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Analog Devices Inc. LT8640AJUDCM-3.3#TRPBF
- Part No.:
- LT8640AJUDCM-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad, 18 Leads
- Datasheet:
-
LT8640AJUDCM-3.3#TRPBF.pdf
- Description:
- IC REG BUCK 3.3V 5A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:4,688
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Product details
Overview
LT8640AJUDCM-3.3#TRPBF from Analog Devices is a 42V input, 3.3V fixed-output synchronous step-down regulator with Silent Switcher architecture, 2.5µA quiescent current in regulation, 30ns minimum on-time, and AEC-Q100 qualification for automotive power supplies delivering up to 5A continuous / 8A peak output.
For engineers reviewing the LT8640AJUDCM-3.3#TRPBF datasheet, LT8640AJUDCM-3.3#TRPBF pinout, LT8640AJUDCM-3.3#TRPBF application, or LT8640AJUDCM-3.3#TRPBF equivalent, key selection criteria include ultralow EMI performance, forced continuous mode support, spread spectrum modulation, thermal robustness to 150°C junction, and compatibility with high-frequency (up to 3MHz) compact designs using 3mm × 4mm QFN.
Technical Context
The LT8640AJUDCM-3.3#TRPBF implements peak current mode control with internal 0.97V reference (mapped to 3.3V via fixed resistor divider), frequency programmable from 200kHz to 3MHz via RT pin, and four selectable operating modes-Burst Mode, Forced Continuous Mode (FCM), Spread Spectrum, and external synchronization-via the SYNC/MODE pin.
It integrates top and bottom NMOS power switches (67mΩ/28mΩ typical RDS(ON)), supports BIAS pin operation for efficiency optimization at VOUT ≥ 3.3V, and features active soft-start/tracking via TR/SS pin with 1.9µA internal pull-up current and fault-safe 200Ω pulldown during shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3.4V to 42V - enables direct battery-fed automotive and industrial supply rails without pre-regulation |
| Output Voltage | Fixed 3.3V ±1.5% - eliminates external feedback resistors and simplifies layout for noise-sensitive digital logic supplies |
| Continuous Output Current | 5A - sufficient for powering multiple microcontrollers, FPGAs, or sensor clusters from single rail |
| Quiescent Current | 2.5µA at 12VIN → 3.3VOUT - extends battery life in always-on automotive modules and IoT edge nodes |
| Switching Frequency | 200kHz–3MHz (RT-programmable) - allows trade-off between inductor size and efficiency across wide load range |
| Minimum On-Time | 30ns - supports high VIN-to-VOUT conversion ratios (e.g., 24V→3.3V) at 2MHz+ switching without pulse-skipping instability |
| EMI Performance | CISPR 25 Class 5 compliant in spread spectrum mode - meets stringent automotive radiated/conducted emission requirements without shielding |
| Junction Temp Range | –40°C to +150°C - qualified per AEC-Q100 Grade 1, enabling under-hood deployment in engine control units |
Pinout & Package
LT8640AJUDCM-3.3#TRPBF uses an 18-lead 3mm × 4mm plastic side-solderable QFN package (UDCM) with exposed SW pad (Pin 21) for thermal enhancement. Pins 5 and 12 are omitted; corner pins serve mechanical support only.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BIAS (1) | Internal regulator bias supply | Connect to VOUT (3.3V) to reduce VIN current draw and improve light-load efficiency |
| INTVCC (2) | Internal 3.4V regulator bypass | Requires ≥1µF low-ESR ceramic capacitor to GND; powers control circuitry and drivers |
| BST (3) | Bootstrap gate drive supply | 0.1µF capacitor between BST and SW provides high-side NMOS gate voltage boost |
| VIN1 (4), VIN2 (13) | Main input power inputs | Each requires dedicated 1µF ceramic bypass to respective GND1/GND2; minimizes high-di/dt loop area |
| GND1 (6,7), GND2 (10,11) | Power switch return paths | Must be tied together and connected to solid ground plane; critical for EMI and thermal performance |
| SW (8,9,21) | Switch node outputs | Pins 8/9 are signal SW; Pin 21 is exposed pad soldered to SW trace - primary thermal path and high-current return |
| EN/UV (14) | Enable and undervoltage lockout | 1.00V rising threshold with 40mV hysteresis - enables input brownout protection and controlled startup |
| RT (15) | Frequency programming | Resistor to GND sets oscillator frequency (e.g., 60.4kΩ = ~700kHz); determines inductor sizing and ripple |
| TR/SS (16) | Soft-start and tracking | 1.9µA internal current charges external capacitor to control VOUT ramp rate; disables tracking above 0.97V |
