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Analog Devices Inc. LTC3851IMSE#PBF
- Part No.:
- LTC3851IMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851IMSE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:173
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Product details
Overview
LTC3851IMSE#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 OPTI-LOOP® compensation for wide output capacitor/ESR optimization. It is used in telecom power supplies requiring high efficiency and tight regulation under dynamic load.
For engineers reviewing the LTC3851IMSE#PBF datasheet, LTC3851IMSE#PBF pinout, LTC3851IMSE#PBF application, or LTC3851IMSE#PBF equivalent, key selection criteria include its RSENSE/DCR current sensing flexibility, selectable light-load modes (Burst/Pulse-Skip/CCM), 99% duty cycle capability, integrated 5V INTVCC regulator, and thermal performance in the –40°C to 125°C industrial temperature range.
Technical Context
The LTC3851IMSE#PBF implements a constant-frequency current-mode control architecture with slope compensation, enabling stable operation across wide duty cycles and input/output combinations. Its transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) drives the ITH node to regulate peak inductor current via voltage-controlled threshold modulation.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, anti-shoot-through logic, and programmable current limit via ILIM pin (30/50/75 mV thresholds). The MODE/PLLIN pin enables mode selection (Burst/Pulse-Skip/CCM) or external clock synchronization, while FREQ/PLLFLTR sets oscillator frequency or serves as PLL loop filter.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide industrial, telecom, and automotive input rails without pre-regulation. |
| Output Voltage Accuracy | ±1% at VFB - ensures precise regulation of downstream digital ICs and analog circuitry. |
| Switching Frequency | 250kHz to 750kHz - adjustable via resistor on FREQ/PLLFLTR; enables trade-off between efficiency and magnetics size. |
| Current Sense Threshold | 30/50/75 mV (ILIM-selectable) - allows accurate, low-loss current limiting with minimal power dissipation in sense elements. |
| Duty Cycle Max | 99% - supports ultra-low dropout operation, critical for high-current, low-VOUT applications like CPU core supplies. |
| INTVCC Regulator | 5.0V ±2% - powers internal logic and gate drivers; eliminates need for external bias supply. |
| Shutdown IQ | 20μA - enables low-power standby in battery-backed or energy-sensitive systems. |
| Operating Temp Range | –40°C to +125°C - qualified for harsh industrial and automotive under-hood environments. |
Pinout & Package
Package: 16-lead plastic MSOP (MSE) with exposed pad (Pin 17 = GND), θJA = 40°C/W, thermally enhanced for high-current DC/DC designs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 1) | Mode selection & sync input | Selects Burst/Pulse-Skip/CCM or accepts external clock up to 750kHz for system-wide timing coherence. |
| FREQ/PLLFLTR (Pin 2) | Oscillator programming / PLL filter | Resistor-to-GND sets nominal frequency; RC network enables PLL lock when synchronized externally. |
| RUN (Pin 3) | Enable control | 1.25V threshold with 130mV hysteresis; internal 2μA pull-up enables simple logic-level enable without external bias. |
| TK/SS (Pin 4) | Soft-start & tracking input | 1μA internal charge current ramps external capacitor for controlled VOUT rise; supports ratiometric tracking of master supplies. |
| ITH (Pin 5) | Error amp output & current threshold | Voltage-controlled peak current setpoint; directly modulates comparator trip point for fast transient response. |
| VFB (Pin 6) | Feedback input | Compares resistive divider output to 0.8V reference; high-impedance input minimizes loading errors. |
| SENSE– (Pin 7) | Current sense inverting input | High-Z node referenced to SW; enables Kelvin connection for accurate DCR or RSENSE sensing. |
| SENSE+ (Pin 8) | Current sense non-inverting input | Accepts voltage from DCR network or sense resistor; common-mode range 0V–5.5V supports high-side sensing. |
| ILIM (Pin 9) | Current limit select | Tri-level logic (GND/FLOAT/INTVCC) selects 30/50/75 mV max sense threshold for design flexibility. |
| GND (Pin 10) | Analog ground reference | Kelvin connection point for FB, SENSE, and compensation components; exposed pad must be soldered for thermal and noise integrity. |
