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Analog Devices Inc. LT3973HDD-3.3#PBF
- Part No.:
- LT3973HDD-3.3#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3973HDD-3.3#PBF.pdf
- Description:
- IC REG BUCK 3.3V 750MA 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:127
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Product details
Overview
LT3973HDD-3.3#PBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic step-down regulator with integrated boost and catch diodes, fixed 3.3V output, 2.5µA quiescent current at 12VIN, and –40°C to 150°C operating junction temperature. It delivers automotive-grade cold-crank performance with 530mV minimum dropout voltage and low-ripple Burst Mode™ operation.
For engineers reviewing the LT3973HDD-3.3#PBF datasheet, LT3973HDD-3.3#PBF pinout, LT3973HDD-3.3#PBF application, or LT3973HDD-3.3#PBF equivalent, key selection criteria include its H-grade thermal rating, fixed 3.3V output accuracy (±1.2% over temperature), integrated diode architecture, and programmable UVLO via EN/UVLO pin - all critical for battery-powered industrial and automotive power rails.
Technical Context
The LT3973HDD-3.3#PBF employs current-mode control with internal slope compensation for fast transient response and loop stability across wide input ranges (4.2V–42V). Its bipolar NPN switch driver uses BOOST-pin bootstrapping to maintain full saturation down to 530mV dropout, enabling reliable operation during automotive cold-crank events.
Burst Mode™ operation reduces no-load supply current to 1.8µA while limiting output ripple to <10mVP-P; the power-good (PG) flag asserts when VOUT reaches 90% of 3.3V, and an accurate programmable undervoltage lockout (UVLO) provides 30mV hysteresis with 0.75µA shutdown current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.2% over –40°C to 150°C junction range - ensures stable logic rail under extreme thermal stress. |
| Input Voltage Range | 4.2V to 42V - supports 12V/24V/36V automotive and industrial battery inputs, including cold-crank dips. |
| Quiescent Current | 2.5µA at 12VIN/3.3VOUT - enables multi-year battery life in always-on sensor nodes. |
| Max Output Current | 750mA continuous - sufficient for powering microcontrollers, CAN transceivers, and analog front-ends. |
| Switching Frequency | 200kHz to 2.2MHz (RT-programmable) - allows optimization of inductor size vs. EMI vs. efficiency. |
| Dropout Voltage | 530mV minimum - maintains regulation when input drops near output, critical for automotive start-stop. |
| Thermal Rating | Junction temperature range –40°C to 150°C - qualified for under-hood and high-ambient industrial environments. |
Pinout & Package
LT3973HDD-3.3#PBF is housed in a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11) soldered to PCB for optimal thermal dissipation (θJA = 40°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT (Pin 1) | Fixed-output feedback node | Internally regulated to 3.3V; connects to output capacitor and load - no external resistor divider required. |
| OUT (Pin 2) | Dropout regulation reference | Tied to VOUT to enforce ≥530mV VIN–VOUT margin; ensures boost capacitor recharge during dropout. |
| EN/UVLO (Pin 3) | Enable and undervoltage lockout input | Active-high enable with 1.19V rising threshold and 30mV hysteresis; programmable UVLO for system brown-out protection. |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch; must be locally bypassed with ≥4.7µF X7R ceramic capacitor. |
| GND (Pin 5 & Exposed Pad 11) | Power and signal ground | Common return for all currents; exposed pad must be soldered to PCB thermal plane for reliability. |
| SW (Pin 6) | Switch node | Connects to inductor; carries high di/dt switching current - requires tight layout and Kelvin grounding. |
| BOOST (Pin 7) | Bootstrap drive voltage | Drives internal NPN switch base; requires external 0.47µF ceramic capacitor between BOOST and SW. |
| BD (Pin 8) | Boost diode anode | Connects to anode of external Schottky diode; supplies bias current to internal regulator when >3.2V. |
| PG (Pin 9) | Power-good open-drain flag | Sinks current when VOUT < 90% of 3.3V; requires external pull-up for system sequencing or fault indication. |
| RT (Pin 10) | Frequency setting | Resistor-to-ground sets switching frequency from 200kHz to 2.2MHz - enables EMI tuning and component miniaturization. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated boost and catch diodes | Eliminates 2 external Schottky diodes, reducing BOM count, board area, and thermal hotspots. |
| Low-ripple Burst Mode™ operation | Maintains <10mVP-P output ripple at light loads while achieving 1.8µA no-load IQ - ideal for always-on IoT sensors. |
| Accurate programmable UVLO | EN/UVLO pin provides precise, hysteresis-controlled startup/shutdown - prevents erratic behavior during battery sag. |
| Power-good (PG) flag with 90% threshold | Enables safe microcontroller reset sequencing and system-level power monitoring without external comparators. |
| H-grade temperature qualification | Guaranteed operation from –40°C to 150°C junction - validated for under-hood automotive and harsh industrial use. |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC I/O Power Rail |
|---|---|
Use Scenario: Powering microcontrollers, CAN transceivers, and sensor interfaces in vehicle door modules and lighting controllers during cold-crank (5V battery dip to 3.2V). IC Role / Device Role / Timing Role: Primary 3.3V buck regulator delivering regulated logic supply with dropout recovery below 4.2V input. Use Value: 530mV dropout and 150°C rating ensure uninterrupted operation in engine-compartment-mounted BCMs. | Use Scenario: Generating isolated 3.3V supply for analog input conditioning circuits and digital isolators in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Fixed-output DC-DC converter providing low-noise, low-quiescent power for precision ADC references and SPI interfaces. Use Value: 2.5µA IQ extends backup battery life; integrated diodes reduce thermal stress in sealed enclosures. |
| Portable Medical Diagnostic Device | Smart Building Sensor Node |
