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Analog Devices Inc. LTC3891EUDC#PBF
- Part No.:
- LTC3891EUDC#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3891EUDC#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:16,920
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Product details
Overview
LTC3891EUDC#PBF from Analog Devices (formerly Linear Technology) is a high-performance, low-quiescent-current synchronous step-down DC/DC controller driving all-N-channel MOSFETs. It operates across 4V–60V input, delivers 0.8V–24V output, supports phase-lockable frequencies up to 750kHz, and features OPTI-LOOP® compensation for optimized transient response-used in automotive always-on systems requiring stable 3.3V/5A power rails.
For engineers reviewing the LTC3891EUDC#PBF datasheet, LTC3891EUDC#PBF pinout, LTC3891EUDC#PBF application, or LTC3891EUDC#PBF equivalent, key selection criteria include its 50μA no-load IQ, selectable light-load modes (Burst/Pulse-Skipping/Continuous), RSENSE or DCR current sensing, 99% duty cycle dropout capability, and integrated 5.1V INTVCC LDO with EXTVCC switchover.
Technical Context
The LTC3891EUDC#PBF implements a constant-frequency current-mode control architecture with an internal transconductance error amplifier (gm = 2 mmho), precision 0.8V reference (±1.2mV over temp), and programmable current limit via ILIM pin selection (22/43/64 mV thresholds). Its dual-gate drivers deliver 2.5Ω TG pull-up and 1.1Ω BG pull-down on-resistance with <30ns dead-time control.
It integrates a phase-locked loop (75–750kHz sync range), programmable oscillator (50–900kHz via FREQ pin resistor), and adaptive power-good monitoring with ±10% trip threshold and 25µs fault reporting delay. The device uses separate SGND and PGND pins, requires bootstrapping (BOOST–SW capacitor + Schottky diode), and supports tracking/soft-start via 10µA-sourced TRACK/SS pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide intermediate bus and battery chemistries including 12V, 24V, and 48V systems. |
| No-Load Quiescent Current | 50µA - extends runtime in battery-powered applications such as portable instrumentation and telematics. |
| Output Voltage Range | 0.8V to 24V - programmable via external resistive divider; enables single-controller flexibility across multiple rail requirements. |
| Switching Frequency Range | 75kHz to 750kHz (sync) or 50kHz to 900kHz (fixed) - allows EMI optimization and inductor size reduction. |
| Current Sense Threshold | Selectable 22/43/64mV via ILIM pin - sets precise overcurrent protection without external scaling components. |
| Duty Cycle Max | 99% - enables ultra-low dropout operation during VIN-to-VOUT ratios near unity (e.g., 5.5V→5V). |
| Power Good Accuracy | ±10% VFB trip with 2.5% hysteresis - provides reliable system-level power sequencing and fault detection. |
| Operating Junction Temp | –40°C to 125°C - qualified for industrial and automotive under-hood environments per E-grade spec. |
Pinout & Package
Package: 20-lead 3mm × 4mm plastic QFN (UDC) with exposed thermal pad (Pin 21 = SGND), θJA = 43°C/W. Requires soldering of exposed pad to PCB ground for rated thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (PLLIN/MODE) | Mode selection & sync input | Configures light-load behavior (Burst/Pulse-Skipping/Continuous) or accepts external clock for PLL synchronization. |
| 2,3,21 (SGND) | Small-signal ground | Must be routed separately from PGND; critical for noise immunity and accurate current sense referencing. |
| 4 (RUN) | Digital enable/shutdown control | 1.16V threshold disables regulation; 0.7V threshold shuts down entire IC, reducing IQ to 14µA. |
| 5 (SENSE–), 6 (SENSE+) | Differential current sense inputs | Accepts RSENSE or DCR network; common-mode range up to 28V enables high-side sensing in buck configurations. |
| 7 (VFB) | Feedback voltage input | Compares output voltage (via resistor divider) to 0.8V reference; ±5nA bias current minimizes divider error. |
| 8 (ITH) | Error amplifier output & compensation node | Directly controls peak inductor current; used for OPTI-LOOP® compensation network placement. |
| 9 (PGOOD) | Open-drain power-good indicator | Asserts low when VFB deviates >10% from setpoint; supports system power sequencing and fault logging. |
| 10 (TG), 13 (BG) | Top/bottom gate drivers | TG swings from SW to (SW + INTVCC); BG swings from PGND to INTVCC; both support N-MOSFETs only. |
| 11 (SW), 12 (BOOST) | Switch node & bootstrap supply | SW connects to inductor; BOOST supplies floating driver via external capacitor/diode - must be decoupled. |
