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Analog Devices Inc. LTC3879EUD#PBF
- Part No.:
- LTC3879EUD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-WFQFN Exposed Pad
- Datasheet:
-
LTC3879EUD#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16QFN
- Quantity:
- Payment:
- Shipping:
Inventory:527
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Product details
Overview
LTC3879EUD#PBF from Analog Devices (formerly Linear Technology) is a synchronous step-down switching regulator controller optimized for high-frequency operation and fast transient response in wide-input-voltage DC/DC converters. It features valley current mode control without external sense resistors, ±1% 0.6V reference, 43ns minimum on-time, and dual N-channel MOSFET drive - enabling high step-down ratios in distributed power systems and embedded computing.
For engineers reviewing the LTC3879EUD#PBF datasheet, LTC3879EUD#PBF pinout, LTC3879EUD#PBF application, or LTC3879EUD#PBF equivalent, key selection considerations include its 4V–38V input range, programmable current limit with foldback, forced continuous/discontinuous mode control via MODE pin, and compatibility with low-ESR ceramic output capacitors.
Technical Context
The LTC3879EUD#PBF implements constant-on-time valley current mode control, eliminating need for slope compensation or external RSENSE. Its architecture supports stable operation at very low duty cycles (e.g., 1.2V out from 28V in) and delivers sub-5μs load transient recovery in forced continuous mode.
It integrates dual gate drivers with 1.2Ω BG pull-down and 2.5Ω TG pull-up resistance, 5.3V INTVCC regulator with ±2% load regulation, and independent RUN/TRACK/SS pins enabling pre-biased start-up and rail tracking. The VRNG pin sets valley current sense threshold from 22mV to 98mV, directly scaling with applied voltage (0.2V–2V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports industrial, telecom, and automotive supply rails without external regulators. |
| Feedback Reference | 0.6V ±1% - enables precise output regulation down to 0.6V with standard resistor dividers. |
| Min On-Time | 43ns - allows high step-down ratios (e.g., 28V→1.2V at 400kHz) without pulse-skipping instability. |
| Switching Frequency | Programmable via ION resistor - maintains pseudo-fixed frequency across VIN variation for predictable EMI behavior. |
| Current Sense Threshold | Adjustable 22mV–98mV via VRNG pin - eliminates discrete sense resistor while supporting diverse MOSFET RDS(ON) values. |
| Gate Drive Capability | TG/BG drivers with 20ns rise/fall times (3300pF load) - ensures efficient switching of logic-level N-MOSFETs up to 15A output. |
| Protection Features | Output overvoltage protection, programmable current limit with foldback, and PGOOD monitoring - reduces need for external supervision circuitry. |
Pinout & Package
The LTC3879EUD#PBF is housed in a thermally enhanced 16-lead (3mm × 3mm) plastic QFN package with exposed SGND pad (Pin 17) requiring PCB soldering for thermal and electrical integrity. θJA = 68°C/W, θJC = 4.2°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TRACK/SS (1) | Soft-start & tracking input | Internal 1μA pull-up; capacitor sets ramp time or resistor divider enables output voltage tracking of external rail. |
| PGOOD (2) | Open-drain power-good flag | Asserts low when VOUT deviates >±10% from regulation point - used for system sequencing and fault reporting. |
| VRNG (3) | VDS sense range control | Sets valley current threshold as 0.133×VRNG (22–98mV); tied to SGND or INTVCC for fixed thresholds. |
| MODE (4) | Continuous/discontinuous mode select | Ground → forced CCM; INTVCC → DCM enabled for light-load efficiency improvement. |
| ITH (5) | Error amplifier output & current limit setpoint | Voltage (0–2.4V) controls valley current threshold; also serves as compensation node for loop stability. |
| SGND (6) | Signal ground reference | Reference for all analog circuitry; must connect to PGND via single-point trace to avoid noise coupling. |
| ION (7) | On-time programming input | Resistor from VIN sets one-shot timer current - determines switching frequency and compensates for VIN variation. |
| VFB (8) | Feedback input | Compares output divider voltage to 0.6V reference; high-impedance (±50nA) for minimal divider loading. |
| RUN (9) | Enable/shutdown control | <0.7V → micropower shutdown (18μA); 0.7–1.5V → bias enabled, no switching; >1.5V → full operation. |
| VIN (10) | Main input supply | 4–38V input; requires RC filter to PGND for noise immunity in noisy environments. |
