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Analog Devices Inc. LT8643SEV#PBF
- Part No.:
- LT8643SEV#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TFQFN Exposed Pad
- Datasheet:
-
LT8643SEV#PBF.pdf
- Description:
- IC REG BUCK ADJ 6A 24LQFN
- Quantity:
- Payment:
- Shipping:
Inventory:3,107
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Product details
Overview
LT8643SEV#PBF from Analog Devices is a 42V, 6A synchronous step-down Silent Switcher 2 regulator with external compensation, 30ns minimum on-time, 2.5µA quiescent current in Burst Mode, and AEC-Q100 qualification for automotive power supplies delivering 5V/6A from 12V input.
For engineers reviewing the LT8643SEV#PBF datasheet, LT8643SEV#PBF pinout, LT8643SEV#PBF application, or LT8643SEV#PBF equivalent, this page provides verified technical context, EMI-optimized layout guidance, fast transient response design values, external loop compensation requirements, and automotive-grade thermal and reliability data.
Technical Context
The LT8643SEV#PBF implements peak current mode control with second-generation Silent Switcher 2 architecture, integrating internal bypass capacitors on VIN, BST, and INTVCC to minimize high-di/dt loop area and reduce radiated EMI without external filtering. Its external VC pin enables precise loop compensation for current sharing and fast load transient response at up to 3MHz switching frequency.
It supports four operating modes via SYNC/MODE pin: Burst Mode (ultralow IQ), forced continuous mode (FCM), spread spectrum (reduced EMI peaks), and external synchronization. The 30ns minimum on-time enables high step-down ratios (e.g., 36V→3.3V) at 2MHz, while low dropout (100mV @1A) ensures regulation under high-load, low-input conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 42V - supports wide automotive battery range including cold-crank (4.5V) and load-dump (40V+) |
| Output Current | 6A continuous, 7A peak - sustains full load across industrial temperature range with proper thermal design |
| Quiescent Current | 2.5µA in Burst Mode (12VIN→3.3VOUT) - enables >1-year battery life in always-on automotive modules |
| Switching Frequency | 200kHz to 3MHz (RT-programmable) - allows optimization of size (high-freq) vs. efficiency (low-freq) |
| Min On-Time | 30ns - enables direct 36V-to-3.3V conversion at 2MHz without intermediate stages |
| Feedback Reference | 0.970V ±0.006V - tight tolerance enables accurate output regulation with standard resistor dividers |
| EMI Performance | CISPR 25 Class 5 compliant - meets automotive radiated emission limits without added filter components |
Pinout & Package
LT8643SEV#PBF uses a 24-lead 4mm × 4mm × 0.94mm LQFN package with exposed GND pads (pins 25–28) requiring PCB soldering for thermal performance. Pin count and footprint match standard QFN-24 but integrate internal bypass capacitors.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BIAS (1) | External bias supply input | Reduces VIN current draw when tied to VOUT ≥3.3V; mandatory for <230µA sleep IQ |
| INTVCC (2) | Internal 3.4V regulator bypass | Must be floated; supplies gate drivers and control logic; sourced from BIAS if >3.1V, else from VIN |
| GND (3,16,25–28) | Power and signal ground | Multiple low-inductance paths required; exposed pad must be soldered for θJC = 7°C/W thermal performance |
| VIN (5,6,13,14) | Main input power | Four parallel pins reduce resistance and inductance; requires local ≥2.2µF ceramic capacitor |
| BST (7) | Bootstrap capacitor connection | Floats externally; internal charge pump generates gate drive voltage >VIN for top FET |
| SW (8–12) | Power switch node | Five parallel SW outputs reduce trace inductance; connect directly to inductor with minimal copper area |
| EN/UV (17) | Enable and undervoltage lockout | 1.00V rising threshold with 40mV hysteresis; resistor divider enables programmable VIN UVLO |
| RT (18) | Frequency setting resistor | Resistor to GND sets fSW: 221kΩ = 210kHz, 60.4kΩ = 700kHz, 18.2kΩ = 1.95MHz |
| CLKOUT (19) | Switching clock monitor | 200ns pulse at fSW in FCM/spread-spectrum/sync modes; low in Burst Mode |
