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Analog Devices Inc. LT3973IMSE-3.3#PBF
- Part No.:
- LT3973IMSE-3.3#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3973IMSE-3.3#PBF.pdf
- Description:
- IC REG BUCK 3.3V 750MA 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:151
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Product details
Overview
LT3973IMSE-3.3#PBF 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 low-ripple Burst Mode™ operation. It delivers automotive-grade performance in cold-crank scenarios with 530mV minimum dropout voltage and power-good flag signaling.
For engineers reviewing the LT3973IMSE-3.3#PBF datasheet, LT3973IMSE-3.3#PBF pinout, LT3973IMSE-3.3#PBF application, or LT3973IMSE-3.3#PBF equivalent, key selection criteria include its 3.3V fixed output accuracy (±1.2% over –40°C to 125°C), 10-lead MSOP package with exposed thermal pad, integrated diode architecture eliminating external components, and programmable UVLO via EN/UVLO pin.
Technical Context
The LT3973IMSE-3.3#PBF employs constant-frequency current-mode control with adjustable switching frequency (200kHz–2.2MHz via RT resistor) and supports extended duty cycle up to ~97.5% during dropout. Its bipolar NPN internal switch is driven by a charge-pump boosted gate voltage (via BOOST pin), enabling full saturation even at low input-to-output differentials.
Burst Mode operation reduces no-load supply current to 1.8µA while maintaining output ripple below 10mVP-P; the power-good (PG) flag asserts when VOUT reaches 90% of regulation, and an internal catch diode current limit (1.15A typical) provides short-circuit protection alongside thermal shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±1.2% over –40°C to 125°C; eliminates external feedback resistors. |
| Input Voltage Range | 4.2V to 42V operating; supports automotive battery transients and industrial 24V/36V rails. |
| Quiescent Current | 2.5µA at 12VIN to 3.3VOUT; enables always-on systems with multi-year battery life. |
| Max Output Current | 750mA continuous; limited by switch peak current (1.65A typ) and catch diode valley current (1.15A typ). |
| Switching Frequency | Programmable 200kHz–2.2MHz via RT pin; balances efficiency, EMI, and passive size. |
| Minimum Dropout Voltage | 530mV at full load; maintains regulation during automotive cold-crank (e.g., 5.5VIN → 3.3VOUT). |
| Power Good Flag | Open-drain PG asserts when VOUT ≥ 90% of 3.3V; enables system sequencing and fault monitoring. |
Pinout & Package
LT3973IMSE-3.3#PBF uses a thermally enhanced 10-lead plastic MSOP package with exposed GND pad (Pin 11), θJA = 45°C/W. The exposed pad must be soldered to PCB for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VOUT (Pin 1) | Fixed-output regulation node | Internally connected to precision 3.3V feedback divider; no external resistors required. |
| OUT (Pin 2) | Dropout regulation & boost capacitor charging node | Tied to VOUT to enable 530mV dropout mode; supplies current to charge BOOST capacitor. |
| EN/UVLO (Pin 3) | Enable and programmable undervoltage lockout input | 1.19V rising threshold with 30mV hysteresis; shutdown draws only 0.75µA. |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch; requires local 4.7µF ceramic bypass. |
| GND (Pin 5 & 11) | Signal and power ground | Pin 11 is exposed thermal pad; must be soldered to PCB copper for thermal management. |
| SW (Pin 6) | Internal switch drain node | Connects to inductor; carries high di/dt switching current; layout critical for EMI. |
| BOOST (Pin 7) | Charge-pump bootstrap drive | Drives internal NPN switch base above VIN; requires 0.47µF ceramic capacitor to SW. |
| BD (Pin 8) | Boost diode anode connection | Accepts external bias >3.2V to improve efficiency; also powers internal regulator. |
| PG (Pin 9) | Power-good open-drain output | Sinks 350µA max; pulled high externally to indicate valid 3.3V output. |
| RT (Pin 10) | Frequency programming input | Resistor to GND sets switching frequency; 215kΩ yields 600kHz per datasheet. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky diodes | Eliminates two external diodes (boost + catch), reducing BOM count, footprint, and thermal stress. |
| Low-ripple Burst Mode™ | Maintains <10mVP-P output ripple at light loads while achieving 1.8µA no-load IQ. |
| Accurate programmable UVLO | EN/UVLO pin allows custom start-up voltage (e.g., 6.5V) with 30mV hysteresis to prevent oscillation. |
| Thermally robust MSOP package | 10-lead MSOP with exposed pad achieves θJA = 45°C/W - suitable for high-density industrial PCBs. |
| Automotive-ready dropout performance | 530mV minimum dropout enables stable 3.3V output down to 3.83V input - meets ISO 16750-2 cold-crank. |
Applications
| Automotive Body Control Module | Industrial Sensor Node Power |
|---|---|
Use Scenario: Powering microcontrollers, CAN transceivers, and LIN interfaces in door modules under cold-crank (5.5V battery). IC Role / Device Role / Timing Role: Primary 3.3V buck regulator with integrated diodes and PG flag for system reset coordination. Use Value: Maintains regulation at 530mV dropout, avoids brown-out resets, and reduces component count vs. discrete diode solutions. | Use Scenario: Supplying ultra-low-power wireless sensor nodes (e.g., LoRaWAN edge devices) with 10-year battery life. IC Role / Device Role / Timing Role: Always-on 3.3V supply with 2.5µA quiescent current and Burst Mode for intermittent wake-up cycles. Use Value: Extends battery life by minimizing no-load losses while preserving low-noise output for ADC references. |
| Portable Medical Instrument Bias | Gate Drive Auxiliary Supply |