Use Scenario: Powering low-power ARM Cortex-M microcontrollers and biopotential amplifiers in handheld ECG monitors powered by single-cell Li-ion batteries. IC Role / Device Role / Timing Role: Primary step-down regulator converting 3.6V–4.2V battery to stable 3.3V rail with ultra-low standby consumption. Use Value: 1.8µA Burst Mode IQ enables multi-year battery life; fixed 3.3V eliminates calibration drift from resistor tolerance. | Use Scenario: Supplying 3.3V to LoRaWAN transceivers, environmental sensors, and real-time clocks in battery-operated occupancy and air-quality nodes deployed in HVAC ducts. IC Role / Device Role / Timing Role: High-efficiency buck converter supporting intermittent transmit bursts and long sleep cycles. Use Value: 750mA peak current handles RF transmit surges; 42V max input accommodates wide-range energy harvesting inputs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3630EMSE-3.3#PBF | Lower 36V max input, 500mA output, 17µA IQ - no integrated catch diode; requires external Schottky. | Targeted at space-constrained but thermally benign applications; lacks cold-crank capability. | Select when board area is critical and ambient temperature stays <85°C; verify external diode thermal design. |
| MPQ4420AGL-AEC1-P | Automotive AEC-Q200 qualified, 42V/2A, 2.5µA IQ, but fixed 3.3V version not available - requires FB resistor network. | Designed for higher-current automotive loads; lacks PG flag and programmable UVLO. | Choose for AEC-Q200 compliance and >750mA needs; add external feedback resistors and PG comparator if required. |
Compared with LTC3630EMSE-3.3#PBF, LT3973HDD-3.3#PBF offers superior cold-crank resilience and integrated diodes; versus MPQ4420AGL-AEC1-P, it provides simpler fixed-output implementation and built-in power-good signaling - both tradeoffs impact BOM count, thermal management, and functional safety architecture.
Availability
LT3973HDD-3.3#PBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC power supplies, and portable medical diagnostics requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3973HDD-3.3#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 its high-performance power management portfolio with rigorous automotive and industrial qualification standards.
The LT3973 family was designed specifically for high-input-voltage, low-quiescent-current buck conversion in harsh environments - emphasizing cold-crank survival, thermal robustness, and integration to reduce external component count.
FAQ
What is the guaranteed operating temperature range for LT3973HDD-3.3#PBF?
The LT3973HDD-3.3#PBF is fully specified and guaranteed over a junction temperature range of –40°C to 150°C. This H-grade rating is validated per Linear Technology's characterization and statistical process controls, making it suitable for under-hood automotive and high-ambient industrial applications where standard E- and I-grade variants would fail.
Does LT3973HDD-3.3#PBF require external feedback resistors to set the output voltage?
No. The LT3973HDD-3.3#PBF features an internally trimmed 3.3V output; Pin 1 is labeled VOUT and connects directly to the output capacitor and load. Unlike the adjustable LT3973 variant, no external resistor divider is needed - simplifying layout and eliminating resistor tolerance-induced output error.
How does LT3973HDD-3.3#PBF achieve 530mV minimum dropout voltage?
The LT3973HDD-3.3#PBF enforces a minimum 530mV difference between VIN and VOUT by regulating the OUT pin (Pin 2) to maintain this margin. When VIN approaches VOUT, the IC extends duty cycle up to ~97.5% and manages boost capacitor recharge to sustain switch saturation - enabling regulation during automotive cold-crank events down to ~3.8V input.
What is the function of the BD pin on LT3973HDD-3.3#PBF?
The BD (Boost Diode) pin on LT3973HDD-3.3#PBF connects to the anode of the external Schottky boost diode. When BD voltage exceeds 3.2V, the IC draws bias current from this pin instead of VIN - improving light-load efficiency. It also supplies current to the internal regulator, reducing VIN supply current during normal operation.
Can LT3973HDD-3.3#PBF be used without the external boost capacitor?
No. The LT3973HDD-3.3#PBF requires a 0.47µF ceramic capacitor between BOOST (Pin 7) and SW (Pin 6) to generate the elevated gate drive voltage needed for full saturation of its internal bipolar NPN switch. Omitting this capacitor causes excessive switch VCE(SAT), thermal runaway, and immediate failure - the datasheet explicitly mandates this component.
LT3973HDD-3.3#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:
- 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 ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3973HDD-3.3#PBF FAQ
1.How can I place an order for LT3973HDD-3.3#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973HDD-3.3#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-3.3#PBF reliable?
The price and inventory of LT3973HDD-3.3#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-3.3#PBF is usually 5 days.
3.What payment methods are accepted for LT3973HDD-3.3#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973HDD-3.3#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973HDD-3.3#PBF?
LT3973HDD-3.3#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973HDD-3.3#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-3.3#PBF?
For technical support, including LT3973HDD-3.3#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973HDD-3.3#PBF requirements.
6.How does Aetrix verify that LT3973HDD-3.3#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973HDD-3.3#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-3.3#PBF meets industry standards.
7.What is the process for return or replacement of LT3973HDD-3.3#PBF?
All LT3973HDD-3.3#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973HDD-3.3#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-3.3#PBF part is unused and in its original packaging.
Return procedure for LT3973HDD-3.3#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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