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Analog Devices Inc. LTC3859ALEFE
- Part No.:
- LTC3859ALEFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3859ALEFE.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
Inventory:4,055
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Product details
Overview
LTC3859ALEFE from Analog Devices is a triple-output synchronous DC/DC controller (buck/buck/boost) driving all-N-channel MOSFET stages, featuring 28µA Burst Mode® quiescent current, 4.5V–38V input range, and phase-lockable switching up to 850kHz. It delivers regulated outputs of 5V/5A, 8.5V/3A, and a programmable boost output tracking or regulating at 10V - ideal for automotive start-stop and battery-powered digital systems.
For engineers reviewing the LTC3859ALEFE datasheet, LTC3859ALEFE pinout, LTC3859ALEFE application, or LTC3859ALEFE equivalent, key selection criteria include its triple-output topology, ultra-low IQ in single-channel sleep mode, cold-crank operation down to 2.5V VIN, OPTI-LOOP™ compensation, and AEC-Q100 qualification for automotive use.
Technical Context
The LTC3859ALEFE implements constant-frequency current-mode control across three independent channels: two buck controllers with 0.8V reference and one boost controller with 1.2V reference. Each channel features dedicated ITH error amplifier outputs, SENSE+/- differential current sensing, and independent RUN pins enabling selective channel enable/disable.
Its architecture supports RSENSE or DCR sensing, 100% duty cycle in boost mode even during Burst Mode®, and selectable light-load operation (Burst Mode®, pulse-skipping, or forced continuous). The PLLIN/MODE pin enables external synchronization or mode selection, while FREQ pin allows resistor-programmable frequency from 50kHz to 900kHz.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Buck/Buck/Boost triple-output synchronous controller - enables compact multi-rail power with shared gate drivers and feedback references. |
| Input Voltage Range | 4.5V to 38V bias supply; operates down to 2.5V after startup when biased from boost output - supports cold-crank automotive conditions. |
| Quiescent Current | 28µA (one buck channel active in Burst Mode®) - extends battery runtime in always-on systems. |
| Switching Frequency | 75kHz–850kHz phase-lockable; 50kHz–900kHz programmable via FREQ pin - enables EMI optimization and inductor size reduction. |
| Feedback References | 0.8V ±1% for buck channels; 1.2V ±1.5% for boost channel - ensures precise regulation across temperature and load. |
| Output Voltage Range | Buck: 0.8V–24V; Boost: up to 60V - supports wide-range rail generation including USB PD, industrial sensors, and display bias. |
| Gate Drive Capability | TG/BG drivers with <1.2Ω pull-down resistance and <2.5Ω pull-up - directly drives high-side/lower-side N-MOSFETs without external drivers. |
Pinout & Package
Package: 38-lead plastic TSSOP (FE package), 5mm × 7mm footprint, exposed PGND pad (Pin 39) requiring PCB soldering for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VBIAS (Pin 24) | Main bias input supply | Accepts 4.5V–38V; powers internal LDO (INTVCC); enables operation down to 2.5V VIN when boosted. |
| RUN1/RUN2/RUN3 (Pins 9,10,11) | Digital enable inputs per channel | Independent shutdown control: <1.17V disables buck; <1.20V disables boost; all <0.7V enters 10µA shutdown. |
| PLLIN/MODE (Pin 2) | Mode selection & sync input | Selects Burst Mode® (GND), pulse-skipping (1.2V–INTVCC–1.3V), or forced continuous (INTVCC); accepts external clock for synchronization. |
| PGOOD1 (Pin 33) | Open-drain power-good indicator | Asserts low when VFB1 deviates >±10% from 0.8V setpoint - enables system sequencing and fault monitoring. |
| OV3 (Pin 17) | Boost overvoltage flag | Open-drain output pulled low when VFB3 exceeds +10% of 1.2V reference - provides dedicated boost fault signaling. |
| TRACK/SS1, SS3 (Pins 34, 3) | Soft-start & tracking inputs | Internal 5µA pull-up enables capacitor-based soft-start ramp; resistive divider on TRACK/SS1/2 allows output voltage tracking during startup. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ compensation | Allows stable loop response across wide range of output capacitance and ESR - eliminates need for compensation redesign when changing bulk capacitors. |
| 100% duty cycle in boost mode | Maintains regulation even during Burst Mode® operation - enables seamless transition to dropout without loss of output control. |
| AEC-Q100 qualification | Rated for –40°C to 125°C junction temperature (LTC3859ALE grade) - validated for automotive always-on and start-stop applications. |
| Triple independent RUN controls | Enables dynamic power partitioning: disable unused rails to reduce system IQ - critical for energy-constrained IoT and portable devices. |
| DCR or RSENSE current sensing | Flexible current sense architecture supports low-loss inductor DCR sensing or precision shunt resistors - optimizes efficiency vs. cost tradeoff. |
Applications
| Automotive Start-Stop Systems | Industrial Distributed Power |
|---|---|
Use Scenario: Vehicle engine restart requires uninterrupted 5V and 8.5V rails during 2.5V cold-crank transients. IC Role / Device Role / Timing Role: Triple-output controller maintains regulation across buck1 (5V), buck2 (8.5V), and boost (10V tracking) during deep undervoltage events. Use Value: 28µA IQ and 2.5V minimum operating VIN ensure microcontroller and sensor power integrity without auxiliary batteries. |
Use Scenario: Programmable logic controllers require isolated 5V, 8.5V, and 10V rails from a common 24V DC bus. IC Role / Device Role / Timing Role: Integrates three independent regulators in one IC - eliminates discrete controller duplication and reduces board area by >40%. Use Value: Phase-lockable frequency enables synchronized switching to minimize conducted EMI in dense industrial enclosures. |
| Battery-Powered Digital Devices | Multioutput Buck-Boost Applications |
