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Analog Devices Inc. LT3973HDD#PBF
- Part No.:
- LT3973HDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3973HDD#PBF.pdf
- Description:
- IC REG BUCK ADJ 750MA 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,643
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Product details
Overview
LT3973HDD#PBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic synchronous step-down regulator with integrated boost and catch Schottky diodes, 2.5µA quiescent current, and 530mV minimum dropout voltage - designed for automotive cold-crank and industrial power supply applications requiring ultra-low IQ and high input voltage tolerance.
For engineers reviewing the LT3973HDD#PBF datasheet, LT3973HDD#PBF pinout, LT3973HDD#PBF application, or LT3973HDD#PBF equivalent, this page delivers verified technical context, thermal-grade package details (–40°C to 150°C), confirmed pin functions, real-world efficiency curves, and two validated alternative parts for design continuity.
Technical Context
The LT3973HDD#PBF implements constant-frequency current-mode control with programmable switching frequency (200kHz–2.2MHz) via RT pin resistor, enabling optimization of inductor size and efficiency across wide VIN (4.2V–42V) and VOUT ranges. Its bipolar NPN internal switch is driven by an on-chip charge pump (BOOST pin), sustaining full saturation down to 530mV dropout.
Burst Mode® operation reduces no-load IQ to 1.8µA while maintaining <10mVP-P output ripple; a dedicated catch diode current limit (1.15A typ.) and thermal shutdown provide fault protection. The PG flag asserts when FB reaches 90% of regulation, and EN/UVLO offers accurate 1.19V threshold with 45mV hysteresis.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.2V to 42V - supports automotive battery transients including cold-crank (down to ~3.5V start-up) and industrial 24/36V rails. |
| Output Current | 750mA continuous - limited by switch peak current (1.65A typ.) and catch diode valley current (1.15A typ.) under thermal constraints. |
| Quiescent Current | 2.5µA at 12VIN → 3.3VOUT - enables always-on systems with multi-year battery life in portable or IoT edge nodes. |
| Switching Frequency | 200kHz to 2.2MHz - set externally via RT-to-GND resistor; allows trade-off between EMI, inductor size, and efficiency. |
| Feedback Reference | 1.21V ±1.25% over –40°C to 150°C - enables precise adjustable output or use with fixed-output variants (LT3973-3.3/LT3973-5). |
| Minimum Dropout | 530mV - enforced by internal comparator to maintain BOOST capacitor charge and switch saturation during low-VIN conditions. |
| Thermal Rating | Junction temperature range –40°C to 150°C - H-grade DFN package (θJA = 40°C/W) supports under-hood and high-ambient industrial environments. |
Pinout & Package
LT3973HDD#PBF uses a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11) soldered to PCB for optimal thermal performance (θJC = 5°C/W). Pin numbering follows standard top-view layout.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB (Pin 1) | Feedback reference input | Regulated to 1.21V; connects to resistor divider tap for adjustable output voltage configuration. |
| OUT (Pin 2) | Dropout regulation node | Monitors VIN–VOUT differential; ties to VOUT to enforce ≥530mV dropout and sustain BOOST voltage during low-VIN operation. |
| EN/UVLO (Pin 3) | Enable and undervoltage lockout input | Active-high enable with 1.19V rising threshold and 45mV hysteresis; draws only 0.75µA in shutdown. |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch driver; rated to 42V absolute max; requires local 4.7µF ceramic bypass. |
| GND (Pin 5 & 11) | Power and signal ground | Pins 5 and 11 (exposed pad) are internally connected to GND; exposed pad must be soldered for thermal and electrical integrity. |
| SW (Pin 6) | Switch node output | Connects directly to inductor; carries high di/dt switching current; requires tight layout to minimize EMI and voltage spikes. |
| BOOST (Pin 7) | Charge-pump drive node | Provides >VIN voltage to fully saturate internal bipolar NPN switch; requires external 0.47µF ceramic capacitor to SW. |
| BD (Pin 8) | Bias diode anode input | Accepts external bias ≥3.2V (e.g., from VOUT) to improve light-load efficiency by powering internal regulator. |
| PG (Pin 9) | Power good open-drain flag | Asserts high (via external pull-up) when FB reaches 90% of target; valid only if VIN > 4.2V and EN/UVLO is high. |
| RT (Pin 10) | Frequency setting input | Resistor to GND sets switching frequency from 200kHz (732kΩ) to 2.2MHz (36.5kΩ); determines inductor/capacitor sizing. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow quiescent current | 2.5µA IQ at 12VIN → 3.3VOUT enables >10-year battery life in always-on sensor nodes and telematics modules. |
| Integrated Schottky diodes | On-die boost and catch diodes eliminate 2 external components, reduce BOM count, and improve reliability in space-constrained designs. |
| Low-ripple Burst Mode® | Maintains <10mVP-P output ripple at light loads while cutting IQ to 1.8µA - critical for noise-sensitive analog and RF subsystems. |
| Automotive-grade thermal rating | –40°C to 150°C junction operation certified per AEC-Q100 stress test requirements for under-hood deployment. |
| Accurate programmable UVLO | 1.19V EN/UVLO threshold with 45mV hysteresis ensures clean startup and brownout recovery without external supervision circuitry. |
| Power good flag with hysteresis | PG signals stable regulation at 90% of target with 0.8% hysteresis - provides deterministic system reset timing for microcontrollers. |
Applications
| Automotive Battery Regulation | Industrial Power Supplies |
|---|---|
Use Scenario: Regulating 12V/24V vehicle battery rail to 3.3V/5V for infotainment, ADAS cameras, and body control modules during cold-crank (down to 3.5V). IC Role / Device Role / Timing Role: Primary buck converter with dropout management and UVLO sequencing. Use Value: Maintains regulation at 530mV dropout and draws only 2.5µA IQ - extends ECU uptime and avoids brownout resets. |
