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Analog Devices Inc. LTC3851AEMSE#PBF
- Part No.:
- LTC3851AEMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851AEMSE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:235
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Product details
Overview
LTC3851AEMSE#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% reference accuracy, supports phase-lockable 250kHz–750kHz switching, and enables Burst Mode™ operation for ultra-low-light-load efficiency - used in telecom power supplies requiring tight regulation under dynamic load transients.
For engineers reviewing the LTC3851AEMSE#PBF datasheet, LTC3851AEMSE#PBF pinout, LTC3851AEMSE#PBF application, or LTC3851AEMSE#PBF equivalent, key selection criteria include its OPTI-LOOP® compensation flexibility, RSENSE/DCR current sensing options, adjustable current foldback, and thermally enhanced 16-lead MSOP package with exposed pad for industrial-grade thermal management.
Technical Context
The LTC3851AEMSE#PBF implements a constant-frequency current-mode control architecture with a transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and precision 0.8V reference (±1% over –40°C to 125°C). Its phase-locked loop accepts external synchronization up to 750 kHz and supports three light-load modes: forced continuous conduction, pulse-skipping, and Burst Mode™ - each selected via MODE/PLLIN pin biasing.
It integrates dual gate drivers (TG/BG) with matched 25 ns rise/fall times, 30 ns dead-time control, and low on-resistance (TG RUP = 2.2 Ω, BG RDOWN = 1.1 Ω). The IC features output overvoltage protection (OV lockout at +10%), undervoltage lockout on INTVCC (3.25 V with 0.4 V hysteresis), and programmable current limit thresholds (30 mV / 50 mV / 75 mV) via ILIM pin configuration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4 V to 38 V - supports wide-input industrial and telecom rails without pre-regulation. |
| Output Voltage Accuracy | ±1% over –40°C to 125°C - ensures stable regulation across automotive and industrial temperature extremes. |
| Switching Frequency Range | 250 kHz to 750 kHz - adjustable via FREQ/PLLFLTR resistor; higher frequencies reduce passive size, lower frequencies improve efficiency. |
| Current Sense Threshold Options | 30 mV / 50 mV / 75 mV - selectable via ILIM pin grounding, floating, or tying to INTVCC for precise MOSFET SOA protection. |
| INTVCC Regulator | 5.0 V ±4% (4.8–5.2 V), 50 mA peak - powers internal circuitry and gate drivers; eliminates need for external bias supply. |
| Shutdown Quiescent Current | 20 µA - enables ultra-low-power system standby states in battery-backed or energy-sensitive applications. |
| Duty Cycle Capability | Up to 99% - supports very low dropout operation (e.g., 12 V → 11.5 V conversion) without loss of regulation. |
Pinout & Package
Package: 16-lead plastic MSOP (MSE) with exposed thermal pad (Pin 17 = GND), rated for –40°C to 125°C junction temperature and θJA = 40°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 15) | Mode selection & external clock sync input | Selects Burst Mode™, pulse-skipping, or forced CCM; accepts external clock up to 750 kHz for EMI control. |
| FREQ/PLLFLTR (Pin 16) | PLL loop filter / frequency programming node | Connects RC network to set oscillator frequency or serve as PLL low-pass filter when synchronized. |
| RUN (Pin 1) | Enable/disable control input | Active-high logic; 1.22 V threshold with 120 mV hysteresis; internal 2 µA pull-up enables simple RC soft-start. |
| TK/SS (Pin 2) | Soft-start and tracking voltage input | Internal 1 µA current charges external capacitor for controlled VOUT ramp; supports ratiometric or coincident tracking. |
| ITH (Pin 3) | Error amplifier output & current threshold control | Voltage sets peak inductor current; also serves as compensation point for OPTI-LOOP® stability optimization. |
| VFB (Pin 4) | Feedback input to error amplifier | Compares resistive divider output against 0.8 V reference; high-impedance (–50 nA bias) minimizes divider error. |
| SENSE+ / SENSE– (Pins 5–6) | Differential current sense inputs | Accept DCR or RSENSE signals; ±1 µA input bias enables accurate low-value sensing networks. |
| ILIM (Pin 7) | Current limit range select | Tie to GND/FLOAT/INTVCC to set max sense threshold to 30/50/75 mV - critical for MOSFET thermal derating. |
| GND (Pins 8, 17) | Signal and thermal ground reference | Exposed pad (Pin 17) must be soldered to PCB ground plane for thermal performance and noise immunity. |
