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Analog Devices Inc. LTC3859ALMPFE
- Part No.:
- LTC3859ALMPFE
- Manufacturer:
- Analog Devices Inc.
- Category:
- DC DC Switching Controllers
- Package:
- 38-TFSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3859ALMPFE.pdf
- Description:
- IC POWER MANAGEMENT
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LTC3859ALMPFE 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, 4.5V–38V input range, and AEC-Q100 qualification for automotive cold-crank operation down to 2.5V. It enables multi-rail power in start-stop systems and battery-powered digital devices.
For engineers reviewing the LTC3859ALMPFE datasheet, LTC3859ALMPFE pinout, LTC3859ALMPFE application, or LTC3859ALMPFE equivalent, key selection criteria include its triple-output topology, ultra-low IQ in Sleep Mode, phase-lockable 75kHz–850kHz switching frequency, OPTI-LOOP compensation, and dual-buck-plus-boost architecture supporting regulated boost output up to 60V.
Technical Context
The LTC3859ALMPFE 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 programmable soft-start via TRACK/SS pins.
Its PLLIN/MODE pin selects among Burst Mode (28µA IQ), pulse-skipping, or forced continuous conduction mode. The FREQ pin supports resistor-programmable fixed frequency (50kHz–900kHz) or external synchronization (75kHz–850kHz), while OPTI-LOOP allows transient optimization across wide output capacitance and ESR ranges.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Dual buck + single boost synchronous controller - enables independent regulation of two step-down and one step-up rails from single input. |
| Input voltage range | 4.5V to 38V bias supply; operates down to 2.5V after startup when biased from boost output - supports automotive cold-crank and wide-input industrial systems. |
| Quiescent current | 28µA in Sleep Mode (one buck channel active) - extends runtime in always-on battery systems without compromising regulation. |
| Switching frequency | Phase-lockable 75kHz–850kHz; programmable 50kHz–900kHz via FREQ pin - enables EMI reduction and layout optimization. |
| Feedback references | 0.8V ±1% for buck outputs; 1.2V ±1% for boost output - ensures precise output voltage regulation across temperature and load. |
| Output voltage range | Buck: 0.8V–24V; Boost: up to 60V - supports diverse rail requirements including USB PD, FPGA core, and sensor bias supplies. |
| Current sensing | RSENSE or DCR sensing per channel - provides flexibility in efficiency vs. cost trade-offs and thermal management. |
| Package | 38-lead TSSOP (FE) with exposed PGND pad - delivers robust thermal performance (θJA = 25°C/W) and automotive-grade mechanical reliability. |
Pinout & Package
Package: 38-Lead Plastic TSSOP (FE), –55°C to 150°C operating junction temperature, exposed PGND pad (Pin 39) requiring PCB soldering for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FREQ (Pin 1) | Oscillator frequency programming | Resistor-to-GND sets fixed frequency (50kHz–900kHz); tied to GND/INTVCC for 350kHz/535kHz - enables EMI control and layout-driven frequency selection. |
| PLLIN/MODE (Pin 2) | Light-load mode selection & sync input | GND = Burst Mode (28µA IQ); INTVCC = forced CCM; 1.2V–(INTVCC–1.3V) = pulse-skipping; external clock = phase-locked operation. |
| 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 - enables dynamic rail sequencing and power gating. |
| VFB1/VFB2/VFB3 (Pins 36,14,6) | Feedback voltage inputs | Compare against 0.8V (buck) or 1.2V (boost) reference - determines output regulation point via external resistor divider. |
| TG1/TG2/TG3 (Pins 32,18,27) | Top-gate N-MOS drivers | Floating high-side gate drives with INTVCC swing over SW node - supports synchronous rectification and >99% duty cycle in buck dropout. |
| PGOOD1 (Pin 33) | Buck1 power-good indicator | Open-drain output asserting low when VFB1 deviates >±10% from setpoint - enables system-level fault detection and sequencing. |
Key Features
| Feature | Design Value |
|---|---|
| 28µA Burst Mode IQ (one channel on) | Enables >100-hour standby in automotive always-on modules without battery drain, verified at –55°C to 150°C. |
