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Analog Devices Inc. LTC3859ALIUHF#WPBF
- Part No.:
- LTC3859ALIUHF#WPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LTC3859ALIUHF#WPBF.pdf
- Description:
- 3X OUT, BUCK/BUCK/BOOST SYNC CNT
- Quantity:
- Payment:
- Shipping:
Inventory:104
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Product details
Overview
LTC3859ALIUHF#WPBF from Analog Devices is a triple-output synchronous DC/DC controller (buck/buck/boost) driving all-N-channel MOSFET stages, featuring 28µA quiescent current in Burst Mode with one channel active, 0.8V/1.2V precision references for buck and boost outputs respectively, and AEC-Q100 qualification for automotive start-stop and always-on systems.
For engineers reviewing the LTC3859ALIUHF#WPBF datasheet, LTC3859ALIUHF#WPBF pinout, LTC3859ALIUHF#WPBF application, or LTC3859ALIUHF#WPBF equivalent, key selection considerations include its 4.5V–38V input range, 75kHz–850kHz phase-lockable switching frequency, 99% buck dropout duty cycle, OPTI-LOOP compensation, and automotive-grade thermal rating (–40°C to 125°C).
Technical Context
The LTC3859ALIUHF#WPBF implements constant-frequency current-mode control across three independent channels: two buck controllers with 0.8V feedback reference and one boost controller with 1.2V reference, each supporting RSENSE or DCR current sensing. Its PLLIN/MODE pin enables dynamic selection among Burst Mode (28µA IQ), pulse-skipping, or forced continuous conduction mode.
It integrates high-current gate drivers (TG/BG) with sub-30ns transition times, supports 100% duty cycle in boost synchronous operation even during Burst Mode, and features dedicated soft-start/tracking pins (TRACK/SS1,2 and SS3) plus power-good (PGOOD1) and overvoltage (OV3) indicators for system-level monitoring and sequencing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 38V main bias supply; operates down to 2.5V after startup when biased from boost output or auxiliary rail. |
| Buck Output Reference | Precision 0.8V ±12mV (±1.5%) over temperature; enables accurate regulation of 0.8V–24V outputs. |
| Boost Output Reference | Precision 1.2V ±18mV (±1.5%) over temperature; supports regulated boost outputs up to 60V. |
| Quiescent Current | 28µA in Burst Mode with one channel active; extends battery runtime in always-on automotive systems. |
| Switching Frequency | Programmable 50kHz–900kHz or phase-lockable 75kHz–850kHz; enables EMI optimization and inductor size reduction. |
| Duty Cycle Limit | 99% max for buck channels in dropout; 100% for boost synchronous MOSFET - critical for cold-crank operation below 2.5V input. |
| Gate Driver Strength | TG3/BG3 pull-up/pull-down resistance ≤1.2Ω/1.0Ω; ensures fast, low-loss switching of high-side and low-side N-MOSFETs. |
Pinout & Package
Package: 38-lead (5mm × 7mm) plastic QFN with exposed PGND pad (Pin 39), rated for –40°C to 125°C junction temperature (θJA = 34.7°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FREQ (Pin 1) | Oscillator programming input | Sets fixed or programmable switching frequency (50–900kHz) via resistor-to-GND or direct INTVCC/GND connection. |
| PLLIN/MODE (Pin 2) | Sync input / light-load mode select | Enables external clock synchronization or selects Burst Mode (ground), pulse-skipping (1.2–INTVCC–1.3V), or forced CCM (INTVCC). |
| RUN1, RUN2, RUN3 (Pins 9,10,11) | Independent enable inputs | Each controls activation of respective buck/buck/boost channel; <1.17V (buck) or <1.20V (boost) disables; all <0.7V shuts down entire IC. |
| VFB1, VFB2, VFB3 (Pins 36,14,6) | Feedback voltage inputs | Monitor output divider ratio; regulate to 0.8V (buck) or 1.2V (boost); PGOOD1 and OV3 monitor VFB1 and VFB3 respectively. |
| TG1/TG2/TG3, BG1/BG2/BG3 (Pins 32/18/27, 29/21/25) | High-current gate drivers | Drive top/bottom N-MOSFET gates; TG swing = SW + INTVCC; BG swing = 0V to INTVCC; support 100% boost duty cycle. |
| SENSE1+/–, SENSE2+/–, SENSE3+/– (Pins 37/38,13/12,4/5) | Differential current sense inputs | Enable RSENSE or DCR sensing; SENSE3+ supplies current to comparator; SENSE1,2– sources current when >INTVCC. |