| BG (Pin 11) | Bottom gate driver | Drives N-MOSFET source-to-GND; 1.1Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (Pin 12) | Internal 5V regulator output | Powers internal circuitry and gate drivers; requires ≥2.2μF low-ESR ceramic/tantalum decoupling to GND. |
| VIN (Pin 13) | Main input supply | Accepts 4V–38V; feeds INTVCC LDO and provides power path to boost capacitor and TG driver. |
| BOOST (Pin 14) | Bootstrap supply | Floats above SW; charges external bootstrap capacitor to drive TG with full swing (INTVCC + VIN). |
| TG (Pin 15) | Top gate driver | High-side floating driver with 2.6Ω pull-up/1.5Ω pull-down; optimized for fast, low-loss N-MOSFET switching. |
| SW (Pin 16) | Switch node | Connects to inductor and external Schottky diode; voltage swings from ~–0.3V to VIN; critical for layout EMI control. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by adapting loop dynamics to actual COUT and ESR - reduces BOM cost and board area. |
| Adjustable Light-Load Operation | Three selectable modes (Burst/Pulse-Skip/CCM) optimize efficiency vs. ripple/noise trade-offs across full load range. |
| DCR or RSENSE Current Sensing | Eliminates sense resistor losses in high-current designs (DCR) or enables precision current limiting (RSENSE). |
| Output Overvoltage Protection | Hardware-based OV comparator disables TG and enables BG immediately upon >10% VOUT overshoot - protects downstream loads. |
| 99% Maximum Duty Cycle | Enables high-efficiency operation at very low VOUT/VIN ratios (e.g., 1.2V out from 12V rail) without dropout. |
| Thermally Enhanced MSOP | Exposed pad and 40°C/W θJA enable reliable 15A+ output current in compact industrial PCB layouts. |
Applications
| Telecom Power Supply | Industrial PLC Module |
|---|---|
|
Use Scenario: 48V backplane-to-3.3V/5V conversion for line-card processors and FPGA I/O banks. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating intermediate bus voltage with tight transient response. Use Value: ±1% VOUT accuracy and 750kHz switching enable compact, high-density power modules meeting GR-1089 EMC requirements. |
Use Scenario: 24V field power to isolated 5V/3.3V rails for microcontroller, ADC, and communication interfaces. IC Role / Device Role / Timing Role: Robust main DC/DC controller operating continuously in –40°C to +85°C ambient with no derating. Use Value: –40°C to +125°C rating and 38V max VIN ensure reliability in unregulated industrial power environments. |
| Automotive ADAS Camera Module | Distributed Data Center PSU |
|
Use Scenario: 12V vehicle battery to 1.2V core and 1.8V I/O for image signal processor in rear-view camera. IC Role / Device Role / Timing Role: High-efficiency synchronous buck controller with soft-start and tracking for multi-rail sequencing. Use Value: TK/SS pin enables ratiometric startup with master 3.3V rail; 99% duty cycle maintains regulation during cold-crank dips. |
Use Scenario: Point-of-load conversion from 12V intermediate bus to 0.8V–1.8V for ASICs and memory in server blades. IC Role / Device Role / Timing Role: Precision current-mode controller supporting DCR sensing to eliminate heat-generating sense resistors. Use Value: RSENSE/DCR flexibility and 50mA INTVCC drive support high-current, low-VOUT designs with <1% load regulation. |
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 | Integrated 4A power stage; 2.8V–42V input; 3.3V/5V fixed or adjustable output; Silent Switcher® architecture. | Lower component count, lower EMI; not pin-compatible; lacks ILIM tri-level current limit and DCR sensing support. | Choose LT8640S for space-constrained, low-EMI designs where integration outweighs configurability needs. |
| MP2918 | Monolithic 12A buck converter; 4.5V–18V input; 0.6V–5.5V output; PMBus interface; 500kHz–2.2MHz programmable frequency. | Includes telemetry and digital control; higher integration but narrower VIN range and no 38V capability. | Choose MP2918 for digitally managed, mid-power systems requiring telemetry and tighter thermal monitoring. |
Compared with LT8640S and MP2918, the LTC3851IMSE#PBF offers superior input voltage range (4V–38V), discrete MOSFET flexibility for high-current scaling, and dedicated DCR/RSENSE current sensing - making it optimal for rugged, high-reliability industrial and telecom power stages where configurability and robustness are prioritized over integration.
