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Analog Devices Inc. LTC3878EGN#PBF
- Part No.:
- LTC3878EGN#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 16-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
LTC3878EGN#PBF.pdf
- Description:
- IC REG CTRLR BUCK 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,545
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Product details
Overview
LTC3878EGN#PBF from Analog Devices (formerly Linear Technology) is a synchronous step-down DC/DC controller IC optimized for high-frequency operation and fast transient response in distributed power systems. It features a wide 4V–38V input range, ±1% 0.8V reference, 43ns minimum on-time, valley current mode control without external sense resistor, and dual N-channel MOSFET synchronous drive in a 16-pin narrow SSOP package.
For engineers reviewing the LTC3878EGN#PBF datasheet, LTC3878EGN#PBF pinout, LTC3878EGN#PBF application, or LTC3878EGN#PBF equivalent, key selection criteria include its no-RSENSE valley current sensing architecture, programmable current limit with foldback, forced continuous/discontinuous mode control via FCB pin, and compatibility with the LTC1778 in EXTVCC-free designs.
Technical Context
The LTC3878EGN#PBF implements constant-on-time valley current mode control, enabling stable operation across wide VIN ranges-including low-duty-cycle conditions-without slope compensation or external current-sense resistors. Its architecture senses inductor valley current via bottom MOSFET RDS(ON), with VRNG pin programmability setting maximum VDS sense threshold from 26.6mV to 266mV.
Switching frequency is set by an external resistor on the ION pin and compensated for VIN variations to maintain line stability. Discontinuous conduction mode (DCM) improves light-load efficiency, while the FCB pin allows forced continuous conduction mode (FCM) to reduce EMI. Safety features include output overvoltage protection, programmable current limit with foldback, and micropower shutdown below 0.7V on RUN/SS.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 38V - supports industrial, telecom, and automotive supply rails without pre-regulation |
| Output Voltage Range | 0.8V to 90% VIN - enables direct regulation of core voltages down to sub-1V levels |
| Reference Voltage Accuracy | ±1% at 0.8V - ensures tight output regulation under load and line transients |
| Min On-Time (tON(MIN)) | 43ns - enables high step-down ratios (e.g., 24V→1.2V) at 400kHz+ switching frequencies |
| Current Sense Architecture | No RSENSE valley current mode - eliminates sense resistor losses and PCB area; uses bottom MOSFET RDS(ON) |
| Switching Frequency Control | Resistor-programmable via ION pin - provides pseudo-fixed frequency with VIN compensation for stable line regulation |
| Protection Features | Programmable current limit with foldback, output overvoltage protection, PGOOD monitoring - prevents damage during short-circuit or fault conditions |
Pinout & Package
Package: 16-lead plastic narrow SSOP (GN), RoHS-compliant, –40°C to +85°C operating temperature range.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RUN/SS | Run enable & soft-start control | Internal 1.2µA current source charges external capacitor; device enters micropower shutdown below 0.7V |
| PGOOD | Open-drain power-good monitor | Asserts low when VOUT deviates >±7.5% from regulation point - enables system sequencing and fault detection |
| VRNG | VDS sense voltage range select | Sets max valley current sense threshold as 0.133×VRNG (26.6mV–266mV); tied to SGND or INTVCC for fixed thresholds |
| FCB | Forced continuous mode control | Connect to SGND to disable DCM and force CCM; connect to INTVCC for automatic DCM at light loads |
| ITH | Error amplifier output & current threshold | Voltage (0–2.4V) sets valley current comparator threshold; 0.8V = zero-current reference |
| SGND | Signal ground reference | Return for all small-signal circuitry; must be connected to PGND at single point to avoid noise coupling |
| ION | On-time current input | External resistor from VIN sets one-shot timer current and thus switching frequency |
| VFB | Feedback input | Connects to resistive divider from VOUT; referenced to 0.8V internal bandgap |
| NC | No connect | Factory test pin; must remain unconnected or tied ≤INTVCC |
| VIN | Main input supply | Accepts 4V–38V; requires RC filter to PGND for noise immunity |
| INTVCC | Internal 5.3V regulator output | Powers gate drivers and control logic; requires ≥1µF ceramic decoupling to PGND |
