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Analog Devices Inc. LTC3851EMSE-1#TRPBF
- Part No.:
- LTC3851EMSE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851EMSE-1#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,396
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Product details
Overview
LTC3851EMSE-1#TRPBF 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 operation. It delivers 0.8V to 5.5V output with ±1% accuracy, supports 4V–38V input, operates up to 750kHz, and features PGOOD monitoring, OPTI-LOOP® compensation, and selectable light-load modes-used in telecom intermediate bus converters and industrial DC/DC power supplies.
For engineers reviewing the LTC3851EMSE-1#TRPBF datasheet, LTC3851EMSE-1#TRPBF pinout, LTC3851EMSE-1#TRPBF application, or LTC3851EMSE-1#TRPBF equivalent, key selection criteria include its 16-pin MSOP package, 0.8V reference precision, phase-lockable frequency range (250–750kHz), PGOOD open-drain output, and compatibility with RSENSE or DCR current sensing for high-efficiency 15A-class buck designs.
Technical Context
The LTC3851EMSE-1#TRPBF implements a constant-frequency current-mode control architecture with an internal transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and slope-compensated PWM logic. Its ITH pin serves as both error amplifier output and current threshold control point, enabling precise transient response tuning via OPTI-LOOP® compensation across wide output capacitance and ESR ranges.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, 30ns dead-time control, and robust protection including output overvoltage lockout (±10% VFB window), current foldback limiting, and undervoltage lockout on INTVCC (3.25V threshold). The MODE/PLLIN pin enables mode selection (Burst/Pulse-Skip/Continuous) and external clock synchronization without requiring PCB layout changes.
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 reference - ensures tight regulation for sensitive digital loads like FPGAs and ASICs. |
| Switching Frequency | 250kHz to 750kHz (phase-lockable) - balances efficiency vs. size: 250kHz minimizes MOSFET switching loss; 750kHz enables compact 0.68μH inductors. |
| Current Sensing | RSENSE or DCR - eliminates sense resistor losses in high-current applications; supports <1mΩ DCR with external RC filter matching L/DCR time constant. |
| Light-Load Efficiency Mode | Selectable Burst Mode®, Pulse-Skipping, or Continuous Conduction - Burst Mode achieves >85% efficiency at 10mA load (VIN=12V, VOUT=3.3V). |
| Shutdown Quiescent Current | 20μA - enables ultra-low-power standby in always-on industrial controllers. |
| Package | 16-Lead MSOP (MSE) with exposed pad - thermally enhanced (θJA = 35–40°C/W) for reliable 15A output capability without heatsink. |
Pinout & Package
Package: 16-Lead Plastic MSOP (MSE) with exposed thermal pad (Pin 17 = GND), rated for –40°C to 85°C operating junction temperature.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| RUN (Pin 3) | Enable control input | Active-high enable with 1.25V threshold and 130mV hysteresis; internal 2μA pull-up allows simple RC soft-start sequencing. |
| TK/SS (Pin 4) | Soft-start/tracking input | 1μA internal charge current ramps output voltage linearly; supports ratiometric or coincident tracking of master supplies. |
| ITH (Pin 5) | Error amplifier output / current threshold | Directly sets peak inductor current; used for loop compensation and current foldback during short-circuit conditions. |
| VFB (Pin 6) | Feedback input | High-impedance node referenced to 0.8V internal bandgap; connects to resistive divider for adjustable output voltage. |
| SENSE+ / SENSE– (Pins 8/7) | Differential current sense inputs | Accept 0–5.5V common-mode range; support Kelvin-connected DCR networks or low-value shunt resistors (max 65mV threshold). |
| PGOOD (Pin 9) | Power-good indicator | Open-drain output pulled low when VFB deviates >±10% from 0.8V or during soft-start; includes 17μs power-bad mask. |
| TG / BG (Pins 15/11) | Top/bottom gate drivers | Drive external N-MOSFETs with 2.6Ω/1.5Ω pull-up/down resistance and 30ns interlock delay to prevent shoot-through. |
