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Analog Devices Inc. LT3973IDD-3.3#TRPBF
- Part No.:
- LT3973IDD-3.3#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3973IDD-3.3#TRPBF.pdf
- Description:
- IC REG BUCK 3.3V 750MA 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,603
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Product details
Overview
LT3973IDD-3.3#TRPBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic step-down regulator with integrated boost and catch Schottky diodes, fixed 3.3V output, 2.5µA quiescent current at 12VIN, and operation down to –40°C. It delivers automotive-grade cold-crank performance with 530mV minimum dropout voltage and low-ripple Burst Mode™ operation.
For engineers reviewing the LT3973IDD-3.3#TRPBF datasheet, LT3973IDD-3.3#TRPBF pinout, LT3973IDD-3.3#TRPBF application, or LT3973IDD-3.3#TRPBF equivalent, key selection criteria include its fixed 3.3V output accuracy (±1.2% over temperature), 10-lead 3mm × 3mm DFN package with exposed thermal pad, integrated diode architecture eliminating external components, and programmable UVLO for battery-supplied systems.
Technical Context
The LT3973IDD-3.3#TRPBF employs current-mode control for fast transient response and stable loop behavior across wide input ranges (4.2V to 42V). Its internal bipolar NPN switch is driven by a bootstrap circuit referenced to the BOOST pin, enabling full saturation even during dropout conditions.
Burst Mode operation reduces no-load supply current to 1.8µA while maintaining output ripple below 10mVP-P. A dedicated power-good (PG) flag asserts when VOUT reaches 90% of regulation, and an accurate programmable EN/UVLO threshold (1.19V rising, 30mV hysteresis) supports reliable startup in automotive battery environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.2% over –40°C to 125°C junction temperature - ensures stable logic rail generation without external feedback resistors. |
| Input Voltage Range | 4.2V to 42V - supports 12V/24V/36V automotive and industrial battery inputs, including cold-crank transients. |
| Quiescent Current | 2.5µA at 12VIN to 3.3VOUT - enables always-on subsystems with multi-year battery life in portable or remote sensors. |
| Maximum Output Current | 750mA continuous - sufficient for powering microcontrollers, CAN transceivers, and analog front-ends in compact designs. |
| Minimum Dropout Voltage | 530mV - maintains regulation when input drops near output, critical for automotive start-stop operation. |
| Switching Frequency Range | 200kHz to 2.2MHz (externally set via RT pin) - allows optimization of inductor size vs. efficiency for space-constrained layouts. |
| Package | 10-lead 3mm × 3mm Plastic DFN with exposed thermal pad - provides low θJA = 40°C/W for high-power-density thermal management. |
Pinout & Package
LT3973IDD-3.3#TRPBF uses a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11) requiring PCB soldering for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Pin 1 (VOUT) | Fixed-output voltage reference node | Internally connected to precision resistor divider; regulates output to 3.3V - no external FB network required. |
| Pin 2 (OUT) | Dropout regulation and boost capacitor charge path | Enables minimum dropout operation; ties to VOUT to activate 530mV dropout comparator and sustain boost voltage during low-VIN. |
| Pin 3 (EN/UVLO) | Enable and undervoltage lockout input | Active-high enable with 1.19V rising threshold and 30mV hysteresis - configurable for battery brownout protection. |
| Pin 4 (VIN) | Main power input | Supplies internal bias and switch driver; rated to 42V absolute max - accepts wide-range unregulated supplies. |
| Pin 5 & Pin 11 (GND) | Power and signal ground | Exposes thermal pad (Pin 11) as GND - mandatory PCB connection for thermal dissipation and noise control. |
| Pin 6 (SW) | Switch node | Connects to inductor; drives external LC filter - carries high di/dt switching current requiring tight layout. |
| Pin 7 (BOOST) | Bootstrap drive voltage source | Accepts external capacitor to generate >VIN gate drive - ensures full NPN switch saturation for low VCE(SAT). |
