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Analog Devices Inc. LTC3891HUDC#PBF
- Part No.:
- LTC3891HUDC#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3891HUDC#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:109
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Product details
Overview
LTC3891HUDC#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 - optimized for automotive always-on systems and battery-powered digital devices.
For engineers reviewing the LTC3891HUDC#PBF datasheet, LTC3891HUDC#PBF pinout, LTC3891HUDC#PBF application, or LTC3891HUDC#PBF equivalent, key selection considerations include its wide VIN range, selectable light-load modes (Burst/Pulse-Skipping/Forced CCM), OPTI-LOOP® compensation, precision 0.8V reference, and integrated power-good indicator with overvoltage protection.
Technical Context
The LTC3891HUDC#PBF implements a constant-frequency current-mode control architecture with dual gate drivers (TG/BG), internal 5.1V LDO (INTVCC), and flexible power sourcing via VIN or EXTVCC. Its error amplifier (EA) compares VFB against a 0.8V reference, modulating ITH to regulate peak inductor current, while the current comparator (ICMP) uses RSENSE or DCR sensing with programmable thresholds via ILIM.
Light-load behavior is determined by the PLLIN/MODE pin: grounding enables Burst Mode (50μA IQ), tying to INTVCC forces continuous conduction, and applying 1.2V–(INTVCC−1.3V) selects pulse-skipping. The TRACK/SS pin enables soft-start or voltage tracking, and PGOOD provides open-drain fault signaling at ±10% VFB deviation.
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, and supercapacitor battery chemistries. |
| No-Load Quiescent Current | 50μA - extends runtime in always-on automotive and portable systems without compromising startup capability. |
| Output Voltage Range | 0.8V to 24V - set via external resistor divider on VFB; includes precision 0.8V ±1.2mV reference (–40°C to 150°C). |
| Switching Frequency | 75kHz to 750kHz - phase-lockable to external clock or programmable via FREQ pin resistor (50kHz–900kHz). |
| Gate Drive Capability | TG/BG drivers with 2.5Ω/1.5Ω pull-up and 2.4Ω/1.1Ω pull-down - supports fast-switching N-MOSFETs with <30ns transition times (3.3nF load). |
| Current Sensing | RSENSE or DCR-based with three selectable max thresholds (22mV/43mV/64mV) via ILIM pin configuration. |
| Thermal Rating | –40°C to +150°C junction temperature - qualified for under-hood automotive applications (H-grade). |
Pinout & Package
Package: 20-lead 3mm × 4mm plastic QFN (UDC) with exposed thermal pad (Pin 21 = SGND). Requires soldering of exposed pad to PCB ground for θJA = 43°C/W thermal performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (PLLIN/MODE) | Mode selection & sync input | Selects Burst Mode (GND), Pulse-Skipping (1.2V–INTVCC−1.3V), or Forced CCM (INTVCC); accepts external clock for phase-locking. |
| 2,3,21 (SGND) | Small-signal ground | Must be routed separately from PGND; pins 2/3 and exposed pad (21) require low-impedance connection to SGND plane. |
| 4 (RUN) | Digital enable/shutdown control | 1.16V threshold disables regulation; 0.7V threshold shuts down INTVCC LDO and reduces IQ to 14μA. |
| 5 (SENSE–), 6 (SENSE+) | Differential current sense inputs | Interface with RSENSE or DCR network; SENSE– supplies comparator bias when > INTVCC − 0.5V. |
| 7 (VFB) | Feedback voltage input | Compares output voltage (via resistive divider) to 0.8V reference; regulates output within ±10% for PGOOD assertion. |
| 8 (ITH) | Error amplifier output & compensation node | Controls peak inductor current; connects to RC network for OPTI-LOOP® compensation across wide ESR/capacitance ranges. |
| 9 (PGOOD) | Open-drain power-good indicator | Pulls low when VFB deviates >±10% from target; includes 2.5% hysteresis and 25μs fault delay. |
| 10 (TG) | Top N-MOSFET gate driver | Floating driver referenced to SW node; swing = INTVCC superimposed on SW; supports bootstrap capacitor recharge in dropout. |
| 11 (SW) | Switch node | Connects to inductor and BOOST capacitor; voltage swings from GND to VIN during operation. |
| 12 (BOOST) | Bootstrap supply for TG driver | Capacitor between BOOST and SW provides floating bias; diode from BOOST to INTVCC prevents reverse discharge. |
| 13 (BG) | Bottom N-MOSFET gate driver | Ground-referenced driver (0V to INTVCC); turns off before inductor current reversal in Burst Mode. |
| 14 (INTVCC) | Internal 5.1V LDO output | Powers gate drivers and control circuitry; sourced from VIN (if EXTVCC < 4.7V) or EXTVCC (if > 4.7V). |
| 15 (EXTVCC) | External bias input for INTVCC LDO | Enables high-efficiency biasing from secondary rail (e.g., converter output); clamped at 14V max. |
| 16 (PGND) | Power ground | Return path for BG driver and CIN negative terminal; must connect to source of bottom MOSFET. |