| SW (Pin 16) | Switch node | Connects to inductor; swings from near-GND to VIN; requires low-inductance layout to minimize EMI and gate drive ringing. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by optimizing phase margin across diverse COUT/ESR combinations - reduces BOM cost and board area in multi-rail systems. |
| DCR or RSENSE Sensing | Eliminates power loss from discrete current-sense resistors in high-current (>10A) applications while maintaining ±5% current limit accuracy. |
| 99% Duty Cycle Operation | Enables ultra-low dropout regulation (e.g., 5V→4.95V at full load), critical for post-regulation in distributed power architectures. |
| Output Overvoltage Protection | Hardware-based OV comparator disables TG and enables BG within microseconds if VFB exceeds 0.88V - protects downstream 3.3V/1.8V logic from fault-induced damage. |
| Thermally Enhanced MSOP | Exposed pad soldered to PCB provides low thermal resistance (θJC = 4.2°C/W in QFN variant; MSE variant optimized for manual assembly and rework). |
Applications
| Telecom Intermediate Bus Converter | Industrial PLC Power Supply |
|---|---|
Use Scenario: Converts 48V backplane to 12V intermediate bus in carrier-grade base station equipment. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing 15A continuous output with strict ripple (<20mVpp) and fast load-step response (<50μs). Use Value: Phase-lockable 500kHz operation synchronizes with system clock to suppress beat frequencies; PGOOD enables hot-swap controller sequencing. |
Use Scenario: Generates isolated 5V/3.3V rails for microcontroller, I/O, and analog front-end in factory automation controllers. IC Role / Device Role / Timing Role: High-reliability step-down controller supporting wide input (18–36V DC) and operating continuously at –40°C to 85°C ambient. Use Value: RSENSE sensing ensures accurate current limiting during motor-driver surge events; shutdown IQ <20μA extends backup battery life. |
| Automotive Infotainment Core Supply | Medical Imaging Subsystem DC/DC |
Use Scenario: Powers SoC core voltage (1.1V @ 12A) from 12V vehicle battery with stringent EMI limits. IC Role / Device Role / Timing Role: Constant-frequency current-mode controller enabling spread-spectrum-compatible design and low-audio-noise pulse-skipping mode. Use Value: Adjustable soft-start prevents inrush current tripping fuse; 0.8V reference tolerance ensures stable CPU operation under load transients. |
Use Scenario: Supplies low-noise 1.8V/3.3V bias to ADCs, sensors, and FPGA configuration circuits in portable ultrasound units. IC Role / Device Role / Timing Role: Precision buck controller with ±1% output accuracy and <10μVrms output noise in Burst Mode at light loads. Use Value: OPTI-LOOP® compensation maintains stability with ceramic capacitors only; PGOOD signals FPGA configuration readiness to host processor. |
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#TRPBF | Integrated 4A power stage (vs. external MOSFETs); higher 2.2MHz max frequency; lower 2.8V min VIN. | Better suited for space-constrained, lower-current (<5A) applications; lacks DCR sensing and ratiometric tracking. | Choose LT8640S for compact, integrated solutions below 5A; LTC3851EMSE-1#TRPBF remains optimal for scalable 10–20A designs with thermal flexibility. |
| TPS53689RTAR | Three-phase capable; supports PMBus interface; 0.5V reference; no PGOOD pin (uses POWER_GOOD flag over SMBus). | Targeted at server VR13/IMVP8 multi-phase CPU supplies; requires digital control infrastructure. | Select TPS53689RTAR only when digital telemetry and multi-phase interleaving are required; LTC3851EMSE-1#TRPBF offers simpler analog control for single-phase industrial use. |
Compared with LT8640S#TRPBF and TPS53689RTAR, the LTC3851EMSE-1#TRPBF provides unmatched analog flexibility for high-current, wide-input industrial buck converters - retaining external MOSFET selection freedom, DCR sensing, and robust analog PGOOD signaling without firmware dependency.
Availability
LTC3851EMSE-1#TRPBF 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 across extended temperature and long product lifecycles.
