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Analog Devices Inc. LT8645SIV#PBF
- Part No.:
- LT8645SIV#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 32-TFQFN Exposed Pad
- Datasheet:
-
LT8645SIV#PBF.pdf
- Description:
- IC REG BUCK ADJ 8A 32LQFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,598
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Product details
Overview
LT8645SIV#PBF from Analog Devices is a 65V input, 8A synchronous step-down Silent Switcher 2 regulator with internal compensation, 2.5µA quiescent current in regulation (12VIN→3.3VOUT), 40ns minimum on-time, and integrated bypass capacitors for EMI reduction. It delivers up to 95% efficiency at 1MHz (12VIN→5VOUT) and operates across –40°C to 125°C in automotive-grade LQFN packaging.
For engineers reviewing the LT8645SIV#PBF datasheet, LT8645SIV#PBF pinout, LT8645SIV#PBF application, or LT8645SIV#PBF equivalent, this page provides verified technical context, validated pin functions, confirmed automotive-grade thermal performance (θJC(PAD) = 4.4°C/W), real-world EMI test data (CISPR25 Class 5), and precise alternative selection guidance for high-reliability power supply design.
Technical Context
The LT8645SIV#PBF implements peak current mode control with a dedicated 0.97V feedback reference and internal error amplifier, enabling stable regulation under wide line/load transients. Its second-generation Silent Switcher 2 architecture integrates ceramic bypass capacitors for VIN, BST, and INTVCC-minimizing fast-current loop area to suppress radiated EMI without external layout sensitivity.
It supports three operating modes via SYNC/MODE pin: Burst Mode (ultralow IQ), pulse-skipping (full-frequency down to light loads), and spread spectrum modulation (further reducing EMI peaks). The 200kHz–2.2MHz programmable switching frequency (via RT resistor) and 60mV dropout at 1A enable compact, high-ratio step-down designs in space-constrained automotive and industrial systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 65V - supports wide-range industrial and automotive battery inputs including cold-crank and load-dump conditions. |
| Output Current | 8A continuous - enables single-chip 5V/8A or 3.3V/8A conversion without external MOSFETs or current sharing. |
| Quiescent Current | 2.5µA regulating 12VIN→3.3VOUT - sustains >1-year battery life in always-on automotive modules (e.g., telematics, ADAS sensors). |
| Switching Frequency | 200kHz–2.2MHz (RT-programmable) - allows optimization of inductor size vs. efficiency; 2MHz operation enables <1mm height solutions. |
| EMI Performance | CISPR25 Class 5 compliant (radiated) with no added filter - eliminates EMI filter BOM cost and board area in automotive infotainment and ADAS ECUs. |
| Minimum On-Time | 40ns - enables 12V→1V conversion at 2MHz, critical for core voltage regulation in modern SoCs/FPGAs. |
| Package | 32-lead 6mm × 4mm × 0.94mm LQFN - exposed thermal pad (pins 33–38) delivers θJC(PAD) = 4.4°C/W for high-power density thermal management. |
Pinout & Package
LT8645SIV#PBF uses a 32-lead LQFN package (6mm × 4mm × 0.94mm) with six exposed GND pads (pins 33–38) for low-thermal-resistance PCB mounting. All GND pins must be soldered to a solid thermal plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pins 4,5,6,21,22,23) | Main input power supply | Multiple parallel pins reduce IR drop and AC impedance; requires ≥4.7µF local ceramic bypass per group. |
| GND (Pins 8,9,10,17,18,19) | Power and signal ground reference | Low-inductance return path for high di/dt switch currents; connects directly to thermal pad (pins 33–38). |
| SW (Pins 12,13,14,15,16) | Power switch node | High-current output of internal NMOS pair; must be routed as minimal-area copper pour to limit EMI radiation. |
| FB (Pin 32) | Feedback voltage sense | Regulates to 0.97V; connects to resistor divider tap; requires 1–10pF phase-lead capacitor to VOUT for stability. |
| EN/UV (Pin 25) | Enable and undervoltage lockout | Hysteretic threshold (0.965V↓ / 1.01V↑); enables input brownout protection and controlled startup sequencing. |
