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Analog Devices Inc. LT8646SIV#PBF
- Part No.:
- LT8646SIV#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 32-TFQFN Exposed Pad
- Datasheet:
-
LT8646SIV#PBF.pdf
- Description:
- IC REG BUCK ADJ 8A 32LQFN
- Quantity:
- Payment:
- Shipping:
Inventory:371
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Product details
Overview
LT8646SIV#PBF from Analog Devices is a 65V input, 8A synchronous step-down DC/DC regulator with external compensation, 2.5µA quiescent current in Burst Mode®, 40ns minimum on-time, and Silent Switcher®2 architecture for ultralow EMI. It delivers up to 95% efficiency at 1MHz (12VIN→5VOUT) and operates across –40°C to 125°C for automotive-grade power conversion in high-noise environments.
For engineers reviewing the LT8646SIV#PBF datasheet, LT8646SIV#PBF pinout, LT8646SIV#PBF application, or LT8646SIV#PBF equivalent, this page provides verified package mapping (32-lead 6mm × 4mm LQFN), confirmed external compensation capability, validated thermal performance (θJC(PAD) = 4.4°C/W), real-world EMI test data (CISPR25 Class 5 compliant), and precise pin-level circuit roles for layout-sensitive high-frequency designs.
Technical Context
The LT8646SIV#PBF implements peak current mode control with an externally compensated error amplifier (VC pin), enabling fast transient response and parallel current sharing in multi-phase configurations. Its Silent Switcher®2 architecture integrates internal bypass capacitors on VIN, BST, and INTVCC pins to minimize high-di/dt loop area and suppress radiated emissions without requiring complex PCB layout mitigation.
It supports four operating modes via the SYNC/MODE pin: Burst Mode® (ultralow IQ), pulse-skipping (full-frequency down to light loads), spread spectrum (±24% frequency dithering), and external synchronization (200kHz–2.2MHz). The 40ns minimum on-time enables high step-down ratios (e.g., 48V→3.3V at 2MHz) while maintaining regulation under all load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 65V - supports wide-range industrial, automotive, and telecom supplies without pre-regulation. |
| Output Current | 8A continuous - sufficient for FPGA core rails, ASIC power domains, or multi-rail point-of-load systems. |
| Quiescent Current (Burst Mode) | 2.5µA at 12VIN→3.3VOUT - enables >10-year battery life in always-on IoT sensors and telematics modules. |
| Switching Frequency Range | 200kHz to 2.2MHz - programmable via RT resistor; allows optimization of size (high-freq) vs. efficiency (low-freq). |
| Minimum On-Time | 40ns - enables direct 48V-to-1V conversion at 2MHz, eliminating intermediate stages in high-density power systems. |
| EMI Performance | CISPR25 Class 5 compliant (radiated) with integrated caps - eliminates need for external EMI filters in automotive infotainment and ADAS ECUs. |
| Thermal Resistance (θJC) | 4.4°C/W (pad) - enables 8A operation with ≤30°C junction rise over ambient on standard 2oz copper PCBs. |
Pinout & Package
LT8646SIV#PBF uses a 32-lead 6mm × 4mm × 0.94mm LQFN package with exposed thermal pad (pins 33–38, GND). The package is RoHS-compliant, AEC-Q100 qualified, and shares footprint with standard QFN layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pins 4,5,6,21,22,23) | Main input power supply connection | Multiple parallel pins reduce IR drop and enable high-current routing; must be locally bypassed with ≥4.7µF ceramic capacitor. |
| GND (Pins 8,9,10,17,18,19,33–38) | Power and signal reference ground | Exposure pad (33–38) is thermally critical - must be soldered to PCB ground plane for θJC = 4.4°C/W performance. |
| SW (Pins 12,13,14,15,16) | Switch node output | High di/dt node - requires minimal trace area and tight coupling to inductor and BST capacitor to suppress EMI. |
| VC (Pin 30) | Error amplifier output | External compensation node - connects to RC network (RC, CC) for loop stability and current-sharing accuracy in multi-phase designs. |
| RT (Pin 26) | Frequency programming input | Resistor-to-ground sets switching frequency (e.g., 60.4kΩ = ~700kHz); tolerance directly impacts timing accuracy and EMI peak placement. |
| SYNC/MODE (Pin 28) | Operating mode selection | Configures Burst Mode®, pulse-skipping, spread spectrum, or external sync - critical for EMI compliance and standby power optimization. |
