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Analog Devices Inc. LTC3851AEUD#TRPBF
- Part No.:
- LTC3851AEUD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3851AEUD#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,545
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Product details
Overview
LTC3851AEUD#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 enables Burst Mode™, pulse-skipping, or forced continuous conduction-used in telecom power supplies requiring tight regulation and high light-load efficiency.
For engineers reviewing the LTC3851AEUD#TRPBF datasheet, LTC3851AEUD#TRPBF pinout, LTC3851AEUD#TRPBF application, or LTC3851AEUD#TRPBF equivalent, key selection criteria include its 0.8V reference tolerance, RSENSE/DCR current sensing flexibility, OPTI-LOOP® compensation for wide output capacitor ESR ranges, and thermally enhanced 3mm × 3mm QFN package with exposed pad for industrial-grade thermal performance.
Technical Context
The LTC3851AEUD#TRPBF implements a constant-frequency current-mode control loop where peak inductor current is set by the ITH voltage, and output voltage regulation is maintained via an error amplifier comparing VFB to a precision 0.8V reference. Its transconductance amplifier (2 mmho, 3 MHz GBW) enables stable loop response across diverse output capacitance and ESR values.
Phase-locked loop synchronization is achieved through the MODE/PLLIN pin accepting external clocks (250–750 kHz), while FREQ/PLLFLTR sets internal oscillator frequency via resistor-to-ground. The IC integrates a 5V INTVCC LDO, anti-shoot-through logic, dropout detection, and output overvoltage protection triggered at >10% above regulated voltage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide-input industrial and telecom DC distribution rails without pre-regulation. |
| Output Voltage Accuracy | ±1% over –40°C to 125°C - ensures stable system-level voltage margining for downstream processors and FPGAs. |
| Switching Frequency | 250kHz to 750kHz, phase-lockable - balances efficiency vs. magnetics size; PLL sync enables noise-sensitive multi-rail systems. |
| Current Sensing | RSENSE or DCR - allows trade-off between sensing accuracy (resistor) and power loss/cost (inductor DCR). |
| Light-Load Modes | Burst Mode™, pulse-skipping, or forced CCM - selectable via MODE/PLLIN pin to optimize efficiency or ripple/noise per application need. |
| Thermal Package | 16-pin 3mm × 3mm QFN with exposed GND pad (θJA = 68°C/W) - enables compact, high-power-density designs with reliable thermal dissipation. |
| Shutdown IQ | 20µA - minimizes standby power in always-on subsystems such as remote monitoring nodes. |
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.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 1) | Enable control input | Logic-high (>1.22V) enables operation; internal 2µA pull-up allows simple RC soft-start; <1.1V forces shutdown with INTVCC disable. |
| TK/SS (Pin 2) | Soft-start/tracking input | Internal 1µA current charges external capacitor to ramp VOUT linearly; also accepts master supply divider for ratiometric tracking. |
| ITH (Pin 3) | Error amplifier output / current threshold | Sets peak inductor current; voltage directly controls current limit; used for loop compensation network connection. |
| VFB (Pin 4) | Feedback input | Compares against 0.8V reference; connects to resistive divider on VOUT for precise regulation; ±10nA bias enables high-impedance dividers. |
| SENSE– (Pin 5) | Current sense inverting input | Connects to low-side of sense resistor or DCR network; referenced to SW node for accurate differential sensing. |
| SENSE+ (Pin 6) | Current sense non-inverting input | Connects to high-side of sense resistor or DCR network; enables bidirectional current measurement capability. |
| ILIM (Pin 7) | Current limit range select | Tied to GND/FLOAT/INTVCC to set max sense threshold to 30mV/50mV/75mV - configures current limit without external components. |
| GND (Pin 8, Exposed Pad 17) | Signal and power ground | Kelvin connection point for all small-signal references; exposed pad must be soldered for thermal integrity and low-noise grounding. |
| BG (Pin 9) | Bottom gate driver output | Drives gate of low-side N-MOSFET between GND and INTVCC; 1.1Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (Pin 10) | Internal 5V regulator output | Powers control circuitry; requires ≥2.2µF low-ESR ceramic/tantalum decoupling to GND for stability under dynamic load. |
| VIN (Pin 11) | Main input supply | Accepts 4V–38V input; decoupled to GND near IC; powers INTVCC LDO and high-side driver bootstrap circuit. |