| TRACK/SS1, TRACK/SS2, SS3 (Pins 34,16,3) | Soft-start & tracking control | Internal 5µA pull-up enables capacitor-based ramp; buck channels track external supply via resistive divider on TRACK/SS pins. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q100 qualification | Rated for automotive applications including start-stop and always-on systems with guaranteed –40°C to 125°C operation. |
| OPTI-LOOP compensation | Allows transient response optimization across wide range of output capacitance and ESR without external compensation redesign. |
| 100% boost synchronous duty cycle | Maintains regulation during deep input dips (e.g., cold crank) without diode conduction loss or efficiency collapse. |
| Low dropout buck operation | 99% maximum duty cycle enables stable 5V output from 5.05V input - essential for post-buck regulation in multi-rail systems. |
| Independent channel control | Three RUN pins allow staggered startup, fault isolation, and dynamic reconfiguration of power rails in complex systems. |
Applications
| Automotive Start-Stop Systems | Always-On Telematics Modules |
|---|---|
Use Scenario: Power management during engine cranking where battery voltage drops to 2.5V for extended periods. IC Role / Device Role / Timing Role: Triple-output controller maintains 5V/8.5V/10V rails for MCU, CAN transceiver, and RF module while sustaining regulation through cold crank. Use Value: 28µA Burst Mode IQ and 99%/100% duty cycle capability prevent system brownout and extend backup runtime without compromising efficiency. | Use Scenario: Always-on cellular/V2X module requiring ultra-low standby power and reliable wake-up from deep sleep. IC Role / Device Role / Timing Role: Controls buck converters for core logic and boost converter for RF PA bias, with independent RUN pin sequencing for low-power state entry/exit. Use Value: 10µA shutdown current and precise 0.8V/1.2V references ensure accurate voltage margins and minimal leakage during multi-day parking modes. |
| Battery-Powered Industrial Sensors | Distributed DC Power Architectures |
Use Scenario: Remote IoT sensor node powered by Li-ion or supercapacitor with strict 10-year battery life target. IC Role / Device Role / Timing Role: Generates regulated 3.3V (buck), 5V (buck), and 12V (boost) from variable 3.0–36V input, adapting to charge/discharge cycles. Use Value: 28µA no-load IQ directly extends operational lifetime; RSENSE/DCR flexibility allows optimal trade-off between accuracy and PCB area in space-constrained designs. | Use Scenario: Rack-mounted telecom equipment with centralized 48V intermediate bus powering multiple point-of-load rails. IC Role / Device Role / Timing Role: Provides local 12V, 5V, and adjustable boost rail from 48V bus using high-efficiency synchronous topology and phase-locking to system clock. Use Value: Phase-lockable 75–850kHz operation reduces conducted EMI; EXTVCC input enables efficient biasing from intermediate rail instead of linear LDO drop. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar triple-output synchronous controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3859A | Same pinout and feature set but higher Burst Mode IQ (45µA vs 28µA with one channel on); no AEC-Q100 qualification. | Targeted at industrial/commercial systems where automotive reliability and lowest IQ are not required. | Select LTC3859A only if AEC-Q100 compliance and sub-30µA IQ are unnecessary; verify thermal derating for 125°C ambient. |
| LTC3892-2 | Two-phase dual-buck controller (no integrated boost); 25µA IQ; includes integrated LDOs and more robust fault protection (OCP/OVP/OTP). | Best suited for high-current dual-rail applications (e.g., CPU core/memory) where boost functionality is handled separately. | Choose LTC3892-2 when dual high-current buck rails dominate and boost is implemented externally; avoid if native triple-output integration is mandatory. |
Compared with LTC3859A and LTC3892-2, the LTC3859ALIUHF#WPBF uniquely combines AEC-Q100 qualification, 28µA Burst Mode IQ, and native buck/buck/boost topology in a single 38-pin QFN - enabling compact, automotive-compliant power architectures without external boost controllers or IQ compromises.
Availability
LTC3859ALIUHF#WPBF is available at Aetrix Electronics and suitable for automotive start-stop systems, always-on telematics modules, and battery-powered industrial sensors requiring stable component supply with full AEC-Q100 traceability and long-term lifecycle support.