| 14 (INTVCC), 15 (EXTVCC) | Internal LDO output & external bias input | INTVCC = 5.1V ±3%; EXTVCC switchover at 4.7V enables efficient self-biasing from regulated output rails. |
| 16 (PGND), 17 (VIN) | Power ground & main input | PGND ties to bottom MOSFET source and CIN(–); VIN requires local 0.1µF + bulk capacitance to SGND. |
| 18 (ILIM) | Current limit threshold select | GND/FLOAT/INTVCC selects 22/43/64mV sense threshold - eliminates need for external current-sense resistor scaling. |
| 19 (TRACK/SS) | Soft-start & tracking control | 10µA internal current source ramps external capacitor; also accepts resistor divider for voltage tracking. |
| 20 (FREQ) | Oscillator frequency programming | Resistor to GND sets frequency (50–900kHz); INTVCC/GND forces fixed 535kHz/350kHz respectively. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® compensation | Enables stable loop response across wide output capacitor ESR and capacitance ranges (e.g., ceramic + polymer combinations) without redesign. |
| Selectably optimized light-load efficiency | Burst Mode (50µA IQ), Pulse-Skipping, or Forced Continuous operation - lets designers trade ripple/noise vs. efficiency per application need. |
| Integrated dual LDO architecture | VIN-powered and EXTVCC-powered 5.1V regulators with automatic switchover - reduces external bias complexity and improves system efficiency. |
| Programmable current foldback | Prevents MOSFET thermal runaway during short-circuit by reducing peak current as VOUT collapses - no external circuitry required. |
| Robust start-up control | TRACK/SS pin supports both soft-start (capacitor ramp) and supply tracking (resistor divider) - ensures controlled power-up in multi-rail systems. |
| High-voltage input tolerance | 65V absolute max VIN rating with internal UVLO (3.8V typ) - suitable for 48V battery systems and transient-prone industrial buses. |
Applications
| Automotive Always-On Systems | Battery-Powered Digital Devices |
|---|---|
|
Use Scenario: Powering infotainment head units and ADAS sensors that remain active during vehicle sleep mode. IC Role / Device Role / Timing Role: Primary 12V-to-3.3V/5V synchronous buck controller with ultra-low 50µA quiescent current and robust cold-crank (4V) operation. Use Value: Enables >1-year battery hold-up time without deep discharge; 99% duty cycle maintains output during engine cranking dips. |
Use Scenario: Regulating power for portable medical monitors and handheld test equipment operating from Li-ion packs. IC Role / Device Role / Timing Role: High-efficiency step-down controller supporting wide input (8–28V) and precise 0.8V–24V output programming. Use Value: Extends runtime via Burst Mode at light loads; OPTI-LOOP® ensures stability with low-ESR ceramic output caps typical in compact designs. |
| Distributed DC Power Systems | Industrial Control & PLC Modules |
|
Use Scenario: Intermediate bus conversion in 48V data center rack PDUs feeding point-of-load regulators. IC Role / Device Role / Timing Role: 48V-to-12V primary controller with phase-lockable 750kHz switching for EMI filtering and layout compactness. Use Value: Synchronizes to system clock to eliminate beat frequencies; EXTVCC input allows self-biasing from downstream 12V rail. |
Use Scenario: Powering FPGA I/O banks and analog front-ends in modular PLC backplanes with 24V nominal input. IC Role / Device Role / Timing Role: Industrial-grade buck controller (–40°C to 125°C) with output overvoltage protection and PGOOD sequencing. Use Value: Ensures safe startup/shutdown in harsh environments; ±10% PGOOD accuracy supports deterministic firmware boot sequences. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP28164GQ-Z | Lower max input (40V vs 60V); fixed 500kHz freq; no PLL sync; 65µA IQ | Suitable for 24V industrial rails but not 48V/automotive cold-crank | Choose for cost-sensitive 24V-only designs where sync and ultra-low IQ are noncritical. |
| TPS546D24ARVFT | Higher integration (integrated MOSFETs); 3–18V input; 500kHz fixed; 25µA IQ | Targeted at space-constrained POL apps; lacks wide VIN and external MOSFET flexibility | Choose when board area is constrained and 18V max input suffices; avoid for 48V or discrete-FET designs. |
Compared with MP28164GQ-Z and TPS546D24ARVFT, the LTC3891EUDC#PBF uniquely combines 60V input, 50µA IQ, PLL synchronization, and full external MOSFET control-making it optimal for high-reliability, wide-input, and EMI-sensitive applications where discrete power stage optimization is required.