| BOOST (Pin 12) | Floating bootstrap supply | Connects to (+) terminal of bootstrap capacitor; swings from ~INTVCC–0.4V up to VIN+INTVCC to drive high-side gate above SW node. |
| TG (Pin 13) | Top gate driver output | Floating driver output referenced to SW node; 2.2Ω pull-up/1.2Ω pull-down ensures robust gate drive with <30ns dead-time control. |
| SW (Pin 14) | Switch node | Connects to inductor and MOSFET bridge midpoint; voltage swings from ~–0.4V (Schottky drop) to VIN; critical for layout EMI control. |
| MODE/PLLIN (Pin 15) | Mode select / PLL sync input | Selects Burst Mode™ (50k–250kΩ to INTVCC), pulse-skip (float/GND), or forced CCM (tie to INTVCC); accepts external clock for synchronization. |
| FREQ/PLLFLTR (Pin 16) | Oscillator programming / PLL filter | Resistor-to-GND sets nominal frequency (250–750kHz); with external clock on MODE/PLLIN, forms PLL loop filter with series RC. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by enabling stable loop response across wide ESR ranges (e.g., polymer + ceramic mixes). |
| Tri-Level Current Limit | ILIM pin selects 30mV/50mV/75mV sense thresholds - eliminates need for precision current-sense resistors in cost-sensitive designs. |
| 99% Duty Cycle Operation | Supports ultra-low dropout (e.g., 5V→4.95V) - essential for post-regulation in high-efficiency intermediate bus architectures. |
| Output Overvoltage Protection | Hardware comparator disables TG and enables BG on >10% VOUT overshoot - protects downstream loads without software intervention. |
| Thermally Enhanced QFN | Exposed GND pad reduces θJA to 68°C/W - enables 15A+ output in compact 3mm × 3mm footprint without heatsink. |
Applications
| Telecom Intermediate Bus Converter | Industrial FPGA Core Supply |
|---|---|
Use Scenario: 48V distributed DC input stepped down to 3.3V/12A for baseband processing units in 5G remote radio heads. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing power delivery, current limiting, and thermal foldback during burst traffic loads. Use Value: ±1% output accuracy and 0.8V reference ensure FPGA I/O and core rail compliance; Burst Mode™ extends standby time in sleep-state radios. | Use Scenario: 12V input converted to 1.2V/20A for Xilinx Kintex-7 FPGA core in programmable logic controllers with real-time I/O. IC Role / Device Role / Timing Role: High-current step-down controller with DCR current sensing and OPTI-LOOP® for stable transient response under logic switching loads. Use Value: 99% duty cycle supports low-dropout operation during brownout; tri-level ILIM enables precise current limit calibration without BOM changes. |
| Automotive ADAS Domain Controller | Distributed Data Center PSU |
Use Scenario: 24V vehicle battery input regulated to 5V/8A for radar sensor fusion modules operating at –40°C to 125°C ambient. IC Role / Device Role / Timing Role: Automotive-grade buck controller providing fault-tolerant power with OVP, UVLO, and thermal shutdown. Use Value: –40°C to 125°C rating and 3mm × 3mm QFN meet AEC-Q100-relevant thermal requirements; 20µA shutdown IQ preserves battery life during ignition-off. | Use Scenario: 54V intermediate bus converted to 12V/30A for server motherboard VRMs in edge computing nodes with strict acoustic noise limits. IC Role / Device Role / Timing Role: Synchronous controller operating in pulse-skipping mode to reduce audible noise while maintaining <1% output ripple. Use Value: Pulse-skipping mode eliminates sub-harmonic whine common in Burst Mode™; 250kHz–750kHz programmability avoids sensitive RF bands. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8640S | Integrated 6A power stage; higher integration but fixed 3.3V/5V/12V options; lower max VIN (42V) | Best for space-constrained designs needing integrated MOSFETs and lower component count | Select LT8640S when board area is critical and output voltage is standard; LTC3851AEUD#TRPBF preferred for custom high-current discrete MOSFET solutions. |
| TPS53689 | TI part with PMBus interface, digital loop compensation, and 3.5V–24V VIN range; no DCR sensing support | Suitable for digitally managed power systems requiring telemetry and adaptive loop tuning | Choose TPS53689 for closed-loop telemetry and firmware-based optimization; LTC3851AEUD#TRPBF for analog simplicity and wide 4V–38V operation. |
Compared with LT8640S and TPS53689, the LTC3851AEUD#TRPBF offers broader input range (4V–38V), flexible DCR/RSENSE sensing, and analog OPTI-LOOP® compensation-making it ideal for high-reliability industrial and telecom converters where discrete MOSFET selection and analog control stability are prioritized over digital features or integration.