| BG (Pin 9) | Bottom N-MOSFET gate driver output | Drives synchronous rectifier; 1.1 Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (Pin 10) | Internal 5 V regulator output | Requires ≥2.2 µF low-ESR ceramic/tantalum decoupling; powers all internal logic and drivers. |
| VIN (Pin 11) | Main input supply connection | Accepts 4–38 V; requires local bulk capacitance near pin to suppress high di/dt switching noise. |
| BOOST (Pin 12) | Floating bootstrap supply for top gate driver | Swings from ~INTVCC–0.7 V to VIN+INTVCC; connects to external bootstrap capacitor anode. |
| TG (Pin 13) | Top N-MOSFET gate driver output | Floating driver with INTVCC swing referenced to SW node; 2.2 Ω pull-up ensures robust high-side turn-on. |
| SW (Pin 14) | Switch node connection | Connects to inductor and MOSFET source/drain junction; high dv/dt node requiring minimized trace area. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by enabling stable loop response across wide COUT/ESR ranges - reduces BOM cost and board space. |
| Programmable Light-Load Operation | Three selectable modes (Burst, Pulse-Skipping, Forced CCM) optimize efficiency vs. ripple/noise trade-offs per application requirement. |
| Output Overvoltage Protection | Hardware-based OV comparator triggers immediate TG off / BG on action for >10% VOUT excursion - protects downstream loads without software delay. |
| DCR or RSENSE Current Sensing | Flexible sensing architecture supports cost-sensitive DCR designs or precision RSENSE layouts - accommodates high-current or high-accuracy needs. |
| Thermally Enhanced MSOP | 16-lead MSOP with exposed GND pad achieves θJA = 40°C/W - enables 15 A output capability in compact footprint without heatsink. |
Applications
| Telecom Power Supply | Industrial DC-DC Converter |
|---|---|
|
Use Scenario: 48 V backplane-to-3.3 V/5 V point-of-load conversion in base station equipment with strict EMI limits and transient load steps. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing dual N-MOSFET stage, providing regulated output with <100 ns transient response. Use Value: Phase-lockable 750 kHz operation enables synchronized switching across multiple rails to suppress beat frequencies and meet EN55022 Class B. |
Use Scenario: DIN-rail mounted 24 V input power module delivering 1.8 V/12 A to FPGA core logic in factory automation PLCs. IC Role / Device Role / Timing Role: High-efficiency step-down controller supporting 99% duty cycle for low-dropout operation during brownout conditions. Use Value: Adjustable current foldback and ±1% VREF ensure reliable operation under motor startup surges and ambient temperature swings from –40°C to 70°C. |
| Automotive Infotainment System | Distributed Data Center PSU |
|
Use Scenario: 12 V vehicle battery to 1.1 V/8 A processor core supply in head unit with cold-crank immunity (4.5 V min). IC Role / Device Role / Timing Role: Synchronous buck controller with Burst Mode™ enabling <15 µA no-load IQ and seamless transition into CCM during audio playback bursts. Use Value: TK/SS pin enables ratiometric tracking with main 5 V rail - ensures safe power sequencing and avoids I/O contention during boot. |
Use Scenario: 12 V intermediate bus converter feeding multiple ASICs in AI accelerator card with high transient current demands. IC Role / Device Role / Timing Role: Precision current-mode controller with RSENSE sensing delivering 0.8 V output with <±10 mV load regulation across 0–100% load. Use Value: Dual gate drivers with matched timing (25 ns tr/tf, 30 ns dead time) minimize shoot-through risk and enable >95% full-load efficiency at 500 kHz. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3851EMSE#PBF | Base LTC3851 variant without PLL improvement; lacks enhanced jitter performance and tighter frequency tolerance vs. LTC3851A. | Lower phase-noise sensitivity in synchronized systems; less suitable for multi-rail EMI-critical telecom designs. | Select LTC3851AEMSE#PBF when PLL stability, wider frequency lock range, or improved light-load efficiency are required. |
| LTC3883IUH#PBF | Digital PMBus-enabled controller with integrated ADC, EEPROM, and telemetry; 12-bit VOUT margining, fault logging, and digital loop compensation. | Supports closed-loop remote monitoring, adaptive compensation, and firmware-upgradable configurations - not available in analog LTC3851A. | Choose LTC3851AEMSE#PBF for cost-sensitive, analog-only designs where digital complexity and PMBus infrastructure are unnecessary. |
Compared with LTC3851EMSE#PBF, the LTC3851AEMSE#PBF offers superior PLL jitter rejection and tighter frequency accuracy; versus LTC3883IUH#PBF, it provides simpler analog control, lower BOM count, and faster loop response - ideal for deterministic real-time power systems without telemetry overhead.
