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Analog Devices Inc. LTC3851AIMSE-1#PBF
- Part No.:
- LTC3851AIMSE-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851AIMSE-1#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:537
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Product details
Overview
LTC3851AIMSE-1#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 operation. It supports 4V–38V input, delivers 0.8V–5.5V output with ±1% accuracy, features phase-lockable 250kHz–750kHz switching, and integrates PGOOD monitoring and OPTI-LOOP® compensation. It is used in telecom intermediate bus converters requiring tight regulation and fast transient response under wide load and input variations.
For engineers reviewing the LTC3851AIMSE-1#PBF datasheet, LTC3851AIMSE-1#PBF pinout, LTC3851AIMSE-1#PBF application, or LTC3851AIMSE-1#PBF equivalent, key selection criteria include its 16-pin MSOP package with exposed thermal pad, 0.8V reference tolerance over –40°C to 125°C, dual-mode light-load control (Burst Mode®/pulse-skipping), and integrated overvoltage protection with 17µs power-bad mask timing.
Technical Context
The LTC3851AIMSE-1#PBF implements a constant-frequency current-mode control architecture with transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz), programmable oscillator via FREQ/PLLFLTR resistor, and PLL synchronization capability on MODE/PLLIN. Its internal 5V INTVCC regulator powers gate drivers and logic, while anti-shoot-through logic prevents simultaneous TG/BG conduction.
It employs precision 0.8V reference with ±1% initial accuracy and <±0.2% load regulation, supports RSENSE or DCR current sensing, and includes dedicated current foldback limiting (VSENSE(MAX) = 40–70 mV depending on grade), output overvoltage protection (±10% trip), and soft-start/tracking via TK/SS with 1 µA pull-up current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 4V to 38V - accommodates 12V/24V/36V battery and intermediate bus systems without external pre-regulation. |
| VOUT Accuracy | ±1% at 0.8V reference - ensures stable core voltage for FPGAs, ASICs, and DSPs across temperature and load. |
| Switching Frequency | 250kHz to 750kHz - adjustable via external resistor; enables optimization of inductor size vs. efficiency trade-off. |
| Light-Load Modes | Burst Mode®, pulse-skipping, or forced continuous - selectable via MODE/PLLIN bias; Burst Mode achieves >90% efficiency at 1mA load. |
| Current Sensing | RSENSE or DCR - supports low-loss, cost-effective inductor-based sensing or high-accuracy shunt-based sensing. |
| Thermal Package | 16-lead MSOP with exposed GND pad - θJA = 40°C/W; enables 15A output with proper PCB copper area and airflow. |
| PGOOD Threshold | ±10% window around VFB with 17µs debounce - provides reliable power sequencing signal for downstream logic and processors. |
Pinout & Package
Package: 16-lead plastic MSOP (MSE) with exposed thermal pad (Pin 17 = GND), rated for –40°C to 125°C junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 1) | Mode selection & external clock sync input | Selects Burst Mode® (50k–250kΩ to INTVCC), pulse-skip (GND), or forced CCM (INTVCC); accepts 250–750kHz external clock. |
| FREQ/PLLFLTR (Pin 2) | Oscillator frequency programming / PLL loop filter | Resistor to GND sets nominal frequency (250–750kHz); RC network required when using external PLL sync. |
| RUN (Pin 3) | Enable/disable control with hysteresis | Turns on at VRUN ≥ 1.22V (120mV hysteresis); internal 2µA pull-up enables simple RC soft-start. |
| TK/SS (Pin 4) | Soft-start and output voltage tracking input | 1µA internal current charges external capacitor; enables linear VOUT ramp or ratiometric/coincident tracking of master supply. |
| ITH (Pin 5) | Error amplifier output & current limit threshold | Voltage controls peak inductor current; also serves as compensation node for OPTI-LOOP® stability tuning. |
| VFB (Pin 6) | Feedback input to 0.8V reference comparator | Monitors resistive divider output; regulates VOUT to 0.8V × (1 + R1/R2); ±10% PGOOD window referenced here. |
| SENSE– (Pin 7) | Current sense comparator inverting input | Connected to low-side of sense resistor or DCR network; enables accurate current foldback during short-circuit events. |
| SENSE+ (Pin 8) | Current sense comparator non-inverting input | Connected to high-side of sense resistor or DCR network; differential sensing rejects common-mode noise. |
| PGOOD (Pin 9) | Open-drain power-good status output | Pulled low when VFB outside ±10%, during soft-start, or RUN = low; requires external pull-up to ≤6V. |
| GND (Pin 10, Exposed Pad 17) | Analog/digital/power ground reference | All small-signal grounds and capacitor negatives must Kelvin-connect here; exposed pad must be soldered for thermal performance. |
