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Analog Devices Inc. LTC3859EUHF#PBF
- Part No.:
- LTC3859EUHF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LTC3859EUHF#PBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,480
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Product details
Overview
LTC3859EUHF#PBF from Analog Devices is a triple-output synchronous DC/DC controller supporting buck/buck/boost topology with all-N-channel MOSFET drive capability. It delivers 5V/5A and 8.5V/3A from dual buck channels plus a programmable boost output up to 60V, operating from 4.5V–38V input (or 2.5V post-startup). Its 55μA no-load quiescent current and OPTI-LOOP compensation make it ideal for automotive start-stop and battery-powered digital systems requiring cold-crank regulation.
For engineers reviewing the LTC3859EUHF#PBF datasheet, LTC3859EUHF#PBF pinout, LTC3859EUHF#PBF application, or LTC3859EUHF#PBF equivalent, key selection criteria include its triple-output phase relationship (buck1/buck2 180° out-of-phase, boost in-phase with buck1), 75kHz–850kHz phase-lockable frequency, independent TRACK/SS control per channel, and 0.8V/1.2V precision references for buck/boost regulation - all in a thermally enhanced 38-pin 5mm × 7mm QFN package.
Technical Context
The LTC3859EUHF#PBF implements constant-frequency current-mode control across three independent switching regulators: two synchronous buck controllers (channels 1 & 2) and one synchronous boost controller (channel 3). Each channel features dedicated ITH error amplifier outputs, differential current sense inputs (SENSE±), and independent RUN pins enabling selective enable/disable.
Its architecture supports RSENSE or DCR current sensing, 100% duty cycle operation for the boost top-side MOSFET, and selectable light-load modes (Burst Mode®, pulse-skipping, or forced continuous) via the PLLIN/MODE pin. The FREQ pin allows resistor-programmable switching frequencies from 50kHz to 900kHz, while PLL synchronization enables precise timing coordination across multiple converters.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Buck/Buck/Boost - enables simultaneous generation of two regulated step-down voltages and one step-up voltage from a single controller IC. |
| Input Voltage Range | 4.5V to 38V (bias supply); operates down to 2.5V after startup when biased from boost output or auxiliary rail - critical for automotive cold-crank survival. |
| Output Voltage References | 0.800V ±12mV (buck channels), 1.200V ±18mV (boost channel) - ensures tight regulation accuracy over –40°C to 125°C junction temperature. |
| Quiescent Current | 55μA (one channel active, sleep mode) - extends battery runtime in always-on portable and telematics applications. |
| Switching Frequency | 75kHz to 850kHz (phase-lockable); 50kHz to 900kHz (programmable via FREQ pin) - balances efficiency, size, and EMI in space-constrained designs. |
| Gate Drive Capability | TG/BG drivers with <1.2Ω pull-down resistance and <2.5Ω pull-up resistance - supports fast, low-loss switching of high-current N-MOSFETs. |
| Protection Features | Current foldback during short-circuit, PGOOD1 (for buck1), OV3 (boost overvoltage), undervoltage lockout (UVLO), and thermal shutdown - ensures robust system-level fault tolerance. |
Pinout & Package
Package: 38-lead (5mm × 7mm) plastic QFN with exposed PGND pad (Pin 39), rated for –40°C to 125°C operating junction temperature (θJA = 34°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1, SW2, SW3 | Switch node connections | Direct connection points to inductor terminals; require low-inductance layout to minimize ringing and EMI in high-dI/dt paths. |
| TG1, TG2, TG3 | Top-gate drivers | Floating high-side gate drives with voltage swing = INTVCC superimposed on SW node - enable synchronous N-MOSFET operation without external bootstrap diodes. |
| BG1, BG2, BG3 | Bottom-gate drivers | Ground-referenced low-side gate drives (0V to INTVCC) - directly drive synchronous rectifier MOSFETs with minimal propagation delay. |
| SENSE1+, SENSE1−, etc. | Differential current sense inputs | Support both RSENSE and DCR sensing; SENSE3+ supplies current to comparator - eliminates need for external current-sense amplifiers in boost channel. |
| VFB1, VFB2, VFB3 | Feedback inputs | High-impedance (±5nA) inputs referenced to 0.8V (buck) or 1.2V (boost); enable precise remote sensing with standard resistor dividers. |
| RUN1, RUN2, RUN3 | Independent enable controls | Digital logic inputs with 1.19V–1.33V threshold; allow staggered startup, power sequencing, or dynamic channel disable for load-matching. |
| TRACK/SS1, TRACK/SS2, SS3 | Soft-start and tracking inputs | Internal 1µA current source enables capacitor-based soft-start ramp or resistor-divider-based voltage tracking - critical for multi-rail system power-up coordination. |