| TR/SS (Pin 29) | Soft-start and tracking control | Programs output voltage ramp rate via external capacitor; enables power sequencing with other rails in complex SoC systems. |
| PG (Pin 31) | Power good open-drain flag | Asserts high when FB is within ±8% of target and no faults exist - used for system enable sequencing and fault monitoring. |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher®2 architecture | Integrated VIN/BST/INTVCC bypass capacitors eliminate layout sensitivity and guarantee CISPR25 Class 5 radiated EMI performance without added filters. |
| External compensation (VC pin) | Enables precise loop tuning for fast transient response (<50µs recovery at 2A step) and accurate current sharing across paralleled LT8646SIV#PBF units. |
| 40ns minimum on-time | Supports single-stage 48V-to-1.2V conversion at 2MHz, reducing BOM count and board area versus two-stage solutions. |
| Burst Mode® with 2.5µA IQ | Extends battery runtime in always-on applications (e.g., vehicle event recorders) while maintaining regulated output without output voltage droop. |
| AEC-Q100 Grade I (–40°C to +125°C) | Validated for under-hood automotive use - includes thermal shutdown, input UVLO, and PG fault reporting for functional safety compliance. |
| Spread spectrum modulation | Reduces peak EMI by >10dB across 200kHz–2.2MHz range - simplifies EMC certification for ADAS camera modules and radar subsystems. |
Applications
| Automotive ADAS Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powers image sensor and ISP in 77GHz radar ECU with strict CISPR25 Class 5 EMI limits. IC Role / Device Role / Timing Role: Primary 12V-to-1.2V/3.3V synchronous buck converter with spread spectrum and external compensation for noise immunity. Use Value: Eliminates discrete EMI filter components, reduces PCB area by 35%, and meets automotive EMC requirements without shielding. |
Use Scenario: Supplies isolated analog front-end and microcontroller in DIN-rail mounted PLC with 24VDC field bus input. IC Role / Device Role / Timing Role: High-reliability 24V-to-3.3V/5V converter with 125°C operation and robust input UVLO protection. Use Value: Maintains regulation during brownouts (down to 3.4V input) and survives 65V transients per ISO 7637-2 Pulse 5a, ensuring uptime in factory automation. |
| GSM Base Station RF Power Amplifier | Medical Imaging Detector Bias |
Use Scenario: Generates 28V bias for GaN PA stages in small-cell base stations with stringent thermal constraints. IC Role / Device Role / Timing Role: 48V-to-28V high-efficiency buck with 2.2MHz switching to minimize inductor size and enable compact form factor. Use Value: Achieves 94% efficiency at full load, limiting junction temperature rise to <25°C on 4-layer board - avoids forced air cooling. |
Use Scenario: Provides ultra-low-noise 5V bias for CMOS X-ray detector arrays requiring sub-10mVP-P ripple. IC Role / Device Role / Timing Role: Low-ripple synchronous buck with external LC filtering and soft-start for controlled detector activation. Use Value: Delivers <8mVP-P output ripple at 8A, preventing image artifacts and enabling 16-bit dynamic range in digital radiography systems. |
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 |
|---|---|---|---|
| LT8645SIV#PBF | Internal compensation; 1.7µA Burst Mode IQ; no VC pin; identical pinout except GND instead of VC at pin 30. | Preferred for cost-sensitive, single-rail designs where loop tuning isn't required and faster time-to-market is critical. | Select LT8645SIV#PBF when external compensation isn't needed and lowest possible quiescent current is mandatory. |
| MPQ4436GL-AEC1-Z | 45V max input; 6A output; 17µA IQ; no spread spectrum; AEC-Q100 qualified but lacks Silent Switcher®2 EMI suppression. | Suitable for less demanding EMI environments (e.g., body control modules) where 65V rating isn't required. | Choose MPQ4436GL-AEC1-Z only if input voltage stays below 45V and CISPR25 Class 5 compliance can be achieved via layout/filtering. |
Compared with LT8645SIV#PBF, the LT8646SIV#PBF trades slightly higher light-load IQ for design flexibility via VC-based loop control and current sharing; versus MPQ4436GL-AEC1-Z, it delivers superior EMI performance and wider input range at higher complexity and cost.
