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Analog Devices Inc. LTC3859AEUHF#PBF
- Part No.:
- LTC3859AEUHF#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-WFQFN Exposed Pad
- Datasheet:
-
LTC3859AEUHF#PBF.pdf
- Description:
- IC REG CTRLR MULT TOPOLOGY 38QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,775
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Product details
Overview
LTC3859AEUHF#PBF from Analog Devices is a triple-output synchronous DC/DC controller (buck/buck/boost) driving all-N-channel MOSFET stages, featuring 55μA no-load quiescent current, 0.8V/1.2V precision references for buck/boost outputs, and phase-lockable switching up to 850kHz. It supports cold-crank operation down to 2.5V input after startup and delivers regulated outputs in automotive start-stop and battery-powered digital systems.
For engineers reviewing the LTC3859AEUHF#PBF datasheet, LTC3859AEUHF#PBF pinout, LTC3859AEUHF#PBF application, or LTC3859AEUHF#PBF equivalent, key selection criteria include its triple-output topology, Burst Mode® optimization for high-input boost regulation, OPTI-LOOP compensation, RSENSE/DCR sensing flexibility, and 38-pin QFN package with exposed PGND pad.
Technical Context
The LTC3859AEUHF#PBF integrates three independent current-mode controllers: two buck channels with 0.8V reference and 99% dropout capability, and one boost channel with 1.2V reference and 100% duty cycle support even in Burst Mode®. Its PLLIN/MODE pin selects among Burst Mode®, pulse-skipping, or forced continuous conduction-each affecting light-load efficiency and output ripple distinctly.
It employs separate gate drivers (TG/BG) per channel with matched rise/fall times (13–28ns), programmable oscillator (50–900kHz), and dual bias options (VBIAS 4.5–38V or EXTVCC ≥4.7V). The device uses SGND/PGND separation, supports soft-start/tracking via dedicated pins, and includes PGOOD1 and OV3 fault indicators with defined hysteresis and trip thresholds.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Triple-output synchronous controller: two buck + one boost, all-N-channel MOSFET drive |
| Input voltage range | 4.5V–38V main bias; operates down to 2.5V after startup when biased from boost output or auxiliary supply |
| Quiescent current | 55μA in Sleep Mode (one channel active), enabling extended runtime in always-on battery systems |
| Reference voltages | 0.8V ±12mV (buck channels), 1.2V ±12mV (boost channel), specified over –40°C to 125°C |
| Switching frequency | Programmable 50–900kHz; phase-lockable 75–850kHz via PLLIN/MODE pin |
| Output voltage ranges | Buck: 0.8V–24V; Boost: up to 60V; supports tracking, soft-start, and adjustable dropout |
| Current sensing | RSENSE or DCR sensing per channel; max sense threshold 57mV with ±10% tolerance over temp |
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 = 34.7°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1, SW2, SW3 | Switch node connections | Drive external inductors; require low-inductance layout and ceramic decoupling at each node |
| TG1, TG2, TG3 | Top-gate drivers | Floating N-channel gate drives with INTVCC-referenced swing; support 100% duty cycle in boost |
| BG1, BG2, BG3 | Bottom-gate drivers | GND-referenced N-channel gate drives; matched timing with TG for synchronous rectification |
| VFB1, VFB2, VFB3 | Feedback inputs | Monitor output voltage via resistive divider; regulate to 0.8V (buck) or 1.2V (boost) |
| SENSE1+/–, SENSE2+/–, SENSE3+/– | Differential current sense inputs | Enable RSENSE or DCR sensing; SENSE3+ supplies current to comparator in boost channel |
| PLLIN/MODE | Mode selection & sync input | Selects Burst Mode®, pulse-skipping, or forced CCM; accepts external clock for synchronization |
| PGOOD1 | Power-good indicator | Open-drain output asserting when VFB1 deviates >±10% from setpoint; 2.5% hysteresis |
| OV3 | Boost overvoltage flag | Open-drain output pulled low when VFB3 exceeds +10% of setpoint; 1.5% hysteresis |
| TRACK/SS1, TRACK/SS2, SS3 | Tracking & soft-start control | Set ramp rate via capacitor; enable output tracking during startup using external voltage dividers |
| ITH1, ITH2, ITH3 | Error amplifier outputs | Compensation points; adjust current limit threshold and transient response via OPTI-LOOP network |
| PGND (Pin 39) | Power ground | Exposed thermal pad; must be soldered to PCB plane for thermal performance and driver return path |
Key Features
| Feature | Design Value |
|---|---|
| Low IQ Sleep Mode | 55μA quiescent current with one channel active enables multi-day battery life in always-on systems |
| Burst Mode® Optimization | Improved light-load efficiency for boost channel when VIN > VOUT, reducing ripple vs. LTC3859 |
| OPTI-LOOP Compensation | Allows stable loop tuning across wide output capacitance and ESR ranges without redesign |
| 100% Duty Cycle Support | Enables true dropout operation in boost channel-even during Burst Mode®-for maximum voltage step-up |
| Flexible Bias Architecture | Accepts VBIAS (4.5–38V) or EXTVCC (≥4.7V) to power INTVCC, improving efficiency in high-VIN applications |
| Cold-Crank Compatibility | Maintains regulation through automotive cold-crank events down to 2.5V input after startup |
Applications
| Automotive Start-Stop Systems | Battery-Powered Digital Devices |
|---|---|
Use Scenario: Power management in vehicles with engine auto-stop/restart, requiring stable 5V/8.5V/10V rails during 2.5–16V battery transients. IC Role / Device Role / Timing Role: Triple-output controller managing buck-buck-boost conversion with cold-crank holdup and fast load-step response. Use Value: Maintains regulation during cranking dips; 55μA IQ extends accessory mode runtime; PGOOD1/OV3 enable system-level fault coordination. |
Use Scenario: Portable test equipment or handheld medical devices needing isolated, low-noise 5V, 8.5V, and variable boost outputs from single Li-ion cell or 12V adapter. IC Role / Device Role / Timing Role: Central power controller delivering sequenced, tracked outputs with soft-start and independent enable control. Use Value: Dual soft-start (TRACK/SS1/2, SS3) ensures safe power-up sequencing; RSENSE/DCR flexibility simplifies layout across varied load profiles. |
