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Analog Devices Inc. LTC3891IUDC#PBF
- Part No.:
- LTC3891IUDC#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3891IUDC#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:387
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Product details
Overview
LTC3891IUDC#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 from 4V to 60V input, delivers 0.8V–24V output, supports phase-lockable switching up to 750kHz, and features 50μA no-load IQ - enabling long battery runtime in automotive always-on and industrial power systems.
For engineers reviewing the LTC3891IUDC#PBF datasheet, LTC3891IUDC#PBF pinout, LTC3891IUDC#PBF application, or LTC3891IUDC#PBF equivalent, key selection criteria include its wide VIN range, selectable light-load modes (Burst/Pulse-Skipping/Continuous), OPTI-LOOP® compensation, precision 0.8V reference, and integrated power-good monitoring with overvoltage protection.
Technical Context
The LTC3891IUDC#PBF implements a constant-frequency current-mode control architecture with dual gate drivers (TG/BG), internal 5.1V LDO for INTVCC (with EXTVCC switchover at 4.7V), and programmable current-sense threshold via ILIM pin selection (GND/FLOAT/INTVCC). Its error amplifier output (ITH) directly controls peak inductor current, while the TRACK/SS pin enables soft-start or supply tracking via internal 10µA pull-up.
It integrates a phase-locked loop (PLLIN/MODE pin) for synchronization to external clocks (75–750kHz), supports RSENSE or DCR sensing, and includes dropout detection with forced TG off-cycle recharging of BOOST capacitor. Current foldback limits MOSFET dissipation during short-circuit conditions without foldback during startup.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports 12V/24V/48V intermediate buses and Li-ion, lead-acid, or supercapacitor battery inputs. |
| Quiescent Current (No Load) | 50µA - extends battery life in always-on automotive or portable systems without compromising regulation. |
| Output Voltage Range | 0.8V to 24V - set via external resistor divider on VFB; precision 0.8V ±1% reference enables accurate low-voltage rail generation. |
| Switching Frequency | Programmable 50kHz–900kHz or syncable 75kHz–750kHz - allows optimization of size (higher f) vs. efficiency (lower f) and EMI filtering. |
| Current Sense Threshold | Selectable 22/43/64mV (ILIM = GND/FLOAT/INTVCC) - sets peak current limit without external scaling resistors. |
| Duty Cycle Max | 99% - enables ultra-low dropout operation (e.g., 12V→11.5V), critical for high-VIN, low-VOUT applications. |
| Power-Good Accuracy | ±10% VFB trip with 2.5% hysteresis - provides reliable system-level power sequencing and fault reporting. |
Pinout & Package
Package: 20-lead 3mm × 4mm plastic QFN (UDC) with exposed thermal pad (Pin 21 = SGND), rated for –40°C to 125°C operating junction temperature (θJA = 43°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SGND (Pins 2,3,21) | Small-signal ground reference | Must be routed separately from PGND; exposed pad soldered to PCB ground for thermal performance and noise immunity. |
| RUN (Pin 4) | Digital enable/shutdown control | 1.16V threshold for control-loop shutdown; 0.7V for full shutdown (IQ < 14µA); internal 7µA pull-up enables floating-for-always-on use. |
| TRACK/SS (Pin 19) | Soft-start and voltage tracking input | Internal 10µA pull-up charges external capacitor for linear VOUT ramp; also accepts resistor-divider input to track another supply. |
| VFB (Pin 7) | Feedback voltage input | Compares output voltage (via external divider) to 0.8V reference; regulates output within ±1% over temp and line/load. |
| ITH (Pin 8) | Error amplifier output / compensation node | Directly sets peak inductor current; connects to RC network for OPTI-LOOP® compensation across wide COUT/ESR ranges. |
| TG (Pin 10) | Top N-MOSFET gate driver output | Floating driver with swing = INTVCC + SW voltage; drives high-side FET with 2.5Ω pull-up / 1.5Ω pull-down. |
| BG (Pin 13) | Bottom N-MOSFET gate driver output | Ground-referenced driver (0V to INTVCC); 2.4Ω pull-up / 1.1Ω pull-down enables fast synchronous rectification. |
| SENSE+ / SENSE– (Pins 6,5) | Differential current sense inputs | Measure voltage across RSENSE or DCR network; common-mode range up to 28V supports high-side sensing. |