| INTVCC (11) | 5.3V internal regulator output | Powers gate drivers and control logic; requires ≥1μF X5R/X7R ceramic decoupling to PGND. |
| BG (12) | Bottom gate driver output | Drives synchronous N-MOSFET source-to-PGND; 1.2Ω pull-down resistance minimizes turn-off delay. |
| PGND (13) | Power ground return | Low-impedance return for bottom MOSFET source, CINTVCC, and CVIN - must be placed adjacent to MOSFET source pad. |
| SW (14) | Switch node | Connects to bootstrap capacitor negative terminal; swings from ~–0.4V to VIN - critical for layout EMI reduction. |
| TG (15) | Top gate driver output | Drives top N-MOSFET gate referenced to SW; 2.5Ω pull-up/pull-down ensures fast transitions under 3300pF load. |
| BOOST (16) | Bootstrap supply | Connects to bootstrap capacitor positive terminal; floats between (INTVCC – 0.4V) and (VIN + INTVCC – 0.4V). |
Key Features
| Feature | Design Value |
|---|---|
| No RSENSE valley current sensing | Uses bottom MOSFET RDS(ON) for current measurement - eliminates power loss and board space of external sense resistor. |
| Stable with ceramic output capacitors | Designed for low-ESR ceramic COUT - avoids need for electrolytic or tantalum capacitors and improves reliability. |
| Pre-biased output start-up | Supports smooth regulation ramp even when output is pre-charged - essential for hot-swap and multi-rail sequencing. |
| Adjustable soft-start or tracking | Single pin (TRACK/SS) configures either timed ramp or synchronous tracking of another supply - simplifies multi-rail power design. |
| Programmable current limit with foldback | Protects against short circuits by reducing current limit when VOUT drops below 50% - prevents thermal runaway during faults. |
Applications
| Telecom Power Supply | Industrial PLC CPU Core |
|---|---|
Use Scenario: 48V intermediate bus converted to 1.2V/15A for FPGA or ASIC core in 4G/5G base station equipment. IC Role / Device Role / Timing Role: Primary step-down controller managing high-current, low-voltage rail with tight transient response requirements. Use Value: 43ns min on-time enables 1.2V output from 48V input at 400kHz; fast transient recovery (<5μs) maintains voltage within ±2% during 10A load steps. | Use Scenario: 24V factory automation input stepped down to 3.3V/8A for programmable logic controller CPU and memory subsystem. IC Role / Device Role / Timing Role: High-efficiency buck controller with robust overvoltage and current protection in harsh industrial environments. Use Value: Output overvoltage protection and programmable foldback current limit prevent damage during field wiring faults or ESD events. |
| Embedded Computing Module | Communications Infrastructure |
Use Scenario: Compact 3.3V/5A power rail for ARM-based edge AI module operating from 12V PoE++ or battery input. IC Role / Device Role / Timing Role: Synchronous buck controller with integrated gate drivers and thermal management for space-constrained designs. Use Value: 3mm × 3mm QFN package with exposed pad achieves 68°C/W θJA; forced CCM mode eliminates audible noise in fanless enclosures. | Use Scenario: Redundant 12V/10A power for optical line terminal (OLT) line cards requiring high reliability and fast fault response. IC Role / Device Role / Timing Role: Dual-MOSFET controller with PGOOD signaling and precise 0.6V reference for system-level power sequencing. Use Value: ±1% reference and PGOOD with 12μs turn-on delay enable deterministic power-up timing across multiple distributed rails. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3891EUF#PBF | Includes integrated 5V/100mA bias supply; wider 4.5V–60V input range; no VRNG pin - fixed 30mV current sense threshold. | Better suited for higher-input-voltage systems (e.g., 48V industrial) where auxiliary bias is needed; lacks VRNG flexibility for MOSFET optimization. | Select LTC3891EUF#PBF when input exceeds 38V or integrated bias is required; not drop-in due to different pinout and sense architecture. |
| MP2918GL-Z | Monolithic 30V/12A buck converter (integrated MOSFETs); fixed 0.6V reference; no TRACK/SS or VRNG; smaller 4mm × 4mm QFN. | Targeted at cost-sensitive, medium-current applications where board space is critical and external MOSFET selection is undesirable. | Choose MP2918GL-Z for simplified BOM and layout in ≤12A applications; not functionally equivalent due to integration and missing programmability. |
Compared with LTC3891EUF#PBF and MP2918GL-Z, the LTC3879EUD#PBF offers unique VRNG-adjustable current sensing and TRACK/SS-configurable soft-start - making it optimal for high-flexibility, high-performance discrete buck designs where MOSFET optimization and multi-rail coordination are critical.