| Pin 8 (BD) | Boost diode anode and bias regulator input | Connects to boost diode cathode; sources internal regulator when >3.2V - improves light-load efficiency. |
| Pin 9 (PG) | Open-drain power-good flag | Asserts high when VOUT ≥ 90% of 3.3V - used for system sequencing or fault monitoring with external pull-up. |
| Pin 10 (RT) | Frequency programming input | Resistor-to-ground sets switching frequency from 200kHz to 2.2MHz - balances EMI, size, and efficiency. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost and catch Schottky diodes | Eliminates 2 external diodes and associated layout area; reduces BOM count and parasitic losses in high-efficiency 3.3V rails. |
| Low-ripple Burst Mode™ operation | Maintains <10mVP-P output ripple at light loads while drawing only 1.8µA - ideal for noise-sensitive analog or RF subsystems. |
| Accurate programmable EN/UVLO | 1.19V rising threshold with 30mV hysteresis - enables precise battery voltage monitoring for graceful shutdown before deep discharge. |
| Thermal shutdown and catch diode current limit | Protects against shorted outputs and overtemperature faults without external circuitry - enhances reliability in unattended industrial nodes. |
| Power-good (PG) flag with 90% threshold | Provides deterministic system reset or enable signaling - simplifies power sequencing in multi-rail embedded controllers. |
Applications
| Automotive Body Control Module (BCM) | Industrial IoT Sensor Node |
|---|---|
Use Scenario: Powering microcontroller, LIN transceiver, and EEPROM in door module with 9V–16V battery input and cold-crank dips to 4.5V. IC Role / Device Role / Timing Role: Primary 3.3V buck regulator providing stable logic supply with dropout recovery and ultra-low IQ for sleep mode. Use Value: Maintains regulation during 4.5V cold-crank events and draws only 2.5µA in vehicle-off state - extends battery life and prevents module reset. |
Use Scenario: Supplying ARM Cortex-M0+ MCU, LoRaWAN transceiver, and environmental sensors in battery-powered field gateway. IC Role / Device Role / Timing Role: Fixed-output DC/DC converter delivering clean 3.3V rail with minimal quiescent consumption and robust ESD immunity. Use Value: Achieves >85% efficiency at 10mA load and <10mV ripple in Burst Mode - preserves battery capacity and avoids RF interference. |
| Medical Portable Diagnostic Device | Factory Automation I/O Module |
Use Scenario: Generating 3.3V for ADC, op-amps, and Bluetooth LE radio from a 12V medical-grade power adapter with variable line impedance. IC Role / Device Role / Timing Role: High-PSRR, low-noise step-down regulator supporting precision analog signal chain and wireless comms. Use Value: Integrated diodes and low EMI Burst Mode reduce conducted noise - meets IEC 60601-1 EMC requirements without added filtering. |
Use Scenario: Powering isolated digital I/O drivers and RS-485 transceivers in DIN-rail mounted PLC peripheral with 24V DC bus. IC Role / Device Role / Timing Role: Robust 42V-input buck regulator handling 40V transients and delivering 750mA to distributed logic rails. Use Value: Withstands 40V surge events per IEC 61000-4-5 and maintains regulation down to 4.2V - ensures uptime in harsh factory environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMR36503RNXR | 3.3V fixed output, 65V max input, 0.3A output, 26µA IQ - lower current rating and higher quiescent current. | Lacks integrated diodes and cold-crank dropout support; requires external catch diode and larger solution size. | Choose for higher input voltage margin (65V) where 750mA load is not required and board space is less constrained. |
| TPS6286518VRGER | 3.3V fixed output, 16V max input, 6A output, 12µA IQ - much higher current but narrower input range. | Uses external MOSFETs; no integrated diodes; unsuitable for automotive battery inputs above 16V. | Choose for high-current, low-voltage industrial applications (e.g., FPGA core rails) where input stays ≤16V and thermal design accommodates 6A. |
Compared with LMR36503RNXR and TPS6286518VRGER, the LT3973IDD-3.3#TRPBF uniquely combines 42V input tolerance, 750mA output, integrated diodes, and sub-3µA quiescent current - making it optimal for space- and power-constrained automotive and industrial 3.3V point-of-load designs.
