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Analog Devices Inc. LTC3851IMSE#TRPBF
- Part No.:
- LTC3851IMSE#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LTC3851IMSE#TRPBF.pdf
- Description:
- IC REG CTRLR BUCK 16MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,926
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Product details
Overview
LTC3851IMSE#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 output with ±1% accuracy, operates up to 750kHz, and features OPTI-LOOP® compensation and selectable light-load modes (Burst, Pulse-Skip, or Continuous). It is used in telecom power supplies requiring tight regulation and high efficiency across wide load ranges.
For engineers reviewing the LTC3851IMSE#TRPBF datasheet, LTC3851IMSE#TRPBF pinout, LTC3851IMSE#TRPBF application, or LTC3851IMSE#TRPBF equivalent, key selection criteria include its 16-pin MSOP package with exposed thermal pad, RSENSE/DCR current sensing flexibility, 0.8V reference precision, phase-lockable oscillator, and robust overvoltage/overcurrent protection for industrial and telecom DC/DC converter designs.
Technical Context
The LTC3851IMSE#TRPBF implements a constant-frequency current-mode control architecture with an internal transconductance error amplifier (gm = 2 mmho, GBW = 3 MHz) and slope-compensated PWM. Its ITH pin serves as both error amplifier output and current threshold control point, enabling dynamic peak-current adjustment across load transients.
It integrates dual gate drivers (TG/BG) with matched 25ns rise/fall times, 30ns dead-time control, and independent pull-up/pull-down resistances (TG: 2.6Ω/1.5Ω; BG: 2.4Ω/1.1Ω). The MODE/PLLIN pin enables mode selection (Burst/Pulse-Skip/Continuous) or external clock synchronization, while FREQ/PLLFLTR sets oscillator frequency from 250kHz to 750kHz via resistor programming.
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% at VFB - ensures stable 0.8V reference tracking for precise output regulation under line/load/temperature variation. |
| Switching Frequency | 250kHz to 750kHz - adjustable via FREQ/PLLFLTR resistor; higher frequencies reduce passive size, lower frequencies improve efficiency. |
| Current Sense Threshold | 30mV / 50mV / 75mV - selectable via ILIM pin (GND/FLOAT/INTVCC) to match RSENSE or DCR sensing network design. |
| Shutdown Quiescent Current | 20μA - enables ultra-low-power disable state for battery-backed or standby systems. |
| Internal Regulator | 5V ±4% (4.8V–5.2V) - powers gate drivers and logic; supports bootstrap capacitor recharge during dropout. |
| Duty Cycle Capability | 99% - allows near-100% conduction for very low dropout operation (e.g., 12V→11.5V conversion). |
Pinout & Package
Package: 16-lead plastic MSOP (MSE) with exposed thermal pad (Pin 17), rated for –40°C to +125°C operating temperature. Exposed pad must be soldered to PCB for thermal and electrical grounding.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MODE/PLLIN (Pin 15) | Mode selection & sync input | Selects Burst/Pulse-Skip/Continuous mode or accepts external clock for forced continuous sync operation. |
| FREQ/PLLFLTR (Pin 16) | Oscillator frequency set & PLL filter | Resistor-to-GND sets nominal frequency; RC network filters PLL loop when synchronized externally. |
| RUN (Pin 1) | Enable control | 1.25V threshold enables IC; internal 2μA pull-up allows simple RC soft-start enable sequencing. |
| TK/SS (Pin 2) | Soft-start & tracking input | 1μA internal current charges external capacitor for linear VOUT ramp; supports ratiometric tracking of master supply. |
| ITH (Pin 3) | Error amp output & current threshold | Directly controls peak inductor current; voltage determines current limit and transient response bandwidth. |
| VFB (Pin 4) | Feedback input | Compares output divider voltage to 0.8V reference; high-impedance input minimizes loading on feedback network. |
| SENSE– (Pin 5) | 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 6) | Current sense non-inverting input | Connects to high-side of sense resistor or DCR network; enables accurate differential current measurement. |
| ILIM (Pin 7) | Current limit range select | Tri-level input (GND/FLOAT/INTVCC) selects 30/50/75mV max sense voltage for optimal RSENSE or DCR scaling. |
| GND (Pin 8) | Analog/digital ground | Kelvin connection point for all small-signal components; exposed pad must be tied to this node. |
| BG (Pin 9) | Bottom gate driver output | Drives source of bottom N-MOSFET between GND and INTVCC; fast 25ns transitions minimize shoot-through risk. |
