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Analog Devices Inc. LTC3851AEGN#PBF
- Part No.:
- LTC3851AEGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3851AEGN#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:104
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Product details
Overview
LTC3851AEGN#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 output with ±1% accuracy, supports phase-lockable 250kHz–750kHz switching, and enables Burst Mode™ for ultra-low-light-load efficiency - used in telecom power supplies and industrial DC/DC converters.
For engineers reviewing the LTC3851AEGN#PBF datasheet, LTC3851AEGN#PBF pinout, LTC3851AEGN#PBF application, or LTC3851AEGN#PBF equivalent, key selection criteria include its RSENSE/DCR current sensing flexibility, OPTI-LOOP® compensation for wide output capacitor/ESR tolerance, adjustable soft-start via TK/SS pin, and selectable light-load operation modes (Burst/Pulse-Skipping/Continuous).
Technical Context
The LTC3851AEGN#PBF implements a constant-frequency current-mode control loop where peak inductor current is set by the ITH voltage, and output regulation is maintained via error amplifier comparison of VFB against a precision 0.8V reference. Its transconductance amplifier (gm = 2 mmho, GBW = 3 MHz) provides stable servo-loop response across temperature and load.
It integrates a 5V internal LDO (INTVCC), dual gate drivers with matched 25ns rise/fall times and <30ns dead-time control, and a robust PLL circuit enabling synchronization to external clocks up to 750kHz. The IC features dedicated overvoltage protection (OV comparator), reverse-current prevention (IREV), and dropout recovery logic that forces periodic top-FET off-time 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 pre-regulation. |
| Output Voltage Accuracy | ±1% over –40°C to 125°C - ensures tight regulation for sensitive digital loads like FPGAs and ASICs. |
| Switching Frequency | 250kHz to 750kHz, phase-lockable - balances efficiency vs. magnetics size; enables EMI reduction via synchronization. |
| Current Sensing | RSENSE or DCR - allows cost-optimized (DCR) or precision (shunt) current limit implementation. |
| Light-Load Modes | Burst Mode™, Pulse-Skipping, Continuous Conduction - selectable via MODE/PLLIN pin for optimal efficiency across load range. |
| Soft-Start/Tracking | Programmable via TK/SS pin with 1µA internal charge current - enables controlled ramp-up and supply sequencing. |
| Shutdown IQ | 20µA - minimizes system standby power in battery-backed or always-on applications. |
Pinout & Package
Package: 16-Lead Plastic SSOP (Narrow), RoHS-compliant, exposed pad not present (GN package). Thermal resistance θJA = 110°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 1) | Mode selection & external clock input | Selects Burst/Pulse-Skipping/Continuous mode or synchronizes oscillator to external clock up to 750kHz. |
| FREQ/PLLFLTR (Pin 2) | PLL filter / frequency programming node | Connects RC network to set free-running frequency (250–750kHz) or serve as PLL loop filter. |
| RUN (Pin 3) | Enable/disable control input | Active-high enable with 1.22V threshold and 120mV hysteresis; internal 2µA pull-up enables simple RC startup delay. |
| TK/SS (Pin 4) | Soft-start and tracking control | Internal 1µA current charges external capacitor to ramp output voltage; supports ratiometric or coincident tracking. |
| ITH (Pin 5) | Error amplifier output & current threshold | Sets peak inductor current; also serves as compensation point for OPTI-LOOP® stability optimization. |
| VFB (Pin 6) | Feedback input | Compares remote-sensed output voltage against 0.8V reference; ±1% accuracy over full temperature range. |
| SENSE– (Pin 7) | Current sense inverting input | Connected to output node for DCR sensing or low-side shunt; rejects common-mode noise. |
| SENSE+ (Pin 8) | Current sense non-inverting input | Connected to DCR network or shunt resistor; enables accurate current foldback during short-circuit. |
| ILIM (Pin 9) | Current limit threshold select | Tri-level logic (GND/FLOAT/INTVCC) sets max sense threshold to 30/50/75mV for flexible overcurrent protection. |
| GND (Pin 10) | Analog and power ground | Kelvin connection point for feedback, compensation, and input/output capacitors; critical for noise immunity. |
