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Analog Devices Inc. LTC3851EGN#PBF
- Part No.:
- LTC3851EGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3851EGN#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:480
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Product details
Overview
LTC3851EGN#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% accuracy, supports phase-lockable 250kHz–750kHz switching, and features OPTI-LOOP® compensation for wide-output-capacitance optimization-used in telecom power supplies requiring stable 3.3V/15A rails.
For engineers reviewing the LTC3851EGN#PBF datasheet, LTC3851EGN#PBF pinout, LTC3851EGN#PBF application, or LTC3851EGN#PBF equivalent, key selection criteria include RSENSE/DCR current sensing flexibility, selectable light-load modes (Burst/Pulse-Skip/CCM), 99% duty-cycle dropout capability, and thermal performance in narrow SSOP packaging.
Technical Context
The LTC3851EGN#PBF implements a constant-frequency current-mode control architecture with transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and precision 0.8V reference (±1% over temperature). Its ITH pin serves as both error amplifier output and current threshold modulator, enabling dynamic peak-current adjustment across load transients.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, anti-shoot-through logic, and programmable current foldback via ILIM pin (30/50/75 mV thresholds). The MODE/PLLIN pin enables mode selection (Burst/Pulse-Skip/CCM) or external clock synchronization up to 750 kHz, while FREQ/PLLFLTR sets oscillator frequency via resistor-to-ground.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide-input industrial and telecom DC distribution without pre-regulation. |
| Output Voltage Accuracy | ±1% at VFB - ensures tight regulation under line/load/temperature variation for sensitive digital loads. |
| Switching Frequency | 250kHz to 750kHz, phase-lockable - balances efficiency vs. magnetics size; PLL sync enables noise-sensitive multi-rail systems. |
| Current Sensing | RSENSE or DCR - eliminates sense resistor losses in high-current designs or enables precise current limiting with discrete resistors. |
| Duty Cycle Max | 99% - enables ultra-low dropout operation (e.g., 12V→11.8V), critical for battery-backed or marginally regulated inputs. |
| Shutdown IQ | 20μA - minimizes standby power in always-on systems such as network edge equipment. |
| Package | 16-lead narrow SSOP (GN) - thermally enhanced layout with θJA = 110°C/W; exposed pad not present in GN variant. |
Pinout & Package
Package: 16-lead plastic narrow SSOP (GN), -40°C to 85°C operating range. Pin 17 (exposed pad) is absent in GN package; thermal dissipation relies on PCB copper area under body.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 1) | Mode selection & sync input | Selects Burst/Pulse-Skip/CCM or accepts external clock up to 750kHz; no pull-up required. |
| FREQ/PLLFLTR (Pin 2) | Oscillator programming / PLL filter | Resistor-to-GND sets frequency; RC network required when using external sync for stable PLL lock. |
| RUN (Pin 3) | Enable control | 1.25V threshold with 130mV hysteresis; internal 2μA pull-up enables simple RC soft-start enable sequencing. |
| TK/SS (Pin 4) | Soft-start/tracking input | 1μA internal charge current ramps capacitor for controlled VOUT rise; supports ratiometric tracking of master supply. |
| ITH (Pin 5) | Error amp output & current threshold | Directly sets peak inductor current; also used for OPTI-LOOP compensation network connection. |
| VFB (Pin 6) | Feedback input | Compares output divider voltage to 0.8V reference; high-impedance input minimizes divider loading error. |
| SENSE– (Pin 7) | Current sense inverting input | Connects to low-side of sense resistor or DCR network; common-mode range 0V–5.5V supports ground-referenced sensing. |
| SENSE+ (Pin 8) | Current sense non-inverting input | Connects to high-side of sense resistor or DCR network; matches SENSE– for accurate differential sensing. |
| ILIM (Pin 9) | Current limit threshold select | GND/FLOAT/INTVCC selects 30/50/75mV max sense voltage - enables scalable overcurrent protection without resistor changes. |
| GND (Pin 10) | Analog ground reference | Kelvin connection point for all small-signal components; separates power and signal return paths to reduce noise coupling. |