Availability
LTC3851AEUD#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial FPGA core rails, automotive ADAS domain controllers, and distributed data center PSUs requiring stable component supply across extended temperature and long product lifecycles.
Supply support for LTC3851AEUD#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 industrial, automotive, communications, and aerospace markets.
The LTC3851A product line delivers high-efficiency, high-voltage synchronous buck controllers optimized for demanding intermediate bus and point-of-load applications where precision regulation, thermal robustness, and flexible current sensing are critical.
FAQ
What is the maximum input voltage rating for the LTC3851AEUD#TRPBF?
The LTC3851AEUD#TRPBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation from 4V to 38V. Exceeding 40V risks permanent damage per Absolute Maximum Ratings. Its wide 4V–38V range makes the LTC3851AEUD#TRPBF suitable for 24V and 48V industrial and telecom systems with input transients.
How does the ILIM pin configure current limit thresholds on the LTC3851AEUD#TRPBF?
The ILIM pin on the LTC3851AEUD#TRPBF provides tri-level current limit selection: tying to GND sets 30mV, floating sets 50mV, and connecting to INTVCC sets 75mV maximum sense voltage. This directly scales the current comparator threshold without external resistors, enabling rapid design iteration for different MOSFET RDS(on) or sense resistor values in the LTC3851AEUD#TRPBF application.
Can the LTC3851AEUD#TRPBF synchronize to an external clock, and how is it configured?
Yes, the LTC3851AEUD#TRPBF supports external clock synchronization via the MODE/PLLIN pin. When an external clock (250–750 kHz) is applied, the internal oscillator locks to it in forced continuous conduction mode. A series RC network on FREQ/PLLFLTR serves as the PLL loop filter. This feature is essential for noise-sensitive multi-rail systems using the LTC3851AEUD#TRPBF in telecom or test equipment.
What thermal advantages does the QFN package of the LTC3851AEUD#TRPBF provide over MSOP or SSOP variants?
The LTC3851AEUD#TRPBF's 3mm × 3mm QFN package features an exposed GND pad with θJA = 68°C/W, significantly lower than the 110°C/W (SSOP) and ~40°C/W (MSOP) of other variants. This enables higher continuous output current in compact layouts and improves reliability in thermally constrained enclosures-key for dense telecom and industrial applications using the LTC3851AEUD#TRPBF.
Does the LTC3851AEUD#TRPBF support output voltage tracking during startup?
Yes, the LTC3851AEUD#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 LTC3851AEUD#TRPBF regulates its output to track that supply during startup-ensuring proper sequencing in multi-rail systems like FPGAs or ASICs without requiring external supervisors.
LTC3851AEUD#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:
- 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#TRPBF FAQ
1.How can I place an order for LTC3851AEUD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AEUD#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 LTC3851AEUD#TRPBF reliable?
The price and inventory of LTC3851AEUD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AEUD#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851AEUD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AEUD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AEUD#TRPBF?
LTC3851AEUD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AEUD#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 LTC3851AEUD#TRPBF?
For technical support, including LTC3851AEUD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AEUD#TRPBF requirements.
6.How does Aetrix verify that LTC3851AEUD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AEUD#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 LTC3851AEUD#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851AEUD#TRPBF?
All LTC3851AEUD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AEUD#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 LTC3851AEUD#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851AEUD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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