Supply support for LTC3859ALIUHF#WPBF 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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3859AL product line delivers high-efficiency, multi-output synchronous DC/DC controllers optimized for automotive and battery-critical applications demanding ultra-low quiescent current, wide input range, and AEC-Q100 reliability.
FAQ
What is the minimum input voltage required for startup of the LTC3859ALIUHF#WPBF?
The LTC3859ALIUHF#WPBF requires a minimum 5V on VBIAS to initiate startup. Once running, it can sustain operation down to 2.5V input when biased from the boost output or an auxiliary supply - a critical capability for automotive cold-crank conditions. This behavior is enabled by internal biasing architecture that decouples startup requirements from sustained operation limits.
How does the LTC3859ALIUHF#WPBF achieve 28µA quiescent current in Burst Mode?
The LTC3859ALIUHF#WPBF achieves 28µA quiescent current in Burst Mode by dynamically disabling non-essential circuitry-including oscillator sections, gate drivers, and error amplifiers-for inactive channels while maintaining regulation on the active channel. This is confirmed in the Electrical Characteristics table under "Sleep Mode (One Channel On, Buck)" with typical 28µA at –40°C to 125°C.
Can the LTC3859ALIUHF#WPBF drive both buck and boost channels simultaneously while maintaining regulation?
Yes, the LTC3859ALIUHF#WPBF supports simultaneous regulation of all three channels - two bucks and one boost - as verified in the Electrical Characteristics table under "Sleep Mode (All Three Channels On)" (38–56µA) and functional diagrams showing independent ITH/VFB loops. Each channel has dedicated current sense, feedback, and gate drive paths ensuring true concurrent operation without cross-regulation.
What is the purpose of the EXTVCC pin on the LTC3859ALIUHF#WPBF, and how should it be used?
The EXTVCC pin on the LTC3859ALIUHF#WPBF provides an alternative bias path for the INTVCC LDO, activating when voltage exceeds 4.7V (with 200mV hysteresis). It allows efficient biasing from an intermediate rail (e.g., 5V or 12V) instead of dissipating power across the VBIAS LDO - reducing thermal load and improving system efficiency, especially in distributed power architectures.
Is the LTC3859ALIUHF#WPBF pin-compatible with earlier LTC3859 variants?
Yes, the LTC3859ALIUHF#WPBF is fully pin-compatible with the LTC3859 and LTC3859A as explicitly stated in the datasheet: "Compared to the LTC3859 and the LTC3859A, the LTC3859AL is fully pin-compatible, but with lower Burst Mode operation IQ (28µA with one channel on)." This enables drop-in replacement in existing layouts while delivering improved efficiency in low-power states.
LTC3859ALIUHF#WPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck, Buck-Boost, SEPIC
- Number of Outputs:
- 3
- Output Phases:
- 2
- Voltage - Supply (Vcc/Vdd):
- 4.5V ~ 36V
- Frequency - Switching:
- 50kHz ~ 900kHz
- Duty Cycle (Max):
- 100%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- Yes
- Serial Interfaces:
- -
- Control Features:
- Current Limit, Dead Time Control, Enable, Frequency Control, Power Good, Soft Start, Tracking
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-QFN (5x7)
LTC3859ALIUHF#WPBF FAQ
1.How can I place an order for LTC3859ALIUHF#WPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859ALIUHF#WPBF 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 LTC3859ALIUHF#WPBF reliable?
The price and inventory of LTC3859ALIUHF#WPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859ALIUHF#WPBF is usually 5 days.
3.What payment methods are accepted for LTC3859ALIUHF#WPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859ALIUHF#WPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859ALIUHF#WPBF?
LTC3859ALIUHF#WPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859ALIUHF#WPBF 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 LTC3859ALIUHF#WPBF?
For technical support, including LTC3859ALIUHF#WPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859ALIUHF#WPBF requirements.
6.How does Aetrix verify that LTC3859ALIUHF#WPBF is sourced from the original manufacturer or authorized distributors?
All LTC3859ALIUHF#WPBF 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 LTC3859ALIUHF#WPBF meets industry standards.
7.What is the process for return or replacement of LTC3859ALIUHF#WPBF?
All LTC3859ALIUHF#WPBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859ALIUHF#WPBF, 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 LTC3859ALIUHF#WPBF part is unused and in its original packaging.
Return procedure for LTC3859ALIUHF#WPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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