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Analog Devices Inc. LT8645SEV#PBF
- Part No.:
- LT8645SEV#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 32-TFQFN Exposed Pad
- Datasheet:
-
LT8645SEV#PBF.pdf
- Description:
- IC REG BUCK ADJ 8A 32LQFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,397
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Product details
Overview
LT8645SEV#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 junction temperature in automotive and industrial power supplies.
For engineers reviewing the LT8645SEV#PBF datasheet, LT8645SEV#PBF pinout, LT8645SEV#PBF application, or LT8645SEV#PBF equivalent, key selection criteria include ultralow IQ in Burst Mode, 65V max input, 8A output capability, EMI-optimized Silent Switcher 2 architecture, and AEC-Q100 qualification for automotive systems requiring robust transient response and thermal stability.
Technical Context
The LT8645SEV#PBF implements peak current mode control with a 40ns minimum on-time, enabling high step-down ratios (e.g., 48V→3.3V) at 2.2MHz switching frequency. Its second-generation Silent Switcher 2 architecture integrates internal VIN, BST, and INTVCC bypass capacitors to minimize fast-current-loop area and eliminate layout sensitivity for CISPR 25 Class 5 radiated EMI compliance.
Burst Mode® operation maintains 2.5µA input quiescent current while regulating 12VIN to 3.3VOUT, and the device supports programmable frequency (200kHz–2.2MHz) via RT resistor, spread spectrum modulation, soft-start/tracking via TR/SS, and power-good monitoring via open-drain PG pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 65V - supports wide-range industrial, automotive, and telecom inputs without pre-regulation. |
| Output Current | 8A continuous - enables single-chip 5V/3.3V supply for FPGA, SoC, or multi-rail systems. |
| Quiescent Current (Burst Mode) | 2.5µA at 12VIN→3.3VOUT - extends battery life in always-on automotive modules. |
| Switching Frequency | 200kHz to 2.2MHz - allows compact magnetics and avoids AM band interference. |
| Minimum On-Time | 40ns - supports high input-to-output voltage ratios (e.g., 48V→1.2V) at 2MHz. |
| EMI Performance | CISPR 25 Class 5 compliant - meets stringent automotive radiated emission limits without external filters. |
| Thermal Range | –40°C to 125°C junction - qualified per AEC-Q100 Grade 1 for under-hood automotive use. |
Pinout & Package
LT8645SEV#PBF is housed in a 32-lead 6mm × 4mm × 0.94mm LQFN package with exposed GND pads (pins 33–38) for enhanced thermal dissipation. The package footprint matches standard 6mm × 4mm QFN layouts and supports JEDEC-compliant reflow.
| 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 enable high-current routing; requires local ≥4.7µF ceramic bypass. |
| GND (Pins 8,9,10,17,18,19,33–38) | Power and signal reference ground | Exposed thermal pad must be soldered to PCB ground plane for θJC(PAD) = 4.4°C/W thermal performance. |
| SW (Pins 12,13,14,15,16) | Switch node connection | High-frequency AC node; must be minimized in area to suppress EMI radiation and ringing. |
| FB (Pin 32) | Feedback voltage sense | Regulates output to 0.97V reference; connects to resistor divider; requires 1–10pF phase-lead capacitor to VOUT. |
| EN/UV (Pin 25) | Enable and undervoltage lockout | Hysteretic threshold (0.965V/1.01V) enables reliable startup and brownout protection. |
| PG (Pin 31) | Power-good status indicator | Open-drain output asserts high when FB is within ±8% of target and no faults (thermal, UVLO, EN low) exist. |
| TR/SS (Pin 29) | Soft-start and output tracking | Internal 1.9µA pull-up enables RC-programmed ramp rate; supports sequencing with other rails. |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher 2 architecture | Integrated VIN/BST/INTVCC bypass capacitors eliminate layout-dependent EMI and guarantee CISPR 25 Class 5 compliance. |
| Ultralow 2.5µA quiescent current | Enables >10-year battery life in automotive always-on modules (e.g., telematics, ADAS sensors). |
| 40ns minimum on-time | Supports direct 48V→1.2V conversion at 2MHz, eliminating intermediate buck stages and reducing BOM count. |
| AEC-Q100 Grade 1 qualification | Validated for automotive applications including engine control, infotainment, and body electronics. |
| Programmable spread spectrum | Reduces peak EMI by >10dB across 24% frequency deviation, easing system-level EMC certification. |
Applications
| Automotive Infotainment Power | Industrial PLC I/O Module Supply |
|---|---|
Use Scenario: Powering 5V/3.3V rails for MCU, display controller, and USB PHY in head-unit systems with 9–16V battery input and cold-crank down to 3.4V. IC Role / Device Role / Timing Role: Primary synchronous buck regulator delivering regulated 5V/8A and 3.3V/5A outputs with soft-start sequencing and fault reporting. Use Value: 2.5µA IQ ensures <10µA system standby current; Silent Switcher 2 eliminates need for EMI shielding cans, reducing cost and board area. |
Use Scenario: Generating isolated 5V/3.3V supplies for analog front-end, digital logic, and communication interfaces in DIN-rail mounted PLCs with 24V/48V DC input. IC Role / Device Role / Timing Role: High-efficiency, high-reliability step-down converter operating continuously at full load in 70°C ambient environments. Use Value: 95% efficiency at 1MHz reduces thermal stress; AEC-Q100 qualification ensures long-term reliability in harsh industrial settings. |
| GSM Base Station RF Power Amplifier Bias | Medical Imaging Sensor Interface |