| INTVCC (Pin 10) | Internal 5V regulator output | Powers internal circuitry; requires ≥2.2μF low-ESR capacitor to GND for stability and gate drive integrity. |
| VIN (Pin 11) | Main input supply | Accepts 4V–38V input; decoupling capacitor required close to pin to suppress high-frequency switching noise. |
| BOOST (Pin 12) | Floating bootstrap supply | Charges external bootstrap capacitor; swings from ~INTVCC–0.4V to VIN+INTVCC for top gate drive. |
| TG (Pin 13) | Top gate driver output | Floating driver referenced to SW node; delivers full INTVCC swing superimposed on switch-node voltage. |
| SW (Pin 14) | Switch node connection | 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 optimizing transient response across wide COUT/ESR variations - reduces BOM cost and board area. |
| Selectably Efficient Light-Load Operation | Three user-selectable modes (Burst, Pulse-Skip, Continuous) allow trade-off between light-load efficiency (>90% at 10mA), output ripple (<20mVpp), and EMI profile. |
| DCR or RSENSE Current Sensing | Supports lossless inductor DCR sensing or precision shunt resistor sensing - enables >95% full-load efficiency in high-current designs. |
| Output Overvoltage Protection | Hardware-based OV comparator triggers immediate TG off / BG on action if VFB exceeds 0.88V - protects downstream loads without software delay. |
| 99% Maximum Duty Cycle | Enables ultra-low dropout operation (e.g., 5.5V out from 5.6V input), critical for post-regulation in distributed power architectures. |
Applications
| Telecom Power Supply | Industrial PLC Power Module |
|---|---|
Use Scenario: 48V intermediate bus converted to 3.3V/15A for baseband processor and FPGA in 4G/5G remote radio units. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-efficiency, high-current DC/DC conversion with precise voltage regulation and thermal-aware current limiting. Use Value: ±1% output accuracy and 750kHz switching enable compact 12mm × 12mm power stage meeting GR-1089 Class B EMI requirements. | Use Scenario: 24V factory automation rail stepped down to 5V/10A for I/O modules and real-time controllers in harsh industrial environments. IC Role / Device Role / Timing Role: Robust step-down controller with wide input range, -40°C to +125°C rating, and integrated overvoltage/overcurrent protection. Use Value: 99% duty cycle and 38V max input support direct conversion from unregulated 24V systems with brownout resilience. |
| Automotive Infotainment System | Distributed DC Power System |
Use Scenario: 12V vehicle battery converted to 1.5V/8A for SoC core supply in head-unit systems with strict automotive qualification requirements. IC Role / Device Role / Timing Role: High-accuracy, high-efficiency buck controller supporting Burst Mode for low-quiescent standby and fast wake-up response. Use Value: 20μA shutdown IQ and programmable soft-start via TK/SS meet ISO 16750-2 cold-crank and sleep-mode current budgets. | Use Scenario: Central 48V server rack bus distributed to multiple 12V/5V/3.3V point-of-load converters in data center power architecture. IC Role / Device Role / Timing Role: Synchronous buck controller with phase-lock capability for synchronized switching across multiple rails to reduce input ripple and EMI. Use Value: MODE/PLLIN synchronization eliminates beat frequencies between parallel converters, simplifying EMI filter design and improving system-level efficiency. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3851-1IMSE#TRPBF | Includes power-good (PGOOD) output; lacks adjustable current limit (fixed ILIM function) | Preferred where system-level power sequencing or fault reporting is required; not suitable when programmable current foldback is needed | Select LTC3851-1IMSE#TRPBF only if PGOOD signal is mandatory and current limit adjustability is unnecessary. |
| MP2918GL-Z | Integrated MOSFETs (not controller-only); 4.5V–36V input; fixed 600kHz frequency; no PLL sync or DCR sensing | Targeted at space-constrained, lower-current applications (<10A); eliminates external FET layout but sacrifices flexibility and high-current scalability | Choose MP2918GL-Z for simplified design with <10A loads where integration outweighs configurability needs. |
Compared with LTC3851-1IMSE#TRPBF, the LTC3851IMSE#TRPBF offers adjustable current limit via ILIM pin but no PGOOD signal; compared with MP2918GL-Z, it provides full external FET control, DCR/RSENSE flexibility, and PLL synchronization - making it superior for high-current, thermally demanding, or multi-rail synchronized systems.