Availability
LT3973IDD-3.3#TRPBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical diagnostics, and factory automation I/O modules requiring stable component supply with guaranteed long-term availability.
Supply support for LT3973IDD-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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors for precision, industrial, automotive, and communications applications.
The LT3973 family was designed specifically for high-reliability, wide-input automotive and industrial DC/DC conversion - emphasizing ultralow quiescent current, integrated power devices, and robust fault protection in compact packages.
FAQ
What is the output voltage tolerance of the LT3973IDD-3.3#TRPBF over temperature?
The LT3973IDD-3.3#TRPBF delivers a fixed 3.3V output with ±1.2% accuracy across its full operating junction temperature range of –40°C to 125°C. This is specified in the Electrical Characteristics table under "LT3973-3.3 Output Voltage" with min/max values of 3.26V and 3.366V at temperature extremes. The part achieves this using an internal precision resistor divider and bandgap reference, eliminating external component drift.
Does the LT3973IDD-3.3#TRPBF require external diodes?
No, the LT3973IDD-3.3#TRPBF integrates both the boost Schottky diode and the catch Schottky diode on-die. This eliminates two external components, reduces PCB footprint, and removes layout sensitivity associated with diode placement and parasitics. The integrated diodes are characterized with forward voltages of 820mV (boost) and 550mV (catch) at rated currents, as confirmed in the Electrical Characteristics table.
How does the LT3973IDD-3.3#TRPBF handle automotive cold-crank conditions?
The LT3973IDD-3.3#TRPBF maintains regulation during cold-crank events via its 530mV minimum dropout voltage and ability to operate down to 4.2V input. When VIN approaches VOUT, it extends duty cycle up to ~97.5% and skips switch-off cycles to sustain output. The OUT pin connection to VOUT activates the dropout comparator, ensuring the internal switch remains saturated even at low VIN - a key feature validated in the "Start-Up and Dropout Performance" graph (G23).
What is the purpose of the BD pin on the LT3973IDD-3.3#TRPBF?
The BD (Boost Diode) pin on the LT3973IDD-3.3#TRPBF serves two functions: it connects to the anode of the external boost diode, and - when held above 3.2V - supplies bias current to the internal regulator instead of drawing from VIN. This improves light-load efficiency by reducing input current draw. The BD pin also enables the internal regulator to remain active during low-VIN conditions, supporting reliable startup and regulation.
Can the LT3973IDD-3.3#TRPBF be synchronized to an external clock?
No, the LT3973IDD-3.3#TRPBF does not support external clock synchronization. Its switching frequency is set solely by the resistor connected between the RT pin and ground, with a programmable range of 200kHz to 2.2MHz. Unlike some newer regulators, it lacks an external sync input or phase-lock capability - this is confirmed by the absence of sync-related pins, timing diagrams, or functional descriptions in the datasheet's Block Diagram and Pin Functions sections.
LT3973IDD-3.3#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- 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):
- 4.2V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 750mA
- Frequency - Switching:
- 195kHz ~ 2.15MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3973IDD-3.3#TRPBF FAQ
1.How can I place an order for LT3973IDD-3.3#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973IDD-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 LT3973IDD-3.3#TRPBF reliable?
The price and inventory of LT3973IDD-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 LT3973IDD-3.3#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3973IDD-3.3#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973IDD-3.3#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973IDD-3.3#TRPBF?
LT3973IDD-3.3#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973IDD-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 LT3973IDD-3.3#TRPBF?
For technical support, including LT3973IDD-3.3#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973IDD-3.3#TRPBF requirements.
6.How does Aetrix verify that LT3973IDD-3.3#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3973IDD-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 LT3973IDD-3.3#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3973IDD-3.3#TRPBF?
All LT3973IDD-3.3#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973IDD-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 LT3973IDD-3.3#TRPBF part is unused and in its original packaging.
Return procedure for LT3973IDD-3.3#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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