–5.5V) allow accurate inductor DCR measurement. External RC filtering must match the L/DCR time constant, as detailed in the Applications Information section of the LTC3851-1 datasheet.
How does the PGOOD function differ between LTC3851EUD-1#PBF and standard LTC3851?
The LTC3851EUD-1#PBF replaces the ILIM pin of the base LTC3851 with PGOOD - a dedicated open-drain power-good indicator. While both share identical control architecture, only the LTC3851EUD-1#PBF provides hardware-monitored ±10% output regulation status with 17μs fault masking, making it preferred for systems requiring strict power sequencing and fault reporting.
Can the LTC3851EUD-1#PBF be synchronized to an external clock?
Yes, the LTC3851EUD-1#PBF supports external synchronization via the MODE/PLLIN pin. When driven with a 250kHz–750kHz clock signal, the internal oscillator locks to the external source and operates in forced continuous conduction mode. An RC network on FREQ/PLLFLTR serves as the PLL loop filter, and the device maintains phase alignment across temperature and supply variations.
What is the purpose of the TK/SS pin on the LTC3851EUD-1#PBF?
The TK/SS pin on the LTC3851EUD-1#PBF serves dual functions: soft-start control and supply tracking. An external capacitor to GND sets the VOUT ramp rate via 1μA internal charging current. For tracking, a resistor divider from a master supply to GND connects to TK/SS, enabling coincident or ratiometric startup - critical for FPGAs and multi-rail processors requiring controlled power sequencing.
LTC3851EUD-1#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:
- 250kHz ~ 750kHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC3851EUD-1#PBF FAQ
1.How can I place an order for LTC3851EUD-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851EUD-1#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 LTC3851EUD-1#PBF reliable?
The price and inventory of LTC3851EUD-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851EUD-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851EUD-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851EUD-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851EUD-1#PBF?
LTC3851EUD-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851EUD-1#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 LTC3851EUD-1#PBF?
For technical support, including LTC3851EUD-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851EUD-1#PBF requirements.
6.How does Aetrix verify that LTC3851EUD-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851EUD-1#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 LTC3851EUD-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851EUD-1#PBF?
All LTC3851EUD-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851EUD-1#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 LTC3851EUD-1#PBF part is unused and in its original packaging.
Return procedure for LTC3851EUD-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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