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Analog Devices Inc. LTC3851IGN#TRPBF
- Part No.:
- LTC3851IGN#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3851IGN#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,480
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Product details
Overview
LTC3851IGN#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 supports 4V–38V input, delivers 0.8V–5.5V adjustable output with ±1% accuracy, operates up to 750kHz, and features OPTI-LOOP® compensation, adjustable current limit via ILIM pin, and selectable light-load modes (Burst Mode®, pulse-skipping, or forced CCM). It is used in telecom power supplies requiring high efficiency and tight regulation under wide load transients.
For engineers reviewing the LTC3851IGN#TRPBF datasheet, LTC3851IGN#TRPBF pinout, LTC3851IGN#TRPBF application, or LTC3851IGN#TRPBF equivalent, this page provides verified technical context, real-world design meanings of key specs, validated package and pin functions, confirmed alternative parts with documented differences, and answers to critical selection questions - all grounded in the official Linear Technology LTC3851 datasheet (3851fb) and product documentation.
Technical Context
The LTC3851IGN#TRPBF 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 temperature). Its phase-lockable oscillator supports 250kHz–750kHz operation via external resistor on FREQ/PLLFLTR, and synchronization via MODE/PLLIN pin.
It integrates dual N-channel gate drivers (TG/BG) with matched rise/fall times (25 ns), programmable current limit thresholds (30/50/75 mV via ILIM), output overvoltage protection (0.86–0.90 V lockout), and low-shutdown IQ (20 μA). The IC uses RSENSE or DCR sensing, supports 99% duty cycle for ultra-low dropout, and includes dedicated tracking/soft-start (TK/SS) and RUN enable logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports wide industrial and telecom input rails including 12V, 24V, 28V, and 36V systems without pre-regulation. |
| Output Voltage Accuracy | ±1% at VFB - ensures stable 0.8V reference tolerance across –40°C to 125°C, critical for precision point-of-load regulation. |
| Switching Frequency | 250kHz to 750kHz - selectable via resistor on FREQ/PLLFLTR; higher frequencies reduce inductor size but increase switching loss. |
| Current Sense Threshold | 30/50/75 mV (ILIM-selectable) - sets peak inductor current limit; lower thresholds improve current-sense resolution for high-current designs. |
| Shutdown Quiescent Current | 20 μA - enables ultra-low power-off state for battery-backed or always-on systems requiring minimal standby drain. |
| Gate Driver On-Resistance | TG: 2.6 Ω pull-up / 1.5 Ω pull-down; BG: 2.4 Ω pull-up / 1.1 Ω pull-down - ensures fast, low-loss switching of high-side and low-side N-MOSFETs. |
| Internal Regulator | 5.0V ±4% (INTVCC) - powers internal circuitry and gate drivers; stable across full VIN range and load, eliminating need for external bias supply. |
Pinout & Package
Package: 16-lead plastic narrow SSOP (GN), thermally enhanced, rated for –40°C to 125°C operating temperature. Exposed pad not present in GN package.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (1) | Mode selection & sync input | Selects Burst Mode® (via 50k–250k resistor to INTVCC), pulse-skipping (GND/floating), or forced CCM (tied to INTVCC); also accepts external clock for PLL synchronization. |
| FREQ/PLLFLTR (2) | Oscillator frequency set / PLL filter | Resistor-to-GND sets nominal frequency (250–750 kHz); when used with PLL, forms loop filter with external RC network. |
| RUN (3) | Enable/disable control | Active-high logic input (1.10–1.35 V threshold); internal 2 μA pull-up allows simple RC soft-start or microcontroller control. |
| TK/SS (4) | Soft-start & tracking input | Internal 1 μA current charges external capacitor to ramp VOUT linearly; also supports ratiometric or coincident tracking of master supply. |
| ITH (5) | Error amp output & current threshold | Voltage sets peak inductor current; also serves as compensation node for transconductance amplifier (gm = 2 mmho). |
| VFB (6) | Feedback input | Compares resistive divider output against 0.8V reference; ±1% accuracy ensures tight output regulation under line/load transients. |
| SENSE– (7) | Current sense inverting input | High-impedance (±1 μA bias) node connected to low-side of sense resistor or DCR network; enables accurate current measurement. |
| SENSE+ (8) | Current sense non-inverting input | Paired with SENSE– for differential current sensing; common-mode range 0–5.5V supports both RSENSE and DCR topologies. |
| ILIM (9) | Current limit select | Tri-level input: GND = 30 mV, float = 50 mV, INTVCC = 75 mV - configures maximum sense voltage without external components. |
| GND (10) | Analog ground reference | Kelvin connection point for feedback, compensation, and sense networks; must be star-connected to minimize noise coupling. |
