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Analog Devices Inc. LT3973IDD#TRPBF
- Part No.:
- LT3973IDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3973IDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 750MA 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,098
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Product details
Overview
LT3973IDD#TRPBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic synchronous step-down regulator with integrated boost and catch diodes, 2.5µA quiescent current, and adjustable switching frequency (200kHz–2.2MHz). It delivers fixed 5V output in DFN-10 package and is used in automotive cold-crank power supplies where ultra-low IQ and dropout robustness are critical.
For engineers reviewing the LT3973IDD#TRPBF datasheet, LT3973IDD#TRPBF pinout, LT3973IDD#TRPBF application, or LT3973IDD#TRPBF equivalent, key selection criteria include its 530mV minimum dropout voltage, 1.21V feedback reference accuracy, integrated diode architecture eliminating external components, and thermal shutdown protection across –40°C to 125°C junction range.
Technical Context
The LT3973IDD#TRPBF employs current-mode control for fast transient response and loop stability, with Burst Mode® operation enabling <10mVP-P output ripple at light loads while maintaining 1.8µA no-load supply current. Its bipolar NPN internal switch is driven via an external BOOST capacitor to ensure full saturation even during automotive dropout events.
It features programmable undervoltage lockout (UVLO) with 1.19V rising threshold and 30mV hysteresis, a power-good flag signaling when VOUT reaches 90% of regulation, and dual current limiting: 1.65A switch peak limit and 1.15A catch diode valley limit - both temperature-compensated and specified over full operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.2V to 42V - supports wide automotive battery transients including cold-crank down to 4.2V |
| Output Voltage | Fixed 5V ±1.2% - internally trimmed; no external feedback resistors required |
| Max Output Current | 750mA - sustained delivery under thermal limits in DFN-10 package with exposed pad |
| Quiescent Current | 2.5µA at 12VIN/5VOUT - enables always-on systems with multi-year battery life |
| Switching Frequency | 200kHz to 2.2MHz - set by RT resistor; allows optimization of size vs. efficiency vs. EMI |
| Minimum Dropout Voltage | 530mV - ensures regulation during VIN sag; enforced via OUT pin sensing |
| Power Good Threshold | 90% of regulated output - open-drain PG pin asserts high when VOUT ≥ 4.5V (for 5V version) |
Pinout & Package
LT3973IDD#TRPBF is housed in a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11), requiring PCB soldering for thermal performance (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB/VOUT (Pin 1) | Feedback input / Fixed-output sense | For LT3973IDD#TRPBF (5V variant), this pin is VOUT - internally connected to fixed 5V divider; no external resistors needed |
| OUT (Pin 2) | Dropout voltage sense node | Must be tied to output rail to enable 530mV minimum dropout regulation; if VOUT > 14V, tie to GND |
| EN/UVLO (Pin 3) | Enable and programmable UVLO input | Active-high enable; 1.19V rising threshold with 30mV hysteresis; shutdown draws only 0.75µA |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch; must be locally bypassed with ≥4.7µF ceramic capacitor |
| GND (Pin 5 & Exposed Pad Pin 11) | Power and signal ground | Exposure pad is electrically GND and mandatory for thermal conduction and EMI reduction |
| SW (Pin 6) | Switch node | Connects to inductor; carries high dI/dt; requires tight layout and low-inductance path to GND |
| BOOST (Pin 7) | Bootstrap drive voltage source | Drives internal NPN switch; requires external 0.47µF ceramic capacitor between BOOST and SW |
| BD (Pin 8) | Bias diode anode input | Accepts external bias (≥3.2V) to improve efficiency; also powers internal regulator when active |
| PG (Pin 9) | Power-good open-drain flag | Asserts low until VOUT ≥ 4.5V; requires external pull-up; valid only when VIN > 4.2V and EN high |
| RT (Pin 10) | Frequency programming node | Resistor to GND sets switching frequency; e.g., 215kΩ yields ~600kHz per datasheet table |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost and catch diodes | Eliminates 2 external Schottky diodes, reducing BOM count, board area, and thermal stress |
| Low-ripple Burst Mode® operation | Maintains <10mVP-P output ripple at light loads while drawing only 1.8µA input current |
| Accurate programmable UVLO | 1.19V threshold with ±30mV hysteresis enables precise battery undervoltage cutoff without external comparators |
| Thermal shutdown with hysteresis | Protects against sustained overload; auto-recovery after junction cools below safe threshold |
| Internal catch diode current limit | 1.15A valley limit prevents damage during short-circuit or startup into heavy capacitive load |
Applications
| Automotive Cold-Crank Power Supply | Industrial 24V-to-5V Bias Rail |
|---|---|
Use Scenario: Powering microcontrollers and CAN transceivers during engine start when battery drops to 4.2V–6V. IC Role / Device Role / Timing Role: Primary 5V buck regulator providing stable, low-noise supply despite extreme input sag. Use Value: 530mV dropout and 2.5µA IQ ensure uninterrupted operation and extended battery reserve life. | Use Scenario: Generating isolated 5V logic supply from unregulated 24V industrial bus with high EMI immunity. IC Role / Device Role / Timing Role: Synchronous step-down converter with integrated diodes reducing component count and layout sensitivity. Use Value: 42V max input rating and 750mA output support long cable runs and transient surges without derating. |
| Portable Medical Sensor Node | Gate Drive Bias for High-Side MOSFETs |