| AEC-Q100 qualified (MP grade) | Validated for automotive applications including start-stop and cold-crank, with guaranteed operation from –55°C to 150°C junction. |
| 100% duty cycle capability in Burst Mode | Maintains regulation during deep input voltage drop (e.g., 2.5V cold crank) without dropout, critical for engine control units. |
| OPTI-LOOP compensation | Allows stable loop response across 10µF–1000µF output capacitors and 1mΩ–100mΩ ESR - reduces design iterations for varying capacitor types. |
| Triple independent soft-start/tracking | TRACK/SS1/2 and SS3 pins support coordinated ramp-up of multiple rails or tracking to external supplies - prevents latch-up in FPGA/CPU power sequences. |
| RSENSE or DCR current sensing | Supports high-efficiency discrete sense resistors or low-loss integrated inductor DCR sensing - optimizes thermal design for high-current buck rails. |
Applications
| Automotive Start-Stop Systems | Battery-Powered Digital Devices |
|---|---|
Use Scenario: Power management in vehicles with engine auto-shutdown at idle, requiring stable 5V/8.5V/10V rails during 2.5V cold-crank events. IC Role / Device Role / Timing Role: Triple-output synchronous controller regulating buck1 (5V/5A), buck2 (8.5V/3A), and boost3 (10V/2A) from 12V battery with seamless transition below 5V. Use Value: 28µA IQ extends battery life between starts; 100% duty cycle maintains regulation at 2.5V input; AEC-Q100 MP grade ensures reliability at –55°C. | Use Scenario: Portable medical monitors requiring isolated 3.3V, 5V, and 12V rails from single Li-ion cell (3.0V–4.2V) with minimal self-discharge. IC Role / Device Role / Timing Role: Dual-buck (3.3V/5V) plus boost (12V) controller enabling simultaneous rail generation with independent enable control and soft-start sequencing. Use Value: Ultra-low 28µA Sleep Mode IQ preserves battery charge during standby; OPTI-LOOP accommodates varied capacitor ESR in compact layouts. |
| Distributed DC Power Systems | Multioutput Buck-Boost Applications |
Use Scenario: Industrial IoT gateway with separate 3.3V MCU, 5V interface, and 24V sensor excitation rails powered from 24V nominal bus with ±20% variation. IC Role / Device Role / Timing Role: High-efficiency triple controller delivering tightly regulated outputs across 4.5V–38V input range using RSENSE current sensing and phase-locked frequency. Use Value: Wide input range eliminates need for pre-regulator; 75kHz–850kHz sync capability reduces conducted EMI in dense board layouts. | Use Scenario: Test equipment requiring programmable 0.8V–24V buck and 5V–60V boost outputs from common 12V supply, with independent voltage adjustment. IC Role / Device Role / Timing Role: Configurable buck/buck/boost controller with per-channel feedback references (0.8V/0.8V/1.2V) and adjustable soft-start via TRACK/SS pins. Use Value: Independent regulation enables flexible rail assignment; 60V boost capability supports high-voltage analog front-ends without external boost stages. |
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; higher Burst Mode IQ (35µA typical with one channel on). | Not qualified for extended temperature automotive use; suitable for commercial/industrial environments with less extreme thermal demands. | Select when AEC-Q100 and –55°C operation are unnecessary and cost optimization is prioritized. |
| LTC3859ALIUHF#WTRPBF | Identical electrical specs and MP-grade temp range; packaged in 5mm × 7mm QFN (UHF) instead of TSSOP (FE); includes automotive reliability reporting. | Superior thermal performance (θJA = 34.7°C/W) and smaller footprint; requires different PCB land pattern and reflow profile. | Select when board space is constrained or enhanced thermal dissipation is required in automotive under-hood applications. |
Compared with LTC3859AIFE#TRPBF and LTC3859ALIUHF#WTRPBF, the LTC3859ALMPFE offers the widest operating temperature range (–55°C to 150°C) in the TSSOP package, making it uniquely suited for under-hood automotive deployments where mechanical robustness and legacy through-hole-compatible packaging are required.