Availability
LTC3891EUDC#PBF is available at Aetrix Electronics and suitable for automotive always-on systems, battery-powered digital devices, and distributed DC power systems requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for LTC3891EUDC#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 full product support, documentation, and manufacturing continuity for the LTC portfolio.
The LTC3891 belongs to Linear's high-voltage synchronous controller family, designed specifically for rugged, high-efficiency DC/DC conversion in automotive, industrial, and telecom infrastructure where wide input range and ultra-low quiescent current are mandatory.
FAQ
What is the maximum input voltage rating for the LTC3891EUDC#PBF?
The LTC3891EUDC#PBF has an absolute maximum input voltage rating of 65V, with a functional operating range of 4V to 60V. This makes it suitable for 48V battery systems and automotive applications subject to load dump transients. Operation above 60V violates the recommended conditions and risks permanent damage, even if below the 65V absolute maximum.
How does the ILIM pin affect current limiting on the LTC3891EUDC#PBF?
The ILIM pin on the LTC3891EUDC#PBF selects one of three maximum current sense thresholds: 22mV (ILIM = GND), 43mV (ILIM = FLOAT), or 64mV (ILIM = INTVCC). This directly sets the peak inductor current trip point without requiring external resistor scaling, simplifying design across varying output current requirements while maintaining accuracy over temperature.
Can the LTC3891EUDC#PBF operate with only ceramic output capacitors?
Yes, the LTC3891EUDC#PBF supports ceramic-only output capacitors thanks to its OPTI-LOOP® compensation architecture, which adapts loop stability across wide ESR and capacitance ranges. Designers can use low-ESR ceramics without adding bulk electrolytics-reducing size, improving reliability, and eliminating aging-related drift in applications like portable medical devices.
What is the purpose of the EXTVCC pin on the LTC3891EUDC#PBF?
The EXTVCC pin on the LTC3891EUDC#PBF allows the internal 5.1V INTVCC regulator to be powered from an external supply (e.g., a downstream regulated rail) instead of VIN. When EXTVCC exceeds 4.7V, the device automatically switches from the VIN-based LDO to the EXTVCC-based LDO-improving overall system efficiency and reducing heat generation in high-input-voltage applications.
Does the LTC3891EUDC#PBF support output voltage tracking during startup?
Yes, the LTC3891EUDC#PBF supports precise output voltage tracking via the TRACK/SS pin. By connecting a resistor divider from another supply to this pin, the LTC3891EUDC#PBF regulates its VFB to match the external voltage ramp-enabling coordinated startup across multiple rails in FPGAs, ASICs, or multi-core processors without additional sequencing ICs.
LTC3891EUDC#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN Exposed Pad
- 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 ~ 60V
- Frequency - Switching:
- 105kHz ~ 835kHz, 350kHz ~ 535kHz
- Duty Cycle (Max):
- 99%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (3x4)
LTC3891EUDC#PBF FAQ
1.How can I place an order for LTC3891EUDC#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3891EUDC#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 LTC3891EUDC#PBF reliable?
The price and inventory of LTC3891EUDC#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3891EUDC#PBF is usually 5 days.
3.What payment methods are accepted for LTC3891EUDC#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3891EUDC#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3891EUDC#PBF?
LTC3891EUDC#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3891EUDC#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 LTC3891EUDC#PBF?
For technical support, including LTC3891EUDC#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3891EUDC#PBF requirements.
6.How does Aetrix verify that LTC3891EUDC#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3891EUDC#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 LTC3891EUDC#PBF meets industry standards.
7.What is the process for return or replacement of LTC3891EUDC#PBF?
All LTC3891EUDC#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3891EUDC#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 LTC3891EUDC#PBF part is unused and in its original packaging.
Return procedure for LTC3891EUDC#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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