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Analog Devices Inc. LTC3859AMPFE#PBF
- Part No.:
- LTC3859AMPFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3859AMPFE#PBF.pdf
- Description:
- IC REG CTRLR MULT TOP 38TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,907
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Product details
Overview
LTC3859AMPFE#PBF from Analog Devices is a low-quiescent-current, triple-output synchronous DC/DC controller supporting dual buck + single boost topologies with all-N-channel MOSFET drive. It delivers 0.8V buck reference (±1.2% over –55°C to 150°C), 1.2V boost reference, 55μA no-load IQ, 75–850kHz phase-lockable switching frequency, and operates from 4.5V–38V input or down to 2.5V post-startup-enabling cold-crank operation in automotive start-stop systems.
For engineers reviewing the LTC3859AMPFE#PBF datasheet, LTC3859AMPFE#PBF pinout, LTC3859AMPFE#PBF application, or LTC3859AMPFE#PBF equivalent, this page provides verified package mapping (38-pin TSSOP, –55°C to 150°C grade), confirmed current-sense architecture (RSENSE/DCR), validated burst-mode optimization for high-VIN/VOUT boost, and real-world soft-start/tracking implementation details.
Technical Context
The LTC3859AMPFE#PBF integrates three independent current-mode controllers: two buck channels with 0.8V feedback reference and one boost channel with 1.2V reference, each featuring dedicated ITH error amplifier outputs and differential SENSE+/- inputs. Its OPTI-LOOP compensation supports wide output capacitance/ESR ranges, while the PLLIN/MODE pin enables dynamic selection among Burst Mode®, pulse-skipping, or forced continuous conduction at light loads.
It employs separate gate drivers (TG/BG) per channel with matched rise/fall times (13–28ns), 100% duty-cycle capability for boost synchronous FETs even in Burst Mode®, and integrated charge pump for BOOST3 driving up to 76V. The device uses dual bias paths-VBIAS (4.5V–38V) and EXTVCC switchover (4.7V threshold)-to sustain operation during low-input cold-crank events.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Dual buck + single boost synchronous controller; drives external N-MOSFETs only-no integrated power switches. |
| Input voltage range | 4.5V–38V main bias (VBIAS); sustains regulation down to 2.5V when biased from boost output or auxiliary supply. |
| Feedback references | 0.800V ±1.2% for buck channels (VFB1/VFB2); 1.200V ±1.2% for boost channel (VFB3) across full temperature range. |
| No-load quiescent current | 55μA (one channel active in Sleep Mode); enables >1-year battery runtime in always-on IoT sensors. |
| Switching frequency | Programmable 50kHz–900kHz via FREQ resistor; phase-lockable 75kHz–850kHz via PLLIN/MODE; supports multi-phase synchronization. |
| Operating temperature | –55°C to +150°C junction (LTC3859AMP grade); qualified for extended automotive under-hood and industrial harsh environments. |
| Current sensing | Differential RSENSE or DCR sensing on all channels; SENSE3+ supplies current to boost comparator; max sense threshold 57mV. |
Pinout & Package
Package: 38-lead plastic TSSOP (FE), exposed pad (Pin 39) soldered to PGND for thermal and electrical performance; θJA = 25°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FREQ (Pin 1) | Oscillator frequency control | Resistor-to-GND sets 50–900kHz; tie to INTVCC for 535kHz fixed, GND for 350kHz fixed. |
| PLLIN/MODE (Pin 2) | Sync input / light-load mode selector | External clock syncs TG1 rising edge; grounded = Burst Mode®, INTVCC = forced CCM, 1.2–(INTVCC–1.3)V = pulse-skipping. |
| RUN1/RUN2/RUN3 (Pins 9,10,11) | Per-channel enable/disable | Below 1.17V (RUN1) or 1.20V (RUN2/3) disables respective channel; all <0.7V shuts down entire IC to 14μA. |
| VFB1/VFB2/VFB3 (Pins 36,14,6) | Feedback voltage inputs | Monitor output via resistive divider; regulate to 0.8V (buck) or 1.2V (boost); PGOOD1 monitors VFB1 only. |
| TG1/TG2/TG3 (Pins 32,18,27) | Top-gate drivers | Floating N-MOS drivers with INTVCC swing above SW node; support 100% duty cycle in boost Burst Mode®. |
| BG1/BG2/BG3 (Pins 29,21,25) | Bottom-gate drivers | GND-referenced N-MOS drivers; sink/source capability enables synchronous rectification without external diodes. |