| 17 (VIN) | Main input supply | Bypassed to SGND with ceramic capacitor; absolute max = 65V; powers INTVCC LDO when EXTVCC is inactive. |
| 18 (ILIM) | Current limit threshold select | GND/FLOAT/INTVCC sets max sense voltage to 22mV/43mV/64mV - adjusts foldback trip point for MOSFET SOA. |
| 19 (TRACK/SS) | Soft-start & tracking input | Internal 10μA pull-up charges external capacitor for linear ramp; also accepts resistor divider for supply tracking. |
| 20 (FREQ) | Frequency programming pin | GND = 350kHz, INTVCC = 535kHz; resistor to GND programs 50kHz–900kHz via internal 20μA current source. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Allows stable loop response across wide output capacitance (22µF–1000µF) and ESR (0.5mΩ–100mΩ) without redesigning compensation network. |
| 99% Maximum Duty Cycle | Enables ultra-low dropout operation (e.g., 12V→11.5V), critical for maintaining regulation during cold-crank or brownout conditions. |
| Programmable Light-Load Modes | Three distinct operating modes (Burst/Pulse-Skipping/Forced CCM) let designers trade off efficiency, ripple, and EMI for specific system requirements. |
| Output Overvoltage Protection | Hardware-based VOVL detection at VFB (±13%) triggers immediate shutdown - protects downstream loads independent of feedback loop integrity. |
| Robust Thermal Grade | H-grade qualification (–40°C to +150°C TJ) ensures reliable operation in engine compartment and industrial control environments. |
| No Current Foldback During Startup | Prevents premature current limiting during soft-start, enabling controlled inrush into large output capacitors without triggering protection. |
Applications
| Automotive Infotainment Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering DSPs, FPGAs, and display controllers in vehicle head units with 12V/24V battery input and strict quiescent current limits. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating 3.3V/5V/12V rails; manages startup sequencing via TRACK/SS and monitors health via PGOOD. Use Value: 50μA no-load IQ preserves battery charge during vehicle sleep mode; 60V abs-max rating withstands load-dump transients. |
Use Scenario: Generating isolated 5V and 3.3V rails for analog sensor interfaces and digital logic in factory automation modules. IC Role / Device Role / Timing Role: High-efficiency step-down controller with RSENSE current sensing for precise current limiting in harsh EMI environments. Use Value: Phase-lockable frequency synchronizes multiple converters to reduce beat frequencies; wide VIN accommodates unregulated 24V industrial supplies. |
| Battery-Powered Test Equipment | Distributed Telecom Power System |
Use Scenario: Portable oscilloscopes and multimeters requiring long runtime from Li-ion packs (8.4V–12.6V) and clean low-noise 3.3V/1.8V outputs. IC Role / Device Role / Timing Role: Main DC/DC controller implementing Burst Mode for µA-level standby and forced CCM for low-ripple active measurement. Use Value: Selectable light-load modes optimize efficiency across dynamic load profiles; 0.8V reference enables accurate low-voltage regulation. |
Use Scenario: Intermediate bus conversion in 48V telecom systems powering remote radio units and baseband processors. IC Role / Device Role / Timing Role: High-input-voltage synchronous controller delivering 12V/5V rails with EXTVCC biasing from local 12V output for improved efficiency. Use Value: EXTVCC option reduces power loss vs. VIN-derived bias; 750kHz max frequency enables compact magnetics for space-constrained RF enclosures. |
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 |
|---|---|---|---|
| LT8640S | Integrated 4A power stage (vs. external MOSFETs); 3.4V–42V VIN; 2.5μA IQ; fixed 2MHz frequency. | Better suited for space-constrained designs where integration outweighs flexibility; lacks RSENSE/DCR selection and wide frequency tuning. | Choose LT8640S for simplified layout and ultra-low IQ; choose LTC3891HUDC#PBF when external MOSFET optimization, wide VIN, or multi-rail synchronization is required. |
| TPS546D24 | 6V–18V VIN; integrated 60A power stage; PMBus interface; 10A output; 10μA shutdown IQ. | Targets high-current server/ASIC rails with digital monitoring; no Burst Mode; requires external EEPROM for configuration. | Choose TPS546D24 for digitally managed, high-current applications; choose LTC3891HUDC#PBF for analog-controlled, wide-input, thermally rugged automotive/industrial use. |
Compared with LT8640S and TPS546D24, the LTC3891HUDC#PBF offers unmatched input voltage range (4V–60V), H-grade temperature support (–40°C to 150°C), and analog configurability - making it the preferred choice for mission-critical, high-reliability buck controller applications where external MOSFET selection, transient robustness, and thermal resilience are paramount.
