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Analog Devices Inc. LTC3851AHMSE#PBF
- Part No.:
- LTC3851AHMSE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851AHMSE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:329
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Product details
Overview
LTC3851AHMSE#PBF 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 features OPTI-LOOP® compensation for optimized transient response-used in telecom power supplies requiring tight regulation under dynamic load steps.
For engineers reviewing the LTC3851AHMSE#PBF datasheet, LTC3851AHMSE#PBF pinout, LTC3851AHMSE#PBF application, or LTC3851AHMSE#PBF equivalent, key selection criteria include its H-grade temperature range (–40°C to 150°C), adjustable current limit via ILIM pin, Burst Mode® operation for light-load efficiency, and compatibility with RSENSE or DCR current sensing in high-reliability industrial DC/DC converters.
Technical Context
The LTC3851AHMSE#PBF implements a constant-frequency current-mode control loop where peak inductor current is set by the ITH voltage, and output voltage is regulated via a precision 0.8V reference compared at the VFB pin. Its transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) enables stable 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 internal 5V INTVCC regulator. The MODE/PLLIN pin selects among Burst Mode®, pulse-skipping, or forced continuous conduction, while FREQ/PLLFLTR configures oscillator frequency or serves as PLL filter node when synchronized to external clock.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide-input industrial and telecom rails without pre-regulation. |
| Output Voltage Accuracy | ±1% over –40°C to 150°C - ensures stable regulation in automotive under-hood or base station environments. |
| Switching Frequency | 250kHz to 750kHz, phase-lockable - enables EMI reduction via synchronization and trade-off between size and efficiency. |
| Current Sense Threshold | 30mV / 50mV / 75mV selectable via ILIM pin - allows precise overcurrent protection tuning for different MOSFET RDS(on) or DCR values. |
| Shutdown Quiescent Current | 20µA - minimizes system standby power loss in always-on infrastructure equipment. |
| Thermal Rating | H-grade: –40°C to 150°C junction - qualified for high-temperature industrial motor drives and power amplifiers. |
| Package | 16-lead MSOP with exposed thermal pad - provides θJA = 40°C/W for high-power density layouts. |
Pinout & Package
Package: 16-lead plastic MSOP (MSE) with exposed GND pad (Pin 17), rated for –40°C to 150°C operation. Exposed pad must be soldered to PCB ground plane for thermal performance and electrical stability.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (15) | Mode selection & sync input | Selects Burst Mode®/pulse-skip/continuous mode; accepts external clock up to 750kHz for EMI control. |
| FREQ/PLLFLTR (16) | Oscillator programming / PLL filter | Resistor-to-GND sets frequency (250–750kHz); RC network enables PLL lock when synchronized. |
| RUN (1) | Enable control | 1.22V threshold with 120mV hysteresis; internal 2µA pull-up enables simple RC soft-start sequencing. |
| TK/SS (2) | Soft-start & tracking input | 1µA internal charge current ramps external capacitor; enables monotonic startup or ratiometric tracking of master supply. |
| ITH (3) | Error amp output & current threshold | Voltage sets peak inductor current; gm = 2 mmho and 3MHz GBW support robust loop compensation. |
| VFB (4) | Feedback input | Compares against 0.8V reference; ±1% accuracy maintained across full temperature range. |
| SENSE– (5), SENSE+ (6) | Current sense differential inputs | Accepts Kelvin-connected DCR network or low-value shunt; ±1µA input bias enables high-accuracy sensing. |
| ILIM (7) | Current limit range select | GND/FLOAT/INTVCC selects 30/50/75mV max sense threshold - matches MOSFET RDS(on) or inductor DCR. |
| GND (8, 17) | Signal & thermal ground | Pins 8 and exposed pad 17 are internally connected; pad soldering required for thermal integrity and noise immunity. |
| BG (9) | Bottom gate driver | Drives low-side N-MOSFET gate from GND to INTVCC (5V); 1.1Ω pull-down ensures fast turn-off. |
| INTVCC (10) | Internal 5V regulator output | Supplies control circuitry; requires ≥2.2µF low-ESR capacitor; load regulation <2% up to 50mA. |