| ILIM (Pin 18) | Current limit threshold select | GND/FLOAT/INTVCC selection configures max sense voltage to 22/43/64mV - eliminates need for external gain resistors. |
| PLLIN/MODE (Pin 1) | Light-load mode & sync input | GND = Burst Mode (50µA IQ); INTVCC = Forced Continuous; 1.2V–(INTVCC–1.3V) = Pulse-Skipping; external clock = PLL sync. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Enables stable loop response across wide output capacitance (10µF–1000µF) and ESR (0.5mΩ–100mΩ) without redesigning compensation network. |
| Selectably Optimized Light-Load Efficiency | Three distinct modes: Burst Mode (50µA IQ), Pulse-Skipping (low ripple), or Forced Continuous (no reverse current) - chosen per system noise/efficiency trade-off. |
| Integrated Power-Good Monitoring | Open-drain PGOOD asserts low when VFB deviates >10% from 0.8V; includes hysteresis and 25µs fault delay to reject transient glitches. |
| Robust Gate Drive Architecture | TG/BG drivers deliver 2.5Ω/2.4Ω pull-up and 1.5Ω/1.1Ω pull-down into 3300pF loads, ensuring fast MOSFET switching and reduced conduction losses. |
| Flexible INTVCC Power Path | Automatic switchover between VIN-powered LDO (4.85–5.35V) and EXTVCC-powered LDO (4.7V threshold) enables high-efficiency self-biasing from output rail. |
Applications
| Automotive Infotainment Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering 3.3V/5V logic rails in head units with cold-crank (4.5V) and load-dump (60V) transients. IC Role / Device Role / Timing Role: Primary step-down controller regulating stable output from unregulated vehicle battery bus. Use Value: 60V abs-max rating and 4V–60V operating range withstand automotive transients; 50µA IQ preserves battery during sleep mode. |
Use Scenario: Generating isolated 12V/24V auxiliary rails for analog sensor interfaces and digital communication ICs in factory automation. IC Role / Device Role / Timing Role: High-reliability DC/DC controller powering fieldbus interface circuits requiring precise voltage accuracy and long-term stability. Use Value: 0.8V ±1% reference and ±10% PGOOD window ensure robust power sequencing; –40°C to 125°C rating suits harsh industrial environments. |
| Battery-Powered Test Equipment | Distributed Telecom Power System |
Use Scenario: Portable oscilloscopes or multimeters using Li-ion packs (8.4V–12.6V) to generate clean 1.8V/3.3V/5V rails. IC Role / Device Role / Timing Role: Efficient, low-noise buck controller minimizing heat buildup and maximizing runtime in handheld enclosures. Use Value: Burst Mode operation reduces no-load power loss; OPTI-LOOP® ensures stability with ceramic output caps common in space-constrained designs. |
Use Scenario: Intermediate bus conversion in 48V telecom systems powering FPGA, DSP, and RF front-end ICs. IC Role / Device Role / Timing Role: High-input-voltage synchronous controller delivering tightly regulated sub-1V core voltages with fast transient response. Use Value: Phase-lockable frequency (75–750kHz) enables synchronized switching across multiple converters to reduce conducted EMI in dense board layouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3892IUDC#PBF | Dual-output version with independent channel control, higher max frequency (850kHz), and enhanced current sharing capability. | Suitable for multi-rail systems requiring coordinated start-up or interleaved operation; not drop-in for single-output designs. | Choose LTC3892IUDC#PBF only when dual outputs or channel synchronization are required - adds complexity and cost for single-rail use. |
| MP2918GL-Z | Monolithic 60V buck controller with integrated MOSFETs; lower IQ (35µA), but fixed 500kHz frequency and no PLL sync capability. | Better for space-constrained, cost-sensitive designs where external FETs are undesirable; lacks programmable light-load modes and tracking. | Choose MP2918GL-Z for simplified BOM and layout where flexibility in frequency, soft-start, and light-load behavior is secondary to integration. |
Compared with LTC3892IUDC#PBF and MP2918GL-Z, the LTC3891IUDC#PBF uniquely balances wide input range, ultra-low IQ, full light-load mode selection, and precise tracking - making it optimal for high-reliability, battery-sensitive, or thermally constrained single-output applications.