Availability
LT8646SIV#PBF is available at Aetrix Electronics and suitable for automotive ADAS systems, industrial PLCs, telecom power supplies, and medical imaging equipment requiring stable component supply, AEC-Q100 qualification, and long-term lifecycle support.
Supply support for LT8646SIV#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 LT8646SIV#PBF belongs to the Silent Switcher®2 family of high-voltage DC/DC regulators, engineered specifically for noise-sensitive automotive and industrial applications demanding ultra-low EMI, high efficiency, and extended temperature operation.
FAQ
What is the maximum input voltage rating for the LT8646SIV#PBF?
The LT8646SIV#PBF has an absolute maximum input voltage rating of 65V on the VIN pins. Operation is guaranteed across 3.4V to 65V input range, making it suitable for 48V industrial buses, 12V/24V automotive systems with load dump protection, and telecom -48V applications. Exceeding 65V risks permanent damage per Absolute Maximum Ratings.
How does the VC pin on the LT8646SIV#PBF enable current sharing in parallel configurations?
The VC pin on the LT8646SIV#PBF is the error amplifier output that controls peak switch current. When multiple LT8646SIV#PBF units operate in parallel, connecting their VC pins through low-value resistors forces equal VC voltage, thereby equalizing peak inductor currents and achieving balanced load sharing within ±5% across units - critical for high-current (>16A) applications.
Can the LT8646SIV#PBF achieve CISPR25 Class 5 radiated EMI compliance without external filtering?
Yes - the LT8646SIV#PBF's Silent Switcher®2 architecture, with integrated VIN/BST/INTVCC bypass capacitors and optimized internal current loops, achieves CISPR25 Class 5 radiated EMI compliance on standard 4-layer PCBs with only the recommended input/output capacitors and inductor. No additional EMI filters or shielding are required in typical automotive implementations per Analog Devices' DC2468A demo board validation.
What is the purpose of the TR/SS pin on the LT8646SIV#PBF, and how is it used for power sequencing?
The TR/SS pin on the LT8646SIV#PBF controls soft-start ramp rate and enables output voltage tracking. By connecting an external capacitor, designers set the output slew rate (e.g., 10ms ramp for 5V rail); when driven by another regulator's output, it tracks that rail for controlled power-up sequencing - essential for FPGAs and multi-core processors requiring strict VCCIO/VCCINT ordering.
Does the LT8646SIV#PBF support synchronization to an external clock, and what is the valid frequency range?
Yes - the LT8646SIV#PBF supports external synchronization via the SYNC/MODE pin. When driven by a clean CMOS clock signal, it locks to frequencies from 200kHz to 2.2MHz, enabling deterministic EMI reduction in systems with multiple switching regulators (e.g., camera + radar modules) and avoiding beat frequencies that cause audible noise or interference.
LT8646SIV#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)
LT8646SIV#PBF FAQ
1.How can I place an order for LT8646SIV#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8646SIV#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 LT8646SIV#PBF reliable?
The price and inventory of LT8646SIV#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8646SIV#PBF is usually 5 days.
3.What payment methods are accepted for LT8646SIV#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8646SIV#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8646SIV#PBF?
LT8646SIV#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8646SIV#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 LT8646SIV#PBF?
For technical support, including LT8646SIV#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8646SIV#PBF requirements.
6.How does Aetrix verify that LT8646SIV#PBF is sourced from the original manufacturer or authorized distributors?
All LT8646SIV#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 LT8646SIV#PBF meets industry standards.
7.What is the process for return or replacement of LT8646SIV#PBF?
All LT8646SIV#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8646SIV#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 LT8646SIV#PBF part is unused and in its original packaging.
Return procedure for LT8646SIV#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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