Supply support for LTC3851EMSE-1#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 its legacy of high-performance analog ICs with rigorous automotive and industrial qualification standards.
The LTC3851-1 belongs to Linear's synchronous buck controller product line, designed specifically for high-efficiency, high-current DC/DC conversion in harsh environments where reliability, thermal performance, and analog control simplicity are prioritized over digital configurability.
FAQ
What is the maximum supported switching frequency for LTC3851EMSE-1#TRPBF?
The LTC3851EMSE-1#TRPBF supports a phase-lockable fixed-frequency range from 250kHz to 750kHz. At RFREQ = 36kΩ, the typical frequency is 750kHz (min 710kHz, max 790kHz). This upper limit enables compact magnetics while maintaining high efficiency in 12V-to-3.3V or 24V-to-5V conversions. Frequency selection is resistor-programmed on the FREQ/PLLFLTR pin.
Does LTC3851EMSE-1#TRPBF support DCR current sensing, and what external components are required?
Yes, LTC3851EMSE-1#TRPBF fully supports DCR current sensing using an external RC network between SENSE+ and SENSE–. To match the inductor's L/DCR time constant, select R1||R2 and C1 such that R1||R2 × C1 = L/DCR. Typical values are R1 = 154kΩ, R2 = 48.7kΩ, C1 = 330pF for a 0.68μH inductor with 0.5mΩ DCR. This eliminates sense resistor losses and improves full-load efficiency by ~1.5%.
How does the PGOOD function behave during startup and fault conditions in LTC3851EMSE-1#TRPBF?
In LTC3851EMSE-1#TRPBF, the PGOOD pin is an open-drain output pulled low during soft-start, RUN pin disable, or whenever VFB falls outside the ±10% window (0.72V–0.88V) around 0.8V. It asserts "high" only after VFB stabilizes within this window and remains there for >17μs (power-bad mask timeout). This ensures clean power-good signaling to FPGAs and microcontrollers without false triggers during transient recovery.
What is the purpose of the TK/SS pin in LTC3851EMSE-1#TRPBF, and how is it used for output voltage tracking?
The TK/SS pin in LTC3851EMSE-1#TRPBF controls soft-start ramp rate and enables output voltage tracking. For ratiometric tracking, connect TK/SS to a resistor divider from a master supply (e.g., 5V rail) so VTK/SS = (R2/(R1+R2)) × VMASTER. For coincident tracking, tie TK/SS directly to the master supply. An internal 1μA current charges the external capacitor, ensuring monotonic, controlled VOUT rise - critical for powering multi-rail ASICs without sequencing violations.
Can LTC3851EMSE-1#TRPBF operate in dropout, and what is its minimum on-time limitation?
Yes, LTC3851EMSE-1#TRPBF supports 99% duty cycle operation for ultra-low dropout, enabling outputs close to VIN (e.g., 12V→11.88V). Its minimum on-time is 90ns (typical), which - combined with OPTI-LOOP® compensation - allows stable regulation even at very high duty cycles. However, sustained dropout requires external bootstrap capacitor (CB) recharging via the bottom FET; a minimum load is recommended to ensure CB replenishment during extended 100% duty operation.
LTC3851EMSE-1#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:
- 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-MSOP-EP
LTC3851EMSE-1#TRPBF FAQ
1.How can I place an order for LTC3851EMSE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851EMSE-1#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 LTC3851EMSE-1#TRPBF reliable?
The price and inventory of LTC3851EMSE-1#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851EMSE-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851EMSE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851EMSE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851EMSE-1#TRPBF?
LTC3851EMSE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851EMSE-1#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 LTC3851EMSE-1#TRPBF?
For technical support, including LTC3851EMSE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851EMSE-1#TRPBF requirements.
6.How does Aetrix verify that LTC3851EMSE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851EMSE-1#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 LTC3851EMSE-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851EMSE-1#TRPBF?
All LTC3851EMSE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851EMSE-1#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 LTC3851EMSE-1#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851EMSE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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