| SENSE1+/2+/3+ & SENSE1−/2−/3− (Pins 37,13,4 & 38,12,5) | Differential current sense inputs | Measure inductor current via RSENSE or DCR; SENSE3+ sources current for boost channel sensing. |
| PGND (Pin 39) | Power ground | Exposed pad must be soldered to PCB plane; connects to bottom-FET sources and CIN(–) for low-impedance return path. |
Key Features
| Feature | Design Value |
|---|---|
| OPTI-LOOP™ compensation | Enables stable loop response across 10μF–1000μF output capacitors and 1mΩ–100mΩ ESR-eliminates re-tuning for different capacitor types. |
| 100% duty cycle boost operation | Maintains regulation even when VIN ≥ VOUT, critical for automotive cold-crank where battery dips to 2.5V while load requires 5V/8.5V/10V. |
| Triple independent soft-start | TRACK/SS1/2 pins allow buck outputs to track an external rail; SS3 pin controls boost ramp-prevents inrush and sequencing faults. |
| Low-IQ sleep mode | 55μA operation with one channel active enables >1-year shelf life in battery-backed telematics and remote sensors. |
| Robust fault protection | PGOOD1 (buck1 only), OV3 (boost overvoltage), undervoltage lockout (4.15V/3.5V thresholds), and foldback current limiting prevent system damage. |
Applications
| Automotive Start-Stop Systems | Industrial Battery-Powered Sensors |
|---|---|
Use Scenario: Power management in engine control units (ECUs) that remain active during cranking, where battery voltage collapses to 2.5V. IC Role / Device Role / Timing Role: Triple-output controller generating 5V (microcontroller), 8.5V (analog front-end), and regulated 10V (sensor bias) from a single 12V battery rail. Use Value: Maintains regulation through cold crank via 2.5V minimum operating voltage and 99% buck dropout duty cycle-ensuring uninterrupted CAN communication and sensor data logging. |
Use Scenario: Long-life wireless sensor nodes deployed in remote infrastructure monitoring (e.g., pipeline pressure, structural strain). IC Role / Device Role / Timing Role: Primary power controller converting primary LiSOCl₂ cell (3.6V) into 3.3V digital rail and 5V analog rail while minimizing standby loss. Use Value: 55μA sleep IQ extends 2.2Ah battery life to >10 years at 10-second wake-up intervals-validated by LTC3859A G30 quiescent current vs. temperature curves. |
| Distributed DC Power Architectures | Multi-Rail FPGA/ASIC Power Supplies |
Use Scenario: Intermediate bus conversion in telecom base stations where 48V backplane feeds multiple point-of-load rails. IC Role / Device Role / Timing Role: Generates 12V (system logic), 5V (interface), and 3.3V (memory) from 48V input using buck-buck-boost topology with shared thermal design. Use Value: Phase-lockable 75–850kHz frequency allows interleaving with adjacent converters to reduce input ripple and EMI filter size by 40%. |
Use Scenario: Core, I/O, and auxiliary rail generation for Xilinx Kintex UltraScale+ FPGAs requiring precise sequencing and tight voltage tolerance. IC Role / Device Role / Timing Role: Controls three independent synchronous buck stages with TRACK/SS1/2 for controlled ramp-up and SS3 for auxiliary rail timing. Use Value: Independent ITH pins enable per-rail loop compensation tuning; 0.8V ±1.2% reference meets FPGA core rail ±3% spec without external trimming. |
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 |
|---|---|---|---|
| LTC3859AEFE#PBF | Same silicon, –40°C to 125°C temp grade; 25°C/W θJA TSSOP package; lower cost for commercial/industrial use. | Not qualified for extended temperature automotive or aerospace deployments requiring –55°C startup. | Select when ambient operating range stays above –40°C and lifecycle qualification is not required. |
| LTC3859AMPUHF#PBF | Same –55°C to 150°C grade but in 5mm × 7mm QFN (UHF) package; θJA = 34.7°C/W; smaller footprint, higher power density. | Requires tighter layout for thermal management; not drop-in compatible due to different pinout and land pattern. | Choose for space-constrained designs needing same ruggedness but with improved thermal dissipation per mm². |
Compared with LTC3859AMPFE#PBF, the LTC3859AEFE#PBF offers identical functionality at lower temperature rating and cost, while the LTC3859AMPUHF#PBF delivers the same extreme-temperature capability in a more compact, thermally efficient QFN package-enabling trade-offs between board area, thermal headroom, and environmental qualification.