| SYNC/MODE (20) | Operating mode control | Ground = Burst Mode; float = FCM; 3–4V = spread spectrum; external clock = sync |
| TR/SS (21) | Soft-start and tracking | 1.9µA pull-up enables RC-programmed ramp; <1.6V enables output tracking function |
| VC (22) | Error amplifier output | External RC network (e.g., 330pF + 8.45kΩ) sets loop compensation for fast transient response |
| PG (23) | Power good indicator | Open-drain output asserts high when FB is within ±7.5% of 0.97V and no faults exist |
| FB (24) | Feedback input | Regulated to 0.970V; connects to resistor divider tap; requires 4.7–22pF phase lead capacitor to VOUT |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher 2 Architecture | Integrated VIN/BST/INTVCC bypass capacitors reduce PCB layout sensitivity and eliminate need for external EMI filters |
| External Compensation (VC Pin) | Enables custom loop tuning for multi-phase current sharing and <20µs 2A→4A transient recovery at 2MHz |
| Ultralow Quiescent Current | 2.5µA IQ (LT8640S) / 120µA IQ (LT8643S w/BIAS=5V) enables always-on automotive subsystems |
| Spread Spectrum Modulation | ±22% frequency dithering reduces peak EMI by >10dB, easing CISPR 25 Class 5 compliance |
| AEC-Q100 Grade | Qualified for automotive applications (-40°C to 125°C junction), with guaranteed reliability and failure rate data |
| Fast Minimum On-Time | 30ns on-time supports single-stage 36V→3.3V conversion at 2MHz, eliminating bulky pre-regulators |
Applications
| Automotive ADAS Power Supply | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering radar sensor SoCs requiring clean 5V/3A with <10mV ripple in engine bay environments. IC Role / Device Role / Timing Role: Primary 42V-input buck converter delivering regulated 5V with ultralow EMI to avoid RF interference with 77GHz radar. Use Value: Silent Switcher 2 architecture meets CISPR 25 Class 5 without ferrite beads, reducing BOM cost and board space by 30%. | Use Scenario: Providing isolated 3.3V/2A power to microcontroller and analog front-end in DIN-rail mounted PLCs. IC Role / Device Role / Timing Role: High-efficiency, wide-input DC/DC stage converting 24V rail to 3.3V with fast transient response to digital I/O switching noise. Use Value: 95% efficiency at 2MHz enables compact 3.3µH inductor; external VC compensation ensures stable operation under 10A/ms load steps. |
| Medical Imaging Sensor Bias | Telecom Remote Radio Unit |
Use Scenario: Generating low-noise 3.3V/1.5A for CMOS image sensor arrays in portable ultrasound devices. IC Role / Device Role / Timing Role: Low-ripple, low-EMI power source where switching noise could corrupt analog pixel readout signals. Use Value: <10mVP-P output ripple and integrated bypass caps prevent SNR degradation; 2.5µA IQ extends battery runtime. | Use Scenario: Converting 48V backplane to 5V/6A for FPGA and transceiver ICs in outdoor 5G RRUs with -40°C to +85°C ambient. IC Role / Device Role / Timing Role: High-reliability, thermally robust buck regulator supporting continuous 6A load at elevated ambient temperatures. Use Value: Exposed-pad LQFN package achieves θJA = 24°C/W on demo board; AEC-Q100 qualification ensures 10-year field life. |
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 |
|---|---|---|---|
| LT8640SEV#PBF | Internal compensation, lower IQ (1.7µA), no VC pin, identical pinout and package | Preferred for fixed-output, cost-sensitive designs without current sharing or aggressive transient requirements | Select LT8640SEV#PBF when loop stability is assured by internal compensation and external tuning is unnecessary |
| MPQ4433AGL-AEC1-Z | 3.8V–60V input, 3.5A, 17µA IQ, no spread spectrum, QFN-20 package | Lower current rating and higher IQ limit use in lower-power automotive modules only | Choose MPQ4433AGL-AEC1-Z only for ≤3.5A loads where footprint reduction outweighs EMI and transient performance trade-offs |
Compared with LT8640SEV#PBF, the LT8643SEV#PBF trades internal simplicity for external loop control-enabling faster transient response and multi-phase current sharing-while MPQ4433AGL-AEC1-Z offers wider input range but sacrifices EMI performance and peak current capability.