| BG (Pin 11) | Bottom gate driver output | Drives low-side N-MOSFET gate between GND and INTVCC; 1.1Ω pull-down ensures fast turn-off. |
| INTVCC (Pin 12) | 5V internal regulator output | Powers control circuitry; requires ≥2.2µF low-ESR capacitor; load regulation ≤2% from 0–50mA. |
| VIN (Pin 13) | Main input supply | Accepts 4–38V; powers INTVCC LDO and high-side driver bootstrap circuit; decoupling mandatory. |
| BOOST (Pin 14) | Bootstrap supply for top gate driver | Swings from ~INTVCC–0.7V to VIN+INTVCC; recharged via external diode during bottom-FET conduction. |
| TG (Pin 15) | Top gate driver output | Floating driver with 2.2Ω pull-up / 1.2Ω pull-down; drives high-side N-MOSFET gate referenced to SW node. |
| SW (Pin 16) | Switch node connection | Connects to inductor and external Schottky catch diode anode; voltage swings from ~–0.4V to VIN. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance and relaxes ESR constraints - simplifies design with ceramic or polymer caps. |
| Dual N-Channel MOSFET Drive | Integrated high- and low-side gate drivers with matched timing and <30ns dead-time - eliminates external driver ICs. |
| 99% Duty Cycle Operation | Enables ultra-low dropout regulation - supports VIN-to-VOUT differentials as low as 100mV at light loads. |
| Output Overvoltage Protection | Hardware-based OV comparator triggers immediate top-FET shutdown and bottom-FET activation - protects downstream loads. |
| Adjustable Current Foldback | Three ILIM-selectable thresholds (30/50/75mV) plus programmable ITH slope - prevents MOSFET thermal runaway during shorts. |
Applications
| Telecom Power Supply | Industrial Motor Control Logic Supply |
|---|---|
|
Use Scenario: Point-of-load conversion in 48V telecom systems powering baseband processors and SerDes interfaces. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating 3.3V/5V rails with tight transient response and high efficiency at partial load. Use Value: Burst Mode™ achieves >85% efficiency at 10mA load, reducing heat buildup in dense chassis; phase-locking suppresses beat frequencies in multi-rail systems. |
Use Scenario: Generating isolated 15V gate drive and 5V logic supply from 24V industrial bus for servo motor drivers. IC Role / Device Role / Timing Role: High-reliability step-down controller with RSENSE current sensing for precise current limiting and fault reporting. Use Value: ±1% output accuracy ensures consistent gate drive voltage; 38V max input withstands load-dump transients per ISO 16750-2. |
| Automotive ADAS Camera Module | Distributed DC Power System |
|
Use Scenario: Powering image sensor and ISP in rear-view camera modules operating from 9–16V automotive battery. IC Role / Device Role / Timing Role: Synchronous buck controller with soft-start and tracking for clean power-up sequencing with FPGA and MIPI interface. Use Value: TK/SS pin enables ratiometric tracking of master 1.8V rail; 125°C junction rating supports under-hood mounting. |
Use Scenario: Secondary regulation stage in modular server power architecture converting 12V intermediate bus to 1.2V CPU core voltage. IC Role / Device Role / Timing Role: High-frequency (750kHz) current-mode controller enabling compact magnetics and fast load-step response. Use Value: 250kHz–750kHz programmability allows optimization for efficiency (low-freq) or size (high-freq); DCR sensing reduces BOM cost and losses. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2451DT-LF-Z | Fixed 500kHz frequency, no PLL sync, no Burst Mode, lower max input (36V), no DCR sensing. | Suitable for cost-sensitive, fixed-frequency designs where light-load efficiency is secondary. | Choose when simplicity and footprint matter more than dynamic frequency control or ultra-low-IQ operation. |
| TPS54332DR | Integrated high-side MOSFET, lower current capability (3.5A), no ILIM tri-level, no OPTI-LOOP®. | Targeted at lower-power applications (<10W); lacks external MOSFET flexibility and advanced compensation. | Prefer when board space is constrained and discrete FETs are unnecessary; avoid for >15A designs or wide-COUT designs. |
Compared with MP2451DT-LF-Z and TPS54332DR, the LTC3851AEGN#PBF offers superior design flexibility through its programmable frequency, three light-load modes, tri-level current limit, and OPTI-LOOP® compensation - making it ideal for high-performance, thermally constrained, or EMI-sensitive applications requiring external FETs.