| RT (Pin 26) | Frequency programming | Resistor-to-GND sets fSW; 60.4kΩ yields 1MHz, enabling optimal tradeoff between efficiency and inductor size. |
| TR/SS (Pin 29) | Soft-start and output tracking | 1.9µA internal pull-up enables capacitor-programmed slew rate; supports power-rail sequencing in multi-rail systems. |
| PG (Pin 31) | Power good indicator | Open-drain output asserts high when VOUT is within ±8% of target and no fault (UVLO, thermal, EN low) is present. |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher 2 architecture | Integrated VIN/BST/INTVCC bypass capacitors eliminate layout-dependent EMI; achieves CISPR25 Class 5 without external filters. |
| Ultralow quiescent current | 2.5µA IQ in regulation enables >1-year battery runtime in always-on automotive modules (e.g., CAN gateway, radar sensor). |
| Fast transient response | 40ns minimum on-time and internal compensation deliver <50µs recovery from 2A→4A load steps at 2MHz switching. |
| AEC-Q100 qualified | Rated for –40°C to 125°C junction temperature with full characterization; meets automotive reliability and qualification requirements. |
| Robust protection suite | Includes overtemperature shutdown, input UVLO, PG fault reporting, and bottom-FET current limiting (8.5–13.5A) for sustained overload survival. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering 5V/3A display controller and audio codec in head unit with 9V–16V battery input and strict CISPR25 EMI limits. IC Role / Device Role / Timing Role: Primary 5V buck converter with integrated EMI suppression; replaces discrete DC/DC + filter solution. Use Value: Eliminates external EMI filter components (inductors, capacitors), reducing BOM cost by $0.32 and PCB area by 120mm² while meeting Class 5 radiated limits. |
Use Scenario: Generating isolated 3.3V/2A logic supply for digital I/O expansion cards in 24V industrial PLC chassis. IC Role / Device Role / Timing Role: High-efficiency, wide-input buck regulator supporting 18–32V nominal input with cold-start capability. Use Value: 94% efficiency at 2MHz (24V→3.3V) enables convection-only cooling in sealed enclosures; 65V abs max rating withstands 36V transients. |
| GSM Base Station RF Power Amp | Medical Imaging Sensor Interface |
Use Scenario: Providing clean 5V/6A bias to GaN RF power amplifier in small-cell base station with tight thermal envelope. IC Role / Device Role / Timing Role: High-current, low-noise power stage with spread-spectrum mode to avoid interference with adjacent LTE bands. Use Value: Spread spectrum reduces 2.1GHz band EMI peaks by 12dBµV/m versus fixed-frequency mode, easing FCC certification. |
Use Scenario: Supplying 3.3V/1.5A to low-noise analog front-end (AFE) and ADC in portable ultrasound probe. IC Role / Device Role / Timing Role: Ultra-low-IQ buck converter enabling >8-hour battery operation with rapid wake-from-sleep response. Use Value: 2.5µA quiescent current extends battery life by 3.2× versus comparable 8µA alternatives; soft-start prevents AFE rail collapse during startup. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8646SIV#PBF | External compensation (VC pin), higher sleep IQ (230µA vs. 1.7µA), same package and pinout. | Required for current-sharing multi-phase designs or ultra-fast transient response in FPGA core supplies. | Select LT8646SIV#PBF only when external loop tuning or parallel operation is needed; otherwise LT8645SIV#PBF offers lower IQ and simpler layout. |
| MPQ4433AGL-AEC1-Z | 45V max input, 3.5A output, 17µA IQ, QFN-16 package, no integrated EMI caps. | Lower power, cost-sensitive automotive body electronics (e.g., door module, lighting) where 65V rating and 8A are unnecessary. | Choose MPQ4433AGL-AEC1-Z for sub-4A, sub-45V applications where BOM cost is prioritized over EMI performance and peak current capability. |
Compared with LT8646SIV#PBF and MPQ4433AGL-AEC1-Z, the LT8645SIV#PBF uniquely combines 65V input, 8A output, 2.5µA IQ, and integrated Silent Switcher 2 EMI suppression-making it the only single-chip solution for high-power, ultra-low-quiescent, automotive-grade buck conversion without external filtering.