Use Scenario: Generating clean 3.3V for analog front-ends and low-noise op-amps in handheld ultrasound probes. IC Role / Device Role / Timing Role: Low-ripple, low-noise DC-DC stage following primary 12V/24V input conversion. Use Value: Delivers <10mVP-P ripple in Burst Mode, avoiding interference with sensitive signal chains. | Use Scenario: Providing isolated 3.3V bias for high-side gate drivers in motor control inverters with 42V bus. IC Role / Device Role / Timing Role: Compact, thermally efficient auxiliary supply replacing discrete boost + LDO chain. Use Value: Integrated diodes and 750mA capability support fast gate charging without external diode thermal derating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3973IMSE#PBF | Adjustable output (1.21V FB pin); requires external R1/R2 divider; same package, temp grade, and specs otherwise. | Used where flexible output voltage (e.g., 2.5V, 3.6V) or dynamic scaling is needed. | Select LT3973IMSE#PBF if output voltage must be reconfigured; LT3973IMSE-3.3#PBF saves BOM cost and layout space for fixed 3.3V. |
| LMR36506RKAR | 65V-input, 600mA, 2.1µA IQ, but uses external catch diode; no integrated boost diode; smaller 3mm × 2mm WSON. | Preferred for higher input voltage margin (>42V) or space-constrained designs where external diode is acceptable. | Choose LMR36506RKAR only if 65V rating is mandatory and board area is critical; LT3973IMSE-3.3#PBF offers superior integration and cold-crank robustness. |
Compared with LT3973IMSE#PBF, the LT3973IMSE-3.3#PBF eliminates feedback resistors and improves design simplicity for 3.3V systems, while the LMR36506RKAR trades integration for wider input range and smaller footprint - neither is pin-compatible, and both require layout revision.
Availability
LT3973IMSE-3.3#PBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical instruments, and gate drive auxiliary supplies requiring stable component supply across extended temperature ranges.
Supply support for LT3973IMSE-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 full product support, datasheets, and application engineering for legacy Linear parts including the LT3973 family.
The LT3973 product line was designed for high-reliability, wide-input-voltage DC-DC conversion in automotive, industrial, and portable applications where low quiescent current, integrated diodes, and robust dropout performance are critical.
FAQ
What is the guaranteed output voltage tolerance for LT3973IMSE-3.3#PBF over temperature?
The LT3973IMSE-3.3#PBF guarantees a 3.3V output with ±1.2% tolerance across the full –40°C to 125°C junction temperature range, as specified in the Electrical Characteristics table (3.26V to 3.34V min/max). This accuracy is achieved via laser-trimmed internal feedback resistors and applies regardless of input voltage or load within rated conditions.
Can LT3973IMSE-3.3#PBF operate with input voltage below 4.2V?
Yes - the LT3973IMSE-3.3#PBF begins switching at ~3V input, but regulation degrades below 4.2V. Below this threshold, the FB reference voltage drops, causing output voltage to fall proportionally. For reliable 3.3V regulation, VIN must remain ≥4.2V; the part's 530mV dropout ensures operation down to 3.83V input under full load.
How does the BOOST pin function in LT3973IMSE-3.3#PBF, and what capacitor value is required?
The BOOST pin supplies gate drive voltage >VIN to fully saturate the internal bipolar NPN switch. A 0.47µF X7R ceramic capacitor must be placed between BOOST and SW pins. This capacitor is charged during switch-off time and replenished each cycle; insufficient capacitance causes increased VCE(SAT) and reduced efficiency, especially at high duty cycles.
Is LT3973IMSE-3.3#PBF compatible with lead-free reflow processes?
Yes - LT3973IMSE-3.3#PBF carries the #PBF suffix indicating 100% matte tin lead-free finish and is qualified for standard Pb-free reflow profiles, including peak temperatures up to 260°C (JEDEC J-STD-020). The MSOP package's maximum soldering temperature is rated at 300°C for 10 seconds, providing process margin.
Does LT3973IMSE-3.3#PBF require an external catch diode?
No - the LT3973IMSE-3.3#PBF integrates both the boost Schottky diode (anode on BD pin) and the catch Schottky diode (cathode on SW pin, anode on OUT pin). No external diodes are needed for basic operation, simplifying layout and improving reliability versus discrete solutions.
LT3973IMSE-3.3#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) 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 ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP-EP
LT3973IMSE-3.3#PBF FAQ
1.How can I place an order for LT3973IMSE-3.3#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973IMSE-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 LT3973IMSE-3.3#PBF reliable?
The price and inventory of LT3973IMSE-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 LT3973IMSE-3.3#PBF is usually 5 days.
3.What payment methods are accepted for LT3973IMSE-3.3#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973IMSE-3.3#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973IMSE-3.3#PBF?
LT3973IMSE-3.3#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973IMSE-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 LT3973IMSE-3.3#PBF?
For technical support, including LT3973IMSE-3.3#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973IMSE-3.3#PBF requirements.
6.How does Aetrix verify that LT3973IMSE-3.3#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973IMSE-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 LT3973IMSE-3.3#PBF meets industry standards.
7.What is the process for return or replacement of LT3973IMSE-3.3#PBF?
All LT3973IMSE-3.3#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973IMSE-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 LT3973IMSE-3.3#PBF part is unused and in its original packaging.
Return procedure for LT3973IMSE-3.3#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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