Availability
LTC3851AEGN#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial motor control logic supplies, automotive ADAS camera modules, and distributed DC power systems requiring stable component supply, long-term lifecycle support, and guaranteed RoHS compliance.
Supply support for LTC3851AEGN#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, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC3851AEGN#PBF belongs to ADI's Power by Linear™ synchronous controller family, designed specifically for high-efficiency, high-reliability DC/DC conversion in demanding industrial, telecom, and automotive environments.
FAQ
What is the maximum input voltage rating for the LTC3851AEGN#PBF?
The LTC3851AEGN#PBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation up to 38V. This allows reliable use in 24V and 36V industrial and telecom systems, including those subject to load-dump transients. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
How does the ILIM pin configure current limit thresholds on the LTC3851AEGN#PBF?
The ILIM pin on the LTC3851AEGN#PBF is a tri-level logic input: tying it to GND selects 30mV, floating selects 50mV, and connecting to INTVCC selects 75mV maximum current sense threshold. These settings directly scale the peak inductor current limit and are confirmed in the Electrical Characteristics table (VSENSE(MAX)) across all temperature grades.
Can the LTC3851AEGN#PBF synchronize to an external clock, and what is the supported frequency range?
Yes, the LTC3851AEGN#PBF can synchronize its internal oscillator to an external clock applied to the MODE/PLLIN pin, supporting input frequencies from 250kHz to 750kHz. When synchronized, the device operates in forced continuous conduction mode, and the FREQ/PLLFLTR pin must be configured with an RC loop filter for stable PLL lock.
What package type and thermal characteristics apply to the LTC3851AEGN#PBF?
The LTC3851AEGN#PBF uses the 16-lead plastic narrow SSOP (GN package) with θJA = 110°C/W. It operates over –40°C to 125°C junction temperature and features no exposed thermal pad. PCB layout must provide adequate copper area and airflow to maintain TJ ≤ 125°C under full load, especially at high VIN/VOUT ratios.
Does the LTC3851AEGN#PBF support both RSENSE and DCR current sensing, and how is selection implemented?
Yes, the LTC3851AEGN#PBF supports both methods: RSENSE uses discrete shunt resistors connected between SENSE+ and SENSE–, while DCR sensing connects the same pins across the inductor's parasitic resistance. No configuration pin is needed - topology is determined solely by external component choice and layout, as validated in the Typical Application and Applications Information sections.
LTC3851AEGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- 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-SSOP
LTC3851AEGN#PBF FAQ
1.How can I place an order for LTC3851AEGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AEGN#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 LTC3851AEGN#PBF reliable?
The price and inventory of LTC3851AEGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AEGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851AEGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AEGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AEGN#PBF?
LTC3851AEGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AEGN#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 LTC3851AEGN#PBF?
For technical support, including LTC3851AEGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AEGN#PBF requirements.
6.How does Aetrix verify that LTC3851AEGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AEGN#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 LTC3851AEGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851AEGN#PBF?
All LTC3851AEGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AEGN#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 LTC3851AEGN#PBF part is unused and in its original packaging.
Return procedure for LTC3851AEGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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