| PGOOD1, OV3 | Status outputs | Open-drain indicators: PGOOD1 signals buck1 regulation status (±10% window); OV3 asserts when boost output exceeds 110% setpoint - simplify system monitoring and fault response. |
Key Features
| Feature | Design Value |
|---|---|
| Triple-output synchronous control | Enables compact, efficient multi-rail power delivery without discrete controllers - reduces BOM count and PCB area in distributed power systems. |
| OPTI-LOOP™ compensation | Allows stable loop response across wide range of output capacitor ESR and capacitance values - eliminates iterative compensation tuning during design validation. |
| Low IQ sleep mode (55μA) | Extends battery life in always-on applications such as automotive infotainment standby or IoT sensor nodes with intermittent wake cycles. |
| 100% duty cycle boost operation | Permits seamless transition to dropout mode where VOUT ≈ VIN, maintaining regulation even when input voltage approaches output level - essential for automotive cold-crank. |
| Independent channel RUN and TRACK/SS | Supports flexible power sequencing, voltage ramp coordination, and dynamic channel enable/disable - simplifies compliance with complex system power-up/down requirements. |
| Phase-lockable frequency (75–850kHz) | Enables EMI reduction through frequency dithering or synchronization to system clock - improves EMC performance in noise-sensitive applications like ADAS cameras. |
Applications
| Automotive Start-Stop Systems | Battery-Powered Telematics |
|---|---|
Use Scenario: Power management in vehicles with engine auto-stop/start functionality, where battery voltage drops to 2.5V during cranking. IC Role / Device Role / Timing Role: Triple-output controller regulating 5V microcontroller core, 8.5V display backlight, and 10V camera sensor rail - all remaining in regulation during cold-crank events. Use Value: Eliminates need for separate LDOs or backup supplies; 55μA sleep IQ preserves battery charge during extended parking periods. |
Use Scenario: Compact GPS tracker with cellular modem, GNSS receiver, and motion sensor - requiring isolated, sequenced power rails from a single Li-ion cell. IC Role / Device Role / Timing Role: Generates 3.3V (buck1), 5V (buck2), and 12V (boost) from 3.0–4.2V battery input using RSENSE current sensing and independent TRACK/SS ramp control. Use Value: Single-chip solution reduces footprint by >40% vs discrete controllers; Burst Mode® operation extends operational time between charges. |
| Distributed DC Power Architecture | Industrial Edge Computing Node |
Use Scenario: Remote I/O module powered from 24V industrial bus, requiring local 5V logic, 3.3V FPGA, and 12V analog sensor bias. IC Role / Device Role / Timing Role: Buck/buck/boost controller delivering tightly regulated outputs with 0.8V/1.2V references and PGOOD1/OV3 fault signaling to host MCU. Use Value: Phase-shifted buck operation reduces input ripple current; 38-pin QFN package supports high-density layout with integrated thermal pad. |
Use Scenario: Fanless edge gateway with ARM SoC, eMMC, and Ethernet PHY - needing clean, low-noise 1.1V core, 3.3V I/O, and 5V USB power from 12V PoE input. IC Role / Device Role / Timing Role: Dual-buck channel powers SoC and memory; boost channel supplies isolated 5V USB port - all synchronized via PLLIN/MODE to suppress beat frequencies. Use Value: Forced continuous mode eliminates audible noise; OPTI-LOOP compensation ensures stability with ceramic capacitors across all rails. |
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 |
|---|---|---|---|
| LTC3855IUFD#PBF | Dual-buck-only controller (no boost channel); 32-pin 5mm × 5mm QFN; supports up to 40V input but lacks VFB3 reference and OV3 output. | Suitable only for dual-rail step-down systems; cannot replace LTC3859EUHF#PBF in boost-dependent applications like camera bias or isolated sensor supplies. | Select when only two regulated outputs are needed and board space is constrained - avoids unused boost circuitry and associated components. |
| MP2918GL-Z | Triple-output controller with buck/buck/boost topology but fixed 600kHz frequency; 0.8V reference only; no PLL synchronization or independent TRACK/SS pins. | Lacks cold-crank capability below 3V and has no soft-start tracking - unsuitable for automotive or multi-rail sequencing applications. | Consider for cost-sensitive, non-automotive applications where fixed frequency and simplified control suffice, and thermal performance is less critical. |
Compared with LTC3855IUFD#PBF and MP2918GL-Z, the LTC3859EUHF#PBF uniquely combines triple-output flexibility, 2.5V cold-crank operation, phase-lockable frequency, and per-channel soft-start - making it the only option for automotive-grade multi-rail systems requiring boost functionality and precise power sequencing.