| VIN (11) | Main input supply | 4V–38V input; powers INTVCC regulator and high-side driver bootstrap circuit via BOOST pin. |
| BOOST (12) | Bootstrap supply | Swings from ~4.3V to VIN + 5V; charges external bootstrap capacitor during low-side conduction. |
| TG (13) | Top gate driver | Floating driver referenced to SW node; 2.2Ω pull-up / 1.2Ω pull-down ensures fast, shoot-through-free switching. |
| SW (14) | Switch node | Connects to inductor and MOSFET sources; swings from ~–0.3V to VIN; requires low-inductance layout. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by enabling stable loop response across wide COUT/ESR variations - reduces BOM cost and board area. |
| Adjustable Light-Load Operation | Three selectable modes (Burst, pulse-skip, continuous) optimize efficiency vs. ripple/noise trade-offs - critical for battery-backed or audio-sensitive systems. |
| Programmable Current Limit | Tri-level ILIM pin (30/50/75mV) enables precise overcurrent protection without external resistors - simplifies design for varying MOSFET RDS(on). |
| Output Overvoltage Protection | Dedicated OV comparator triggers immediate top-FET shutdown on >10% VOUT overshoot - prevents damage to downstream logic or memory. |
| Very Low Dropout Support | 99% duty cycle capability enables operation with VIN only ~100mV above VOUT - extends usable input range in brownout conditions. |
Applications
| Telecom Power Supply | Industrial Motor Drive Control |
|---|---|
|
Use Scenario: 48V intermediate bus conversion to 3.3V/5V for FPGA, DSP, and interface ICs in 5G base station radios. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating point-of-load voltage with fast transient response to bursty data traffic loads. Use Value: ±1% output accuracy and OPTI-LOOP® ensure stable core voltage during RF transmit bursts; H-grade rating sustains operation at 125°C ambient. |
Use Scenario: 24V–36V DC bus regulation to 12V for gate drivers, sensors, and MCU in servo motor controllers. IC Role / Device Role / Timing Role: High-efficiency step-down controller powering isolated gate driver supplies with tight ripple requirements. Use Value: Burst Mode® operation achieves >85% efficiency at 10mA load; 99% duty cycle supports undervoltage ride-through during motor stall events. |
| Automotive ADAS Camera Module | Distributed DC Power System |
|
Use Scenario: Powering image sensor and ISP in rear-view camera modules exposed to under-hood temperatures up to 105°C. IC Role / Device Role / Timing Role: Regulating 1.2V/1.8V/2.8V rails from vehicle battery (9V–16V) with low-noise, low-ripple performance. Use Value: Pulse-skipping mode eliminates audible noise; H-grade qualification ensures reliability at 150°C junction during parking mode. |
Use Scenario: Secondary-side regulation in modular server PSUs converting 12V backplane to 0.8V–3.3V for ASICs and memory. IC Role / Device Role / Timing Role: Synchronous buck controller synchronized to system clock via MODE/PLLIN to reduce conducted EMI. Use Value: Phase-lockable 250kHz–750kHz operation enables deterministic EMI filtering; RSENSE/DCR flexibility supports cost-optimized designs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3851AIMSE#PBF | I-grade (–40°C to 125°C) vs H-grade (–40°C to 150°C); identical electrical specs and pinout. | Not suitable for sustained 150°C junction environments such as enclosed industrial enclosures or automotive power stages. | Select LTC3851AHMSE#PBF when operating junction temperature exceeds 125°C or long-term reliability at elevated temperature is required. |
| LTC3851AEMSE#PBF | E-grade (0°C to 85°C) with same package; lower temp qualification and reduced VFB accuracy drift over temperature. | Restricted to commercial-temperature applications like office equipment or non-critical embedded systems. | Choose LTC3851AHMSE#PBF for extended temperature validation, especially where thermal derating or lifetime assurance is mandated. |
Compared with LTC3851AIMSE#PBF and LTC3851AEMSE#PBF, the LTC3851AHMSE#PBF provides guaranteed performance up to 150°C junction temperature, tighter VFB drift control across that range, and validated long-term reliability for mission-critical industrial and automotive deployments - making it the only option for designs requiring full H-grade qualification.