| Distributed DC Power Systems | Multioutput Buck-Boost Applications |
Use Scenario: Industrial IoT gateway with 24V backplane powering multiple subsystems: MCU core (5V), interface logic (8.5V), and sensor bias (10V+). IC Role / Device Role / Timing Role: High-efficiency triple regulator replacing discrete solutions; supports remote sensing and thermal derating via ITH feedback. Use Value: Phase-lockable frequency avoids beat frequencies in dense board layouts; EXTVCC option improves efficiency at high input voltages. |
Use Scenario: Telecom line card requiring 3.3V, 5V, and 12V rails from a 48V intermediate bus, where some loads exceed input voltage. IC Role / Device Role / Timing Role: Integrated buck-buck-boost controller eliminating need for separate boost IC and associated layout complexity. Use Value: Single-chip solution reduces BOM count and PCB area; 60V boost capability supports legacy 48V-to-12V conversion with margin. |
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#PBF | Same electrical specs and pinout; rated for –40°C to 125°C but in TSSOP-38 package (θJA = 25°C/W) | Preferred where board space allows larger TSSOP and lower thermal resistance is critical | Select for cost-sensitive industrial designs where QFN assembly infrastructure is unavailable |
| LTC3859AHUHF#PBF | Identical QFN-38 package and functionality; rated for –40°C to 150°C junction temperature | Suitable for under-hood automotive or high-ambient industrial environments exceeding 125°C | Choose when extended temperature operation is required without changing layout or thermal design |
Compared with LTC3859AEUHF#PBF, the TSSOP variant offers better thermal dissipation in open-air conditions but requires more PCB area, while the AH-grade QFN maintains identical footprint and layout compatibility while supporting higher ambient temperatures.
Availability
LTC3859AEUHF#PBF 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 assurance, and traceable sourcing.
Supply support for LTC3859AEUHF#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 LTC3859A product line delivers high-efficiency, low-quiescent-current multi-output controllers designed specifically for demanding automotive, battery-powered, and distributed power applications where reliability and thermal robustness are critical.
FAQ
What is the minimum input voltage required for LTC3859AEUHF#PBF startup?
The LTC3859AEUHF#PBF requires a minimum VBIAS of 4.5V to initiate startup. However, once running-and when biased from the boost output or another auxiliary supply-it can sustain operation with input as low as 2.5V, making it suitable for automotive cold-crank scenarios where battery voltage dips transiently below 5V.
Does LTC3859AEUHF#PBF support both RSENSE and DCR current sensing?
Yes, the LTC3859AEUHF#PBF supports both RSENSE and DCR current sensing on all three channels. The SENSE+ and SENSE– pins are configured for differential measurement, and internal circuitry adapts bias currents accordingly-e.g., SENSE3+ supplies current in boost mode, while SENSE1,2– sources current when VOUT exceeds INTVCC by >0.5V.
How does the PLLIN/MODE pin configure light-load operation for LTC3859AEUHF#PBF?
The PLLIN/MODE pin configures LTC3859AEUHF#PBF light-load behavior: grounded or floating (via internal 100kΩ pull-down) enables Burst Mode®; tied to INTVCC forces continuous conduction; biased to 1.2V–(INTVCC–1.3V) selects pulse-skipping. This pin also accepts external clocks for synchronization across multiple regulators.
What is the purpose of the exposed pad (Pin 39) on the LTC3859AEUHF#PBF QFN package?
The exposed pad (Pin 39) on the LTC3859AEUHF#PBF is designated PGND and serves as the primary power ground return for all gate drivers and high-current paths. It must be soldered to a large PCB copper plane to ensure rated thermal performance (θJA = 34.7°C/W) and low-impedance grounding-failure to do so degrades efficiency and may cause thermal shutdown.
Can LTC3859AEUHF#PBF generate a 12V boost output from a 5V input?
Yes, the LTC3859AEUHF#PBF supports boost output voltages up to 60V. With proper external components-including a 6.5µH inductor, 8mΩ sense resistor, and appropriate MOSFETs-it can reliably generate 12V from a 5V input, as validated in Figure 12 of the datasheet and confirmed by its 100% duty-cycle capability in boost mode.
LTC3859AEUHF#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)
LTC3859AEUHF#PBF FAQ
1.How can I place an order for LTC3859AEUHF#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859AEUHF#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 LTC3859AEUHF#PBF reliable?
The price and inventory of LTC3859AEUHF#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859AEUHF#PBF is usually 5 days.
3.What payment methods are accepted for LTC3859AEUHF#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859AEUHF#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859AEUHF#PBF?
LTC3859AEUHF#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859AEUHF#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 LTC3859AEUHF#PBF?
For technical support, including LTC3859AEUHF#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859AEUHF#PBF requirements.
6.How does Aetrix verify that LTC3859AEUHF#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3859AEUHF#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 LTC3859AEUHF#PBF meets industry standards.
7.What is the process for return or replacement of LTC3859AEUHF#PBF?
All LTC3859AEUHF#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859AEUHF#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 LTC3859AEUHF#PBF part is unused and in its original packaging.
Return procedure for LTC3859AEUHF#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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