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Analog Devices Inc. LT8640AJUDCM#PBF
- Part No.:
- LT8640AJUDCM#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad, 18 Leads
- Datasheet:
-
LT8640AJUDCM#PBF.pdf
- Description:
- IC REG BUCK ADJ 5A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,450
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Product details
Overview
LT8640AJUDCM#PBF from Analog Devices is a 42V input, 5A continuous/8A peak synchronous step-down regulator with Silent Switcher architecture, 2.5µA quiescent current in regulation, 30ns minimum on-time, and AEC-Q100 qualification for automotive applications. It delivers up to 96% efficiency at 1MHz (12VIN→5VOUT) and supports spread spectrum, Burst Mode, and forced continuous operation via SYNC/MODE pin control.
For engineers reviewing the LT8640AJUDCM#PBF datasheet, LT8640AJUDCM#PBF pinout, LT8640AJUDCM#PBF application, or LT8640AJUDCM#PBF equivalent, key selection criteria include ultralow EMI emissions (CISPR25 Class 5 compliant), wide 3.4V–42V input range, fixed 3.3V output option (LT8640AJUDCM-3.3#PBF), thermal robustness to 150°C junction, and side-solderable 3mm × 4mm QFN package with exposed SW pad.
Technical Context
The LT8640AJUDCM#PBF implements peak current mode control with internal 0.97V reference (adjustable version) and integrated power switches. Its Silent Switcher architecture uses symmetrical layout and integrated bypass capacitors to suppress magnetic field emissions, enabling compliance with CISPR25 Class 5 conducted/radiated EMI limits without external shielding.
Four operating modes-Burst Mode (SYNC/MODE = GND), forced continuous (floating), spread spectrum (SYNC/MODE = 3–4V), and external synchronization (clock input)-are selected via a single pin. Frequency is programmable from 200kHz to 3MHz using an RT resistor, with fast 30ns minimum on-time enabling high VIN-to-low VOUT conversion at 2MHz+ switching.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 42V - supports automotive cold-crank (4.5V) and industrial 24/36V rails without pre-regulation. |
| Output Current | 5A continuous, 8A peak - sustains transient loads in engine control units and ADAS modules. |
| Quiescent Current | 2.5µA at full regulation - enables always-on systems (e.g., telematics, infotainment standby) with multi-year battery life. |
| Switching Frequency | 200kHz to 3MHz (RT-programmable) - allows compact magnetics: 1µH inductor at 3MHz, 3.3µH at 1MHz. |
| Minimum On-Time | 30ns - enables direct 42V→3.3V conversion at 2MHz, eliminating intermediate stages. |
| EMI Performance | CISPR25 Class 5 compliant (conducted/radiated) - meets automotive EMC requirements without ferrite beads or metal cans. |
| Junction Temp Range | –40°C to +150°C - qualified per AEC-Q100 Grade 1, suitable for under-hood and powertrain applications. |
Pinout & Package
LT8640AJUDCM#PBF uses an 18-lead, 3mm × 4mm plastic side-solderable QFN (UDCM package) with exposed SW pad (Pin 21) for thermal and electrical connection. Pins 5 and 12 are omitted; corner pins are mechanical only.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BIAS (1) | Internal regulator bias supply | Reduces VIN current draw when tied to ≥3.1V (e.g., VOUT); enables >90% light-load efficiency. |
| INTVCC (2) | Internal 3.4V regulator output | Bypassed with ≥1µF ceramic capacitor; powers control circuitry; not for external loading. |
| BST (3) | Bootstrap voltage supply | Drives top MOSFET gate via 0.1µF capacitor; critical for high-side switch turn-on reliability. |
| VIN1/VIN2 (4,13) | Main input power inputs | Require dedicated 1µF ceramic caps each; dual-input path reduces high-frequency loop inductance. |
| GND1/GND2 (6,7,10,11) | Power switch ground returns | Must be tied together and connected to low-impedance ground plane; minimizes EMI and dropout. |
| SW (8,9,21) | Switch node outputs | Pins 8/9 and exposed pad (21) are electrically common; must connect to inductor and BST cap with minimal trace area. |
| EN/UV (14) | Enable and undervoltage lockout | Hysteretic threshold (0.96V/1.00V) enables input rail sequencing and brownout protection. |