| BG (Pin 11) | Bottom N-MOSFET gate driver output | Drives low-side switch between GND and INTVCC; 1.1Ω pull-down / 2.1Ω pull-up ensures fast turn-off/turn-on. |
| INTVCC (Pin 12) | Internal 5V LDO output | Supplies gate drivers and internal circuitry; requires ≥2.2µF low-ESR ceramic/tantalum decoupling to GND. |
| VIN (Pin 13) | Main input supply connection | Accepts 4V–38V; requires local bulk and high-frequency ceramic capacitors; absolute max = 40V. |
| BOOST (Pin 14) | Floating bootstrap supply for top gate driver | Swings from ~INTVCC–0.4V to VIN+INTVCC; connects to (+) terminal of bootstrap capacitor. |
| TG (Pin 15) | Top N-MOSFET gate driver output | Floating driver with swing = INTVCC superimposed on SW node; 1.2Ω pull-down / 2.2Ω pull-up minimizes shoot-through risk. |
| SW (Pin 16) | Switch node connection to inductor | Connects to inductor and external Schottky diode cathode; voltage swings from ~–0.4V to VIN. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by enabling stable loop response across wide range of COUT ESR values (e.g., polymer, ceramic, electrolytic). |
| 99% Maximum Duty Cycle | Enables ultra-low dropout operation - supports VOUT = 3.3V from 3.6V input in battery-powered systems. |
| Programmable Current Foldback | VSENSE(MAX) adjustable from 35mV to 70mV (grade-dependent); limits MOSFET power dissipation during sustained overload or short-circuit. |
| Output Overvoltage Protection | Dedicated comparator trips at ±10% VFB; forces BG on and TG off until fault clears - protects downstream loads from transient overshoot. |
| Thermally Enhanced MSOP | Exposed GND pad reduces θJA to 40°C/W; allows full 15A output capability with 2oz copper and 4 thermal vias under pad. |
Applications
| Telecom Intermediate Bus Converter | Industrial 24V-to-5V/3.3V Point-of-Load |
|---|---|
|
Use Scenario: Converting 48V telecom rectified bus to isolated 12V intermediate rail feeding multiple DC/DC modules. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating 12V at up to 15A with precise current limit and PGOOD signaling for system-level power sequencing. Use Value: Wide 4V–38V input range accommodates brownout conditions; ±1% output accuracy maintains downstream converter stability; 750kHz max frequency enables compact magnetics. |
Use Scenario: Generating 5V/3.3V rails from 24V factory automation PLC backplane for microcontrollers and I/O drivers. IC Role / Device Role / Timing Role: High-efficiency step-down controller with Burst Mode® operation to maintain >85% efficiency at 10mA–15A load range. Use Value: Low 20µA shutdown IQ extends standby time; TK/SS pin enables synchronized startup with main CPU rail; robust UVLO (3.25V) prevents erratic behavior during undervoltage events. |
| Automotive Infotainment Power Supply | Distributed Data Center DC Power System |
|
Use Scenario: Regulating 12V vehicle battery to 1.8V/1.2V for SoC cores in head-unit systems with strict EMI and thermal constraints. IC Role / Device Role / Timing Role: Synchronous buck controller with programmable frequency (460kHz typical) and spread-spectrum-capable PLL to reduce conducted emissions. Use Value: Phase-lockable oscillator synchronizes to system clock to avoid beat frequencies; DCR sensing eliminates shunt resistor losses and improves thermal margin. |
Use Scenario: Providing redundant 12V-to-3.3V conversion in server rack power distribution units with hot-swap and telemetry requirements. IC Role / Device Role / Timing Role: Controller with PGOOD output and precise current foldback for fault isolation and graceful degradation in parallel-configured supplies. Use Value: ±10% PGOOD window with 17µs debounce ensures clean power-good assertion; current foldback prevents cascading failures during output short. |
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 power stage (4A), 2.8V–42V input, Silent Switcher® architecture, fixed 3.3V/5V options only | Lower solution size but fixed output; no adjustable VOUT or external MOSFET flexibility | Choose LT8640S for space-constrained designs needing <4A with ultra-low EMI; retain LTC3851AIMSE-1#PBF for >10A, programmable VOUT, or discrete MOSFET optimization. |
| MP2918 | Monolithic 12A buck, 4.5V–18V input, 0.6V reference, no PLL sync, lower max frequency (1MHz) | Higher integration but narrower input range and no tracking/soft-start flexibility | Choose MP2918 for cost-sensitive 12V-input applications where 12A monolithic solution suffices; LTC3851AIMSE-1#PBF remains preferred for 24V/36V inputs, precision tracking, or thermal design control. |
Compared with LT8640S and MP2918, the LTC3851AIMSE-1#PBF offers wider input range (4V–38V), fully adjustable output (0.8V–5.5V), advanced soft-start/tracking, and PLL synchronization - making it uniquely suited for high-reliability industrial and telecom systems requiring design flexibility and long-term component availability.