Availability
LTC3851IMSE#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLCs, and automotive ADAS modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LTC3851IMSE#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, serving industrial, automotive, communications, and healthcare markets.
The LTC3851 belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding DC/DC conversion in telecom infrastructure, industrial automation, and distributed power systems where precision, reliability, and thermal resilience are critical.
FAQ
What is the maximum input voltage rating for the LTC3851IMSE#PBF?
The LTC3851IMSE#PBF has an absolute maximum input voltage (VIN) rating of 40V, with guaranteed operation from 4V to 38V. This wide input range makes it suitable for 24V and 48V industrial and telecom systems, including those subject to load dump or line transients. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
How does the ILIM pin affect current limiting on the LTC3851IMSE#PBF?
The ILIM pin on the LTC3851IMSE#PBF provides tri-level current limit selection: grounding sets 30mV threshold, floating sets 50mV, and tying to INTVCC sets 75mV. This directly scales the maximum allowable VSENSE differential, enabling precise, lossless current limiting tailored to MOSFET RDS(on), sense resistor value, or DCR network gain - all without changing external components.
Can the LTC3851IMSE#PBF synchronize to an external clock, and how is it configured?
Yes, the LTC3851IMSE#PBF can synchronize to an external clock via the MODE/PLLIN pin (Pin 1). When driven with a clean square wave (250kHz–750kHz), the internal PLL locks and forces continuous conduction mode. The FREQ/PLLFLTR pin (Pin 2) must be connected to GND through an RC network to serve as the PLL loop filter - ensuring stable lock and low jitter in synchronized systems.
What package type and thermal characteristics apply to the LTC3851IMSE#PBF?
The LTC3851IMSE#PBF uses a 16-lead plastic MSOP (MSE) package with exposed thermal pad (Pin 17 = GND). Its thermal resistance is θJA = 40°C/W (typical), significantly lower than SSOP variants, enabling higher power density in industrial designs. The exposed pad must be soldered to a thermal pad on the PCB for effective heat dissipation and noise reduction.
Does the LTC3851IMSE#PBF support output voltage tracking, and how is it implemented?
Yes, the LTC3851IMSE#PBF supports ratiometric output voltage tracking via the TK/SS pin (Pin 4). By connecting an external resistor divider from a master supply to GND at this pin, the controller ramps its output to match the master's rise profile. This enables safe, sequenced startup of multiple rails - essential in FPGA, DSP, and multi-core processor applications where voltage sequencing prevents latch-up.
LTC3851IMSE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) 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:
- 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-MSOP-EP
LTC3851IMSE#PBF FAQ
1.How can I place an order for LTC3851IMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851IMSE#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 LTC3851IMSE#PBF reliable?
The price and inventory of LTC3851IMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851IMSE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851IMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851IMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851IMSE#PBF?
LTC3851IMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851IMSE#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 LTC3851IMSE#PBF?
For technical support, including LTC3851IMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851IMSE#PBF requirements.
6.How does Aetrix verify that LTC3851IMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851IMSE#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 LTC3851IMSE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851IMSE#PBF?
All LTC3851IMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851IMSE#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 LTC3851IMSE#PBF part is unused and in its original packaging.
Return procedure for LTC3851IMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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