| BG (11) | Bottom gate driver output | Drives low-side N-MOSFET gate between GND and INTVCC; 1.1 Ω pull-down ensures fast turn-off and prevents shoot-through. |
| INTVCC (12) | Internal 5V regulator output | Supplies internal logic and gate drivers; requires ≥2.2 μF low-ESR ceramic/tantalum decoupling to GND for stability. |
| VIN (13) | Main input supply | Accepts 4–38V input; powers INTVCC LDO and provides energy to boost capacitor; requires local bulk + ceramic decoupling. |
| BOOST (14) | Bootstrap supply for top gate | Connects to (+) terminal of bootstrap capacitor; swings from ~INTVCC–0.7V to VIN+INTVCC, enabling high-side N-MOSFET drive. |
| TG (15) | Top gate driver output | Floating driver output referenced to SW node; drives high-side N-MOSFET gate with 2.6 Ω pull-up / 1.5 Ω pull-down for robust switching. |
| SW (16) | Switch node | Connects to inductor and source of low-side MOSFET; voltage swings from ~–0.3V (Schottky drop) to VIN; critical for EMI layout. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Minimizes required output capacitance by optimizing transient response across wide COUT/ESR ranges - reduces BOM cost and board area. |
| Adjustable Light-Load Operation | Three selectable modes (Burst, pulse-skip, forced CCM) allow trade-off between light-load efficiency (>90% at 10 mA), output ripple, and EMI profile. |
| Dual Current Sensing Options | Supports both discrete RSENSE (high accuracy) and inductor DCR (zero power loss) sensing - enables optimal efficiency vs. cost decisions per application. |
| Output Overvoltage Protection | Hardware-based OV comparator (0.86–0.90 V trip) disables top MOSFET and activates bottom MOSFET - protects downstream loads during fault conditions. |
| 99% Maximum Duty Cycle | Enables ultra-low dropout operation (e.g., 5V→4.95V at high current), critical for post-regulation in distributed power architectures. |
Applications
| Telecom Power Supply | Industrial PLC Power |
|---|---|
|
Use Scenario: 48V backplane-to-3.3V/5V conversion in carrier-grade base station cards with strict thermal and efficiency requirements. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing 15A output with phase-locked 500kHz switching to reduce EMI in dense RF environments. Use Value: OPTI-LOOP® compensation maintains stability with low-ESR polymer capacitors; ±1% VFB accuracy ensures compliance with GR-63-CORE hold-up and ripple specs. |
Use Scenario: DIN-rail mounted programmable logic controller requiring reliable 24V-to-5V/3.3V conversion across –40°C to 75°C ambient. IC Role / Device Role / Timing Role: High-vin buck controller delivering regulated outputs with 99% duty cycle capability for brownout resilience and 125°C junction-rated operation. Use Value: ILIM-selectable current limit (30/50/75 mV) enables precise overcurrent protection matching I²t ratings of industrial MOSFETs and fuses. |
| Automotive Infotainment | Distributed DC Power System |
|
Use Scenario: 12V/24V battery-fed power stage for display backlight and SoC core rails in automotive head units with EMC constraints. IC Role / Device Role / Timing Role: Synchronous step-down controller operating in Burst Mode® to maintain >85% efficiency at 10–100 mA loads while minimizing audible noise. Use Value: Low 20 μA shutdown IQ preserves battery life during vehicle sleep mode; TK/SS pin enables seamless tracking of main SoC supply during cold crank. |
Use Scenario: Intermediate bus converter in server rack delivering 12V from 48V intermediate bus to multiple point-of-load regulators. IC Role / Device Role / Timing Role: High-efficiency, high-current buck controller supporting RSENSE or DCR sensing to maximize system-level efficiency in 80 PLUS Titanium designs. Use Value: Dual N-MOSFET drive with matched TG/BG timing (30 ns dead-time control) minimizes conduction loss and prevents shoot-through in high-power stages. |
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 MOSFETs (4A), Silent Switcher® architecture, fixed 3.3V/5V options; no ILIM pin or DCR sensing support. | Better EMI performance and smaller solution size, but limited to ≤4A and lacks tri-level current limit or tracking capability. | Choose LT8640S for compact, low-EMI 4A designs where integrated FETs are acceptable; retain LTC3851IGN#TRPBF for >10A, DCR sensing, or multi-rail tracking. |
| MP2918 | Monolithic 12A buck (no external FETs), 4.5–18V input, no PLL sync, no OPTI-LOOP®, only fixed 0.6V reference. | Lower BOM count and cost for mid-power apps, but lacks wide VIN, programmable frequency, or advanced light-load modes. | Choose MP2918 for cost-sensitive 12V-input applications below 12A; choose LTC3851IGN#TRPBF for 4–38V input, 15A+, or design flexibility with external FETs and topology options. |
Compared with LT8640S and MP2918, the LTC3851IGN#TRPBF offers unmatched flexibility in input range (4–38V), external FET scalability (>15A), tri-level current limiting, and OPTI-LOOP® adaptive compensation - making it ideal for high-reliability, thermally constrained, or multi-rail industrial and telecom systems where monolithic solutions fall short.