Availability
LTC3851IMSE#TRPBF is available at Aetrix Electronics and suitable for telecom power supplies, industrial PLC modules, and automotive infotainment systems requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LTC3851IMSE#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, Inc. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LTC3851 product line was designed as a high-efficiency, flexible synchronous buck controller family targeting industrial, telecom, and automotive power systems requiring precision regulation, wide input range, and robust protection features.
FAQ
What is the maximum input voltage rating for the LTC3851IMSE#TRPBF?
The LTC3851IMSE#TRPBF has an absolute maximum input voltage (VIN) rating of 40V, with recommended continuous operation from 4V to 38V. Exceeding 40V may cause permanent damage. This wide input range allows direct use from unregulated 24V or 48V industrial and telecom buses without front-end pre-regulation.
How does the ILIM pin affect current limiting on the LTC3851IMSE#TRPBF?
The ILIM pin on the LTC3851IMSE#TRPBF sets the maximum current sense threshold to 30mV (ILIM = GND), 50mV (ILIM = FLOAT), or 75mV (ILIM = INTVCC). This directly scales the peak inductor current limit, enabling precise matching to RSENSE value or DCR network gain - critical for achieving accurate overcurrent protection across temperature and process variation.
Can the LTC3851IMSE#TRPBF synchronize to an external clock, and how is it configured?
Yes, the LTC3851IMSE#TRPBF can synchronize to an external clock via the MODE/PLLIN pin. When an external clock signal (250kHz–750kHz) is applied, the internal oscillator locks to it and forces continuous conduction mode. A series RC network on FREQ/PLLFLTR serves as the PLL loop filter; the external clock should be applied before enabling RUN to avoid startup frequency instability.
What is the purpose of the TK/SS pin on the LTC3851IMSE#TRPBF, and how is it used?
The TK/SS pin on the LTC3851IMSE#TRPBF provides output voltage soft-start and ratiometric tracking. An internal 1μA current charges an external capacitor to generate a linear voltage ramp, controlling VOUT rise time. For tracking, an external resistor divider from a master supply connects to TK/SS, enabling coordinated startup with other rails - essential for FPGA or multi-rail SoC power sequencing.
Does the LTC3851IMSE#TRPBF support DCR current sensing, and what are the design considerations?
Yes, the LTC3851IMSE#TRPBF supports DCR current sensing using the SENSE+ and SENSE– pins. Design requires matching the R1||R2•C1 time constant to the L/DCR time constant of the inductor. Accurate DCR measurement (via RLC meter) and careful PCB layout to minimize noise coupling are essential. DCR sensing eliminates power loss from shunt resistors, improving efficiency in high-current applications.
LTC3851IMSE#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TFSOP (0.118", 3.00mm Width) Exposed Pad
- 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-MSOP-EP
LTC3851IMSE#TRPBF FAQ
1.How can I place an order for LTC3851IMSE#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3851IMSE#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 LTC3851IMSE#TRPBF reliable?
The price and inventory of LTC3851IMSE#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3851IMSE#TRPBF is usually 5 days.
3.What payment methods are accepted for LTC3851IMSE#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3851IMSE#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3851IMSE#TRPBF?
LTC3851IMSE#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3851IMSE#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 LTC3851IMSE#TRPBF?
For technical support, including LTC3851IMSE#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3851IMSE#TRPBF requirements.
6.How does Aetrix verify that LTC3851IMSE#TRPBF is sourced from the original manufacturer or authorized distributors?
All LTC3851IMSE#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 LTC3851IMSE#TRPBF meets industry standards.
7.What is the process for return or replacement of LTC3851IMSE#TRPBF?
All LTC3851IMSE#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3851IMSE#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 LTC3851IMSE#TRPBF part is unused and in its original packaging.
Return procedure for LTC3851IMSE#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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