Availability
LTC3891HUDC#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLCs, and battery-powered test equipment requiring stable component supply across extended temperature and voltage ranges.
Supply support for LTC3891HUDC#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, inheriting its legacy of high-performance power management ICs with emphasis on precision, efficiency, and ruggedness.
The LTC3891HUDC#PBF belongs to Linear's high-voltage synchronous controller product line, designed specifically for demanding automotive, industrial, and telecom applications requiring wide input range, low IQ, and robust thermal performance.
FAQ
What is the maximum allowable input voltage for the LTC3891HUDC#PBF?
The LTC3891HUDC#PBF has an absolute maximum input voltage rating of 65V on the VIN pin. Its operational input range is specified from 4V to 60V, making it suitable for 48V systems and automotive applications subject to load dump transients. Exceeding 65V risks permanent damage per Absolute Maximum Ratings.
How does the ILIM pin affect current limiting in the LTC3891HUDC#PBF?
The ILIM pin on the LTC3891HUDC#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 for foldback protection and defines MOSFET safe operating area during short-circuit events.
Can the LTC3891HUDC#PBF operate with only the VIN supply, or is EXTVCC required?
The LTC3891HUDC#PBF can operate fully with only VIN applied - its internal LDO generates INTVCC from VIN when EXTVCC is below 4.7V. EXTVCC is optional and used to improve efficiency by powering INTVCC from a secondary regulated rail (e.g., 5V or 12V output), reducing power loss in the VIN LDO.
What is the purpose of the exposed thermal pad (Pin 21) on the LTC3891HUDC#PBF QFN package?
The exposed thermal pad (Pin 21) on the LTC3891HUDC#PBF is electrically and thermally connected to SGND. It must be soldered to a PCB copper pour tied to the SGND plane to achieve the specified θJA of 43°C/W. Omitting this connection degrades thermal performance and risks exceeding maximum junction temperature under load.
Does the LTC3891HUDC#PBF support output voltage tracking during startup?
Yes, the LTC3891HUDC#PBF supports precise output voltage tracking via the TRACK/SS pin. Connecting an external resistor divider from a master supply to TRACK/SS causes the LTC3891HUDC#PBF output to ramp in proportion to that supply, ensuring controlled power sequencing across multiple rails without additional ICs.
LTC3891HUDC#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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (3x4)
LTC3891HUDC#PBF FAQ
1.How can I place an order for LTC3891HUDC#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3891HUDC#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 LTC3891HUDC#PBF reliable?
The price and inventory of LTC3891HUDC#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3891HUDC#PBF is usually 5 days.
3.What payment methods are accepted for LTC3891HUDC#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3891HUDC#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3891HUDC#PBF?
LTC3891HUDC#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3891HUDC#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 LTC3891HUDC#PBF?
For technical support, including LTC3891HUDC#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3891HUDC#PBF requirements.
6.How does Aetrix verify that LTC3891HUDC#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3891HUDC#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 LTC3891HUDC#PBF meets industry standards.
7.What is the process for return or replacement of LTC3891HUDC#PBF?
All LTC3891HUDC#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3891HUDC#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 LTC3891HUDC#PBF part is unused and in its original packaging.
Return procedure for LTC3891HUDC#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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