Availability
LTC3879EUD#PBF is available at Aetrix Electronics and suitable for distributed power systems, embedded computing, and communications infrastructure requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for LTC3879EUD#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 power management portfolio with rigorous qualification and long-term product support.
The LTC3879 belongs to Linear's high-frequency synchronous buck controller family, designed specifically for demanding DC/DC conversion in telecom, industrial, and embedded systems where efficiency, transient response, and design flexibility are paramount.
FAQ
What is the minimum on-time specification for the LTC3879EUD#PBF and why does it matter?
The LTC3879EUD#PBF has a minimum on-time of 43ns, specified at ION = 180μA. This ultra-short on-time enables stable operation at very high step-down ratios - for example, generating 1.2V from a 28V input at 400kHz without pulse-skipping or subharmonic oscillation. It directly determines the lowest practical output voltage achievable at a given input and frequency, making the LTC3879EUD#PBF especially valuable in intermediate bus architectures.
How does the VRNG pin affect current sensing in the LTC3879EUD#PBF?
The VRNG pin on the LTC3879EUD#PBF sets the maximum valley current sense threshold as 0.133 × VRNG, allowing adjustment from 22mV to 98mV by applying 0.2V–2V. This lets designers match the controller's sensitivity to the RDS(ON) of their selected bottom MOSFET - optimizing signal-to-noise ratio and minimizing conduction loss without external components. When VRNG is tied to SGND or INTVCC, the LTC3879EUD#PBF defaults to 30mV or 75mV thresholds respectively.
Can the LTC3879EUD#PBF start up into a pre-biased output, and how is this enabled?
Yes, the LTC3879EUD#PBF supports smooth start-up into a pre-biased output. This is enabled by default - no configuration required - because its valley current mode architecture and independent RUN pin control allow the controller to monitor VFB before enabling switching. When RUN rises above 1.5V, the LTC3879EUD#PBF begins regulating without forcing reverse current through the output capacitor, preventing inrush stress and ensuring safe hot-swap capability.
What is the role of the MODE pin on the LTC3879EUD#PBF, and how does it impact efficiency?
The MODE pin on the LTC3879EUD#PBF selects between forced continuous conduction mode (CCM) and discontinuous mode (DCM). Tying MODE to SGND forces CCM for consistent EMI profile and best heavy-load efficiency; tying to INTVCC enables DCM at light loads, reducing switching losses and improving light-load efficiency by skipping pulses. This dual-mode capability makes the LTC3879EUD#PBF adaptable across wide load ranges without sacrificing performance at either extreme.
Does the LTC3879EUD#PBF require an external sense resistor for current limiting?
No, the LTC3879EUD#PBF does not require an external sense resistor. It implements No RSENSE™ valley current mode control by measuring the voltage drop across the bottom N-channel MOSFET's RDS(ON) between SW and PGND pins. The VRNG pin scales the current sense threshold, eliminating power loss, board area, and tolerance errors associated with discrete sense resistors - a key advantage of the LTC3879EUD#PBF in high-efficiency designs.
LTC3879EUD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 4V ~ 38V
- Frequency - Switching:
- -
- Duty Cycle (Max):
- -
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Enable, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-QFN (3x3)
LTC3879EUD#PBF FAQ
1.How can I place an order for LTC3879EUD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3879EUD#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 LTC3879EUD#PBF reliable?
The price and inventory of LTC3879EUD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3879EUD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3879EUD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3879EUD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3879EUD#PBF?
LTC3879EUD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3879EUD#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 LTC3879EUD#PBF?
For technical support, including LTC3879EUD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3879EUD#PBF requirements.
6.How does Aetrix verify that LTC3879EUD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3879EUD#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 LTC3879EUD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3879EUD#PBF?
All LTC3879EUD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3879EUD#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 LTC3879EUD#PBF part is unused and in its original packaging.
Return procedure for LTC3879EUD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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