Availability
LTC3891IUDC#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC modules, and battery-powered test equipment requiring stable component supply, extended temperature operation, and long-term lifecycle support.
Supply support for LTC3891IUDC#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) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving aerospace, industrial, automotive, and communications markets.
The LTC3891IUDC#PBF belongs to Linear's high-voltage synchronous controller product line, designed specifically for rugged, efficient DC/DC conversion in automotive always-on, battery-powered, and distributed power systems where reliability and low quiescent current are critical.
FAQ
What is the maximum absolute input voltage rating for the LTC3891IUDC#PBF?
The LTC3891IUDC#PBF has an absolute maximum input supply voltage (VIN) rating of 65V. Operation must remain within the functional range of 4V to 60V; exceeding 65V risks permanent damage. This rating enables robust handling of automotive load-dump transients and industrial surge events.
How does the ILIM pin affect current limiting on the LTC3891IUDC#PBF?
The ILIM pin on the LTC3891IUDC#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 external resistor networks, simplifying design and improving accuracy across temperature.
Can the LTC3891IUDC#PBF operate with an external 5V supply on EXTVCC?
Yes - the LTC3891IUDC#PBF supports EXTVCC operation from 4.7V to 14V. When EXTVCC exceeds 4.7V, the internal LDO automatically switches from VIN to EXTVCC to power INTVCC, reducing power loss and heat generation. This enables efficient self-biasing from a downstream converter output.
What is the purpose of the TRACK/SS pin on the LTC3891IUDC#PBF?
The TRACK/SS pin on the LTC3891IUDC#PBF serves dual functions: soft-start (via internal 10µA pull-up charging an external capacitor) and supply tracking (via resistor divider from another rail). It forces VFB to follow the TRACK/SS voltage until it reaches 0.8V, enabling controlled, glitch-free power-up sequences.
Does the LTC3891IUDC#PBF support synchronization to an external clock source?
Yes - the LTC3891IUDC#PBF supports external clock synchronization via the PLLIN/MODE pin. When driven by a clean external clock (75kHz–750kHz), the internal phase-locked loop aligns the rising edge of TG to the external clock's rising edge, enabling EMI reduction through switching frequency coordination across multiple converters.
LTC3891IUDC#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)
LTC3891IUDC#PBF FAQ
1.How can I place an order for LTC3891IUDC#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3891IUDC#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 LTC3891IUDC#PBF reliable?
The price and inventory of LTC3891IUDC#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3891IUDC#PBF is usually 5 days.
3.What payment methods are accepted for LTC3891IUDC#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3891IUDC#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3891IUDC#PBF?
LTC3891IUDC#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3891IUDC#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 LTC3891IUDC#PBF?
For technical support, including LTC3891IUDC#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3891IUDC#PBF requirements.
6.How does Aetrix verify that LTC3891IUDC#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3891IUDC#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 LTC3891IUDC#PBF meets industry standards.
7.What is the process for return or replacement of LTC3891IUDC#PBF?
All LTC3891IUDC#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3891IUDC#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 LTC3891IUDC#PBF part is unused and in its original packaging.
Return procedure for LTC3891IUDC#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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