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Analog Devices Inc. LTC3851AEMSE#TRPBF
- Part No.:
- LTC3851AEMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851AEMSE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:11,063
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Product details
Overview
LTC3851AEMSE#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™ for ultra-low-light-load efficiency. It is used in telecom power supplies requiring tight regulation and fast transient response under wide input and load variations.
For engineers reviewing the LTC3851AEMSE#TRPBF datasheet, LTC3851AEMSE#TRPBF pinout, LTC3851AEMSE#TRPBF application, or LTC3851AEMSE#TRPBF equivalent, key selection criteria include its OPTI-LOOP® compensation flexibility, selectable light-load operating modes (Burst/Pulse-Skip/CCM), RSENSE or DCR current sensing, 99% duty cycle capability, and thermally enhanced 16-lead MSOP package with exposed pad.
Technical Context
The LTC3851AEMSE#TRPBF implements a constant-frequency current-mode control loop with transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and precision 0.8V reference (±1% over –40°C to 125°C). Its ITH pin serves as both error amplifier output and current threshold control, enabling dynamic peak-current adjustment across load transients.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, 30ns dead-time control, and independent pull-up/pull-down resistances (TG: 2.2Ω/1.2Ω; BG: 2.1Ω/1.1Ω). The internal 5V INTVCC regulator (4.8V–5.2V, ±2% load regulation) powers all logic and drivers, while the PLL circuit accepts external synchronization up to 750kHz via MODE/PLLIN and uses FREQ/PLLFLTR for loop filtering.
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% - ensures stable system-level voltage margins for sensitive digital loads. |
| Switching Frequency Range | 250kHz to 750kHz - adjustable via resistor on FREQ/PLLFLTR; enables optimization of size vs. efficiency. |
| Light-Load Efficiency Mode | Burst Mode™, Pulse-Skipping, or Forced CCM - selectable via MODE/PLLIN; Burst Mode achieves >85% efficiency at 1mA load. |
| Current Sensing Options | RSENSE or DCR - supports cost-sensitive (DCR) or precision (shunt) designs without external op-amps. |
| Thermal Package | 16-Lead MSOP with exposed pad (θJA = 40°C/W) - enables high-power density layouts with direct PCB thermal conduction. |
| Shutdown Quiescent Current | 20µA - minimizes standby power in battery-backed or always-on systems. |
Pinout & Package
Package: 16-Lead Plastic MSOP (MSE) with exposed thermal pad (Pin 17 = GND), rated for –40°C to 125°C junction temperature. Exposed pad must be soldered to PCB ground plane for thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 15) | Mode selection & external clock sync input | Selects Burst Mode™ (via 50k–250k resistor to INTVCC), Pulse-Skipping (float/GND), or Forced CCM (tie to INTVCC); also accepts external clock up to 750kHz for synchronization. |
| FREQ/PLLFLTR (Pin 16) | Oscillator frequency programming / PLL filter node | Sets nominal frequency (250–750kHz) via resistor-to-GND; when PLL active, hosts RC loop filter for stable synchronization. |
| RUN (Pin 1) | Enable/disable control with hysteresis | Turns IC on above 1.22V (120mV hysteresis); pulls down to <1.1V to shut down entire controller and INTVCC regulator. |
| TK/SS (Pin 2) | Soft-start and tracking control | Internal 1µA current charges external capacitor to ramp VOUT linearly; also supports ratiometric or coincident tracking of master supply. |
| ITH (Pin 3) | Error amplifier output & current threshold control | Directly sets peak inductor current; voltage range 0.4V–1.6V defines current limit and loop dynamics. |
| VFB (Pin 4) | Feedback input to error amplifier | Compares remote-sensed output voltage against 0.8V reference; high-impedance (–50nA bias) enables precision divider networks. |
| SENSE– (Pin 5) | Inverting current sense input | Connects to low-side of sense resistor or DCR network; referenced to SW node for accurate differential measurement. |
| SENSE+ (Pin 6) | Non-inverting current sense input | Connects to high-side of sense resistor or DCR network; enables Kelvin sensing to reject PCB trace resistance errors. |
| ILIM (Pin 7) | Tri-level current limit select | GND = 30mV, Float = 50mV, INTVCC = 75mV - configures maximum sense threshold without external components. |
| GND (Pin 8 + Exposed Pad) | Signal and power ground reference | All small-signal paths (FB, SENSE, ITH) must Kelvin-connect here; exposed pad is mandatory thermal path to PCB ground plane. |
| BG (Pin 9) | Bottom N-MOSFET gate driver output | Drives low-side switch between GND and INTVCC; 1.1Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (Pin 10) | Internal 5V regulator output | Powers internal logic and gate drivers; requires ≥2.2µF low-ESR ceramic/tantalum decoupling to GND. |