| BG (Pin 11) | Bottom gate driver output | Drives low-side N-MOSFET gate between GND and INTVCC (5V); 1.1Ω pull-down ensures fast turn-off. |
| INTVCC (Pin 12) | Internal 5V regulator output | Powers control circuitry; requires ≥2.2μF low-ESR ceramic/tantalum bypass to GND for stability. |
| VIN (Pin 13) | Main input supply | Accepts 4V–38V; decoupling capacitor must be placed close to pin to minimize high-frequency loop inductance. |
| BOOST (Pin 14) | Floating bootstrap supply | Charges external bootstrap capacitor during BG on-time; swings from ~VIN+5V down to ~VIN–0.4V. |
| TG (Pin 15) | Top gate driver output | Drives high-side N-MOSFET gate referenced to SW node; 2.6Ω pull-up/1.5Ω pull-down ensures robust switching. |
| SW (Pin 16) | Switch node connection | Connects to inductor and external Schottky diode cathode; high dv/dt node requiring minimized trace area. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by adapting loop gain to actual COUT/ESR - reduces BOM cost and board space in high-COUT applications. |
| Tri-level ILIM Programming | Single-pin selection (GND/FLOAT/INTVCC) sets 30/50/75mV current sense thresholds - eliminates external resistor networks for current limit scaling. |
| 99% Maximum Duty Cycle | Enables near-dropout operation (e.g., 5.5V out from 5.55V input), extending usable input range in battery or PoE-powered systems. |
| Three Light-Load Operating Modes | Burst Mode (20μA IQ), Pulse-Skip, or forced CCM - allows trade-off between light-load efficiency, output ripple, and EMI in system-level optimization. |
| Output Overvoltage Protection | Hardware comparator triggers immediate TG off/BG on during >10% VOUT overshoot - protects downstream ICs without software intervention. |
Applications
| Telecom Power Supply | Industrial PLC Power |
|---|---|
|
Use Scenario: Generating isolated 3.3V/15A rail from 48V backplane in LTE base station power shelf. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-efficiency conversion with tight transient response to bursty RF load demands. Use Value: 90%+ efficiency at full load and 85% at 10% load (Burst Mode) reduces thermal stress in densely packed chassis. |
Use Scenario: Providing 5V/10A auxiliary supply for I/O modules in modular industrial controller with 24V DC input. IC Role / Device Role / Timing Role: Non-isolated step-down controller delivering regulated output with ±1% accuracy across wide temperature (-40°C to 85°C). Use Value: RSENSE/DCR flexibility allows optimal trade-off between sensing accuracy and conduction loss in high-current, space-constrained modules. |
| Automotive Infotainment | Distributed DC Power System |
|
Use Scenario: Converting 12V vehicle battery to 1.5V core supply for SoC in head-unit application with strict EMI limits. IC Role / Device Role / Timing Role: High-frequency (750kHz) synchronous controller enabling compact magnetics and low-profile design. Use Value: Phase-lockable oscillator synchronizes to system clock, eliminating beat frequencies and easing CISPR-25 compliance. |
Use Scenario: Local point-of-load regulation in data center rack where 12V intermediate bus powers multiple ASICs. IC Role / Device Role / Timing Role: High-current (15A+) buck controller supporting remote sensing and ratiometric tracking for multi-rail sequencing. Use Value: TK/SS pin enables precise coincident start-up with master 12V rail, preventing latch-up in cascaded power domains. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2918GQZ | Integrated MOSFETs (40V/12A), fixed 500kHz, no PLL sync or DCR sensing. | Suitable for lower-current, space-constrained designs where integration outweighs flexibility. | Choose MP2918GQZ when board area is critical and 12A max output suffices; avoid if DCR sensing or external clock sync is required. |
| ISL8113IRZ-T7A | 40V input, 3.5MHz max frequency, dual-phase capable, no tri-level ILIM or OPTI-LOOP. | Targets higher-frequency, multi-phase CPU/GPU VRMs with tighter transient response. | Choose ISL8113IRZ-T7A for >1MHz designs needing phase interleaving; LTC3851EGN#PBF remains superior for 250–750kHz telecom/industrial single-phase. |
Compared with MP2918GQZ and ISL8113IRZ-T7A, the LTC3851EGN#PBF offers unmatched flexibility in frequency tuning, current sensing method, light-load mode selection, and thermal management in narrow SSOP-making it ideal for high-reliability, medium-frequency, high-current industrial and telecom power stages.
