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Analog Devices Inc. LT3973IMSE-5#PBF
- Part No.:
- LT3973IMSE-5#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
LT3973IMSE-5#PBF.pdf
- Description:
- IC REG BUCK 5V 750MA 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:407
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Product details
Overview
LT3973IMSE-5#PBF from Analog Devices (formerly Linear Technology) is a 42V, 750mA monolithic step-down DC/DC regulator with integrated boost and catch diodes, 2.5µA quiescent current, fixed 5V output, and operation down to 4.2V input - designed for automotive cold-crank and industrial power supply applications where ultra-low IQ and dropout robustness are critical.
For engineers reviewing the LT3973IMSE-5#PBF datasheet, LT3973IMSE-5#PBF pinout, LT3973IMSE-5#PBF application, or LT3973IMSE-5#PBF equivalent, key selection considerations include its 530mV minimum dropout voltage, programmable UVLO via EN/UVLO pin, open-drain power good flag, and thermal shutdown protection in the 10-lead MSOP package.
Technical Context
The LT3973IMSE-5#PBF implements constant-frequency current-mode control with adjustable switching frequency (200kHz–2.2MHz) set by an external RT resistor. Its internal bipolar NPN switch is driven by a charge-pump boosted gate voltage, enabling full saturation even during low-VIN dropout conditions.
Burst Mode® operation maintains high efficiency at light loads (<10mVP-P output ripple), while integrated protection includes catch diode current limiting (1.15A typ), thermal shutdown, and accurate 90% power-good detection referenced to the regulated 5V output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 5.0V ±1.2% over –40°C to 125°C junction temperature |
| Input Voltage Range | 4.2V to 42V - supports automotive battery transients and wide industrial rails |
| Quiescent Current | 2.5µA at 12VIN/5VOUT - enables always-on systems with multi-year battery life |
| Output Current | 750mA continuous - limited by thermal design and switch/catch diode current limits |
| Minimum Dropout | 530mV - ensures regulation during automotive cold-crank (e.g., 5.5VIN → 5VOUT) |
| Switching Frequency | Programmable 200kHz–2.2MHz via RT pin - balances efficiency, size, and EMI |
| Power Good Flag | Open-drain PG asserts when VOUT reaches 90% of 5V (4.5V) - enables system sequencing |
Pinout & Package
LT3973IMSE-5#PBF is housed in a thermally enhanced 10-lead plastic MSOP package (3mm × 3mm footprint) with exposed pad (Pin 11) required to be soldered to PCB ground for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| FB/VOUT (Pin 1) | Feedback / Fixed-output sense | For LT3973IMSE-5#PBF: internally connected to 5V regulation divider - no external resistors needed |
| OUT (Pin 2) | Dropout regulation node | Enables minimum dropout enforcement (530mV); tie to VOUT for standard operation |
| EN/UVLO (Pin 3) | Enable & undervoltage lockout input | Active-high enable with 1.19V threshold (30mV hysteresis); sets shutdown IQ = 0.75µA |
| VIN (Pin 4) | Main power input | Supplies internal circuitry and switch; must be locally bypassed with ≥4.7µF ceramic |
| GND (Pin 5 & Exposed Pad 11) | Power and signal reference | Exposure pad is electrically GND and mandatory for thermal conduction (θJA = 45°C/W) |
| SW (Pin 6) | Switch node | Connects to inductor; carries high di/dt - requires tight layout and Kelvin return path |
| BOOST (Pin 7) | Charge-pump bootstrap supply | Drives internal NPN switch gate above VIN; requires 0.47µF ceramic capacitor to SW |
| BD (Pin 8) | Boost diode anode bias | Accepts external bias >3.2V to improve efficiency; also powers internal regulator |
| PG (Pin 9) | Power good open-drain output | Sinks ≥220µA when active; requires external pull-up to monitor 5V rail stability |
| RT (Pin 10) | Frequency programming | Resistor to GND sets switching frequency (e.g., 215kΩ → 600kHz per datasheet Table 1) |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow quiescent current | 2.5µA IQ enables >10-year battery life in always-on automotive sensors and IoT edge nodes |
| Integrated power diodes | On-die boost and catch Schottky diodes eliminate 2 external components and reduce board area |
| Low-ripple Burst Mode® | Maintains <10mVP-P output ripple at light loads while sustaining >85% efficiency at 1mA |
| Accurate programmable UVLO | EN/UVLO pin allows custom start-up voltage (e.g., 5.5V) with 30mV hysteresis to prevent chatter |
| Robust dropout performance | 530mV enforced minimum dropout preserves regulation during 6V automotive cranking events |
| Thermal and fault protection | Thermal shutdown + catch diode current limit + open-drain PG provide layered reliability for unattended systems |
Applications
| Automotive Body Control Module (BCM) | Industrial PLC I/O Power |
|---|---|
Use Scenario: Powering microcontrollers, CAN transceivers, and sensor interfaces in under-hood BCMs exposed to 4V–42V battery transients and –40°C–125°C ambient. IC Role / Device Role / Timing Role: Primary 5V point-of-load regulator delivering stable rail despite cold-crank (5.5VIN) and load dump (42VIN) events. Use Value: 2.5µA IQ extends backup battery life; 530mV dropout ensures uninterrupted MCU operation during cranking; integrated diodes reduce BOM count by two. |
Use Scenario: Generating isolated 5V logic supply for digital I/O modules in factory automation controllers operating continuously in 45°C enclosures. IC Role / Device Role / Timing Role: High-reliability buck converter powering FPGA configuration, level shifters, and opto-isolator LEDs. Use Value: Thermal shutdown and current limiting protect against sustained overloads; PG flag enables safe firmware-initiated shutdown before thermal derating. |
| Portable Medical Instrumentation | Gate Drive Bias Supply |