| VIN (Pin 11) | Main input supply connection | Accepts 4V–38V; feeds INTVCC LDO and high-side driver bootstrap circuit; requires local bulk capacitance. |
| BOOST (Pin 12) | Floating high-side driver supply | Connects to bootstrap capacitor (+) terminal; swings from ~INTVCC–0.4V to VIN+INTVCC for top-gate drive. |
| TG (Pin 13) | Top N-MOSFET gate driver output | Floating driver with swing = INTVCC superimposed on SW node; 2.2Ω pull-up ensures robust turn-on under high dV/dt. |
| SW (Pin 14) | Switch node connection | Connects to inductor and MOSFET drains; voltage swings from ~–0.4V (Schottky drop) to VIN; critical for EMI layout. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by allowing stable loop tuning across wide ranges of COUT and ESR - eliminates need for trial-and-error compensation. |
| Tri-Level ILIM Programming | Hardware-selectable current limits (30/50/75mV) enable precise overcurrent protection without trimming resistors or DACs. |
| 99% Duty Cycle Operation | Supports ultra-low dropout applications (e.g., 12V→11.5V) where minimal voltage difference demands maximum on-time. |
| Output Overvoltage Protection (OVP) | Hardware-based comparator triggers immediate TG off/BG on during >10% VOUT overshoot - protects downstream ICs without software intervention. |
| Integrated 5V INTVCC Regulator | Eliminates need for external bias supply; delivers 50mA peak current to drive external MOSFET gates and internal logic reliably. |
Applications
| Telecom Power Supply | Industrial PLC Module |
|---|---|
Use Scenario: 48V DC input converted to isolated 3.3V/5V rails for baseband processing and FPGA I/O in 4G/5G remote radio units. IC Role / Device Role / Timing Role: Primary non-isolated buck controller regulating intermediate bus; synchronizes to system clock via MODE/PLLIN to reduce spectral noise. Use Value: Phase-lockable 750kHz operation enables smaller magnetics; Burst Mode maintains >90% efficiency at standby load (50mA), reducing thermal stress in sealed enclosures. | Use Scenario: DIN-rail mounted programmable logic controller requiring reliable 5V/3A rail from 24V industrial supply with wide ambient temperature range. IC Role / Device Role / Timing Role: High-efficiency synchronous buck controller managing fieldbus interface and microcontroller core voltage; uses DCR sensing to eliminate shunt resistor losses. Use Value: ±1% output accuracy and –40°C to 125°C guaranteed operation ensure deterministic behavior across factory floor temperatures; 99% duty cycle supports brownout tolerance down to 22V input. |
| Distributed DC Power System | Automotive Infotainment Head Unit |
Use Scenario: Central 28V battery bus distributed to multiple point-of-load converters powering DSPs, ADCs, and memory in avionics-grade equipment. IC Role / Device Role / Timing Role: POL controller implementing ratiometric tracking (via TK/SS) to match master 1.2V core rail during power-up sequencing. Use Value: Coincident tracking ensures safe power sequencing without external supervisors; OPTI-LOOP® accommodates diverse output caps across multiple boards using same design files. | Use Scenario: 12V automotive battery supplying clean 1.8V/2A core voltage to SoC in head unit, subject to cold-crank (4.5V) and load-dump (40V) transients. IC Role / Device Role / Timing Role: Robust buck controller with 4V–38V input range and integrated OVP; uses RSENSE sensing for accurate current limiting during fault conditions. Use Value: Absolute max ratings (VIN = 40V, SW = –5V) and shutdown IQ = 20µA meet ISO 16750-2 requirements; ILIM pin allows hardware-set 5A limit for short-circuit survival. |
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 |
|---|---|---|---|
| LTC3851EMSE#TRPBF | Base version without A-grade PLL enhancement; slightly lower phase margin stability under wide COUT/ESR variation. | Lacks improved PLL jitter suppression; less suitable for noise-sensitive RF subsystems requiring tight clock alignment. | Lower-cost option for non-synchronized or fixed-frequency applications where Burst Mode efficiency is primary concern. |
| MP2918GL-Z | Monolithic 30V buck converter (integrated MOSFETs); no external FET drive; fixed 500kHz frequency; no PLL sync or DCR sensing. | Not a controller - lacks flexibility for high-current (>15A) or high-input-voltage (>30V) designs; no soft-start tracking. | Only viable for space-constrained, medium-power (<8A), fixed-frequency applications where integration outweighs configurability. |
Compared with LTC3851EMSE#TRPBF, the LTC3851AEMSE#TRPBF offers tighter PLL jitter control and optimized light-load transient recovery; versus MP2918GL-Z, it provides full external FET control, wider VIN, and advanced features like ratiometric tracking - making it superior for high-reliability, multi-rail, or thermally demanding systems.