Availability
LTC3859ALMPFE 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 across extended temperature ranges and long production lifecycles.
Supply support for LTC3859ALMPFE 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 triple-output synchronous DC/DC controllers optimized for automotive and industrial applications demanding ultra-low quiescent current, wide input voltage tolerance, and AEC-Q100 reliability - specifically targeting start-stop systems and always-on battery-powered equipment.
FAQ
What is the minimum input voltage for LTC3859ALMPFE after startup?
The LTC3859ALMPFE can operate from an input supply as low as 2.5V after startup when biased from the boost converter output or another auxiliary supply. This capability is essential for automotive cold-crank conditions where battery voltage dips below 5V, and is guaranteed across the full –55°C to 150°C junction temperature range specified for the MP grade.
How does the LTC3859ALMPFE achieve 28µA quiescent current?
The LTC3859ALMPFE achieves 28µA quiescent current in Burst Mode operation with one channel active through proprietary circuitry that disables non-essential internal blocks while maintaining regulation loop integrity. This ultra-low IQ is measured with VFB1/2 at 0.83V and VFB3 at 1.25V under no-load conditions, and is validated for the MP temperature grade (–55°C to 150°C).
Is LTC3859ALMPFE pin-compatible with other variants in the LTC3859AL family?
Yes, the LTC3859ALMPFE is fully pin-compatible with the LTC3859 and LTC3859A variants. All share identical pin configuration, electrical interface, and functional behavior - differing only in guaranteed temperature range, quiescent current specification, and qualification status (e.g., AEC-Q100 MP grade for LTC3859ALMPFE).
What is the purpose of the OPTI-LOOP compensation in LTC3859ALMPFE?
The OPTI-LOOP compensation in LTC3859ALMPFE allows the transient response to be optimized across a wide range of output capacitance values (10µF to 1000µF) and equivalent series resistance (1mΩ to 100mΩ). This eliminates the need for iterative compensation network redesign when changing capacitor types or quantities in final system validation.
Can LTC3859ALMPFE drive both buck and boost channels simultaneously?
Yes, the LTC3859ALMPFE is designed to operate all three channels - two bucks and one boost - simultaneously. Its independent RUN1/RUN2/RUN3 pins allow individual channel enable/disable, and its shared INTVCC regulator and gate drivers support concurrent switching with phase-lockable frequency synchronization across all channels.
LTC3859ALMPFE 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:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 38-TSSOP-EP
LTC3859ALMPFE FAQ
1.How can I place an order for LTC3859ALMPFE through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3859ALMPFE 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 LTC3859ALMPFE reliable?
The price and inventory of LTC3859ALMPFE are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3859ALMPFE is usually 5 days.
3.What payment methods are accepted for LTC3859ALMPFE?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3859ALMPFE transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3859ALMPFE?
LTC3859ALMPFE orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3859ALMPFE 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 LTC3859ALMPFE?
For technical support, including LTC3859ALMPFE datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3859ALMPFE requirements.
6.How does Aetrix verify that LTC3859ALMPFE is sourced from the original manufacturer or authorized distributors?
All LTC3859ALMPFE 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 LTC3859ALMPFE meets industry standards.
7.What is the process for return or replacement of LTC3859ALMPFE?
All LTC3859ALMPFE units undergo pre-shipment inspection (PSI). If there is an issue with LTC3859ALMPFE, 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 LTC3859ALMPFE part is unused and in its original packaging.
Return procedure for LTC3859ALMPFE:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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