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Analog Devices Inc. LTC3891HFE#PBF
- Part No.:
- LTC3891HFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3891HFE#PBF.pdf
- Description:
- IC REG CTRLR BUCK 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:438
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Product details
Overview
LTC3891HFE#PBF from Analog Devices (formerly Linear Technology) is a high-performance, low-quiescent-current 60V synchronous step-down DC/DC controller driving all-N-channel MOSFETs. It delivers 0.8V–24V programmable output voltage, operates from 4V–60V input, supports phase-lockable switching up to 750kHz, and features 50μA no-load IQ - enabling long battery runtime in automotive always-on systems and industrial distributed power rails.
For engineers reviewing the LTC3891HFE#PBF datasheet, LTC3891HFE#PBF pinout, LTC3891HFE#PBF application, or LTC3891HFE#PBF equivalent, key selection considerations include its H-grade (–40°C to 150°C) junction temperature rating, selectable light-load modes (Burst/Pulse-Skipping/Forced CCM), OPTI-LOOP® compensation, and dual current-sense options (RSENSE or DCR).
Technical Context
The LTC3891HFE#PBF implements a constant-frequency current-mode control architecture with an internal transconductance error amplifier (gm = 2 mmho) and precision 0.8V reference (±0.8% over –40°C to 150°C). Its PLLIN/MODE pin selects among Burst Mode®, pulse-skipping, or forced continuous conduction - directly altering light-load efficiency and ripple behavior without changing external components.
It integrates dual gate drivers (TG/BG) with <30ns transition times, internal 5.1V LDO for INTVCC (with EXTVCC switchover at 4.7V), and robust protection including output overvoltage detection (±10% VFB trip), current foldback, and 99% maximum duty cycle for ultra-low dropout operation - all validated for extended high-temperature operation per its H-grade qualification.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 60V - supports wide intermediate bus voltages and 12V/24V/48V battery systems without pre-regulation. |
| Output Voltage Range | 0.8V to 24V - set via external resistor divider on VFB; 0.8V reference tolerance ±0.8% over full H-grade temp range. |
| No-Load Quiescent Current | 50μA - extends battery life in always-on automotive modules and portable instrumentation. |
| Switching Frequency Range | 75kHz to 750kHz - phase-lockable to external clock or programmable via FREQ pin resistor (50kHz–900kHz). |
| Max Junction Temperature | 150°C - qualified for under-hood automotive and high-ambient industrial environments. |
| Current Sense Options | RSENSE or DCR sensing - enables flexible, low-loss current monitoring with selectable ILIM thresholds (22mV/43mV/64mV). |
| Gate Driver Strength | TG pull-up: 2.5Ω, BG pull-down: 1.1Ω - drives large N-channel MOSFETs with fast 25ns rise/fall times (3300pF load). |
Pinout & Package
Package: 20-lead plastic TSSOP (FE package) with exposed pad (Pin 21 = SGND); thermal resistance θJA = 38°C/W. Designed for high-power density and reliable thermal performance in constrained layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| TRACK/SS (Pin 1) | Soft-start & tracking control | Internal 10μA pull-up charges external capacitor for linear VOUT ramp; accepts external voltage divider for supply tracking. |
| FREQ (Pin 2) | VCO frequency programming | 20μA internal pull-up sets oscillator frequency; GND = 350kHz, INTVCC = 535kHz, resistor-to-GND enables 50–900kHz tuning. |
| PLLIN/MODE (Pin 3) | Light-load mode selection | GND = Burst Mode®, INTVCC = forced CCM, 1.2V–(INTVCC–1.3V) = pulse-skipping - determines efficiency/ripple trade-off. |
| SGND (Pins 4,5) | Small-signal ground reference | Must be routed separately from PGND; both pins and exposed pad (Pin 21) require low-impedance connection to system ground. |
| RUN (Pin 6) | Enable/shutdown control | 1.16V threshold disables regulation; 0.7V threshold enables ultra-low-IQ shutdown (<14μA). |
| SENSE– (Pin 7) | Current sense common-mode reference | Serves as bias source for differential comparator when > INTVCC – 0.5V; supports high-side or DCR sensing topologies. |
| SENSE+ (Pin 8) | Current sense positive input | Connected to RSENSE or DCR network; combined with ITH voltage and ILIM setting defines peak current limit. |
| VFB (Pin 9) | Feedback voltage input | Compares output voltage (via resistive divider) to 0.8V internal reference; PGOOD monitors ±10% window around this value. |
| ITH (Pin 10) | Error amplifier output & compensation node | Directly controls peak inductor current; OPTI-LOOP® allows stable loop compensation across wide ESR/capacitance ranges. |
| PGOOD (Pin 11) | Power-good status indicator | Open-drain output pulled low if VFB deviates >±10% from target; 25μs fault reporting delay ensures noise immunity. |
| TG (Pin 12) | Top N-MOSFET gate driver | Floating driver with swing = INTVCC superimposed on SW node; supports bootstrap operation up to 65V absolute max. |
| SW (Pin 13) | Switch node connection | Connects to inductor and MOSFET sources; voltage swings from 0V to VIN during operation; absolute max = 65V. |
| BOOST (Pin 14) | Bootstrap supply for TG driver | Capacitor between BOOST and SW provides floating bias; Schottky diode from BOOST to INTVCC prevents reverse discharge. |