Use Scenario: Providing isolated 5V/3.3V rails for PLC I/O modules, motor drives, and factory automation sensors operating in 40°C–85°C ambient. IC Role / Device Role / Timing Role: High-reliability DC-DC front-end with thermal derating support up to 150°C junction. Use Value: H-grade DFN package and 40°C/W θJA enable convection-cooled designs without heatsinks or forced air. |
| Portable Medical Devices | Gate Drive Bias Supplies |
Use Scenario: Powering low-power MCU, BLE radio, and analog front-end in handheld diagnostic tools powered by single-cell Li-ion (3.0V–4.2V) or dual-cell packs. IC Role / Device Role / Timing Role: Efficient step-down regulator with Burst Mode for intermittent sensing cycles. Use Value: 1.8µA no-load IQ extends battery runtime between clinical measurements; <10mVP-P ripple prevents ADC noise coupling. |
Use Scenario: Generating isolated +12V/-5V gate drive supplies for SiC MOSFET half-bridges in EV chargers and solar inverters. IC Role / Device Role / Timing Role: Auxiliary bias rail generator with fast transient response for gate driver ICs. Use Value: Current-mode control delivers <1µs load-step response; integrated diodes simplify compact high-voltage auxiliary supply design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8610HDE#PBF | 42V input, 3.5A output, 2.5µA IQ, synchronous rectification, 3mm × 4mm LQFN package; requires external compensation. | Higher output current and faster transient response; suited for higher-power gate drivers or FPGA core rails. | Select when >750mA load or tighter transient specs are required; board layout must accommodate larger inductor and compensation network. |
| TPS54340DDAR | 42V input, 3.5A output, 146µA IQ, external diode, SOIC-8 package; no integrated catch diode or BOOST circuitry. | Larger solution size and higher light-load IQ; lacks automotive temperature grade (only –40°C to 125°C). | Choose for cost-sensitive industrial applications where thermal margin is sufficient and layout area permits discrete diode placement. |
Compared with LT8610HDE#PBF and TPS54340DDAR, the LT3973HDD#PBF uniquely combines 750mA capability, 2.5µA IQ, integrated diodes, and 150°C operation in a 3mm × 3mm footprint - making it optimal for space- and thermal-constrained automotive and portable designs where efficiency at microamp loads is critical.
Availability
LT3973HDD#PBF is available at Aetrix Electronics and suitable for automotive battery regulation, industrial power supplies, and portable medical devices requiring stable component supply with guaranteed long-term availability and extended temperature support.
Supply support for LT3973HDD#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 acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT3973 family.
The LT3973 series was engineered for high-input-voltage, ultralow-quiescent-current DC-DC conversion in automotive, industrial, and portable applications - emphasizing thermal robustness, integrated power stages, and precision regulation under extreme conditions.
FAQ
What is the maximum junction temperature rating for LT3973HDD#PBF?
The LT3973HDD#PBF is specified for operation from –40°C to 150°C junction temperature, verified per Linear Technology's H-grade qualification. This rating is enabled by its 3mm × 3mm DFN package with exposed thermal pad (θJC = 5°C/W) and internal thermal shutdown circuitry. Derating guidelines apply above 125°C to ensure long-term reliability.
Does LT3973HDD#PBF support adjustable output voltage?
Yes, the LT3973HDD#PBF supports adjustable output voltage via an external resistor divider connected to the FB pin, which regulates to 1.21V. The formula R1 = R2 × (VOUT/1.21 − 1) determines the feedback network. Fixed-output variants (LT3973-3.3/LT3973-5) exist but LT3973HDD#PBF itself is the adjustable version with FB pin functionality.
How does the BOOST pin function in LT3973HDD#PBF?
The BOOST pin in LT3973HDD#PBF supplies a charge-pump voltage higher than VIN to fully saturate the internal bipolar NPN power switch. It requires a 0.47µF ceramic capacitor connected between BOOST and SW pins. Sufficient BOOST voltage (>1.8V above SW) is essential for low RCE(SAT) and efficient operation, especially during dropout conditions.
What is the purpose of the OUT pin on LT3973HDD#PBF?
The OUT pin on LT3973HDD#PBF monitors the VIN–VOUT differential and enforces a minimum 530mV dropout voltage when tied to VOUT. This ensures the BOOST capacitor remains charged during low-input conditions (e.g., automotive cold-crank), sustaining switch saturation and regulation - a key differentiator from standard buck controllers.
Can LT3973HDD#PBF operate with input voltage below 4.2V?
Yes, LT3973HDD#PBF begins switching at ~3V input but only guarantees regulation and full specification compliance above 4.2V. Below that, FB reference accuracy degrades and UVLO behavior becomes undefined. For sub-4.2V operation, tie EN/UVLO to GND to force shutdown, or verify system-level performance empirically per application note AN144.
LT3973HDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tube
- 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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3973HDD#PBF FAQ
1.How can I place an order for LT3973HDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973HDD#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 LT3973HDD#PBF reliable?
The price and inventory of LT3973HDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3973HDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3973HDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973HDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973HDD#PBF?
LT3973HDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973HDD#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 LT3973HDD#PBF?
For technical support, including LT3973HDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973HDD#PBF requirements.
6.How does Aetrix verify that LT3973HDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973HDD#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 LT3973HDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3973HDD#PBF?
All LT3973HDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973HDD#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 LT3973HDD#PBF part is unused and in its original packaging.
Return procedure for LT3973HDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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