| SYNC/MODE (17) | Operating mode selection | GND = Burst Mode; float = FCM; INTVCC = spread spectrum; external clock = sync - no external components needed |
| GND (18) | System ground reference | Connect directly to PCB ground plane; separates signal ground from power ground return paths |
| PG (19) | Power good open-drain output | Asserts high when VOUT is within ±7.5% of 3.3V and no fault - used for system sequencing and monitoring |
| VOUT (20) | Fixed 3.3V regulated output | Internally connected to 11.33MΩ feedback divider - no external resistors required for 3.3V configuration |
Key Features
| Feature | Design Value |
|---|---|
| Silent Switcher architecture | Reduces radiated/conducted EMI by >30dB vs conventional buck regulators - eliminates need for ferrite beads or metal shields |
| Ultralow 2.5µA quiescent current | Enables >10-year battery life in always-on telematics modules and ADAS sensors without compromising regulation accuracy |
| 30ns minimum on-time | Supports 24V→3.3V conversion at 2MHz with stable operation - enables <2mm² inductor footprint in space-constrained ECUs |
| AEC-Q100 Grade 1 qualification | Validated for –40°C to +150°C operation with full parametric testing - suitable for engine bay, transmission, and brake control units |
| Spread spectrum modulation | ±22% triangular frequency dithering reduces peak EMI amplitude - helps pass CISPR 25 Class 5 without filter redesign |
| Forced Continuous Mode (FCM) | Eliminates low-frequency output ripple and improves transient response - essential for powering real-time microcontrollers and ADCs |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC I/O Module |
|---|---|
Use Scenario: Powering 32-bit ARM Cortex-M7 MCU, CAN transceiver, and analog front-end in under-hood ECU exposed to 125°C ambient and load dump transients. IC Role / Device Role / Timing Role: Primary 3.3V system rail regulator with integrated EMI suppression and thermal resilience. Use Value: Eliminates external EMI filters and heatsinks while maintaining 3.3V ±3% regulation across –40°C to 150°C junction temperature. | Use Scenario: Generating isolated 3.3V logic supply for digital I/O expansion cards in factory automation controllers with strict EMC compliance. IC Role / Device Role / Timing Role: High-efficiency, low-noise DC/DC converter feeding FPGA configuration and serial interface ICs. Use Value: Achieves CISPR 25 Class 5 radiated emissions margin without shielded enclosures or board-level filtering components. |
| ADAS Camera Module | Medical Portable Diagnostic Device |
Use Scenario: Supplying image sensor, ISP, and Wi-Fi SoC in compact rear-view camera housing with limited airflow and high ambient temperature. IC Role / Device Role / Timing Role: Compact, high-frequency 3.3V power stage enabling miniaturized optics-integrated PCB design. Use Value: 3MHz operation allows use of 1µH inductor, reducing solution size by 40% vs 500kHz alternatives while maintaining <10mVP-P ripple. | Use Scenario: Battery-powered ultrasound probe requiring ultra-low standby current and clean 3.3V supply for sensitive analog signal chain. IC Role / Device Role / Timing Role: Primary system regulator with Burst Mode enabling multi-week battery life in sleep state. Use Value: 2.5µA IQ extends lithium-polymer battery runtime to >18 months in intermittent-use diagnostic mode. |
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 |
|---|---|---|---|
| LT8645S-3.3#TRPBF | 6A continuous / 10A peak output, same 3.3V fixed option, identical pinout and package, but higher current capability and improved thermal resistance (θJA = 26°C/W vs 29°C/W) | Required where sustained >5A loads exist (e.g., multi-core processors), or where lower thermal rise is critical in sealed enclosures | Select LT8645S-3.3#TRPBF when output current headroom or thermal margin exceeds 5A/8A limits of LT8640AJUDCM-3.3#TRPBF |
| MPQ4433AGL-AEC1-P | 3.3V fixed output, 6A continuous, 36V max input, 17µA IQ in sleep mode, QFN-16 (3×4mm), no spread spectrum or Silent Switcher architecture | Lower EMI performance requires external filtering for automotive Class 5 compliance; lacks AEC-Q100 full-grade validation | Consider MPQ4433AGL-AEC1-P only for cost-sensitive non-safety-critical applications where EMI filtering is acceptable and thermal derating is managed externally |
Compared with LT8645S-3.3#TRPBF, the LT8640AJUDCM-3.3#TRPBF offers tighter EMI control and lower quiescent current but less current headroom; versus MPQ4433AGL-AEC1-P, it delivers certified automotive EMI performance and thermal reliability without added BOM cost or layout complexity.