Availability
LTC3851AHMSE#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial motor drive control, automotive ADAS camera modules, and distributed DC power systems requiring stable component supply with extended temperature capability.
Supply support for LTC3851AHMSE#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, serving industrial, automotive, communications, and healthcare markets.
The LTC3851A family is designed as a high-efficiency, high-temperature synchronous step-down controller targeting demanding power conversion applications where precision regulation, light-load efficiency, and thermal robustness are critical.
FAQ
What is the maximum operating junction temperature for LTC3851AHMSE#PBF?
The LTC3851AHMSE#PBF is rated for a maximum junction temperature of 150°C, with guaranteed specifications over the full –40°C to 150°C operating junction temperature range. This H-grade qualification distinguishes it from I-grade (–40°C to 125°C) and E-grade (0°C to 85°C) variants of the LTC3851A, enabling use in high-ambient industrial and automotive under-hood applications where thermal margin is constrained.
How does the ILIM pin configure current limit thresholds on LTC3851AHMSE#PBF?
The ILIM pin on LTC3851AHMSE#PBF is a tri-state input that selects one of three maximum current sense thresholds: 30mV when tied to GND, 50mV when left floating, and 75mV when connected to INTVCC. This direct hardware configuration eliminates need for external resistors or DACs, allowing rapid adaptation to different MOSFET RDS(on) or inductor DCR values while maintaining accurate overcurrent protection across the full H-grade temperature range.
Can LTC3851AHMSE#PBF synchronize to an external clock, and what pins are involved?
Yes, LTC3851AHMSE#PBF supports external clock synchronization via the MODE/PLLIN pin, which functions as both mode selector and phase detector input. When an external clock signal (250kHz–750kHz) is applied to MODE/PLLIN, the internal oscillator locks to it in forced continuous conduction mode. The FREQ/PLLFLTR pin must be configured with an RC network to serve as the PLL loop filter - enabling deterministic EMI reduction in noise-sensitive systems like medical imaging or radar power supplies.
What is the purpose of the TK/SS pin on LTC3851AHMSE#PBF, and how is it used?
The TK/SS pin on LTC3851AHMSE#PBF serves dual functions: soft-start control and supply tracking. An internal 1µA current source charges an external capacitor to generate a linear voltage ramp, controlling output voltage slew rate during startup. Alternatively, connecting a resistor divider from a master supply to TK/SS enables ratiometric or coincident tracking - essential for sequencing multiple rails in FPGAs or processors where voltage ordering prevents latch-up or inrush damage.
Does LTC3851AHMSE#PBF support both RSENSE and DCR current sensing?
Yes, LTC3851AHMSE#PBF supports both RSENSE (shunt resistor) and DCR (inductor winding resistance) current sensing methods. SENSE+ and SENSE– accept differential inputs with ±1µA input bias current, enabling high-accuracy sensing using either approach. DCR sensing reduces power loss and BOM cost in high-current applications, while RSENSE provides superior accuracy for precise current limiting - both are fully supported without external op-amps or compensation networks.
LTC3851AHMSE#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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-MSOP-EP
LTC3851AHMSE#PBF FAQ
1.How can I place an order for LTC3851AHMSE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851AHMSE#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 LTC3851AHMSE#PBF reliable?
The price and inventory of LTC3851AHMSE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851AHMSE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851AHMSE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851AHMSE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851AHMSE#PBF?
LTC3851AHMSE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851AHMSE#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 LTC3851AHMSE#PBF?
For technical support, including LTC3851AHMSE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851AHMSE#PBF requirements.
6.How does Aetrix verify that LTC3851AHMSE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851AHMSE#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 LTC3851AHMSE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851AHMSE#PBF?
All LTC3851AHMSE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851AHMSE#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 LTC3851AHMSE#PBF part is unused and in its original packaging.
Return procedure for LTC3851AHMSE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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