Use Scenario: Providing clean, low-noise 5V bias for GaN RF power amplifiers in small-cell base stations with 48V backplane input and strict spectral mask requirements. IC Role / Device Role / Timing Role: EMI-optimized primary DC/DC stage feeding downstream LDOs; synchronized to system clock via SYNC/MODE pin. Use Value: Spread spectrum modulation lowers peak emissions below -40dBµV/m at 900MHz, avoiding costly filter redesigns during FCC testing. |
Use Scenario: Powering low-noise analog signal chains (ADCs, op-amps, sensors) in portable ultrasound or MRI coil interface modules requiring ultra-low ripple and stable 3.3V/2A output. IC Role / Device Role / Timing Role: Low-ripple, high-PG-accuracy buck regulator with <10mVP-P output noise and ±0.5% line/load regulation. Use Value: Integrated bypass caps and optimized SW node layout achieve <10mVP-P ripple without external ferrite beads, preserving SNR in sub-16-bit data acquisition. |
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 |
|---|---|---|---|
| LT8646SEV#PBF | External compensation (VC pin), higher sleep IQ (230µA), no internal compensation network | Required for current sharing, faster transient response, or custom loop shaping in high-performance power systems | Select LT8646SEV#PBF when design demands adjustable bandwidth, parallel operation, or tighter dynamic regulation. |
| MPQ4333GL-AEC1-Z | 40V max input, 3.5A output, 17µA IQ, no integrated bypass caps, QFN-16 package | Limited to lower-power automotive domains (e.g., lighting, HVAC); lacks Silent Switcher EMI performance | Choose MPQ4333GL-AEC1-Z only for cost-sensitive, lower-current (<4A), non-EMI-critical applications where footprint is constrained. |
Compared with LT8645SEV#PBF, LT8646SEV#PBF offers superior transient response and flexibility at the cost of higher light-load IQ and added external components, while MPQ4333GL-AEC1-Z provides AEC-Q100 compliance in a smaller package but sacrifices input voltage range, output current, and EMI robustness.
Availability
LT8645SEV#PBF is available at Aetrix Electronics and suitable for automotive infotainment systems, industrial PLC power supplies, and medical sensor interfaces requiring stable component supply, long lifecycle support, and guaranteed AEC-Q100 conformance.
Supply support for LT8645SEV#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 industrial, automotive, communications, and healthcare markets.
The LT8645S product line delivers high-efficiency, low-EMI synchronous step-down regulation for demanding automotive and industrial applications where input voltage range, thermal robustness, and electromagnetic compatibility are critical.
FAQ
What is the maximum input voltage rating for the LT8645SEV#PBF?
The LT8645SEV#PBF has an absolute maximum input voltage rating of 65V on the VIN pins. This allows direct operation from 48V industrial buses, 36V automotive systems, and telecom -48V supplies without external pre-regulation. Operation above 65V risks permanent damage per Absolute Maximum Ratings.
How does the LT8645SEV#PBF achieve ultralow quiescent current in Burst Mode?
The LT8645SEV#PBF achieves 2.5µA quiescent current in Burst Mode by completely disabling its internal oscillator, gate drivers, and error amplifier between energy bursts. Only a minimal bias circuit remains active to monitor output voltage, enabling efficient regulation at microamp load levels typical in automotive standby modes.
Is the LT8645SEV#PBF pin-compatible with the LT8646SEV#PBF?
No, the LT8645SEV#PBF and LT8646SEV#PBF are not pin-compatible. While both use the same 32-lead LQFN package, Pin 30 is GND on the LT8645SEV#PBF but VC (error amplifier output) on the LT8646SEV#PBF. Swapping them without PCB revision will cause functional failure or damage.
What thermal performance can be expected from the LT8645SEV#PBF in a standard JEDEC board layout?
In a JEDEC-standard board layout, the LT8645SEV#PBF exhibits θJA = 30°C/W and θJC(PAD) = 4.4°C/W. With 8A output at 95% efficiency and 12VIN→5VOUT, power dissipation is ~2.1W, resulting in ~63°C junction rise above ambient - well within the 125°C max rating when ambient is ≤62°C.
Does the LT8645SEV#PBF require external bypass capacitors on the BIAS pin?
Yes - if the BIAS pin is connected to a supply other than VOUT (e.g., a separate 5V rail), a 1µF local ceramic bypass capacitor must be placed directly at the BIAS pin. When BIAS is tied to VOUT, no additional capacitor is required, as the output capacitor serves this function.
LT8645SEV#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)
LT8645SEV#PBF FAQ
1.How can I place an order for LT8645SEV#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8645SEV#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 LT8645SEV#PBF reliable?
The price and inventory of LT8645SEV#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8645SEV#PBF is usually 5 days.
3.What payment methods are accepted for LT8645SEV#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8645SEV#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8645SEV#PBF?
LT8645SEV#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8645SEV#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 LT8645SEV#PBF?
For technical support, including LT8645SEV#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8645SEV#PBF requirements.
6.How does Aetrix verify that LT8645SEV#PBF is sourced from the original manufacturer or authorized distributors?
All LT8645SEV#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 LT8645SEV#PBF meets industry standards.
7.What is the process for return or replacement of LT8645SEV#PBF?
All LT8645SEV#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8645SEV#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 LT8645SEV#PBF part is unused and in its original packaging.
Return procedure for LT8645SEV#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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