Availability
LT8640AJUDCM-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC I/O modules, ADAS camera systems, and medical portable diagnostics requiring stable component supply with AEC-Q100 qualification and long-term production continuity.
Supply support for LT8640AJUDCM-3.3#TRPBF 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 precision instrumentation, industrial automation, communications, and automotive markets.
The LT8640A product line delivers high-efficiency, low-EMI synchronous buck regulators optimized for demanding automotive and industrial environments where reliability, thermal robustness, and electromagnetic compatibility are non-negotiable.
FAQ
What is the maximum continuous output current of the LT8640AJUDCM-3.3#TRPBF?
The LT8640AJUDCM-3.3#TRPBF delivers up to 5A continuous output current at 3.3V with proper PCB layout and thermal management. Its peak transient capability reaches 8A for short durations, supporting dynamic loads such as microcontroller wake-up bursts or sensor initialization sequences. Derating applies above 100°C ambient or with insufficient copper area on the SW-exposed pad.
Does the LT8640AJUDCM-3.3#TRPBF require external feedback resistors?
No, the LT8640AJUDCM-3.3#TRPBF does not require external feedback resistors. It integrates an internal 11.33MΩ resistor divider that fixes the output to 3.3V, connecting directly to the VOUT pin (Pin 20). This eliminates component count, layout sensitivity, and tolerance drift associated with external resistor networks - a key advantage over adjustable variants like the LT8640A.
How does the LT8640AJUDCM-3.3#TRPBF achieve ultralow EMI performance?
The LT8640AJUDCM-3.3#TRPBF achieves ultralow EMI through Analog Devices' patented Silent Switcher architecture, which employs symmetrical internal power switch layouts and integrated bootstrap capacitors to cancel magnetic fields. Combined with optional spread spectrum modulation (enabled via SYNC/MODE pin), it meets CISPR 25 Class 5 conducted and radiated emission limits without external shielding or ferrite beads - verified on the DC3099A demo board.
Can the LT8640AJUDCM-3.3#TRPBF operate in forced continuous mode (FCM)?
Yes, the LT8640AJUDCM-3.3#TRPBF supports forced continuous mode (FCM) by leaving the SYNC/MODE pin floating. In FCM, the regulator maintains constant switching frequency across all load conditions, eliminating low-frequency output ripple and improving transient response - critical for powering real-time microcontrollers, ADCs, and communication interfaces without output voltage droop.
What is the purpose of the BIAS pin on the LT8640AJUDCM-3.3#TRPBF?
The BIAS pin (Pin 1) on the LT8640AJUDCM-3.3#TRPBF supplies current to the internal 3.4V regulator, reducing VIN current draw and improving light-load efficiency. For the 3.3V output version, BIAS must be connected to VOUT. This configuration lowers total input quiescent current to 2.5µA - essential for battery-powered automotive modules and always-on IoT edge devices.
LT8640AJUDCM-3.3#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- Silent Switcher®1
- Package/Case:
- 20-WFQFN Exposed Pad, 18 Leads
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.9V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- 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-3.3#TRPBF FAQ
1.How can I place an order for LT8640AJUDCM-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT8640AJUDCM-3.3#TRPBF 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-3.3#TRPBF reliable?
The price and inventory of LT8640AJUDCM-3.3#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT8640AJUDCM-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT8640AJUDCM-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT8640AJUDCM-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT8640AJUDCM-3.3#TRPBF?
LT8640AJUDCM-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT8640AJUDCM-3.3#TRPBF 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-3.3#TRPBF?
For technical support, including LT8640AJUDCM-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT8640AJUDCM-3.3#TRPBF requirements.
6.How does Aetrix verify that LT8640AJUDCM-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT8640AJUDCM-3.3#TRPBF 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-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT8640AJUDCM-3.3#TRPBF?
All LT8640AJUDCM-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT8640AJUDCM-3.3#TRPBF, 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-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT8640AJUDCM-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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