Availability
LTC3851AEMSE#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLC modules, and distributed DC power systems requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LTC3851AEMSE#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 and maintains full product support, documentation, and manufacturing continuity for all Linear ICs including the LTC series.
The LTC3851A belongs to Linear's high-performance power controller family, designed specifically for demanding DC/DC conversion in telecom infrastructure, industrial automation, and automotive electronics where efficiency, reliability, and thermal performance are critical.
FAQ
What is the maximum supported switching frequency for the LTC3851AEMSE#TRPBF?
The LTC3851AEMSE#TRPBF supports a phase-lockable switching frequency up to 750kHz, achievable by setting the FREQ/PLLFLTR resistor to 36kΩ. At this frequency, minimum on-time is 90ns, enabling high-VIN-to-low-VOUT conversions (e.g., 36V→1.2V) with practical inductor values. Operation above 750kHz is not specified or guaranteed.
How does the ILIM pin configure current limit thresholds on the LTC3851AEMSE#TRPBF?
The ILIM pin on the LTC3851AEMSE#TRPBF provides tri-level hardware programming: tying to GND selects 30mV, floating selects 50mV, and connecting to INTVCC selects 75mV maximum current sense threshold. These correspond to precise peak inductor current limits without external resistors, enabling rapid fault-response tuning for different MOSFET RDS(on) and sense resistor values.
Can the LTC3851AEMSE#TRPBF operate with an input voltage below 4V?
No - the LTC3851AEMSE#TRPBF has a specified minimum operating input voltage of 4V per Absolute Maximum Ratings and Electrical Characteristics tables. Below 4V, the INTVCC regulator cannot sustain 5V output, causing undervoltage lockout (UVLO) activation at 3.25V, and gate drivers lose sufficient voltage headroom for reliable N-MOSFET turn-on.
Does the LTC3851AEMSE#TRPBF support output voltage tracking during startup?
Yes - the LTC3851AEMSE#TRPBF supports both coincident and ratiometric tracking via the TK/SS pin. When an external resistor divider connects a master supply to TK/SS, the controller ramps VOUT to track that reference. This ensures controlled power-up sequencing in multi-rail systems, preventing latch-up or back-powering of unpowered ICs.
What thermal considerations apply to the exposed pad on the LTC3851AEMSE#TRPBF MSOP package?
For the LTC3851AEMSE#TRPBF in the 16-lead MSOP package, the exposed pad (Pin 17) is electrically and thermally connected to GND. It must be soldered to a PCB copper pour with ≥4 thermal vias (0.3mm diameter) to an internal or bottom-layer ground plane. This achieves θJA = 40°C/W; omitting the pad connection degrades thermal performance by >50% and risks thermal shutdown under sustained 5A+ loads.
LTC3851AEMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) 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-MSOP-EP
LTC3851AEMSE#TRPBF FAQ
1.How can I place an order for LTC3851AEMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AEMSE#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 LTC3851AEMSE#TRPBF reliable?
The price and inventory of LTC3851AEMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AEMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851AEMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AEMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AEMSE#TRPBF?
LTC3851AEMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AEMSE#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 LTC3851AEMSE#TRPBF?
For technical support, including LTC3851AEMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AEMSE#TRPBF requirements.
6.How does Aetrix verify that LTC3851AEMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AEMSE#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 LTC3851AEMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851AEMSE#TRPBF?
All LTC3851AEMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AEMSE#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 LTC3851AEMSE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851AEMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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