Use Scenario: Powering low-power ADCs, sensors, and BLE radios in battery-operated diagnostic devices. IC Role / Device Role / Timing Role: Always-on 5V regulator enabling multi-year operation on coin-cell or LiSOCl₂ batteries. Use Value: 1.8µA no-load current in Burst Mode extends usable battery capacity by >3× versus standard buck ICs. | Use Scenario: Providing clean, regulated 5V gate bias for high-side N-channel MOSFET drivers in motor control H-bridges. IC Role / Device Role / Timing Role: Dedicated bias supply decoupled from noisy power stage, minimizing shoot-through risk. Use Value: Integrated BD pin allows self-bias from output, improving efficiency and eliminating auxiliary winding or LDO. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3973EDD#TRPBF | Same electrical specs and pinout; rated for 0°C to 125°C junction (vs. –40°C to 125°C for LT3973IDD#TRPBF) | Not suitable for extended ambient temperature environments like under-hood automotive | Select LT3973IDD#TRPBF for guaranteed operation at –40°C startup and full industrial temp range. |
| LT3973IMSE#TRPBF | Same functionality but in 10-lead MSOP package; θJA = 45°C/W (vs. 40°C/W for DFN); no exposed thermal pad | Lower power density handling; less effective heat dissipation in compact layouts | Choose LT3973IDD#TRPBF when thermal performance or board space is constrained. |
Compared with LT3973EDD#TRPBF and LT3973IMSE#TRPBF, the LT3973IDD#TRPBF provides guaranteed –40°C operation and superior thermal resistance via its exposed-pad DFN package - critical for automotive and industrial designs requiring reliability across full temperature extremes and high ambient loads.
Availability
LT3973IDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial 24V-to-5V conversion, and portable medical sensor nodes requiring stable component supply with long-term lifecycle assurance.
Supply support for LT3973IDD#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT3973 family.
The LT3973 series was designed as a high-input-voltage, ultralow-IQ buck regulator targeting automotive, industrial, and battery-powered systems needing robust cold-crank performance and minimal standby power loss.
FAQ
What is the guaranteed operating temperature range for LT3973IDD#TRPBF?
The LT3973IDD#TRPBF is specified for –40°C to 125°C junction temperature. This grade (I-grade) ensures full electrical performance across the entire range, including startup at –40°C and sustained operation at 125°C ambient with proper thermal design. The DFN package's exposed pad must be soldered to a thermal plane to achieve θJA = 40°C/W and meet this specification. LT3973IDD#TRPBF is not rated for 150°C operation - that requires the H-grade variant.
Does LT3973IDD#TRPBF require external feedback resistors to set the 5V output?
No. The LT3973IDD#TRPBF is the fixed 5V version of the LT3973 family. Pin 1 is labeled VOUT (not FB), and the internal resistor divider is factory-trimmed to deliver 5V ±1.2% over temperature and line. External resistors are unnecessary and must not be connected - doing so would disrupt regulation. Only the adjustable LT3973 (without suffix) requires FB resistors.
How does the LT3973IDD#TRPBF maintain regulation during automotive cold-crank events?
The LT3973IDD#TRPBF maintains regulation during cold-crank via three coordinated mechanisms: (1) a minimum dropout voltage of 530mV enforced by the OUT pin connection, (2) extended duty cycle up to ~97.5% using BOOST capacitor charge recycling, and (3) current-mode control preserving loop stability at low VIN. Together, these allow continuous 5V output even as input sags to 4.2V - verified in datasheet Figure G22 and cold-crank test conditions.
What is the purpose of the BD pin on LT3973IDD#TRPBF, and how should it be connected?
The BD (Bias Diode) pin on LT3973IDD#TRPBF accepts an external bias voltage ≥3.2V - typically connected to the regulated 5V output. When active, it powers the internal control circuitry instead of drawing from VIN, improving light-load efficiency by ~5–10%. If unused, BD may be left floating or tied to GND; however, connecting it to VOUT is recommended for optimal efficiency. The BD pin also supplies current to the internal regulator during startup.
Can LT3973IDD#TRPBF be synchronized to an external clock?
No. The LT3973IDD#TRPBF does not support external synchronization. Its switching frequency is set solely by the RT-to-GND resistor and operates in free-running constant-frequency PWM mode (200kHz–2.2MHz). Unlike some newer regulators, it lacks an SYNC pin or phase-lock capability. For noise-sensitive applications requiring frequency alignment, designers must select alternate parts such as the LT86xx series or use spread-spectrum techniques at the system level.
LT3973IDD#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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.2V
- Voltage - Input (Max):
- 42V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 24V
- 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#TRPBF FAQ
1.How can I place an order for LT3973IDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973IDD#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#TRPBF reliable?
The price and inventory of LT3973IDD#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#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3973IDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973IDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973IDD#TRPBF?
LT3973IDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973IDD#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#TRPBF?
For technical support, including LT3973IDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973IDD#TRPBF requirements.
6.How does Aetrix verify that LT3973IDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3973IDD#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#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3973IDD#TRPBF?
All LT3973IDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973IDD#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#TRPBF part is unused and in its original packaging.
Return procedure for LT3973IDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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