| RT (15) | Frequency programming | Resistor to GND sets fSW: 221kΩ = 210kHz, 60.4kΩ = 700kHz, 18.2kΩ = 1.95MHz. |
| TR/SS (16) | Soft-start and tracking | 1.9µA internal current source enables controlled VOUT ramp; supports output voltage sequencing. |
| SYNC/MODE (17) | Operating mode selection | GND = Burst Mode; float = FCM; 3–4V = spread spectrum; clock input = sync - single-pin multimode control. |
| GND (18) | System ground reference | Connects to system ground plane; separates signal ground from power ground paths. |
| PG (19) | Power good open-drain output | Asserts high when FB/VOUT is within ±8% of target and no fault; drives external enable chains. |
| FB (20) | Feedback voltage sense | Regulates to 0.970V; connects to resistor divider for adjustable output; requires 4.7–22pF phase lead cap. |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher architecture | Integrated symmetric layout and internal bypass caps reduce radiated EMI by >30dB vs conventional buck regulators. |
| Ultralow 2.5µA IQ in regulation | Enables >10-year battery life in always-on automotive modules (e.g., CAN gateway wake-up circuits). |
| 30ns minimum on-time | Supports direct 42V→3.3V conversion at 2MHz, eliminating cascaded regulators and saving board space. |
| AEC-Q100 Grade 1 qualification | Validated for –40°C to +150°C operation with lifetime testing; approved for powertrain and chassis applications. |
| Spread spectrum modulation | ±22% frequency dithering reduces peak EMI amplitude by 10–15dB, easing CISPR25 Class 5 compliance. |
| Side-solderable QFN package | Eliminates voiding risk in reflow; improves solder joint reliability in thermally cycled automotive environments. |
Applications
| Automotive ADAS Camera Power | Industrial PLC I/O Module |
|---|---|
|
Use Scenario: Powering 3.3V image sensor and ISP in forward-facing camera module exposed to under-hood temperatures. IC Role / Device Role / Timing Role: Primary 42V→3.3V buck converter with Burst Mode for sleep state and FCM for active imaging. Use Value: 2.5µA IQ extends vehicle battery life during parking mode; 150°C rating ensures reliability at 125°C ambient. |
Use Scenario: Generating isolated 5V rail for digital I/O channels in DIN-rail mounted programmable logic controller. IC Role / Device Role / Timing Role: High-efficiency, low-noise DC/DC stage converting 24V field bus to 5V logic supply. Use Value: CISPR25 Class 5 compliance prevents interference with analog sensor inputs; 5A output supports 16-channel expansion. |
| Automotive Infotainment Core Supply | Medical Portable Diagnostic Device |
|
Use Scenario: Providing stable 5V core supply to SoC and DDR memory in head-unit with variable 9–16V battery input. IC Role / Device Role / Timing Role: Main step-down regulator with spread spectrum enabled to suppress noise coupling into audio DACs. Use Value: <10mVP-P output ripple and <30ns on-time ensure clean power for high-speed memory interfaces. |
Use Scenario: Battery-powered ultrasound probe requiring quiet, efficient 3.3V supply for FPGA and ADC front-end. IC Role / Device Role / Timing Role: Primary buck converter operating in Burst Mode during standby and FCM during scan bursts. Use Value: 96% efficiency at 1A/5V extends single-charge runtime; side-solderable QFN ensures manufacturability in compact assemblies. |
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 |
|---|---|---|---|
| LT8645SUDC#PBF | 6A continuous, 10A peak; LQFN package; external compensation; higher max fSW (4MHz) | Higher current demand (e.g., radar modules); requires external loop compensation tuning | Select when >5A continuous load or >3MHz switching is required; larger footprint and design effort. |
| MPQ4433AGL-AEC1-Z | 45V input, 3.5A continuous; AEC-Q100 Grade 1; no spread spectrum; 50ns min on-time | Cost-sensitive automotive body electronics; lacks Silent Switcher EMI suppression | Choose for non-EMI-critical applications where lower BOM cost outweighs EMI filter savings. |
Compared with LT8640AJUDCM#PBF, LT8645SUDC#PBF offers higher current and frequency headroom but increases PCB area and design complexity, while MPQ4433AGL-AEC1-Z reduces cost and size at the expense of EMI performance and light-load efficiency.