Availability
LTC3851AEMSE#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial DC-DC converters, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to 125°C operation.
Supply support for LTC3851AEMSE#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LTC3851A belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding industrial, telecom, and automotive DC-DC conversion where precision regulation, thermal robustness, and flexible light-load operation are critical.
FAQ
What is the maximum supported switching frequency for the LTC3851AEMSE#PBF?
The LTC3851AEMSE#PBF supports a phase-lockable fixed-frequency range of 250 kHz to 750 kHz. At RFREQ = 36 kΩ, the typical nominal frequency is 750 kHz, with absolute maximum specified at 810 kHz. This upper limit ensures reliable gate drive timing and MOSFET switching integrity under worst-case process/voltage/temperature conditions.
How does the ILIM pin configure current limit thresholds on the LTC3851AEMSE#PBF?
The ILIM pin on the LTC3851AEMSE#PBF selects one of three maximum current sense thresholds: 30 mV (ILIM = GND), 50 mV (ILIM = floating), or 75 mV (ILIM = INTVCC). These settings directly scale the peak inductor current trip point, enabling precise MOSFET SOA protection across varying output power levels and thermal conditions.
Can the LTC3851AEMSE#PBF operate with a 3.3 V input supply?
No - the LTC3851AEMSE#PBF has a minimum operating input voltage of 4 V, as specified in its Absolute Maximum Ratings and Electrical Characteristics. Attempting to power it from 3.3 V will prevent INTVCC regulation (requires >6 V input to start) and cause UVLO shutdown; use LTC3855 or LTC3880 for sub-4 V inputs.
What is the purpose of the exposed thermal pad (Pin 17) on the LTC3851AEMSE#PBF MSOP package?
The exposed thermal pad (Pin 17) on the LTC3851AEMSE#PBF is electrically and thermally connected to GND. It must be soldered to a PCB copper pour for effective heat dissipation - reducing θJA from 110°C/W (SSOP) to 40°C/W (MSOP) and enabling sustained 15 A output capability without thermal throttling.
Does the LTC3851AEMSE#PBF support output voltage tracking during power-up?
Yes - the LTC3851AEMSE#PBF supports both ratiometric and coincident tracking via the TK/SS pin. By connecting an external resistor divider from a master supply to TK/SS, the output voltage ramps proportionally, ensuring safe sequencing for FPGAs, ASICs, or multi-rail processors without external supervisors.
LTC3851AEMSE#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:
- 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#PBF FAQ
1.How can I place an order for LTC3851AEMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AEMSE#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 LTC3851AEMSE#PBF reliable?
The price and inventory of LTC3851AEMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AEMSE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851AEMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AEMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AEMSE#PBF?
LTC3851AEMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AEMSE#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 LTC3851AEMSE#PBF?
For technical support, including LTC3851AEMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AEMSE#PBF requirements.
6.How does Aetrix verify that LTC3851AEMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AEMSE#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 LTC3851AEMSE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851AEMSE#PBF?
All LTC3851AEMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AEMSE#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 LTC3851AEMSE#PBF part is unused and in its original packaging.
Return procedure for LTC3851AEMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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