Availability
LT8643SEV#PBF is available at Aetrix Electronics and suitable for automotive ADAS systems, industrial PLCs, medical imaging sensors, and telecom remote radio units requiring stable component supply with AEC-Q100 qualification and long-term production support.
Supply support for LT8643SEV#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.
The LT8643SEV#PBF belongs to the Silent Switcher 2 family, engineered specifically for noise-sensitive automotive and industrial applications demanding ultra-low EMI, high efficiency at high frequencies, and AEC-Q100 reliability.
FAQ
What is the maximum output current capability of the LT8643SEV#PBF under continuous operation?
The LT8643SEV#PBF delivers 6A continuous output current across its full operating temperature range (-40°C to 125°C junction), verified with thermal design using the exposed GND pad soldered to PCB. Peak current capability reaches 7A for short durations, limited by internal current sense thresholds and thermal headroom.
How does the LT8643SEV#PBF achieve ultralow EMI without external filters?
The LT8643SEV#PBF integrates ceramic bypass capacitors for VIN, BST, and INTVCC inside the LQFN package, minimizing high-di/dt loop area. Combined with symmetrical layout and Silent Switcher 2's balanced magnetic fields, this enables CISPR 25 Class 5 compliance on standard PCBs without ferrite beads or common-mode chokes.
Can the LT8643SEV#PBF be synchronized to an external clock, and what is the required signal format?
Yes, the LT8643SEV#PBF supports external synchronization via the SYNC/MODE pin. Drive this pin with a CMOS-level clock (0V to ~3.4V) matching the desired switching frequency. The part operates in forced continuous mode during sync, with CLKOUT providing a 200ns pulse aligned to each switch transition.
What is the purpose of the VC pin on the LT8643SEV#PBF, and how is it used in circuit design?
The VC pin on the LT8643SEV#PBF is the error amplifier output, enabling external loop compensation. Designers connect an RC network (e.g., 330pF capacitor and 8.45kΩ resistor to GND) to set gain and phase margin-critical for achieving fast transient response and stable current sharing in multi-phase configurations.
Is the LT8643SEV#PBF qualified for automotive applications, and what grade does it meet?
Yes, the LT8643SEV#PBF is AEC-Q100 qualified for automotive applications. It is rated for operation from –40°C to 125°C junction temperature and manufactured under automotive quality systems. The "E" suffix denotes the extended temperature grade, meeting stringent reliability and failure rate requirements for ADAS and powertrain systems.
LT8643SEV#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Silent Switcher®2
- Package/Case:
- 24-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):
- 42V
- Voltage - Output (Min/Fixed):
- 0.97V
- Voltage - Output (Max):
- 42V
- Current - Output:
- 6A
- Frequency - Switching:
- 200kHz ~ 3MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-LQFN (4x4)
LT8643SEV#PBF FAQ
1.How can I place an order for LT8643SEV#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8643SEV#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 LT8643SEV#PBF reliable?
The price and inventory of LT8643SEV#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8643SEV#PBF is usually 5 days.
3.What payment methods are accepted for LT8643SEV#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8643SEV#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8643SEV#PBF?
LT8643SEV#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8643SEV#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 LT8643SEV#PBF?
For technical support, including LT8643SEV#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8643SEV#PBF requirements.
6.How does Aetrix verify that LT8643SEV#PBF is sourced from the original manufacturer or authorized distributors?
All LT8643SEV#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 LT8643SEV#PBF meets industry standards.
7.What is the process for return or replacement of LT8643SEV#PBF?
All LT8643SEV#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8643SEV#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 LT8643SEV#PBF part is unused and in its original packaging.
Return procedure for LT8643SEV#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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