Availability
LTC3851AIMSE-1#PBF is available at Aetrix Electronics and suitable for telecom intermediate bus converters, industrial 24V point-of-load supplies, and automotive infotainment power systems requiring stable component supply, extended temperature support (–40°C to 125°C), and long-lifecycle assurance.
Supply support for LTC3851AIMSE-1#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 and maintains full product support, documentation, and manufacturing continuity for all Linear ICs including the LTC3851A family.
The LTC3851A-1 belongs to Linear's high-performance power controller product line, designed specifically for demanding synchronous buck applications in telecom, industrial, and automotive environments where precision regulation, thermal robustness, and flexible control modes are critical.
FAQ
What is the maximum input voltage rating for the LTC3851AIMSE-1#PBF?
The LTC3851AIMSE-1#PBF has an absolute maximum input voltage (VIN) rating of 40V. Continuous operation is specified from 4V to 38V, making it suitable for 24V and 36V industrial and telecom bus systems. Exceeding 40V risks permanent damage per Absolute Maximum Ratings.
Does the LTC3851AIMSE-1#PBF support output voltage tracking during startup?
Yes, the LTC3851AIMSE-1#PBF supports both coincident and ratiometric output voltage tracking via the TK/SS pin. An external resistor divider from a master supply to GND applied to TK/SS enables precise alignment of VOUT ramp with other rails - a key feature for FPGA and multi-rail processor sequencing.
How does the PGOOD function behave during soft-start on the LTC3851AIMSE-1#PBF?
The PGOOD pin on the LTC3851AIMSE-1#PBF remains low during soft-start and only transitions high after VFB enters and remains within the ±10% regulation window for more than 17µs. This built-in debounce prevents false power-good assertions during voltage ramp-up or transient disturbances.
Can the LTC3851AIMSE-1#PBF operate with DCR current sensing?
Yes, the LTC3851AIMSE-1#PBF fully supports DCR current sensing through its differential SENSE+ and SENSE– inputs. This eliminates power loss and cost associated with shunt resistors and is especially advantageous in high-current (>10A) applications where thermal management is critical.
What is the thermal resistance (θJA) of the LTC3851AIMSE-1#PBF in its MSOP package?
The LTC3851AIMSE-1#PBF in the 16-lead MSOP (MSE) package has a typical junction-to-ambient thermal resistance (θJA) of 40°C/W when mounted on a 2-layer PCB with 2oz copper and the exposed pad properly soldered to a thermal plane. This value assumes standard JEDEC 51-7 test conditions.
LTC3851AIMSE-1#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:
- Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP-EP
LTC3851AIMSE-1#PBF FAQ
1.How can I place an order for LTC3851AIMSE-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AIMSE-1#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 LTC3851AIMSE-1#PBF reliable?
The price and inventory of LTC3851AIMSE-1#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AIMSE-1#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851AIMSE-1#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AIMSE-1#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AIMSE-1#PBF?
LTC3851AIMSE-1#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AIMSE-1#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 LTC3851AIMSE-1#PBF?
For technical support, including LTC3851AIMSE-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AIMSE-1#PBF requirements.
6.How does Aetrix verify that LTC3851AIMSE-1#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AIMSE-1#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 LTC3851AIMSE-1#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851AIMSE-1#PBF?
All LTC3851AIMSE-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AIMSE-1#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 LTC3851AIMSE-1#PBF part is unused and in its original packaging.
Return procedure for LTC3851AIMSE-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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