Availability
LT8640AJUDCM#PBF is available at Aetrix Electronics and suitable for automotive ADAS, industrial PLCs, and medical portable diagnostics requiring stable component supply, AEC-Q100 qualification, and ultra-low EMI compliance.
Supply support for LT8640AJUDCM#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 automotive, industrial, communications, and healthcare markets.
The LT8640A product line delivers high-efficiency, low-EMI synchronous step-down regulators for demanding automotive and industrial applications where reliability, thermal robustness, and EMC compliance are critical.
FAQ
What is the maximum junction temperature rating for the LT8640AJUDCM#PBF?
The LT8640AJUDCM#PBF is rated for operation from –40°C to +150°C junction temperature and is AEC-Q100 Grade 1 qualified. Thermal derating begins above 125°C, and the device includes overtemperature protection that activates above 150°C. The UDCM package's θJA is 29°C/W on demo board, enabling 5A operation at 60°C ambient with proper layout.
Does the LT8640AJUDCM#PBF support fixed 3.3V output without external resistors?
Yes - the LT8640AJUDCM#PBF is the adjustable version (FB pin), but Analog Devices also offers the pin-compatible LT8640AJUDCM-3.3#PBF variant with internal 3.3V feedback divider. The LT8640AJUDCM#PBF requires external R1/R2 to set output voltage; typical 5V design uses 100kΩ/24.3kΩ for 0.97V reference scaling.
How does the SYNC/MODE pin configure spread spectrum operation on the LT8640AJUDCM#PBF?
When the SYNC/MODE pin is biased to 3V–4V (e.g., tied to INTVCC), the LT8640AJUDCM#PBF enters spread spectrum mode with forced continuous operation and ±22% triangular frequency modulation. This reduces EMI peak amplitudes by 10–15dB, aiding CISPR25 Class 5 compliance without altering PCB layout or adding filters.
What is the purpose of the dual VIN1/VIN2 and GND1/GND2 pins on the LT8640AJUDCM#PBF?
The dual VIN and GND pins on the LT8640AJUDCM#PBF create separate high-frequency input current paths to minimize loop inductance and EMI. Each pair (VIN1/GND1 and VIN2/GND2) must be decoupled with its own 1µF ceramic capacitor placed adjacent to the pins. This layout reduces voltage spikes and improves stability at 2–3MHz switching frequencies.
Can the LT8640AJUDCM#PBF safely handle reverse current from the output during light-load FCM operation?
Yes - the LT8640AJUDCM#PBF is designed to safely sink reverse current from the output during forced continuous mode, returning charge to the input. This capability improves load-step transient response and prevents output overshoot. The bottom NMOS remains active during negative inductor current, with 28mΩ on-resistance ensuring low conduction loss.
LT8640AJUDCM#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Silent Switcher®1
- Package/Case:
- 20-WFQFN Exposed Pad, 18 Leads
- Packaging:
- Tray
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.9V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 0.97V
- Voltage - Output (Max):
- 41.58V
- Current - Output:
- 5A
- Frequency - Switching:
- 200kHz ~ 3MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount, Wettable Flank
- Supplier Device Package:
- 20-QFN (3x4)
LT8640AJUDCM#PBF FAQ
1.How can I place an order for LT8640AJUDCM#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8640AJUDCM#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 LT8640AJUDCM#PBF reliable?
The price and inventory of LT8640AJUDCM#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8640AJUDCM#PBF is usually 5 days.
3.What payment methods are accepted for LT8640AJUDCM#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8640AJUDCM#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8640AJUDCM#PBF?
LT8640AJUDCM#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8640AJUDCM#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 LT8640AJUDCM#PBF?
For technical support, including LT8640AJUDCM#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8640AJUDCM#PBF requirements.
6.How does Aetrix verify that LT8640AJUDCM#PBF is sourced from the original manufacturer or authorized distributors?
All LT8640AJUDCM#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 LT8640AJUDCM#PBF meets industry standards.
7.What is the process for return or replacement of LT8640AJUDCM#PBF?
All LT8640AJUDCM#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8640AJUDCM#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 LT8640AJUDCM#PBF part is unused and in its original packaging.
Return procedure for LT8640AJUDCM#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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