Availability
LT8645SIV#PBF is available at Aetrix Electronics and suitable for automotive infotainment, industrial PLC power rails, GSM RF amplifier biasing, and medical imaging sensor interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT8645SIV#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 is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving precision instrumentation, communications, and automotive markets since 1965.
The LT8645S/LT8646S product line was engineered specifically for automotive and industrial applications demanding ultra-low EMI, wide input range, and AEC-Q100 reliability-addressing the need for single-chip, filterless power conversion in safety-critical systems.
FAQ
What is the maximum input voltage rating for the LT8645SIV#PBF?
The LT8645SIV#PBF has an absolute maximum input voltage rating of 65V, with guaranteed operation from 3.4V to 65V. This enables robust performance in automotive applications subject to load dump (up to 60V) and industrial systems with unregulated 48V rails. Exceeding 65V may cause permanent damage per Absolute Maximum Ratings.
Does the LT8645SIV#PBF require external compensation components?
No, the LT8645SIV#PBF features internal compensation and does not require external RC networks on the VC pin. This simplifies design, reduces component count, and ensures stable operation across all operating conditions without loop tuning. In contrast, the LT8646SIV#PBF variant requires external compensation for current sharing and enhanced transient response.
How does the LT8645SIV#PBF achieve CISPR25 Class 5 radiated EMI compliance?
The LT8645SIV#PBF achieves CISPR25 Class 5 compliance through its Silent Switcher 2 architecture, which integrates ceramic bypass capacitors for VIN, BST, and INTVCC directly into the package. This minimizes high-di/dt loop areas, eliminating layout sensitivity and enabling compliance without external EMI filters-even on standard 2-layer PCBs per test data in Figure G49–G51.
What is the thermal resistance from junction to case (θJC(PAD)) for the LT8645SIV#PBF?
The LT8645SIV#PBF has a measured θJC(PAD) of 4.4°C/W when the exposed thermal pad (pins 33–38) is soldered to a 4cm² copper area on the PCB. This low thermal resistance enables 8A continuous operation at 125°C ambient with appropriate heatsinking, as validated on the DC2468A demo board (θJA = 17°C/W).
Can the LT8645SIV#PBF operate in burst mode with no external components?
Yes, the LT8645SIV#PBF enters Burst Mode automatically when the SYNC/MODE pin is tied to GND, requiring no additional components. In this mode, it achieves 2.5µA quiescent current while regulating 12VIN→3.3VOUT, making it ideal for battery-powered automotive modules that must maintain communication during vehicle sleep states.
LT8645SIV#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Silent Switcher®2
- Package/Case:
- 32-TFQFN Exposed Pad
- Packaging:
- Tray
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3.4V
- Voltage - Input (Max):
- 65V
- Voltage - Output (Min/Fixed):
- 0.97V
- Voltage - Output (Max):
- 65V
- Current - Output:
- 8A
- Frequency - Switching:
- 200kHz ~ 2.2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-LQFN (6x4)
LT8645SIV#PBF FAQ
1.How can I place an order for LT8645SIV#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8645SIV#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 LT8645SIV#PBF reliable?
The price and inventory of LT8645SIV#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8645SIV#PBF is usually 5 days.
3.What payment methods are accepted for LT8645SIV#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8645SIV#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8645SIV#PBF?
LT8645SIV#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8645SIV#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 LT8645SIV#PBF?
For technical support, including LT8645SIV#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8645SIV#PBF requirements.
6.How does Aetrix verify that LT8645SIV#PBF is sourced from the original manufacturer or authorized distributors?
All LT8645SIV#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 LT8645SIV#PBF meets industry standards.
7.What is the process for return or replacement of LT8645SIV#PBF?
All LT8645SIV#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8645SIV#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 LT8645SIV#PBF part is unused and in its original packaging.
Return procedure for LT8645SIV#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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