Availability
LTC3859EUHF#PBF is available at Aetrix Electronics and suitable for automotive start-stop systems, battery-powered telematics, and distributed DC power architectures requiring stable component supply, long-term lifecycle support, and guaranteed traceability.
Supply support for LTC3859EUHF#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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.
The LTC3859EUHF#PBF belongs to Analog Devices' Power by Linear™ family of high-efficiency DC/DC controllers, designed specifically for demanding automotive and battery-operated applications requiring ultra-low quiescent current, wide input range, and robust fault protection.
FAQ
What is the minimum input voltage required for LTC3859EUHF#PBF startup?
The LTC3859EUHF#PBF requires a minimum 5V on VBIAS to initiate startup, as specified in the typical application diagram. Once running, it can sustain operation down to 2.5V input when biased from the boost output or an auxiliary supply - a key feature for automotive cold-crank resilience. This behavior is enabled by internal biasing circuitry that switches to the boosted rail after initial turn-on.
Does LTC3859EUHF#PBF support RSENSE and DCR current sensing simultaneously across all channels?
Yes, the LTC3859EUHF#PBF supports both RSENSE and DCR sensing per channel. Channels 1 and 2 (buck) accept differential SENSE± inputs compatible with either method, while Channel 3 (boost) uses SENSE3+ as a current source and SENSE3– as the comparator input - optimized for DCR sensing but also usable with precision RSENSE networks. The datasheet confirms identical max sense voltage (57mV) and common-mode ranges for all channels.
How does the PLLIN/MODE pin configure light-load operation for LTC3859EUHF#PBF?
The PLLIN/MODE pin selects light-load behavior: grounded or floating (via internal 100kΩ pull-down) enables Burst Mode®; tied to INTVCC forces continuous conduction; and biased to 1.2V–(INTVCC–1.3V) enables pulse-skipping. This single pin controls all three channels simultaneously, ensuring consistent efficiency optimization across the entire output set without requiring separate configuration lines.
What is the thermal performance difference between the QFN and TSSOP packages for LTC3859EUHF#PBF?
The LTC3859EUHF#PBF uses the 38-lead 5mm × 7mm QFN package with θJA = 34°C/W, compared to the TSSOP variant's θJA = 25°C/W. While the TSSOP offers slightly better natural convection cooling, the QFN's exposed PGND pad provides superior thermal path to PCB copper - especially when soldered to a large ground plane - making it preferred for high-power density layouts despite the higher θJA rating.
Can LTC3859EUHF#PBF regulate its boost output to track an external voltage reference?
No - the LTC3859EUHF#PBF supports tracking only on the buck channels (via TRACK/SS1 and TRACK/SS2), where the output follows the lower of 0.8V or the applied TRACK voltage. The boost channel (Channel 3) uses SS3 solely for soft-start ramping to its fixed 1.2V reference; it does not support external voltage tracking. This limitation is explicitly stated in the PIN FUNCTIONS section of the datasheet.
LTC3859EUHF#PBF 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 ~ 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-QFN (5x7)
LTC3859EUHF#PBF FAQ
1.How can I place an order for LTC3859EUHF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859EUHF#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 LTC3859EUHF#PBF reliable?
The price and inventory of LTC3859EUHF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859EUHF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3859EUHF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859EUHF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859EUHF#PBF?
LTC3859EUHF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859EUHF#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 LTC3859EUHF#PBF?
For technical support, including LTC3859EUHF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859EUHF#PBF requirements.
6.How does Aetrix verify that LTC3859EUHF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3859EUHF#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 LTC3859EUHF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3859EUHF#PBF?
All LTC3859EUHF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859EUHF#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 LTC3859EUHF#PBF part is unused and in its original packaging.
Return procedure for LTC3859EUHF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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