| BG (Pin 15) | Bottom N-MOSFET gate driver | Ground-referenced driver (0V to INTVCC); complements TG to enable synchronous rectification and high efficiency. |
| INTVCC (Pin 16) | Internal LDO output | 5.1V ±3% regulated supply for logic and drivers; decoupled with ≥2.2µF ceramic to PGND; powered from VIN or EXTVCC. |
| EXTVCC (Pin 17) | External bias input for INTVCC LDO | Enables switchover to external 4.7–14V supply; reduces power loss vs. VIN-derived LDO in high-input-voltage applications. |
| PGND (Pin 18) | Power ground return | Connects to bottom MOSFET source and CIN (–) terminal; must be low-inductance path to minimize switching noise coupling. |
| VIN (Pin 19) | Main input supply | Accepts 4–60V; bypassed with ceramic capacitor to SGND; absolute max = 65V. |
| ILIM (Pin 20) | Current limit threshold select | GND/INTVCC/FLOAT configures max sense voltage to 22mV/43mV/64mV - sets peak current limit without external resistors. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP® Compensation | Enables stable loop response across diverse output capacitors (ceramic, polymer, electrolytic) and ESR values - eliminates iterative compensation tuning. |
| Selectably Optimized Light-Load Efficiency | Burst Mode® achieves >85% efficiency at 1mA load; pulse-skipping balances ripple and efficiency; forced CCM maintains low-noise operation for sensitive analog circuits. |
| Robust High-Temperature Operation | H-grade qualification (–40°C to 150°C TJ) with guaranteed electrical specs - suitable for engine control units and industrial motor drives without derating. |
| Flexible Current Sensing | Supports both discrete shunt (RSENSE) and lossless DCR sensing - reduces BOM cost and conduction losses in high-current designs. |
| Integrated Protection Suite | Includes output overvoltage lockout (±10% VFB), current foldback during short-circuit, and undervoltage lockout (3.8V rising threshold) - minimizes external protection components. |
Applications
| Automotive Engine Control Unit (ECU) Power Supply | Industrial Programmable Logic Controller (PLC) I/O Module |
|---|---|
Use Scenario: Powers microcontroller, CAN transceiver, and sensor interfaces in under-hood ECU with 12V/24V battery input and ambient temperatures up to 125°C. IC Role / Device Role / Timing Role: Primary synchronous buck controller regulating 3.3V/5V rails from unregulated vehicle battery; handles cold-crank (4.5V) and load-dump (60V) transients. Use Value: 50μA quiescent current prevents battery drain during vehicle sleep mode; 150°C junction rating ensures reliability without heatsink or airflow. | Use Scenario: Generates isolated 12V and 5V rails for digital I/O, analog signal conditioning, and communication interfaces in DIN-rail mounted PLCs operating in factory environments. IC Role / Device Role / Timing Role: High-efficiency, wide-input buck controller delivering stable output despite fluctuating 24VDC plant power; supports hot-swap and brownout recovery. Use Value: 4V–60V input range accommodates 24V nominal with ±25% tolerance; programmable soft-start prevents inrush into downstream capacitive loads. |
| Portable Medical Diagnostic Device | Distributed Telecom Power System |
Use Scenario: Powers FPGA, ADCs, and wireless modem in handheld ultrasound or glucose monitor using single-cell Li-ion (3.0–4.2V) or multi-cell pack (8–24V). IC Role / Device Role / Timing Role: Step-down controller generating precise 1.2V core and 3.3V I/O supplies; manages battery discharge profile and runtime optimization. Use Value: 50μA no-load IQ maximizes battery life; selectable Burst Mode® extends operational time between charges without compromising transient response. | Use Scenario: Provides point-of-load (POL) conversion from 48V intermediate bus to 12V/5V/3.3V rails in 5G base station remote radio units (RRUs) and edge compute nodes. IC Role / Device Role / Timing Role: Synchronous buck controller supporting phase synchronization across multiple converters to reduce EMI and improve thermal distribution. Use Value: Phase-lockable 75–750kHz operation enables deterministic switching alignment; 60V rating covers telecom surge standards (IEC 61000-4-5). |
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 |
|---|---|---|---|
| LTC3891IFE#PBF | I-grade (–40°C to 125°C TJ), identical electrical specs except max junction temperature and some parametric limits at extremes. | Suitable for non-under-hood automotive, industrial control, and commercial equipment where ambient ≤85°C. | Select when 125°C max TJ suffices and cost sensitivity favors standard grade over H-grade. |
| MP2451DT-LF-Z | Monolithic 60V buck converter (integrated MOSFETs), fixed 3.3V/5V/12V options, 250μA IQ, no phase-lock or DCR sensing. | Targeted at space-constrained, lower-current (≤0.6A) applications where integration outweighs flexibility. | Choose for simplified layout and BOM reduction in sub-1A loads; avoid when >150°C operation or external MOSFET control is required. |
Compared with LTC3891IFE#PBF, the LTC3891HFE#PBF offers extended high-temperature capability critical for under-hood use, while MP2451DT-LF-Z trades configurability and thermal robustness for monolithic simplicity and smaller footprint in less demanding environments.