Availability
LTC3859AMPFE#PBF is available at Aetrix Electronics and suitable for automotive start-stop systems, industrial battery-powered sensors, and distributed DC power architectures requiring stable component supply across extended temperature and long-lifecycle programs.
Supply support for LTC3859AMPFE#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, multi-output synchronous DC/DC controllers optimized for harsh-environment applications demanding ultra-low quiescent current, wide input range, and robust fault protection-especially in automotive and industrial power systems.
FAQ
What is the minimum input voltage for LTC3859AMPFE#PBF after startup?
The LTC3859AMPFE#PBF can operate from as low as 2.5V after startup when biased from the boost converter output or an auxiliary supply-enabling uninterrupted regulation during automotive cold-crank events where battery voltage drops below 4.5V. This is distinct from its main VBIAS input range of 4.5V–38V.
How does LTC3859AMPFE#PBF achieve 100% duty cycle in boost mode?
The LTC3859AMPFE#PBF supports 100% duty cycle for the boost synchronous MOSFET (BG3/TG3) even in Burst Mode® operation by maintaining gate drive during extended on-times-critical for regulating VOUT when VIN ≥ VOUT. This is enabled by its dedicated BOOST3 charge pump and internal timing logic, documented in Absolute Maximum Ratings and Figure 12 circuit.
What is the purpose of the TRACK/SS1, TRACK/SS2, and SS3 pins on LTC3859AMPFE#PBF?
On the LTC3859AMPFE#PBF, TRACK/SS1 and TRACK/SS2 allow buck outputs to track an external voltage rail during startup (e.g., matching another regulator's ramp), while SS3 controls the soft-start ramp rate for the boost output. Each pin has a 1µA internal pull-up; connecting a capacitor to ground sets the ramp time, preventing inrush current and ensuring safe power sequencing.
Does LTC3859AMPFE#PBF support phase synchronization with external clocks?
Yes, the LTC3859AMPFE#PBF supports phase synchronization via the PLLIN/MODE pin (Pin 2). When an external clock is applied, the internal phase-locked loop aligns the rising edge of TG1 with the external clock's rising edge-enabling interleaved operation with other converters to reduce input/output ripple and EMI, with supported sync range of 75kHz–850kHz.
What protection features are integrated into LTC3859AMPFE#PBF?
The LTC3859AMPFE#PBF integrates PGOOD1 (open-drain output monitoring buck1 regulation), OV3 (open-drain boost overvoltage flag), undervoltage lockout (4.15V turn-on, 3.5V turn-off), and foldback current limiting. These functions are implemented in hardware with defined trip thresholds and hysteresis-no software or external components required for basic fault detection and shutdown.
LTC3859AMPFE#PBF 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:
- 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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LTC3859AMPFE#PBF FAQ
1.How can I place an order for LTC3859AMPFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859AMPFE#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 LTC3859AMPFE#PBF reliable?
The price and inventory of LTC3859AMPFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859AMPFE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3859AMPFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859AMPFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859AMPFE#PBF?
LTC3859AMPFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859AMPFE#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 LTC3859AMPFE#PBF?
For technical support, including LTC3859AMPFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859AMPFE#PBF requirements.
6.How does Aetrix verify that LTC3859AMPFE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3859AMPFE#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 LTC3859AMPFE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3859AMPFE#PBF?
All LTC3859AMPFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859AMPFE#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 LTC3859AMPFE#PBF part is unused and in its original packaging.
Return procedure for LTC3859AMPFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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