| BG | Bottom gate driver output | Drives gate of synchronous N-MOSFET between PGND and INTVCC; 0.7Ω pull-down resistance |
| PGND | Power ground | High-current return for bottom MOSFET source, CINTVCC (–), and CVIN (–); must be placed near MOSFET source |
| SW | Switch node | Connects to inductor, bootstrap capacitor (–), and bottom MOSFET drain; swings from –0.3V to VIN |
| TG | Top gate driver output | Drives gate of high-side N-MOSFET between SW and BOOST; 2.5Ω pull-up / 1.2Ω pull-down resistance |
| BOOST | Bootstrap floating supply | Connects to bootstrap capacitor (+); floats with SW to provide gate drive above VIN for top MOSFET |
Key Features
| Feature | Design Value |
|---|---|
| No RSENSE valley current sensing | Eliminates external sense resistor, reducing BOM cost, board space, and power loss while maintaining accurate current limiting |
| Wide 4V–38V input range | Supports unregulated 5V, 12V, 24V, and 28V rails common in communications infrastructure and embedded computing |
| 43ns minimum on-time | Enables high step-down conversion (e.g., 24V→1.2V @ 400kHz) without duty-cycle limitation or external frequency scaling |
| Programmable current limit with foldback | Protects against short circuits by progressively lowering current limit when VOUT drops below 50% of regulation |
| Forced continuous/discontinuous mode control | FCB pin selects CCM for low-noise operation or DCM for high light-load efficiency - no external logic required |
| Pin-compatible with LTC1778 (no EXTVCC) | Drop-in replacement in legacy designs omitting EXTVCC functionality, with improved gate drive and reduced dead time |
Applications
| Telecom Power Supply | Server CPU Core Regulator |
|---|---|
Use Scenario: 48V intermediate bus converted to 1.2V/15A for ASIC/FPGA core supply in 1RU telecom equipment. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-current, low-voltage regulation with fast load-step response. Use Value: 43ns tON(MIN) and valley current mode enable stable 48V→1.2V conversion at 400kHz; no-RSENSE reduces thermal stress and improves efficiency. | Use Scenario: Point-of-load regulator delivering 0.8V–1.8V at up to 15A to multi-core server CPUs with dynamic load changes. IC Role / Device Role / Timing Role: High-bandwidth step-down controller providing precise voltage regulation and <12µs PGOOD assertion delay. Use Value: ±1% 0.8V reference and fast transient response minimize voltage droop during CPU burst loads; VRNG pin allows optimization for low-RDS(ON) MOSFETs. |
| Industrial PLC Power Module | Networking Switch ASIC Supply |
Use Scenario: 24V field bus input regulated to 3.3V/5A for I/O controller and communication interface in harsh industrial environments. IC Role / Device Role / Timing Role: Robust DC/DC controller with wide VIN range and integrated OVP/UVLO for reliable operation under brownout conditions. Use Value: 4V–38V input range tolerates 24V rail sag; programmable current limit with foldback protects against field-wiring faults without external circuitry. | Use Scenario: Compact 12V→1.0V converter powering high-speed SerDes and packet processing ASICs in 10G/25G Ethernet switches. IC Role / Device Role / Timing Role: High-frequency synchronous buck controller supporting tight output ripple (<10mVpp) and rapid transient recovery. Use Value: Stable ceramic-capacitor support and discontinuous mode operation maintain >85% efficiency at 100mA idle load; TG/BG drivers with 15ns dead-time control minimize shoot-through. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC1778EGN#PBF | Lacks EXTVCC pin; lower gate drive strength; no FCB pin for DCM/FCM selection; higher dead time | Legacy design requiring EXTVCC is incompatible; less efficient at high load due to weaker drivers | Select LTC3878EGN#PBF for new designs requiring higher efficiency, better light-load performance, or VRNG-based current sensing flexibility |
| MP2491D-LF-Z | Fixed 500kHz frequency; no VRNG or FCB pins; integrated MOSFETs; narrower 4.5V–36V input range | Not suitable for ultra-low-VOUT or high-step-down ratio applications; limited current sense adjustability | Choose MP2491D-LF-Z only for cost-sensitive, space-constrained applications where integrated power stage suffices and programmability is not required |
Compared with LTC1778EGN#PBF, LTC3878EGN#PBF delivers higher efficiency via improved gate drivers and reduced dead time, while MP2491D-LF-Z trades configurability for integration and lower BOM count - making LTC3878EGN#PBF optimal for high-performance, discrete-power-stage designs demanding precision and flexibility.