Availability
LTC3891HFE#PBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC I/O modules, and portable medical diagnostic devices requiring stable component supply across extended temperature and voltage ranges.
Supply support for LTC3891HFE#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, manufacturing, and qualification for legacy Linear parts including the LTC3891 family.
The LTC3891 product line delivers high-voltage, low-IQ synchronous buck controllers optimized for automotive always-on systems, battery-powered instrumentation, and industrial distributed power architectures - emphasizing thermal resilience, light-load efficiency, and design flexibility.
FAQ
What is the maximum junction temperature specification for the LTC3891HFE#PBF?
The LTC3891HFE#PBF is qualified for a maximum junction temperature of 150°C, with guaranteed electrical performance over the full operating junction temperature range of –40°C to 150°C. This H-grade rating enables reliable operation in under-hood automotive and high-ambient industrial environments where standard I-grade parts (125°C max) would require derating or thermal mitigation.
How does the LTC3891HFE#PBF achieve 50μA quiescent current, and what conditions apply?
The LTC3891HFE#PBF achieves 50μA typical no-load quiescent current in Burst Mode® operation at 25°C with VIN = 12V and VFB = 0.83V. This ultra-low IQ is enabled by internal circuitry shutdown during sleep cycles, where both MOSFETs are turned off and the error amplifier output is parked. The value increases to 75μA maximum over temperature and drops to <14μA in RUN-pin-initiated shutdown.
Can the LTC3891HFE#PBF synchronize its switching frequency to an external clock, and how is it configured?
Yes, the LTC3891HFE#PBF supports external synchronization via the PLLIN/MODE pin. Applying a clean CMOS/TTL clock signal (75kHz–750kHz) to this pin locks the internal VCO to the external source and forces forced continuous conduction mode. The rising edge of the external clock aligns with the rising edge of the TG signal, enabling deterministic EMI reduction and multi-phase interleaving in systems with multiple LTC3891HFE#PBF controllers.
What are the three current limit threshold options provided by the ILIM pin on the LTC3891HFE#PBF?
The ILIM pin on the LTC3891HFE#PBF selects among three maximum current sense voltage thresholds: tying ILIM to SGND sets 22mV, to INTVCC sets 43mV, and leaving it floating (or connecting to no bias) sets 64mV. These correspond to peak current limits scalable with sense resistor or DCR value, enabling precise overcurrent protection without additional external components or trimming.
Does the LTC3891HFE#PBF support both RSENSE and DCR current sensing, and how is sensing topology selected?
Yes, the LTC3891HFE#PBF natively supports both RSENSE and DCR current sensing through its differential SENSE+ and SENSE– inputs. No configuration pin or register setting is required - topology selection is determined solely by the external network: a shunt resistor between SENSE+ and power ground for RSENSE, or a series RC network across the inductor for DCR. The ITH voltage and ILIM setting jointly define the resulting current trip point in either configuration.
LTC3891HFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) 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-TSSOP-EP
LTC3891HFE#PBF FAQ
1.How can I place an order for LTC3891HFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3891HFE#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 LTC3891HFE#PBF reliable?
The price and inventory of LTC3891HFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3891HFE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3891HFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3891HFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3891HFE#PBF?
LTC3891HFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3891HFE#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 LTC3891HFE#PBF?
For technical support, including LTC3891HFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3891HFE#PBF requirements.
6.How does Aetrix verify that LTC3891HFE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3891HFE#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 LTC3891HFE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3891HFE#PBF?
All LTC3891HFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3891HFE#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 LTC3891HFE#PBF part is unused and in its original packaging.
Return procedure for LTC3891HFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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