Use Scenario: Powering low-power ADCs, Bluetooth LE radios, and touch controllers in handheld diagnostic devices powered by single-cell Li-ion (3.0V–4.2V) with boost-buck architecture. IC Role / Device Role / Timing Role: Secondary 5V rail generator accepting wide-input upstream DC/DC output (e.g., 5V–24V). Use Value: Burst Mode® delivers <10mVP-P ripple for noise-sensitive analog front-ends; 0.75µA shutdown IQ preserves standby battery capacity. |
Use Scenario: Providing clean, regulated 5V bias for high-side gate drivers in motor inverters and SMPS half-bridges requiring precise timing margins. IC Role / Device Role / Timing Role: Dedicated auxiliary supply decoupled from main power stage to avoid switching noise coupling into gate drive paths. Use Value: Low EMI due to programmable frequency and integrated diodes; PG flag synchronizes driver enable with stable 5V rail establishment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#PBF | 42V input, 5V fixed, 2A output, 2.5µA IQ, synchronous rectification, 3mm × 4mm LQFN | Higher output current (2A vs 750mA); requires external compensation; no integrated catch diode | Select when >1A load or tighter thermal constraints demand synchronous efficiency; verify loop stability with external compensation network. |
| TPS54331DR | 28V input, 5V fixed, 3A output, 4.5µA IQ, external diode, SOIC-8 | Lower max input (28V vs 42V); higher IQ; no integrated diodes; larger SOIC-8 footprint | Choose for cost-sensitive industrial supplies where 28V input suffices and external diode layout is acceptable; not suitable for automotive cold-crank. |
Compared with LT3973IMSE-5#PBF, LT8609SIV#PBF offers higher current and synchronous efficiency but lacks integrated catch diode protection, while TPS54331DR provides greater output current at lower cost but sacrifices automotive-grade input range and ultra-low IQ performance.
Availability
LT3973IMSE-5#PBF is available at Aetrix Electronics and suitable for automotive body electronics, industrial PLC power supplies, portable medical instrumentation, and gate drive bias circuits requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3973IMSE-5#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 legacy of high-performance power management ICs targeting demanding analog-intensive applications.
The LT3973 product line was designed specifically for automotive and industrial DC/DC conversion where ultralow quiescent current, wide input range, and robust dropout behavior are non-negotiable requirements.
FAQ
What is the guaranteed operating temperature range for LT3973IMSE-5#PBF?
The LT3973IMSE-5#PBF is specified for operation from –40°C to +125°C junction temperature. This "I" grade rating makes it suitable for under-hood automotive applications and industrial environments where ambient temperatures exceed 85°C. The MSOP package's θJA of 45°C/W requires adequate PCB copper area on the exposed pad for thermal management.
Does LT3973IMSE-5#PBF require external feedback resistors to set the 5V output?
No - LT3973IMSE-5#PBF is the fixed 5V variant; its internal resistor divider is factory-trimmed to deliver 5.0V ±1.2% over temperature. Pin 1 is labeled VOUT (not FB), confirming the fixed-output configuration. External resistors are only required for the adjustable LT3973 version.
How does the LT3973IMSE-5#PBF achieve 530mV minimum dropout voltage?
The LT3973IMSE-5#PBF enforces a minimum 530mV dropout by regulating the OUT pin (Pin 2) relative to VIN. When OUT is tied to VOUT, the internal comparator ensures VOUT stays at least 530mV below VIN - preserving sufficient boost capacitor voltage to fully saturate the internal NPN switch during low-VIN conditions like automotive cold-crank.
Can LT3973IMSE-5#PBF operate with input voltages below 4.2V?
Yes - the LT3973IMSE-5#PBF begins switching at ~3V, but regulation degrades below 4.2V input. The 4.2V minimum is specified for accurate 5V output and stable feedback reference (1.21V). Below this, output voltage drops proportionally and PG flag becomes invalid; use only for non-regulated pre-bias or brown-out detection scenarios.
What is the purpose of the BD pin on LT3973IMSE-5#PBF?
The BD (Bias Diode) pin on LT3973IMSE-5#PBF accepts an external voltage >3.2V (e.g., from the regulated 5V output) to power the internal bias regulator. This improves efficiency by reducing VIN current draw, especially at high input voltages, and lowers self-heating compared to VIN-only biasing.
LT3973IMSE-5#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):
- 5V
- 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-5#PBF FAQ
1.How can I place an order for LT3973IMSE-5#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3973IMSE-5#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-5#PBF reliable?
The price and inventory of LT3973IMSE-5#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-5#PBF is usually 5 days.
3.What payment methods are accepted for LT3973IMSE-5#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3973IMSE-5#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3973IMSE-5#PBF?
LT3973IMSE-5#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3973IMSE-5#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-5#PBF?
For technical support, including LT3973IMSE-5#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3973IMSE-5#PBF requirements.
6.How does Aetrix verify that LT3973IMSE-5#PBF is sourced from the original manufacturer or authorized distributors?
All LT3973IMSE-5#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-5#PBF meets industry standards.
7.What is the process for return or replacement of LT3973IMSE-5#PBF?
All LT3973IMSE-5#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3973IMSE-5#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-5#PBF part is unused and in its original packaging.
Return procedure for LT3973IMSE-5#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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