Availability
LTC3878EGN#PBF is available at Aetrix Electronics and suitable for distributed power systems, embedded computing platforms, and communications infrastructure requiring stable component supply, long-term lifecycle support, and guaranteed RoHS-compliant sourcing.
Supply support for LTC3878EGN#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. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC3878EGN#PBF belongs to ADI's Power by Linear™ family of high-efficiency DC/DC controllers, designed specifically for high-frequency, high-step-down-ratio synchronous buck converters in demanding industrial and communications applications.
FAQ
What is the minimum on-time specification for LTC3878EGN#PBF and why does it matter?
The LTC3878EGN#PBF has a minimum on-time (tON(MIN)) of 43ns. This parameter determines the lowest achievable output voltage at a given input voltage and switching frequency - for example, enabling stable 24V→1.2V conversion at 400kHz. A short tON(MIN) prevents dropout during low-duty-cycle operation and supports high step-down ratios without external frequency scaling or pulse-skipping modes. The LTC3878EGN#PBF achieves this via its constant-on-time valley current mode architecture.
How does the VRNG pin affect current sensing in LTC3878EGN#PBF?
The VRNG pin on the LTC3878EGN#PBF sets the maximum allowable bottom MOSFET VDS sense voltage as 0.133×VRNG, directly determining the valley current sense threshold (e.g., 93mV typical when VRNG = SGND; 186mV typical when VRNG = INTVCC). This allows designers to match the controller's current sensing range to the RDS(ON) of selected MOSFETs - optimizing accuracy and margin across temperature and process variation. The LTC3878EGN#PBF supports VRNG voltages from 0.2V to 2.0V, yielding a full sense range of 26.6mV to 266mV.
Can LTC3878EGN#PBF replace LTC1778EGN#PBF without PCB changes?
Yes - the LTC3878EGN#PBF is pin-compatible with the LTC1778EGN#PBF in applications that do not use the EXTVCC pin (LTC1778 Pin 9), as LTC3878EGN#PBF uses Pin 9 as NC. However, the LTC3878EGN#PBF offers improved gate drive strength, reduced dead time, and added features like FCB and VRNG. While no PCB layout change is required, functional verification is recommended due to differences in startup behavior, current limit foldback, and shutdown latch-off timing. The LTC3878EGN#PBF is not a drop-in replacement if EXTVCC functionality is used.
What protection features does LTC3878EGN#PBF include?
The LTC3878EGN#PBF integrates multiple hardware-level protections: output overvoltage protection (OVP) triggered by VFB excursion beyond ±7.5%; programmable current limit with foldback (reducing limit when VOUT falls below 50% of regulation); PGOOD open-drain output with 12µs turn-on delay; INTVCC undervoltage lockout (3.3V to 3.9V); and micropower shutdown below 0.7V on RUN/SS. These features operate independently of external components, ensuring robust fault handling in mission-critical power systems using the LTC3878EGN#PBF.
Does LTC3878EGN#PBF require an external current-sense resistor?
No - the LTC3878EGN#PBF implements No RSENSE™ valley current mode control, using the on-resistance (RDS(ON)) of the external bottom N-channel MOSFET to sense inductor valley current between the SW and PGND pins. This eliminates the need for a discrete sense resistor, reducing power loss, board area, and BOM cost. Current sensing accuracy depends on MOSFET RDS(ON) tolerance and temperature coefficient, with VRNG pin adjustment allowing calibration across MOSFET variants. The LTC3878EGN#PBF datasheet confirms "No external sense resistor or slope compensation is required."
LTC3878EGN#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 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
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
LTC3878EGN#PBF FAQ
1.How can I place an order for LTC3878EGN#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3878EGN#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 LTC3878EGN#PBF reliable?
The price and inventory of LTC3878EGN#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3878EGN#PBF is usually 5 days.
3.What payment methods are accepted for LTC3878EGN#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3878EGN#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3878EGN#PBF?
LTC3878EGN#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3878EGN#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 LTC3878EGN#PBF?
For technical support, including LTC3878EGN#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3878EGN#PBF requirements.
6.How does Aetrix verify that LTC3878EGN#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3878EGN#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 LTC3878EGN#PBF meets industry standards.
7.What is the process for return or replacement of LTC3878EGN#PBF?
All LTC3878EGN#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3878EGN#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 LTC3878EGN#PBF part is unused and in its original packaging.
Return procedure for LTC3878EGN#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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