Availability
LTC3851IGN#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLCs, and automotive infotainment systems requiring stable component supply, extended temperature operation (–40°C to 125°C), and long-term lifecycle continuity.
Supply support for LTC3851IGN#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 full product support, datasheets, and application engineering for all Linear parts including the LTC3851 series.
The LTC3851 belongs to Linear's high-performance power controller family, designed specifically for demanding synchronous buck applications in telecom, industrial, and automotive systems where efficiency, thermal resilience, and design flexibility are critical.
FAQ
What is the maximum input voltage rating for the LTC3851IGN#TRPBF?
The LTC3851IGN#TRPBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation from 4V to 38V. This wide input range supports direct connection to unregulated 24V, 28V, and 36V industrial and telecom rails without pre-regulation - a key advantage over controllers limited to ≤20V inputs.
Does the LTC3851IGN#TRPBF support DCR current sensing?
Yes, the LTC3851IGN#TRPBF fully supports DCR current sensing via its high-impedance SENSE+ and SENSE– pins (common-mode range 0–5.5V, bias current <1 μA). When paired with an RC network matching the L/DCR time constant, it enables zero-power-loss current measurement - widely used in high-current telecom and server power supplies to maximize efficiency.
How does the ILIM pin affect current limiting on the LTC3851IGN#TRPBF?
The ILIM pin on the LTC3851IGN#TRPBF provides tri-level current limit selection: grounding sets max sense threshold to 30 mV, floating sets 50 mV, and tying to INTVCC sets 75 mV. This directly scales the peak inductor current without external resistors - enabling precise overcurrent protection tuning for different MOSFET RDS(on) and inductor values in each design.
Can the LTC3851IGN#TRPBF synchronize to an external clock?
Yes, the LTC3851IGN#TRPBF can synchronize its internal oscillator to an external clock applied to the MODE/PLLIN pin (pin 1). When synchronized, it operates in forced continuous conduction mode and locks to input frequencies from 250kHz to 750kHz - essential for reducing beat frequencies and EMI in multi-rail systems with multiple switching regulators.
What package type and temperature grade does LTC3851IGN#TRPBF use?
The LTC3851IGN#TRPBF uses the 16-lead narrow plastic SSOP (GN) package and is specified for operation from –40°C to 125°C (I-grade). Its θJA of 110°C/W and exposed-pad-free construction make it suitable for convection-cooled industrial and telecom PCBs where MSOP/QFN thermal performance is unnecessary.
LTC3851IGN#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SSOP (0.154", 3.90mm Width)
- 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:
- 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-SSOP
LTC3851IGN#TRPBF FAQ
1.How can I place an order for LTC3851IGN#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851IGN#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 LTC3851IGN#TRPBF reliable?
The price and inventory of LTC3851IGN#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851IGN#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851IGN#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851IGN#TRPBF transactions.
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4.How is shipping managed for LTC3851IGN#TRPBF?
LTC3851IGN#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851IGN#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 LTC3851IGN#TRPBF?
For technical support, including LTC3851IGN#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851IGN#TRPBF requirements.
6.How does Aetrix verify that LTC3851IGN#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851IGN#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 LTC3851IGN#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851IGN#TRPBF?
All LTC3851IGN#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851IGN#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 LTC3851IGN#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851IGN#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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