Use Scenario: Portable medical monitors operate from Li-ion (3.0–4.2V) and require 5V USB, 8.5V display, and 10V analog front-end rails. IC Role / Device Role / Timing Role: Uses boost channel to generate 10V from low VIN; bucks derive lower rails - avoids inefficient intermediate conversion stages. Use Value: 28µA Burst Mode® IQ extends runtime by >30% versus comparable dual-buck controllers with external boost. |
Use Scenario: Test equipment needs programmable output voltages where input varies widely (e.g., 5–36V) and outputs must track or regulate independently. IC Role / Device Role / Timing Role: Leverages TRACK/SS1/2 and SS3 pins to implement voltage sequencing, soft-start, and VIN-following behavior in boost channel. Use Value: Adjustable soft-start charge current (3–8µA) enables precise ramp rate control for sensitive analog loads without external circuitry. |
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 |
|---|---|---|---|
| LTC3859AIFE#TRPBF | Same pinout and function but rated for –40°C to 125°C (I-grade); identical 28µA IQ and feature set. | No functional difference; differs only in temperature screening and part marking. | Select when full industrial temperature validation is required beyond standard E-grade qualification. |
| LTC3859ALEUHF#TRPBF | Identical electrical specs but in 38-lead 5mm×7mm QFN (UHF) package; θJA = 34.7°C/W vs. 25°C/W for TSSOP. | Better thermal performance in high-power density layouts; requires different PCB footprint and reflow profile. | Choose for space-constrained designs needing lower thermal resistance despite larger assembly complexity. |
Compared with LTC3859AIFE#TRPBF, the LTC3859ALEFE offers identical functionality at lower cost for commercial-automotive applications; compared with LTC3859ALEUHF#TRPBF, it trades slightly higher thermal resistance for simpler TSSOP assembly and legacy footprint compatibility.
Availability
LTC3859ALEFE is available at Aetrix Electronics and suitable for automotive start-stop systems, battery-powered digital devices, and distributed DC power systems requiring stable component supply, long-term lifecycle support, and AEC-Q100-compliant sourcing.
Supply support for LTC3859ALEFE 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-rail synchronous controllers optimized for automotive and battery-critical applications - emphasizing ultra-low IQ, cold-crank resilience, and AEC-Q100 reliability.
FAQ
What is the minimum input voltage for LTC3859ALEFE during cold-crank conditions?
The LTC3859ALEFE maintains regulation with input as low as 2.5V after startup when biased from the boost output or an auxiliary supply. This capability is enabled by its wide 4.5V–38V primary bias range and internal architecture that allows operation below the nominal VBIAS minimum - making LTC3859ALEFE suitable for automotive cold-crank scenarios where battery voltage dips transiently.
How does LTC3859ALEFE achieve 28µA quiescent current?
The LTC3859ALEFE achieves 28µA IQ in Burst Mode® with one channel active through integrated low-power bias circuitry, selective channel gating, and optimized internal reference and oscillator design. This specification is measured with one buck channel enabled (RUN1=5V), VFB1=0.83V, and no load - confirming LTC3859ALEFE's suitability for always-on automotive subsystems where standby power is critical.
Can LTC3859ALEFE drive both buck and boost channels simultaneously?
Yes, LTC3859ALEFE supports simultaneous operation of all three channels - two bucks and one boost - with independent RUN pin control, dedicated SENSE+/– pairs, and separate ITH compensation nodes. Its architecture allows concurrent regulation of 5V, 8.5V, and a tracking 10V rail, verified in typical application circuits with full load testing across temperature.
What package options are available for LTC3859ALEFE?
LTC3859ALEFE is supplied exclusively in the 38-lead plastic TSSOP (FE) package with exposed PGND pad. While other variants like LTC3859ALEUHF exist in QFN, the LTC3859ALEFE designation specifically identifies the TSSOP version - confirmed by orderable part number LTC3859ALEFE#TRPBF and FE package marking in Analog Devices' official documentation.
Is LTC3859ALEFE qualified for automotive applications?
Yes, LTC3859ALEFE is AEC-Q100 qualified for automotive use, rated for –40°C to 125°C operating junction temperature (E-grade), and designed for automotive always-on and start-stop systems. Its qualification includes stress testing per AEC-Q100 Rev H standards - ensuring reliability in harsh automotive environments where LTC3859ALEFE is deployed in infotainment, ADAS, and body control modules.
LTC3859ALEFE Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- 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 ~ 38V
- Frequency - Switching:
- 115kHz ~ 835kHz, 350kHz ~ 535kHz
- Duty Cycle (Max):
- 99%, 100%
- Synchronous Rectifier:
- Yes
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- 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-TSSOP-EP
LTC3859ALEFE FAQ
1.How can I place an order for LTC3859ALEFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859ALEFE 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 LTC3859ALEFE reliable?
The price and inventory of LTC3859ALEFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859ALEFE is usually 5 days.
3.What payment methods are accepted for LTC3859ALEFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859ALEFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859ALEFE?
LTC3859ALEFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859ALEFE 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 LTC3859ALEFE?
For technical support, including LTC3859ALEFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859ALEFE requirements.
6.How does Aetrix verify that LTC3859ALEFE is sourced from the original manufacturer or authorized distributors?
All LTC3859ALEFE 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 LTC3859ALEFE meets industry standards.
7.What is the process for return or replacement of LTC3859ALEFE?
All LTC3859ALEFE units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859ALEFE, 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 LTC3859ALEFE part is unused and in its original packaging.
Return procedure for LTC3859ALEFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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