Availability
LTC3851EGN#PBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLCs, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and guaranteed -40°C to 85°C operation.
Supply support for LTC3851EGN#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 its high-performance analog and power management portfolio with rigorous qualification standards for industrial and automotive applications.
The LTC3851EGN#PBF belongs to Linear's high-efficiency synchronous controller product line, designed specifically for demanding DC/DC conversion in telecom infrastructure, industrial automation, and distributed power architectures where reliability, efficiency, and design flexibility are paramount.
FAQ
What is the maximum input voltage rating for the LTC3851EGN#PBF?
The LTC3851EGN#PBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation from 4V to 38V. Exceeding 40V risks permanent damage per Absolute Maximum Ratings. The device maintains full functionality-including current-mode control, OPTI-LOOP compensation, and mode selection-across this entire 4V–38V range.
Does the LTC3851EGN#PBF support DCR current sensing, and how is it implemented?
Yes, the LTC3851EGN#PBF supports DCR current sensing via dedicated SENSE+ and SENSE– pins with 0V–5.5V common-mode range. Implementation requires an RC network matching the L/DCR time constant across the inductor windings; the voltage across the capacitor scales the DCR drop for accurate peak-current detection without sense resistor losses.
How does the ILIM pin configure current limit thresholds on the LTC3851EGN#PBF?
The ILIM pin on the LTC3851EGN#PBF provides tri-level current limit programming: tying to GND sets 30mV threshold, floating sets 50mV, and connecting to INTVCC sets 75mV. This directly configures the maximum allowable VSENSE differential, enabling scalable overcurrent protection without changing external sense components.
Can the LTC3851EGN#PBF synchronize to an external clock, and what pins are involved?
Yes, the LTC3851EGN#PBF supports external clock synchronization via the MODE/PLLIN pin, which functions as a phase detector input. When driven by a clean clock signal (250–750kHz), the internal oscillator locks to it. The FREQ/PLLFLTR pin must be configured with an RC low-pass filter to stabilize the PLL loop dynamics.
What thermal considerations apply to the LTC3851EGN#PBF in narrow SSOP (GN) package?
The LTC3851EGN#PBF in GN package has θJA = 110°C/W and no exposed pad; thermal performance depends heavily on PCB copper area under the IC body and adjacent ground planes. For 15A operation, ≥4 cm² of 2-oz copper connected to Pin 10 (GND) is recommended to maintain junction temperature below 125°C at 85°C ambient.
LTC3851EGN#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- 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:
- 250kHz ~ 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 ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LTC3851EGN#PBF FAQ
1.How can I place an order for LTC3851EGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851EGN#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 LTC3851EGN#PBF reliable?
The price and inventory of LTC3851EGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851EGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC3851EGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851EGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851EGN#PBF?
LTC3851EGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851EGN#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 LTC3851EGN#PBF?
For technical support, including LTC3851EGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851EGN#PBF requirements.
6.How does Aetrix verify that LTC3851EGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3851EGN#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 LTC3851EGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC3851EGN#PBF?
All LTC3851EGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851EGN#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 LTC3851EGN#PBF part is unused and in its original packaging.
Return procedure for LTC3851EGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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